Thoracic sonography for diagnosis and intervention

Chris L. Sistrom, MD, received his BS from the University of Oregon at Eugene and his medical degree from the Oregon Health Sciences University in Portland. His residency in radiology was completed at the University of Virginia, Charlottesville, where he remained as assistant professor of radiology in the body imaging section; he later became the director of ultrasound at the same institution. After completing a fellowship in cardiovascular and interventional radiology at the Medical University of South Carolina in Charleston, Dr. Sistrom returned to western Virginia to enter private practice. He is presently a ciinical associate professor of radiology at the University of Virginia.

K.K. Wallace, MD, received his BS degree from Hampden-Sydney College, Hampden-Sydney, Virginia. His medical degree was obtained at the Medical College of Virginia, Richmond, Virginia and he served as a resident in radiology at Duke University, Durham, North Carolina. Dr. Wallace practiced radiology in Virginia Beach, Virginia and he became active in the Medical Society of Virginia and the American College of Radiology (ACR). He served as the chairman of the Board of Chancellors of the ACR from 1992-1994 and was its president in 19941995. He is currently professor of radiology at the University of Virginia, Charlottesville, Virginia.

Spencer B. Gay, MD, received his BS in Chemistry from the University of Miami and his medical degree from the University of Virginia in Charlottesville, where he completed a fellowship in body imaging. He subsequently joined the faculty in the Radiology Department and is currently an associate professor and director of the body CT section. Dr. Gay also serves as director of the radiology residency program at the University of Virginia and is active in such organizations as ACR, AUR, ARRS, and RSNA.

Curr Probl

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.

Thoracic

Sonography

for Diagnosis

and Intervention

Many physicians believethat ultrasound has limited usefulnessin chest disease.Our clinical experiencesand a review of the literature in preparation for this monograph have convinced us that sonography can be a very useful and versatile tool for thoracic diagnosis and intervention. Although there are some limitations caused by interposed ribs and air-containing lung, almost all of the compartments of the chest can be evaluated with ultrasound, which gives unique and clinically useful information. Ultrasound guidance for biopsy and drainage doestake some time to learn, but we feel that the effort is very worthwhile. The same advantagesultrasound enjoys for other body regions make it a modality that will seeincreased use in the chest as well. We hope that this monograph will stimulate our colleagues to explore and expand upon the techniques described.

he two mainstays for imaging of chest disease in most centers in the United States are chest radiography and computed tomography (CT). Until recently, ultrasound has enjoyed only limited use, mostly to localize pleural fluid. Pediatric radiologists were among the earliest users of ultrasound in the chest because infants and children are much easier to scan.’ The uses of thoracic sonography have broadened to include many applications in adults as we11.2 European and Asian radiologists have done much of the pioneering work in applying ultrasound diagnostic and interventional techniques to chest disease. This may be because CT scanners are in limited supply in these countries and ultrasound is a less expensive means of obtaining cross-sectional images, better tissue characterization than radiographs, and to guide biopsy and drainage. As the medical economy changes, we will be faced with many of the same constraints that our colleagues overseas have lived with, and ultrasound will become more attractive. This is already beginning to happen as shown by Simeone et a1.,3 who found a 200% increase in the use of chest ultrasound over a 4-year period. During our review of the literature, we were surprised by the progress that has been made in sonographic diagnosis and guidance for intervention in every compartment of the chest as applied to many disease processes. In addition to lower cost, ultrasound has several other advantages over CT. The machines are portable so that 6

patients too ill to leave their nursing units can be scanned in bed. Yu et a1.4 examined 41 patients in the intensive care unit (ICU) at their hospital, and they thought it helpful to diagnose 66% and to treat 90%. In some specific areas, ultrasound gives diagnostic information that cannot be obtained with CT alone, including Doppler flow characteristics, subtle tissue differentiation, and the ability to see physiologic movements in real time. Additionally, sonography can give a better understanding of anatomic relations because of an infinite variability in scanning orientation. We still rely on CT to give an overview of the chest for primary diagnosis and staging in many cases, and ultrasound cannot replace this function. However, we have found the dictum; “try ultrasound first” to be very rewarding, especially for interventional procedures in the thorax, as in other body regions. Although real-time ultrasound biopsy and drainage guidance takes some time to learn, it is very rapid and safe. Nolsoe et al.’ analyzed 8000 cases of intervention using sonography for guidance and found complication and mortality rates of 0.19% and 0.04%, respectively. With these considerations in mind, we hope to give an overview of the uses of sonographic techniques for diagnosis and intervention as applied to the pleural space, lungs, mediastinum, chest wall, and diaphragm. Diagnosis

of Pleural

Disease

Ultrasound is well suited for evaluating pleural abnormalities because they almost always abut the inner chest Curr Probl

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FIG. 2. Complex array scan through tiple septations.

FIG. 1. Anechoic malignant effusion curved-array scan from the posterior just before thoracentesis, The diaphragm [arrows)

(breast approach

which yielded and underlying

cancer). A, Longitudinal showing anechoic fluid

malignant cytologic evidence. lung are seen (open arrows).

B, Posterior view from bone scan with diffusely increased activity in the right hemithorax (black arrows). This scintigraphic finding is predictive of malignant effusion.

wall and simple fluid, complicated collections, solid thickening, and masses can usually be distinguished. Sonography is as sensitive as CT in detecting small pleural effusions. Collections of 30 cc can be seen easily in Curr

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1997

malignant a lower

effusion interspace

(breast with

cancer). complex

Oblique fluid

having

curvedmul-

most patients. 6,7The best method for finding free pleural fluid is to scan in the posterior and lateral lower interspaces with the patient sitting upright by using a linear or curved-array transducer. There are numerous clues to the character of a pleural collection on ultrasound. Echogenic or septated effusions are almost always transudative, whereas anechoic collections prove to be transudates and exudates with about equal frequency.*-‘I Figs. 1 and 2 show examples of anechoic and complex malignant effusions. Echogenic fluid collections are usually either empyema (Fig. 3) or hemothorax.9 Occasionally empyema will contain small amounts of gas produced by the organisms, and these are seen as tiny bright foci (Fig. 4). In our experience, acute hemothorax will display some swirls of greater hyperechogenicity because of partial clotting, and the collection will become septated with time (Fig. 5). Underlying lung consolidation or mass is associated with exudative effusion (Fig. 6). The adjacent lung is often atelectatic, even with transudates, but this can usually be distinguished from consolidation by its hyperechogenicity, caused by crowding of air-filled bronchi (Fig. 7). Visceral pleural thickening (Fig. 8) also is predictive of an exudate, and this is often malignant, especially if discrete nodules are present. 9~12Subtle thickening of the diaphragmatic pleura with a shaggy appearance (Fig. 9) was always indicative of exudative effusion, even without the other signs described previously in one series.13 7

FIG. 4. Empyema (anaerobic). Curved-array Pleural collection with numerous bright foci Diaphragm is outlined (arrows) and parietal

scan through lower chest. representing air bubbles. pleura is indicated (open

arrows).

FIG. 3. Large empyema (bacterial). A, Sector scan through the lateral left chest showing a large echogenic collection with underlying collapsed pleural

lung (arrows). collection and

B, CT scan through lower collapsed lung (arrows).

chest

with

isodense

Tuberculous effusions are often found to have thick echogenic “winding” strands (Fig. 10) within them, although in our practices, this appearance is more often seen with other processes, as active tuberculosis is rare in our referral population.14 Some pleural collections may not yield fluid during thoracentesis even with large-bore needles (Fig. 11). This is either because the fluid is very viscous or because the process actually represents solid pleural thickening or a mass.15 The best indicators that an anechoic pleural collection will yield fluid on aspiration are a change in its shape or movement of thin septations (Fig. 12) with respiration.1*J”J7 If the collection is isoechoic or hyperechoic and is a fluid, the echoes can be seen to 8

swirl around slowly, but in a solid or complex process (Fig. 13), they will move very little if at all.llJs We also look at the underlying lung, which is often atelectatic with larger collections, to see if it moves with respiration or cardiac pulsations as a predictor of success on a subsequent aspiration (Fig. 7). Recently another sign was described to help determine whether an anechoic pleural collection will yield fluid during a thoracentesis attempt. This involves the use of color Doppler. The authors looked for a broad flash of color when the gate was placed over the pleural collection in synchrony with patient respiration (Fig. 14). The key to success in this method is to set the color Doppler frequency sensitivity to a relatively low velocity (0.2 m/set to 0.3 m/set); the wall filter must be set between 25 and 50 Hz. In two recent series, the investigators achieved sensitivities of 89% and 95% for successful aspiration of fluid when there was a positive “fluid color sign.” When there was no flash of color (Fig. 15), fluid was never obtained on subsequent thoracentesis attempts, giving a specificity of 100% in both studies.18,19 Ultrasound can be very helpful in diagnosing partial or complete opacification of a hemithorax. In this situation, there is some combination of one or more of the following: pleural fluid or thickening, lung consolidation, lung collapse with elevation of the diaphragm, or underlying mass. Occasionally with large pleural collections or lung masses, the diaphragm may be inverted. Radiographically the presence and extent of each of these Curr

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FIG. 5. Hemothorax through lower lateral representing B, Curved-array and

blood

postoperative

partly

(acute and organizing). chest. Mildlyechogenicfluid

A, Curved-array with swirling

clotted blood [open arrows). Diaphragm, scan through lower chest. Multiple septations

elements)

within

anechoicfluid

(serum)

in this

scan echoes

arrows. (fibrin

1 -month-old

Diagn

Radiol,

left chest rowheads).

A, Chest radiograph scan through lower

with lateral

showing anechoic fluid surrounding an isoechoic mass (arThe aorta is deep to the mass (curved arrow). The fluid and

then the mass coaxial needle

were sampled and ultrasound

through the same puncture guidance. Both were positive

by using a for malig-

nancy.

hemothorax.

features can often only be inferred by volume changes because all are of soft-tissue density except aerated lung. A much better understanding is usually obtained with CT as compared with chest radiograph. Ultrasound compliments the findings at chest radiograph and CT and is relatively inexpensive and easy to perform. CT has been shown to be somewhat superior to ultrasound in diagnosing mediastinal masses and adenopathy. In one series, ultrasound showed a distinct advantage with respect to subtle pleural thickening, which is sometimes missed at CT when it has the same density as adjacent fluid.20 In such cases, ultrasound can specifically target biopsy of the thickening, which would be impossible with CT. We have performed combined pleural fineCurr Probl

FIG. 6. Malignant effusion (lung cancer). large pleural effusion on the left. 8, Sector

January/February

1997

needle or core biopsy and thoracentesis through the same puncture by using coaxial technique on a few occasions (Fig. 16). Several articles described the ultrasound appearance of pneumothorax. 21-23Normally the visceral pleura can be seen to move under the parietal pleura during respiration. This has been termed the “gliding sign,” and it is usually easy to see because of small inhomogeneities in the peripheral lung, which produce comet-tail artifacts.24 With pneumothorax, both of these appearances are lost, and a bright static interface representing the pleural air is seen (Fig. 17). Hydropneumothorax will produce what has been termed the “curtain sign” in upright patients. 23This is the result of the pleural air col9

FIG. through

8.

Parietal lower

pleural lateral

and anechoic fluid lignant effusion.

FIG. 7. Transudative Sector scans through lection.

Atelectatic

above

(malignant).

Hypoechoic the diaphragm

Curved-array

solid thickening (arrows)

scan

(open

are seen

arrows),

in this ma-

effusion with atelectasis (heart failure). A and 6, lower right chestwith large anechoic pleural collung (open

arrows)

Note the crowding of air-filled bronchi wedge shape. Diaphragm, arrows.

is seen to move

with

and the peripheral

respiration. apex

of the

lection moving down to obscure basilar fluid and underlying lung (Fig. 18). During ultrasound-guided lung biopsy, the target lesion will disappear under an echogenic interface (Fig. 19) when pneumothorax occursz5 We recently reported on a blinded trial of five radiologists interpreting videotaped scans of 57 hemithoraces, of which 25% had pneumothorax (by chest radiograph done within 10 minutes of the scans). They achieved an average sensitivity of 73% and specificity of 68%. These same readers were unable to accurately determine the size of the pleural air collections.26 Therefore although chest radiography will still be needed to make this diagnosis in the majority of cases, ultrasound may be useful in some circumstances. We have used sonography to localize loculated pneumothoraces for tube placement in critically ill patients who could not be moved from the ICU. Another use for ultrasound to detect pneumothorax is during or immediately after lung biopsy or pleural drainage with ultrasound guidance. 10

thickening

chest.

FIG. 9. lrregulardiaphragmatic

pleura

(malignant).

Curved-array scan

through lower posterior chest. Note the shaggy hyperechoic thickening of the diaphragmatic pleura [arrows). This is indicative of an exudate.

Pleural masses or solid thickening may be caused by primary neoplasms, inflammatory processes, direct invasion by lung malignancy, or seeding from lung or mediastinal tumors and can accompany malignant effusion from a distant site.8J1~12Benign primary pleural tumors are mostly either lipomas or fibrous tumors. Lipomas vary in appearance from virtually anechoic to speckled echogenicity (Fig. 20). Their shape is usually lenticular, and the margins of the mass blend smoothly into the adjacent parietal pleural surface.27 Fibrous tumors are often lobular or even pedunculated and have more obtuse angles. I1 Malignant mesothelioma is usuCurr

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Diagn

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1997

FIG.

10. Thick,

winding

pleural

strand

(lymphoma).

lower chest with a mobile echogenic strand These are described mostly with tuberculous with other processes causing exudates.

Sector

floating effusions

scan through

in fluid (arrows). but can be seen

ally seen as solid, variably nodular pleural thickening, often with pleural fluid superimposed (Fig. 21). Lymphoma, thymoma, and lung tumors can seed the pleural space, especially after surgery, and cause discrete solid masses. Solid pleural thickening may accompany malignant effusions or be seen without any fluid in other cases of pleural metastases. Asbestos plaques have been demonstrated with ultrasound and are mostly hypoechoic, smooth, and lenticular when not calcified (Fig. 22). Calcification of the diaphragmatic pleura is best seen by scanning from below by using the liver or spleen as a window. It is manifested by quite echogenic foci that cause comet tail and short linear reverberation artifacts.28

Pleural Intervention Perhaps the most frequent indication for chest ultrasound in most centers is to provide guidance for thoracentesis. Large layering pleural effusions probably do not require ultrasound localization. Moderate-sized collections can be marked with ultrasound guidance and tapped later in the clinic or on the ward. Small or loculated effusions should be aspirated under direct ultrasound control. In one large series involving sonographically guided diagnostic pleural taps, the authors achieved a success rate of 97%.29 Their early referrals were for small collections, loculated fluid, previously failed thoracentesis attempts, or high-risk patients. Toward the end of the study, many more patients were referred directly to the ultrasound laboratory for the initial tap because of perCurr

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FIG.

11. Solid

A, Linear collection.

1997

anechoic

pleural

collection

(metastatic

parotid

cancer).

scan through posterolateral chest shows an anechoic pleural B, Curved-array scan during thoracentesis. Aspiration with

an 1 B-gauge needle (arrows) sanguinous fluid, positive for tion.

in the collection malignant cells

produced on cytologic

scant seroexamina-

ceived safety and the high success rate. This experience correlates with that of others in that ultrasound-guided thoracentesis is much safer and more often successful than are nonguided methods.30 The utility of image-guided percutaneous catheter placement for drainage of parapneumonic effusion, empyema, hemothorax, and malignant effusions has been well documented in several series and recently reviewed.31-35 In several of these studies, a varying frac11

FIG.

12. Mobile

scan

through

fibrin lower

strand chest.

(parapneumonic Thin

mobile

effusion).

strands

(open

success in obtaining fluid on thoracentesis.Arrows outline in this oblique scan done parallel to an interspace.

Curved-array arrows)

predict

the diaphragm

FIG. 14. Positive fluid-color sign (heart failure). Broad flash of color within low-frequency color Doppler gate over an anechoic pleural collection. One liter of straw-colored fluid was obtained during thoracentesis. Arrows,

FIG.

13.

Solid

echogenic

pleural

collection

(metastatic

carcinoma).A, Curved-array scan through lateral ral thickening with lung edge displaced [solidarrows) (open arrows). 9, Same position and transducer

endometrial

chest. Lobular pleuand a rib shadow with multiple focal

zones. This shows the echogenic nature of the mass much better. At real-time scanning, the echoes did not swirl around, and the collection did not change shape with respiration. No fluid was obtained on aspiration, nant cells.

12

and

a sample

for

cytologic

examination

yielded

malig-

the diaphragm.

tion of the procedures (7% to 100%) were performed in cases in which surgical thoracostomy had failed.31-34 Success, as defined by clinical improvement and resolution of radiographic abnormalities, was achieved in 72% to 92% of cases. The authors often mentioned that as their experience with the technique grew, patients were increasingly referred directly to the radiology department for both diagnostic and therapeutic care. The use of ultrasound as the primary method for guidance ranged from 6% to 70%, and ultrasound combined with fluoroscopy was used 59% of the time in one series.31s33x34 Pleural biopsy by using reverse-bevel (Cope) needles has long been a mainstay of diagnosis in suspected malignant and tuberculous pleural involvement. Typically this has been done without direct image guidance when a fairly large effusion is present. Ultrasound guidance for this procedure is safer and can allow samples to be obtained when very small collections are present.36 When pleural thickening is seen, diagnostic material can be obtained by using ultrasound to guide tine-needle aspiration or core biopsy.37 The choice of which modality to use for pleural intervention is dictated by physician preference, position and conspicuity of the abnormality, and availability of facilities. In our hospitals, CT scanning time is at a premium, and we prefer to use CT as a diagnostic tool to gain an overview of the pathologic condition and use ultrasound guidance whenever possible to perform Curr

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FIG.

16.

Lobular

omyosarcoma). nodular parietal

pleural Oblique pleural

thickening

and

fluid

(metastatic

uterine

lei-

sector scan through lateral chest. Marked thickening [open arrows) with anechoic fluid

underneath. The fluid was drained for cytologic examination, and core samples of the thickening were obtained for histologic study through one

FIG. 15. Negative A, Curved-array ral collection

and

fluid-color scan through underlying

sign (chronic lower chest consolidated

puncture

by using

coaxial

technique

and

ultrasound

guidance.

parapneumonic effusion). posteriorly. Anechoic pleulung (arrows)

are shown.

B,

Same orientation with color Doppler turned on. When patient breathes, only the hyperechoic structures in the consolidated lung (arrows) give color signals. No fluid could be obtained from the collection 18-gauge needle under real-time guidance. Rib shadows, rows

in both

with open

an ar-

scans.

interventional procedures. Many pleural effusions are free flowing and are best accessed when the patient is upright, which is impossible with CT and impractical with fluoroscopy. Ultrasound machines are portable, and this allows thoracentesis and percutaneous catheter drainage to be easily done in the ICU.3,38,39 We have performed thoracentesis, guidance for surgical thoracostomy, and catheter drainage of pleural collections and loculated pneumothorax by using portable equipment with gratifying resu1ts.A multidrawer mechanic’s tool chest can be loaded with all of the necessary supplies, which saves considerable time at the bedside. With Curr

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FIG. 17. Normal

pleural

lung interface

and pneumothorax.

Linear

scans

of the anterior chest (left and right) on a split-screen image. The right side has a pneumothorax, and the thicker, featureless, and brighter interface is well seen. Black arrows, a single reverberation artifact.

Radiol,

January/February

1997

any planned intervention in the chest, special care must be taken in patients having interstitial disease, chronic obstructive pulmonary disease (COPD), and on ventilatory support, especially with positive end-expiratory pressure (PEEP), as these conditions make the risks and consequences of pneumothorax greater than those in the general population. In the next section, we describe our techniques for marking fluid, diagnostic aspiration, and drainage catheter placement in the pleural space. Obviously, the methods we have become comfortable with represent a subset of the available techniques, and the 13

FIG.

18.

Curtain

sign

in hydrapneumothorax.

A,

Frontal

chest

radiograph

with

right

hydropneumothorax

(open

longitudinal scan through lateral lower right chest with patient in expiration. Basilar fluid with underlying lung (wh?e arrows). C, Same scan plane with patient in partial inspiration. The air/fluid level (open arrows) has partly in full inspiration.

The

air/fluid

level

[open

arrows)

has covered

almost

reader is encouraged to find a routine that suits his or her preferences and patient mix. Before marking a pleural fluid collection for subsequent thoracentesis, the physician should review the chest radiograph. For scanning the patient should, if at all possible, be upright. He or she may sit on the side of the stretcher and rest the arms on an adjustable bedside tray. If this can not be done, a decubitus position may be used. Examination of the entire thorax including the axillary line and the anterior chest should be done first to get an overview of the findings. The most inferior and thickest area of fluid is found and marked. It is best to avoid placing the mark too medial, especially on the left side, as this avoids the possibility of puncturing the great vessels and heart. The movement of the diaphragm 14

arrows).

B, Curved

array

(black arrows) and diaphragm obscured the image. D, Patient

all of the image.

during breathing should be noted, and the mark made above its highest position. Once a spot is chosen, a dent may be made in the appropriate interspace with the end of a straw placed on the skin and rotated. After completely wiping the gel away with a towel, the spot can be marked with an indelible pen by using the straw indentation as a guide. We make one line parallel to the interspace and another perpendicular to it at the site for entry. This allows rechecking for accuracy by scanning longitudinally and in the plane of the interspace with the pen mark as a guide. We also note the depth from the skin to the parietal pleura and the depth of the fluid. When thoracentesis is to be performed in the ultrasound laboratory, the same steps described are performed to mark a spot. The site is cleaned and anesthetized with Curr

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FIG. 20. lenticular

FIG.

19.

Pneumothorax

anterior lateral small peripheral are seen. The mass are seen.

during

lung

biopsy.

A, Curved-array

scan

of

lower chest before ultrasound-guided needle biopsy. A mass (black arrows) and rib shadows [open arrows)

B, Same

scan

has disappeared,

plane

with a small and

two

pneumothorax

reverberations

after artifacts

Probl

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1997

fat density

mass

[open

arrows)

posteriorly.

biopsy. (arrows)

lidocaine. Often a 1.5-inch, 25-gauge needle will enter the pleural space during local anesthesia and may yield a reassuring puff of pleural fluid on aspiration. When the actual puncture is done, the patient should be asked to suspend respiration. It is best to have the patient take in a breath and hold it. This causes the diaphragm to move down out of the way, and if the patient must breathe, it will first be expiration, and the intrapleural pressure will be positive rather than negative as with inspiration. We use an 1 S-gauge Amplatz sheath needle (Becton Dickinson, Franklin Lakes, NJ.) for thoracentesis and usually perform the initial attempt without realtime ultrasound guidance. The central stylet is removed and the needle advanced with gentle suction from a 10 Curr

Pleural lipoma. A, Curved-array scan with virtually anechoic pleural mass. With patient breathing, the lesion does not appear to move with the underlying lung (arrows), which glides under it or with the overlying chest wall. B, CT scan through lower chest with

or 20 ml syringe. Care should be taken to go above the lower rib, and if adequate local anesthesia has been administered, the needle can be “walked” up over it. Once fluid return is obtained, the needle is held in place, and 10 to 20 ml is aspirated. This is to ensure that at least enough fluid for laboratory analysis and culture is obtained. The outer sheath is then advanced into the collection, and the needle removed. We prefer to attach an extension tube and stopcock connected to a drainage bag. A large syringe is then used to “pump” the fluid into the bag. Having the patient sit straight up or lean slightly back may facilitate more complete removal of fluid. Often the lung bumps up against the cannula and for this reason, only gentle suction should be used to avoid breaching the visceral pleura. Our patients sometimes complain of increased pleuritic pain and an urge 15

FIG. 21, Malignant through the anterior

mesothelioma.8, Frontal chest left chest showing a spherical,

radiograph isoechoic,

“gliding sign.“Solid arrow, Comet-tail artifact. C, Scan through a hypoechoic asbestos plaque containing calcification (arrows).

with pleural fluid, nodularthickening, heterogeneous pleural mass. The the lateral

to cough as the last of the fluid is evacuated. This results from apposition of inflamed pleural membranes and usually resolves fairly quickly. If fluid is not easily obtained on the first pass with the needle, a transducer (sector or curved array) should be covered with a sterile sleeve and used to guide needle placement during a second pass. If real-time monitoring shows the tip to be in the collection, and no fluid returns, it is probably too thick to come out through the needle or may be solid. If clinical indications and ultrasound appearances are consistent with thick fluid, the plastic cannula can be left in place and a guide wire placed into the collection for drainage-tube placement. 16

chest

with

heterogeneous

and discrete masses. underlying lung (open pleural

thickening

6, Curved-array scan arrows) exhibited

(open

arrows)

the

displacing

Often even a small (6F to 8F) tube will subsequently allow fluid to be aspirated. We usually leave the drain in place until a Gram’s stain can be performed and then pull it if no white cells are seen. If frankly purulent fluid is aspirated, an on-the-spot decision may be made to place a large bore drainage catheter. The advantage to using the Amplatz sheath needle is that a guide wire can be placed immediately, allowing subsequent dilation and tube placement.As described previously, some (even anechoic) pleural collections seen on ultrasound may actually be solid. In the event of a “dry tap” in which real-time scanning confirms correct position of a large-bore needle within the abnormality, consider subCurr

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1997

FIG. 22. Asbestos calcification (open shadow [arrowsJ.

(open

plaque arrow).

arrows).

and calcification. B, Longitudinal C, Longitudinal

A, Frontal cumed-array right

subcostal

chest radiograph with left lateral plaque scan through lateral left chest with sessile scan

with

focal

mitting what little material is obtained for cytologic analysis. We have been pleasantly surprised after doing this with a definitive diagnosis on several occasions (Fig. 11). The material can either be washed into saline or smeared on a slide, depending on the local cytopathology laboratory’s preferences. When placement of a drainage tube is planned, the same steps outlined for marking and thoracentesis are carried out first. We use a 0.038 guide wire with a 1.5 cm diameter J-tip through the plastic cannula of the Amplatz needle. A skin nick should have been already made if tube drainage is planned. The dermatotomy can be made alongside the wire and enlarged with a hemoCurr

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calcification

of the

(black arrows), and a tiny hypoechoic plaque (arrows)

diaphragmatic

pleura

making

right diaphragmatic interrupted by a rib a comet-tail

artifact

stat if conversion of thoracentesis to catheter drainage is needed. We do not usually use fluoroscopic control for the subsequent steps, although this may be helpful in difficult cases. Drainage catheters are available in a variety of sizes and configurations. We use All Purpose Drains with large holes (APDL, Medi-tech, Watertown, Mass.) in 6F through IOF and Von-Sonnenberg Chest Drains (same company) in 12F and 14F. The choice of size depends on the thickness of the fluid and physician preference. It is probably best to err on the side of a larger tube to avoid having to upsize it later. Serial dilations from 6F through the planned drainage-tube size (in 2F increments) are performed. The patient should 17

FIG. 23. Posterior

Drainage of loculated empyema. A, Frontal sector scans taken during ultrasound-guided

E, Chest

radiograph

with tube

in place

and

loculus

chest radiograph with left subpulmonic catheter placement. The needlefarrows), drained

loculation (arrows). 6, C, D, (arrows) are seen sequentially.

completely.

be asked to suspend respiration during dilation because air can enter the chest through the dilator around the wire, especially with larger sizes. The drainage tube is placed over the wire with its stiffening cannula in place. Once the side holes have entered the chest, the cannula and wire are fixed, and the tube advancedinto the collection. We prefer to attach the drainage tube to water seal-type suction in most cases, although bulb suction or bag drainage can sometimes be used for small col18

fluid and a posterior wire, and catheter

lections. Using a Percufix (Medi-tech) device to secure the drain to the skin and choosing a locking pigtail version of the drainage catheter ensure against inadvertent pulling of the tube. Fig. 23 shows the steps in draining a loculated empyema under ultrasound guidance. Once a tube is in place and the probable origin of the fluid has been determined by laboratory analysis of the initial aspirate, a more definitive plan for therapy can be made. The decision on when to remove the catheter Curr

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is made based on several criteria. Clinical response (mainly resolution of fever and leukocytosis), radiographic resolution, and decrease in drainage are good indicators. In some cases, the output will decrease to near nothing, but there will still be significant pleural thickening or loculations on follow-up radiographs or CT scanning. One approach to this problem is to insert additional catheters into the undrained collections. However, before taking this step, the patency, correct position, and optimal size of the indwelling tube should be established. We have had consistent success with instilling urokinase solution into the original catheter in this situation and rarely find it necessary to insert a second drain. The practice of pleural lavage with lytic agents (mainly streptokinase) was initially described in the 1940s and 1950s for use in empyema and hemothorax.40,41The main drawback to this method was a high rate of systemic febrile reactions within hours of treatment. More than 3 decades later, treatment of parapneumonic effusion, empyema, and hemothorax with urokinase instilled through image-guided catheters was shown to be very effective and to have no significant systemic reactions. 42-44Experimental work with various effusions has shown that there is a balance between fibrinolytic and procoagulant activity that favors the latter in exudates and that gives some clues as to why the technique works as well as it does.45 The concern for causing a systemic lytic state with either agent seems to be minimal, as shown by performing coagulation studies on patients undergoing intrapleural lytic therapy.42,43a46 We use urokinase instead of streptokinase in spite of the increased cost because we believe it to be safer in terms of systemic response.44 Before starting therapy, a patent chest tube or drainage catheter should be confirmed to be in the pleural space and attached to waterseal suction. A single vial containing 250,000 IU of urokinase is diluted into 250 ml of sterile saline and mixed well. The doses used for each treatment range between 50 and 100 ml (50,000 to 100,000 IU). To instill the urokinase, we simply clamp the rubber connecting hose between the drainage catheter or chest tube and the water seal (at the end near the patient) and inject the solution proximally after carefully sterilizing the tubing. A small amount of air can be injected as a “chaser” to push the solution. During the ensuing hour, the patient is asked to assume several positions to distribute the urokinase around the pleural cavity. After that, the tube is unclamped for at least 3 to 4 hours before the next instillation. Marks on the reservoir of Curr

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the water-seal device help to determine results of each treatment. If multiple drains have been placed, one must clamp all of them during the treatment phase and then open them all for evacuation. By putting the urokinase solution into each tube in sequence during successive treatments, more complete drainage may be obtained. We keep the urokinase solution in a refrigerator and try to use it within 24 hours because of the concern for loss of enzyme activity with time. Treatments can be repeated up to 9 or 10 times, but in our experience, a point of diminishing returns is reached at around half that number. With increasing emphasis on shortened hospital stays, early use of intrapleural urokinase in patients with parapneumonic effusion, empyema, and hemothorax will probably become increasingly popular. Diagnosis

of Lung Abnormalities

Although interposed bone and air-containing lung can make it impossible to study some pulmonary parenchyma1 lesions with sonography, a large fraction of patients with lung abnormalities can benefit from a careful ultrasound examination. In one series of 221 patients being evaluated for ultrasound-guided biopsy of pulmonary infiltrates or masses, 195 (88%) of these were visible.47 In another study, the same authors found that 161 (95%) of 170 patients with infiltrates on chest radiography could be evaluated with ultrasound.48 Pleural fluid often is present with lung abnormalities of various causes and is very helpful in providing an acoustic window. When a patient is placed supine with his or her arms over the head, curved-array and sector scanning in the intercostal spaces allows visualization of -3/4 of the surface of the lungs. To see posteriorly, it is best to have the patient sitting upright and facing away from the examiner (as described for pleural evaluation). Scanning can be done either longitudinally or obliquely to coincide with rib interspaces. A methodical sequence of scanning around the circumference of the chest at several levels from cephalic to caudal provides complete coverage. Once the abnormality is located, switching to a higher frequency or linear transducer or both may allow better evaluation of subtle architectural detail and Doppler findings. Comparison with the liver to represent solid tissue and the gallbladder for fluid is useful in characterizing the echogenicity of the lesion. Most of the articles cited subsequently use these comparisons either specifically or implicitly when describing lung abnormalities. Infiltrates tend to be relatively hypoechoic compared with the normal pleural/lung interface and will gener19

FIG. 24. Bacterial in a child.

pneumonia.

Consolidated

lung

Curved-array scan occupies

most

through of the scan

lateral and

vessels (open arrows) and bronchi centrally. With Doppler, shown had characteristics of a pulmonary vein. There subpulmonic fluid above the diaphragm (arrows).

chest

contains the vessel is some

ally display a wedge shape with the apex located toward the hilum of the lung (Fig. 24). Uncomplicated bacterial pneumonia is characterized by a hypoechoic or isoechoic slightly heterogeneous background through which anechoic tubular structures (pulmonary arteries and veins) and hyperechoic branching linear structures are seen (Fig. 25). These have been called “sonographic air bronchograms .“4g The periphery of uncomplicated infiltrates will display hypoechoic bands, and the deep borders are irregular and hyperechoic (Fig. 26).50Additionally, anechoic nonpulsatile tubular spaces are seen in many consolidations; these have been termed “fluid bronchograms.” They can be distinguished from pulmonary vessels with color Doppler sonography by virtue of their having no flow. 5oMicroabscess formation is characterized by small, discrete anechoic spaces within the consolidated lung. These sometimes are surrounded by a subtle bright ring. 48,51Fig. 27 is an example of an upper-lobe pneumonia in which such an area is targeted during ultrasound-guided needle aspiration for culture. If a frank lung abscess develops, the normal echoarchitecture of the lung is replaced by complex fluid of varying echogenicity, sometimes with multiple bright foci representing air pockets (Fig. 28) or an air/fluid level.51 Atelectasis can best be appreciated with surrounding pleural fluid and is characterized by a reversal of the wedge shape (apex peripheral rather than deep) and crowding of the air bronchograms.49 Fig. 7 depicts 20

FIG. 25. Air bronchograms of left atrium

(aspiration

in this adolescent

with

pneumonia).A,

CTscan

meningomyelocele.

There

at level is lower-

lobe consolidation with prominent air bronchograms. B, Curved-array scan done posteriorly in an interspace shows consolidation with bronchograms

(open

air

arrows).

atelectasis with a large pleural effusion. Lobar collapse tends to contain prominent and numerous fluid bronchograms and no air bronchograms (Fig. 29). If present, a central mass can frequently be seen because of a bulge in the contour of the consolidation or because it has different echoarchitecture compared with the peripheral consolidation.48%52 Figs. 30 and 31 are examples of bronchogenic cancer with postobstructive pneumonitis. Diffuse lung disease has not been studied much with ultrasound. Targhetta et a1.53examined 12 patients with sarcoidosis by using 7.5 Mhz probes and found peripheral irregularities of the lung surface in all Curr

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FIG. 26. Peripheral and deep features of consolidation. Curved-array scan through a lower interspace shows a band of hypoechoic tissue (open arrows) representing fluid-filled alveoli in the outer lung. The deep borders case (arrows).

FIG. 27.

of infiltrates

Early

microabscess

are often

irregular

in pneumonia.

aspiration of an upper-lobe infiltrate. rows) is seen within the consolidated

and

Sector

ill defined,

scan

done

as in this

during

A subtle bright ring (open arlung during needle placement

(arrows).

and tiny nodules in 9 of them.53We examinedone patient with active alveolar proteinosis and saw what seemedto be a slight decreasein the echogenicity of the peripheral interface, which was also somewhatirregular.Lung contusioncan be very subtle and is seen as a peripheral band of hypoechoic lung, presumably becauseof blood replacing air in alveoli (Fig. 32). Lung abnormalities distal to pulmonary embolism (PE) can be detectedby ultrasoundin a large majority of caseswithin hours of the event. Miller et al.54examined 183 patients with 63 suspectedof having PE Curr

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and found that 34 (94%) of 36 with positive ventilation/perfusionscanshad demonstrableultrasoundfindings in correspondinglung segments.In a more recent article, Mathis et al.55reportedfinding 69 ultrasound abnormalitiesin 42 (78%) of 54 patientsprovento have pulmonary embolism by scintigraphy or angiography. He calculated sensitivity and specificity of 98% and 66% from the entire study population of 58 subjects. The findings describedwereirregular,generallywedgeshapedhypoechoic lesions in the lung periphery with or without pleural fluid. Both authorspostulated that the described findings at ultrasound may be visible without obvious infiltrates on correspondingchestradiographs,which werepositive in only 21% of patients in the latter series.54,55 In the casesthat go on to pulmonary infarction, ultrasound shows a smaller and more well defined hypoechoic lesion in the involved segmentthat often has a bright central echo within it (Fig. 33). Color Doppler hasbeen applied to evolving infarctions aswell. In the acutephase,no flow can be obtained in the involved lung, whereas subacuteand chronic infarctions show a gradual increasein vascular signals during resolution.s6 Pulmonary sequestrationcan readily be seenin infants andchildren asa well-defined hypoechoicareaof abnormallung in the typical basilar locations.57-61 One casewas reportedin an adult.62The key to making this diagnosisis in color andduplex Doppler analysis.The authorsdescribe a large tortuous vesselin the lesion. This representsthe anomaloussystemicfeeding artery. SpectralDoppler of this vesselrevealsa pulsatile waveform resembling those obtained from renal arteries.62 Two casesof pulmonary arteriovenousmalformation (AVM) were describedrecently.In both, a small complex anechoic structurewas seenat ultrasoundin the lung periphery.63,64 In one, high-velocity flow was detected at Doppler sonographywith the feeding artery anddraining vein clearly discernible.64 Lung massescan be seenquite frequently as many contact the visceral pleura, are surroundedby pleural fluid, or causeatelectasis/consolidationin the periphery that contactsthe pleural surface(Fig. 34). In one recentstudy,65 74 (59%) of 126patientshaving a parenchymal mass were able to be evaluatedby ultrasound. Peripheral lung lesions are typically hypoechoic to isoechoic, homogeneous,and well defined. They frequently display a bandof bright echoesin the scandeep to the inner border.If the point of contactwith the lung edgeis small, the edgesof the lesion may be straightby virtue of shadowingby the interposednormal lung be21

FIG. 28. Lung abscess (Pseudomonas). A, CT scan through upper chest with three abscess cavities. 6, Oblique sector scan of posterior before drainage. The abscess has somewhat irregular borders (open arrows) and foci of air centrally. The air/fluid level is to the right C, Radiograph done after catheter placement.

tween the visceral pleura and the surface of the lesion as it curves away (Fig. 35). Larger lesions tend not to show this feature because the angles they make with the pleura are less acute. ~5%~~ Also larger masses tend to be more echogenic and heterogeneous as compared with smaller ones (Fig. 36). In one series, relative hyperechogenicity correlated with a malignant mass in 94%. When the lesion was hypoechoic, the authors were unable to tell whether it would be benign or malignant with any certainty. 68 Doppler flow analysis has been applied to peripheral masses to discriminate benign from malignant disease. Yuan et a1.65 were able to obtain Doppler signals from 54 (69%) of 78 peripheral masses 22

left chest (arrows).

and found that the average resistive index was significantly lower (0.52 vs 0.90) in the malignant lesions. By setting cutoff levels at -2 SD from these mean values, they were able to achieve 100% sensitivity and 95% specificity. Probably the most frequent cause of benign peripheral lung masses seen on ultrasound is granulomatous or fungal infection (Fig. 37). These have both been described as sometimes having small bright spots within them and irregular margins.69,70 More often such lesions are included in descriptions of ultrasound-guided biopsy series, and their prevalence varies up to 10% of all positively diagnosed masses.71-74 Once cancer is diagnosed in a peripheral pulmonary Curr Prabl

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1997

FIG.

29.

with right posteriorly [open

Lobar

collapse

lower shows

arrows]

(mucus

lobe collapse heterogeneous

and

plug). [arrows). collapsed

A, CT scan through

lower

chest

B, Curved-array scan done lung with fluid bronchograms

no air bronchograms.

mass, ultrasound findings can be useful in therapeutic decision making. The extent of pleural or chest-wall invasion is very important in planning successful surgical excision for cure. If the lesion is growing through the parietal pleura an en bloc resection of the overlying involved soft tissues may be required, as well as perioperative radiation therapy. Ultrasound is more accurate than CT in this regard because of its ability to detect respiratory motion in real time and to resolve small structures and subtle tissue characteristics.A scoring system has been proposed to codify these findings.75 This system has four classes numbered UP-O through UP-~. Lesions that do not touch the visceral pleural surface are not clearly visible, except perhaps as a minute dimple in the visceral pleura. These are given a score of UP-O. When the nodule contacts the lung surface along Curr

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1997

FIG. 30. Lobar

collapse

left lower

collapse.

lobe

(central 9, Sector

carcinoma].A, scan

through

Chest poster

radiograph left chest.

with Ho-

mogeneous isoechoic lung with a hypoechoic central mass [open arrowsJ. This was sampled with ultrasound guidance, yielding squamous cell carcinoma. Arrows, the diaphragm.

a short segment of its diameter, the visceral pleura will be intact and seen as a bright line, perhaps with some thinning (up-l; Fig. 38). In the next class (UP-~), the visceral pleural line is interrupted by the tumor, and there may be subtle thickening of the overlying pleural space, but the parietal pleura is intact (Fig. 39). Finally, in up-3 lesions, the mass interrupts the parietal pleura and may grow into the chest wall (Figs. 40 and 41). A 23

FIG.

31.

central rather

Middle-lobe

mass (open than different

collapse arrows} and echogenicity.

(central

carcinoma).

A, Chest

radiograph

showing

middle-lobe

collapse.

peripheral collapse/consolidation (arrows). In this scan, the mass C, Higher resolution view with color Doppler of the postobstructive

B, Right

is mainly discernible pneumonia with

parasternal

sonogram

with

by the bulge that it causes fluid bronchograms (open

arrows).

very important sign is that of respiratory motion of the mass on real-time observation. In the proposed system, UP-O and up-1 lesions always display free motion, whereas the mass is firmly fixed to the chest wall with up-3 lesions. Other authors stressed the importance of real-time observation of decreased respiratory motion in detecting chest-wall invasion.‘j6-@

Lung Biopsy and Abscess Drainage Percutaneous biopsy of pulmonary masses and infiltrates that contact the pleural surface can be done quickly, safely, and inexpensively by using ultrasound for needle guidance. As described previously, a large fraction of lesions are visible during ultrasound examination of the chest and are thus amenable to biopsy. Ultrasound has several specific advantages over 24

CT and fluoroscopy as a guidance method for lung biopsy. Although the learning curve in doing these procedures is rather long, we have found the time and effort spent to be very rewarding. We consider ultrasound as the first choice to guide lung biopsy and use CT or fluoroscopy only if the lesion is not adequately visualized. We briefly review the literature on the subject and describe our methods for ultrasound-guided lung biopsy and abscess drainage. The first report of using ultrasound to guide percutaneous biopsy of pulmonary masses was by Chandrasekhar et a1.76They used B-mode scanning for planning the route, A-mode to visualize the needle tip, and manual core-biopsy needles. His four patients had no complications, and accurate results were obtained in three. Since then, there have been many advances in Curr

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1997

FIG. 33. eral

Evolving

right

lung

pulmonary consolidation

infarction. done

found at pulmonary arteriography. regular but well defined, and there row).

FIG. 32. Lung contusion.A, CTscan through lower chest of a child run over by a car. Subtle lung contusion in lateral basilar right lower lobe (open arrows). B, Linear oblique scan over right lateral chest. The contusion

is a subtle,

irregular

band

lung [open arrows). A thin remains aerated (arrows).

rim

of hypoechogenicity of lung

just

under

in the peripheral the visceral

pleura

Probl

Diagn

Radiol,

January/February

1997

are characteristic

FIG. 34. Necrotic parasternal scan see a necrotic (open arrows) well as some

scanner, transducer, and biopsy-needle technology. Three subsequent series of lung biopsies with core-biopsy needles reported definitive diagnosis in 87% to 96% of malignant lesions and 71% to 94% of benign masses.47,68,77The rate of pneumothorax ranged from 0 to 4% and that of hemoptysis up to 8%. Fine-needle aspiration biopsy (FNAB) with 22-gauge through 18gauge needles for cytologic study has been reported, and the positive diagnosis rate for benign lesions decreased considerably (0 to 64%), whereas the rate for correct identification of malignancy remained high (90% to 100%). In these four series, there was only one report Curr

These

features

lung carcinoma where lingular

Curved-array

3 weeks

after

scan

lower

The deep borders is a central bright of subacute

of periph-

lobe embolism [arrows) are irfocus [open ar-

infarctions.

(poorly differentiated). consolidation provides

Oblique a window

left to

tumor (arrows). There is fluid in an obstructed bronchus peripheral to the mass forming a fluid bronchogram, as pericardial

fluid

(P).

of hemoptysis, and pneumothorax occurred in 0 (two), 3%, and S%.66,67.71,72Tw o articles report using FNAB or core-biopsy needles with benign diagnostic results between the numbers described previously and similar high rates for diagnosis of malignancy.73v74 These findings parallel those obtained with other guidance methods for transthoracic needle biopsy of lung lesions. In general, larger-bore core biopsy allows better tissue typing of malignant lesions and a higher rate of success in diagnosing benign disease, while carrying a somewhat greater risk of bleeding complications.78 Lesions that are ~3 cm should probably not be considered for core 25

FIG. 36. Peripheral mass are well seen rather larger

PIG. 35. Small irregular mass reveals straight

peripheral carcinoma. A, CT at level of aortic root with that just contacts the pleural surface. B, Linear scan lateral borders of the lesion (open arrows) caused by

shadowing from aerated lung between deeper parts the transducer. This is enhanced through transmission

of the lesion and deep to the le-

sion (arrows).

biopsy.47 However, FNAB guided by ultrasound works very well for small peripheral nodules, with a positive diagnostic rate of 90% in one study.79 Pulmonary consolidation often contacts the visceral 26

broadly. tumors

carcinoma (squamous cell). The borders of the with no shadowing because it contacts the pleura

There is some on ultrasound.

internal

heterogeneity,

characteristic

of

pleura, and a biopsy can easily be performed with ultrasound for guidance. Yang et a1.48performed 67 FNAB procedures with 22-gauge needles into lung infiltrates, of which 5 (7%) had hemoptysis or pneumothorax. A definitive culture or diagnosis was obtained in 38% of uncomplicated pneumonia, 8 1% of necrotizing pneumonia, 95% of obstructive pneumonitis with tumor, and 100% of diffuse malignancy, such as bronchoalveolar carcinoma. The same authors performed biopsies of 30 mostly benign infiltrates with FNAB and 16-gauge core needles and obtained a definite diagnosis in 30% and 57%, respectively. In a few cases, the methods were complementary, giving a combined diagnostic yield of 63%.80 Bronchoalveolar carcinoma was diagnosed with 100% accuracy by using core biopsy and 50% of the time on FNAB in another small series.8’ Complicated bacterial pneumonias, cryptococcal pneumonia, and tuberculosis have all been sampled with FNAB, yielding positive culture rates ranging -9O%.3x,5’,69,7oIn these suspected infectious infiltrates, the key to the high rate of success was in targeting anechoic areas or bright rings representing microabscesses, which yielded varying amounts of pus for culture (Fig. 27). Obstructive pneumonitis is a special case with unique bacteria in the infiltrate itself and frequently having an underlying mass that can be seen and targeted for biopsy. Fluid bronchograms, a lack of air bronchograms, and a cenCurr Probl

Diagn

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1997

FIG. 38. up-1 lesion (poorly differentiated carcinoma). tacts the pleura along a small portion of its periphery through transmission intact [open arrows).

(blackarrows). The nodule

This lesion conand has marked

The visceral pleura moved with respiration

is thinned but on real-time

scanning.

FIG. 37. Aspergilloma. A, CT scan below the carina with a history of leukemia. There is an irregular right with with

some pleural reaction. B, Curved-array scan ultrasound guidance. The borders are irregular,

ening is seen (open procedure, allowing

arrows). specific

Fungal treatment.

infection

was

in an 8-year-old lower lobe mass before aspiration and pleural thickconfirmed

by the

tral mass are key findings in identifying these consolidations (Figs. 30 and 3 1). Liaw et a1.8”performed FNAB of 26 postobstructive infiltrates and were able to culture a total of 16 bacterial strains from 9 (35%) of them. More often the nature of any underlying tumor is of greater interest, and ultrasound has been shown to be well suited to guide biopsies that specifically target the mass 4~,5~,~0 In several clinical situations, ultrasound may be specifically indicated over CT and fluoroscopy to guide percutaneous biopsy of pulmonary masses or consolidation. One of these is the apical or Pancoast’s tumor (Fig. 42). Often these are difficult or hazardous to reach from standard posterior or anterior approaches because Curr

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1997

FIG. 39. up-2 lesion

(metastatic

laryngeal

carcinoma).

The nodule

con-

tacts the visceral pleura over -1 cm and partly interrupts it. The parieta1 pleura (open arrows) is intact. The lesion moved with respiration during

real-time

observation

(arrowj.

of the intervening scapula or large vessels. Ultrasound allows imaging in the coronal plane to guide biopsy from the supraclavicular approach.83 Small peripheral nodules may not be visible in two planes at fluoroscopy and can move so much with respiration as to make CT guidance impractical. This is especially likely when the lesion is near the diaphragm (Fig. 43). Guidance with 27

FIG. vades

40.

up-3

through

lesion both

(poorly pleural

differentiated membranes,

carcinoma). which

are intact

The

mass

on either

inside

(open arrows), and out into the chest wall for a small distance (arrows). At real-time scanning, the lesion was completely fixed to the chest wall, as evidenced

by no motion

seen

with

breathing.

ultrasound is ideally suited for such lesions and has been shown to be very effective. 66-68,72,76,79 Ultrasound can be a very useful adjunct to fluoroscopy in preparing for biopsy of lung lesions. 74 Even when a C-arm unit is available and the lesion is visible in two orthogonal planes, the procedure time is prolonged by having to rotate the unit through 90 degrees at least once with the needle in the lung to confirm correct position. To eliminate this extra time, we can use ultrasound to calculate a depth for lesions on which we will perform biopsies, with the needle parallel to the beam, and then use fluoroscopy to center the needle on the lesion (Fig. 44). Likewise, when the needle will be perpendicular to the beam, the entry site directly over the lesion can be marked with ultrasound and the correct depth ascertained with fluoroscopy during puncture. When small peripheral lesions are visible only in one plane at fluoroscopy, ultrasound will allow the procedure to be completed by helping to mark the puncture site or calculating the depth for biopsy, as described previously (Fig. 45). These techniques are especially helpful if only single-plane fluoroscopy is available, as is true in many smaller departments, and is a good way for those who have used mainly fluoroscopic guidance to become comfortable with ultrasound-directed lung biopsy. Eventually with practice, 28

FIG.

41.

up-3

lesion

(adenocarcinoma).

rows) rows).

between ribs, which The lesion is rather

large

malignant

This

mass

invades

are intact and produce shadows hyperechoic, which is frequently

(black

ar-

(open arseen with

neoplasms.

there is no need to use fluoroscopy as long as the lesion is visible on ultrasound. Our method for ultrasound-guided lung biopsy varies somewhat depending on the nature of the lesion and the suspected pathologic condition. The two major choices involve whether or not to use a transducer with a needle guide and FNAB for cytologic study versus a larger needle for core samples to be submitted for histologic examination. We generally do not use a biopsy guide and believe that it is safer for the needle to be free to move with respirations during confirmation of its position and aspiration, whereas a guiding channel tends rigidly to hold the needle in place. Additionally, biopsy guides force a fixed geometry between the transducer and the needle, whereas freehand biopsy allows optimal choice of biopsy path and transducer position, depending on lesion structure, chest-wall configuration, Curr

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1997

FIG. right

42. Apical biopsy (adenocarcinoma). apical mass [open arrows). B, Curved

A, Chest radiograph array coronal scan

during needle biopsy by using innominate artery is superficial

the supraclovicular and medial (open

was introduced

laterally,

and

samples

to avoid tip.

necrosis.

Dotted

central

were

line, The

taken

path

approach.

arrows). from

with done

The right The needle

the periphery

of the needle;

arrow,

its

and respiratory motion. Finally during freehand biopsy, it is much easier to sample a wide area of the lesion by moving the needle tip into different regions during aspiration. Even given the relative safety of core biopsy described previously, aspiration with a small needle should be considered a first step. Success with FNAB depends largely on the comfort of the local pathology staff with cytology, which can vary considerably. In many centers, pathologists are willing to come to the ultrasound suite, stain the slides on the spot, and examine the material for adequacy. When this is done, the diagnosis can often be obtained after only one pass with Curr

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Diagn

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1997

FIG. 43. Aspiration A, CT scan through

of small mobile lung lower chest showing

lesion (cryptococcal an 8 mm peripheral

nodule). nodule

(open arrow). B, Sector scan done during ultrasound-guided needle aspiration. The lesion (solid arrows) and the needle (open arrows) are well seen. Fungal elements were found in the aspirate, and the organism eventually

grew

in culture,

a 22-gauge needle. If two or three passes for cytologic examination do not give satisfactory results, we switch to an automated core-biopsy gun (Monopty, Bard Inc., Covington, Ga.) or a hand-operated spring-actuated core needle (Temno, Bauer Medical Inc., Clearwater, Fla.). Another popular choice is a core needle with an incorporated locking syringe (Percucut, E-Z-EM, Inc., Westbury, N.Y.). These devices come in different sizes ranging from 22 gauge to 16 gauge. If the abnormality consists of consolidation, consider making one or two passes with a fine needle for culture and one or more biopsies with the core needle for histologic examina29

FIG. 44. Ultrasound to aid fluoroscopic lung biopsy (example). A, Curved array longitudinal scan of the posterior left chest to mark depth of a peripherol nodule (arrows) immediately before biopsy. B, Spot image

made

during

aspiration

of the

same

lesion

(open

arrows).

A

depth stop was placed on the needle (solid arrow) based on ultrasound measurements, and the biopsy was done very quickly with single-plane fluoroscopy.

tion. Specifically targeting any small fluid collections in the consolidated lung and underlying mass lesions greatly improves the chances for successful diagnosis in these challenging cases. In practice, the biopsy procedure begins with a brief sonographic examination (usually with a 3.5 mHz or 5 30

mHz curved-array transducer) of the entire hemithorax to obtain an overview. We then concentrate on the area of abnormality, often switching transducers (different frequency, linear, or microcase sector) to obtain the best view of the lesion. Turning on color Doppler at this time helps to see any large vessels to plan a biopsy path to avoid them. During this survey, the transducer that seems to give the best view of the lesion and the planned needle path is chosen for biopsy guidance. Marking the needle entry site, sterile skin preparation, draping, and local anesthesia are done in the usual fashion. The needle is then advanced under the transducer, covered with a sterile sleeve, in parallel with the imaging plane toward the lesion. If the tip is not readily apparent as it passes into the field of view, the hub of the needle is jiggled to create tissue motion at the needle tip to facilitate its detection. Another trick is to pull the stylet back slightly into the cannula to introduce a little air. It is often easier to see the needle tip as it approaches and enters the abnormal (often hypoechoic) tissue. With the patient’s breathing suspended, suction is applied to the needle hub with a 20 ml syringe, and it is briskly moved in and out through a 1 to 2 cm path and removed. The aspirates are placed on sterile slides and transferred to the cytopathologist for preparation. If the lesion yields blood that enters the aspirating syringe, it can be washed into cytologic solution to be spun down later and examined or allowed to clot and submitted in formalin for histologic examination as a cell block. If lymphoma is in the differential, consider washing material from one or more of the passes into a special solution for subsequent flow cytometry, which can greatly aid in subtyping the tumor. When core biopsy is required, the device is placed in the ready position before puncture. A small skin nick may be helpful with these larger needles. An 1S- or 20gauge core-biopsy needle is much easier to see than the smaller ones typically used for cytologic study. By using real-time guidance, we place the tip just within the superficial edge of the target and fire while the patient holds his or her breath. The device is quickly removed while breathing is still suspended, and the core sample is placed in formalin solution. The path of the biopsy site is usually clearly visible on ultrasound for a few minutes because of small bubbles of air and tissue disruption. If the lesion is still visible and the adjacent lung edge displays the “gliding sign,” we can be reassured that at least a large pneumothorax has not occurred. At least one chest radiograph should be done after the procedure to exclude pneumothorax or other complicating features. Curr

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1997

DEPTH

,

STOP

I~

NEEDLE LESION

LESION

NEEDLE

X-RAY

B FIG.

45.

Ultrasound

fluoroscopy fluoroscopy

lung

biopsy

used to locate to guide depth

(diagram).

A, Ultrasound

center of the lesion. of placement.

Most lung abscesses are caused by aspiration of oral flora into dependent portions of the lung with subsequent necrotizing pneumonia. Pneumonia caused by Staphylococcus aureus, Klebsiella, and Streptococcus pyogenes may be complicated by abscess formation. Occasionally lung abscess may be the result of septic emboli in cases of endocarditis, septic thrombophlebitis, or intravenous drug abuse. Ultrasound can be very helpful to guide sampling of these processes for culture, which allows more specific antibiotic choices.48,51 Conservative medical therapy leads to resolution in 80% to 90% of cases.35z84 If symptoms and radiographic findings do not improve after a trial of specific antibiotics, percutaneous drainage is Curr

Probl

Diagn

Radiol,

X-RAY

D

to aid fluoroscopic

plane (needle parallel) (needle perpendicular)

TUBE

January/February

1997

used

C, Ultrasound

to measure used

depth

to mark

TUBE

of the lesion skin

over

center

as in Fig. 44, of mass.

A. 6, Single-

D, Single-plane

the procedure of choice. Ultrasound can be used to guide catheter placement, sometimes supplemented with fluoroscopy, if the abscess is peripheral.35,84 In such cases, the inflammatory process usually causes adhesion of the pleural surfaces, and the catheter can be easily placed by using the same techniques described previously for pleural drainage. We prefer to use fairly large-bore tubes because there is usually necrotic debris in the cavity and place them to water-seal suction. The abscess shown in Fig. 28 was drained by using ultrasound for guidance. A few smaller abscess cavities in the same patient resolved after antibiotic treatment modified based on culture of the drainage-tube output. 31

FIG. 46. Normal scan. The aortic

suprasternal arch (AO),

sonogram. A, Oblique sagittal sector left carotid (C), left subclavian artery (S),

pulmonary artery (PA), and the superior pericardial recess (arrow) are all well seen. B, Angled axial sector scan. The aorta (AO), superior vena cava (SVC), pulmonary recess (arrow) are marked.

Mediastinal

artery

(PA), and

the superior

pericardial

Diagnosis

Considering the potential difficulties, a surprisingly large number of mediastinal compartments are very well visualized with ultrasound when 3.5 MHz sector or curvedarray transducers are applied to the proper windows. Bruggemann et a1.85 performed real-time scanning of 100 healthy adults to determine which structures were reliably visible. He found that from the suprasternal approach (Fig. 46), the aortic arch arteries and trachea were seen in all cases, the brachiocephalic veins and superior vena cava (SVC) were visible in 98%, and the pulmonary artery and the aortopulmonary window (APW) were seen in 92% of subjects. The parasternal windows were scanned with the patient in a decubitus position and the side of interest dependent. The left side gave the best 32

results (Fig. 47), with the heart and great vessels seen 91% and 59% of the time, as opposed to 32% and 28% for the right side. Finally, the infrasternal window allowed visualization of the pericardial region, the central portion of the diaphragm, and the juxtamediastinal pleura in 88%, 93%, and 92% of cases, respectively. Wernecke et a1.86compared CT of the upper mediastinum and sonography via the suprastemal approach in 12 patients with known tumors or adenopathy. Eleven (92%) of 12 abnormalities detected at CT were well seen on ultrasound, whereas one paravertebral neurofibroma was not visualized.86 The same group then made a similar comparison in 27 patients with anterior mediastinal or subcarinal masses by using parasternal windows. They found that 15 (94%) of 16 anterior mediastinal tumors were detected by sonography and that 16 (94%) of 17 subcarinal lesions were visible.87 These results were further refined in larger series that compared chest radiographs with CT and ultrasound.88 There were 182 patients, of whom 134 had mediastinal masses of various origins, including lymphoma, lung cancer, primary mediastinal tumors, and metastases from distant sites. The supraaortic, paratracheal, prevascular, and pericardial tumors were detected with an average sensitivity of 95%. Subcarinal andAPW lesions were somewhat harder to see, with the sensitivity of ultrasound being 69% and 8 l%, respectively. The posterior mediastinum and paravertebral regions were poorly seen, with 6% and 11% sensitivities. In all regions, the specificity of ultrasound was 99% or 100%. In all but the paravertebral compartment, sonography was far superior to radiography, with CT as the “gold standard.” Adenopathy is the most common abnormality that will be encountered during ultrasound scanning of the mediastinum. Diseased nodes are mostly hypoechoic, whether from lymphoma, metastatic cancer, or inflammatory processes. Calcification is characterized by bright-shadowing foci, as in other locations. Normal lymph nodes are virtually invisible because they are isoechoic with respect to relatively bright mediastinal fat, irrespective of their size.89 After specific treatment, abnormal lymph nodes shrink and become more hyperechoic until they are invisible. Therefore ultrasound may be more specific and sensitive than CT in detecting adenopathy because CT relies on size alone to discriminate normal from diseased nodes.86,8g The normal thymus gland is hyperechoic (similar to thyroid tissue) and sharply defined with a tongue-like configuration until puberty. After that, it becomes impossible to differentiate from mediastinal fat as it invoCurr

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January/February

1997

FIG. scan.

47. The

Normal right

left porasternal ventricle

atrium (LA) are seen. pulmonary artery(P),

(RV),

sonogram.

A,

outflow

and

aorfic

B, Transverse and left atrium

Longitudinal valve

sector scan. The (LA) are marked.

[AV), aorfic

sector and roof

left [A),

lutes. In many disease states, the adult thymus becomes visible again because of enlargement, involvement with masses or cysts, or changes in echogenicity.8g Lymphoma involves the thymus in up to 56% of cases, with cysts in an enlarged gland being the most specific ultrasound finding.90 Without cyst formation, it may be hard to distinguish anterior mediastinal adenopathy from actual thymic involvement. After treatment, the lymphomatous thymus can be distinguished by its typical shape, and it often remains visible even when sterile.90%91 In experienced hands, ultrasound is a reliable method for providing short-interval follow-up during and after treatment of lymphoma involving the thymus and lymph nodes of the mediastinum.9’ Thymomas are seen as homogeneous hypoechoic masses with smooth borders (Fig. 48), and germ-cell tumors are more variable in Curr

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Diagn

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January/February

1997

FIG. 48. the carina

Anferior shows

mediastinal a discrete

mass mass

(benign

anterior

parasternal ultrasound with a homogeneous anterior to the pulmonary artery [P). Open

thymoma). to pulmonary

A, CT scan artery.

at

8, Left

hypoechoic mass(arrowsj, arrows mark a rib shadow.,

their echogenicity, with some being calcified.89 Esophageal duplication cysts, pleuropericardial cysts, and bronchogenic cysts have all been described.8g,g2 They usually have typical cystic features at ultrasound, and some may have septae or debris in them (Fig. 49). Thyroid and parathyroid masses or cysts may be substernal. These should be sought during thyroid/parathyroid ultrasound by switching to a lower frequency sector or curved-array transducer for scanning of the upper mediastinum through the suprasternal window. Because they are often located in the posterior mediastinum or paravertebral spaces, neurogenic tumors are infrequently seen by using the suprasternal and parasternal windows. Sometimes scanning posteriorly may be rewarding, and when seen, these tumors will be round, sharply marginated, and hyperechoic. 89Vascular abnormalities involv33

FIG. 49. Mediastinal and vaguely seen preparation rows) with diaphragm with contrast. demonstrable

for

cyst. A, Chest radiograph with right pleural fluid underlying mass. B, Posterior sector scan done in

drainage

of pleural

effusion

(P). Large

a debris/fluid level in the lower mediastinum (arrows). The cyst was subsequently aspirated Cytologic connection

examination with any

was adjacent

benign, and structures.

cyst

[open

ar-

just above the and injected there

was

no

ing the brachiocephalic vessels, aorta, and SVC can be evaluated especially when color Doppler imaging is used. Fig. 50 shows a lymphangioma with supraclavicular and superior mediastinal components.Aortic dissection may be visualized, and involvement of the arch vessels diagnosed if the flap extends up into them.89 Ko et a1.93evaluated 30 patients with SVC syndrome with ultrasound, and they found a mass involving the upper mediastinum in 27.g3 The brachiocephalic confluence or WC was often narrowed or obliterated, and they saw collateral vessels in the lower neck and upper chest in many cases (Fig. 51). 34

FIG. 50. Lymphangioma neck and supraclavicular tends better

behind the thyroid. detail of the mass

extending into mediastinum. A, CT of lower region. Complex cyst on the left (arrows) ex8, Linear sonogram through same level gives (arrows), which extends behind the carotid(C)

and thyroid (7). C, CT through upper mediastinum with intrathoracic portion (arrows) between the arch vessels and the trachea (J). D, Suprasternal curved array mass is outlined (arrows), (Vj and

the left common

ultrasound showing the same structures. and the right innominate artery(A) and carotid

Curr Probl

artery

Diagn

[C) are

Radiol,

The vein

labeled.

January/February

1997

Mediastinal Intervention The majority of our experiencewith ultrasound-assisted mediastinalintervention is in needlebiopsy of indeterminate masses.This is reflected in the literature, which is almost exclusively concerned with this method. Pedersonet a1.g4 performedfreehandultrasound-guided FNAB in 19 patientswith mediastinal massesand obtained a positive diagnosisin 16 (85%). Of note is that in 9 of them, attempts at fluoroscopically guided biopsyhad failed. There was a minimal pneumothoraxin onepatient.Sawhneyet a1.95 performedcorebiopsy with a 14-gaugeneedlein 25patientswith mediastinalmasses by using sonographyfor guidanceand obtaineddiagnostic tissuein all of them (100%).A biopsy guide was used and, in addition to parasternaland suprasternal approaches,6 of the lesionswerereachedfrom the posterior aspectof the chest.There wereno complications. Results of an additional 111 ultrasound-guidedbiopsies of mediastinal lesions are contained in four reports.93,96-98 Theseauthorsuseda combination of FNAB andlarger-borecoreneedlesin eachseries.Often they performed FNAB first and obtained core samplesfor histologic examinationif the cytologic appearancewas indeterminate.With this combined biopsy technique, the rate of positive diagnosis for malignant lesions rangedfrom 89% to lOO%,and the rate for benign lesionswas between78% and 100%. There were no reported complications after any of the procedures.As in other areas,the consensusof theseauthorsis that malignant lesions yield diagnostic tissue with FNAB for cytologic examination in upward of 90% of cases, whereasbenign massesare less well diagnosedby cytologic study alone(at best,50% success).Core biopsy is somewhatmore risky, especiallynearlargevesselsin the mediastinum, but can be done safely and gives superior results with benign lesions. Almost every possible mass lesion of the mediastinum has been diagnosedby sonographically guided needle puncture. These include lymphoma, bronchogeniccarcinoma,metastaticcancer,granulomatous infection, neurogenictumors,substernalthyroid masses, and benign cysts.Thymic tumors presenta problem in that it seemsto be very hard to differentiate between malignantthymoma andmore benignlesions,especially when only cytologic study is obtained.g4~g6~Q7 Our expe- FIG. 51. Superior vena cava syndrome (adenocarcinoma).A, CT scan rience parallels that describedpreviously, and we have just above carina with large right mediastinal mass(arrowheads) comfound a freehandtechniqueto be the easiestto imple- pressing the superior vena cava (open arrow). 6, Right parasternal transscan reveals the mass (open arrows) to be quite hypoechoic and ment. The newer microcasetransducersareespecially verse lobular. C, Parasternal longitudinal scan with color Doppler shows the helpful in guiding biopsy from the suprasternaland same echo-poor mass (arrows) compressing the superior vena cava parasternalapproaches. The small sizemakesthesetrans- (open arrows) anteriorly. Curr

Probl

Diagn

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January/February

1997

35

FIG. 53. Malignant fibrous with a densely enhancing

FIG. 52. Large synovial radiograph with severe

cyst (rheumatoid arthritic changes.

shoulder). B, Linear

over swelling in the pectoral region, showing a complex arrows) extending from the shoulder joint medially muscles. ile, and

This was drained was very viscous,

with ultrasound consistent with

guidance, joint fluid.

A, Right shoulder ultrasound done collection (open and displacing proved

to be ster-

ducers less cumbersome in tight spaces, and their small footprint is especially helpful when only a narrow sonographic window is available. 36

histiocytoma.A, subcutaneous

CTscan through midthorax mass behind the lower left

scapula. 8, Linear ultrasound shows isoechoic, and slightly heterogeneous. with low-resistance flow demonstrated

the mass to be well encapsulated, There were many small vessels by Doppler.

Diagnosis

Abnormalities

of Chest-Wall

With the advent of high-resolution linear and curvedarray probes, ultrasound has become very useful in evaluating the chest wall. Superficial structures are well seen, and recent work has shown that bony abnormalities also can be characterized. If a patient is scanned both in supine and prone positions with the arms over the head, virtually the entire chest is accessible to the sonographer. However, CT has the advantage of a similar overview and is less physician intensive. Additionally, a few areas are invisible at sonography, such as behind the scapula and around the spine. Ultrasound may be viewed as an adjunct to CT, radiography, and scintigraphy, with some unique advantages. Fluid collections range from anechoic to isoechoic, depending on their contents (Fig. 52). Acute hematomas tend to be hyperechoic and become less echogenic and septated as they mature into Curr

Probl

Diagn

Radiol,

January/February

1997

seromas.Soft-tissuetumors may arisefrom subcutaneous tissues,muscles, and fascia of the chest wall and have the samerange of histologic and ultrasound appearancesas elsewherein the body.g9Typically, pathologic masses are heterogeneously isoechoic to hypoechoic(Fig. 53). Color Doppler is especiallysatisfying becausemost of thesesuperficial processeshave no significant artifacts, excessivemotion, or other imaging problems, and neoplastic massescan be distinguishedfrom hematomasandcomplex fluid collections by virtue of flow within them. Enlarged lymph nodes arediagnosedbasedon location (axillary, supraclavicular, and mammary chains), as well as ovoid or lobular shape.Normal nodesareusually smaller (11.5 cm) and have a central bright echo complex at the hilum. Although diseasedlymph nodesareusually hypoechoic, adenopathycanbe completelyanechoic,especiallywith lymphoma. loo Peripheral nerve tumors, such as schwannomas,may also be virtually anechoic.rO’More typically, they areheterogeneouslyhypoechoic,ovoid, andwell defined (Fig. 54). In onesmall series,a neurofibrosarcomahadirregularmargins.‘02Schwannomasof anintercostalnervewith similar characteristicshavebeen describedin the subcostalspace.lo3 The axillary andsubclavianvesselsaretypically easy to evaluatein all but the most obesepatients.Analysis of thesevesselsfor venousthrombosisor arterialocclusive diseaseis done the sameway as in the legs. True aneurysmsand pseudoaneurysms,.eitheriatrogenic or posttraumatic, display characteristicpatterns at greyscaleandDoppler imaging (Fig. 55).The internal mammary vesselslie between 1.0 and 1.5 cm. (-0.3 cm) lateral to the sternalborder.lo4Doppler ultrasoundaccurately depicts these vessels in the upper anterior interspaces,and their location should be determined before any parastemalneedleprocedures.i0s The deeperstructuresof thechestwall itself havebeen well described.When intact, the ribs presenta curved bright echowith completeshadowingbehindthem.The intercostal musclesin three hypoechoiclayers are visible with high-frequencylinear probes.lo6The vessels andnerveslie betweenthe middle andinnermostlayers just below the undersurfaceof eachrib (Fig. 56). Deep to theintercostalmusclesis the “echogenicpleural line” that on correlation with cadaverspecimensrepresents the parietal pleura, endothoracicfascia, and a variable amountof fat.lo6Tumors that invadethe chestwall from the lung, arise in the pleural space,or are confined to the chestwall canbe differentiatedwith ultrasound.The key to localizing such processesis to observethem in Curr

Probl

Diagn

Radiol,

January/February

1997

FIG.

54.

Malignant

schwannoma.

A, CT scan

of upper

chest

with

a

moderately enhancing mass (open arrows) beneath the pectoral muscles. B, Transverse sonogram through the lesion (open arrows) shows it to be well defined, somewhat heterogeneous, and isoechoic. The tumor had invaded through which moved freely underneath Ultrasound accumulated

the chest wall to contact the lung, at real-time scanning (arrows). C,

of tumor bed ‘2 weeks after resection. on both sides of a synthetic patch

superficial collection was drained deep collection resolved.

with

a small

Fluid (arrows) (open arrow). catheter

(8F),

and

had The the

real time and note how the lesion moves with respirations. A massof the chestwall will move in synchrony with theribs andintercostalmuscles,whereasa massin thelung will move with the lung or be fixed. If the“glid37

FIG. 56. Intercostal anatomy. Linear longitudinal done to localize CI nodule (arrows). The three layers

scan of lateral chest of intercostal muscles

are well seen, and the outermost and innermost are indicated arrows). The intercostal vessels [open arrow) are tucked under cephalic middle

FIG.

55. Axillary

artery

pseudoaneurysm

(gunshot

wound).A,

CT scan

through upper mass (arrows)

thorax in the

3 days after the injury showing a large isodense left axilla. B, Sector scan of anterior axilla with

thick walled, pseudoaneurysm.

pulsatile, and anechoic collection representing C, Color Doppler reveals characteristic swirling

a flow.

ing sign” is lost, this indicates that the mass breeches both pleural membranes and probably arises from the lung. Pleural lesions, such as lipomas, change shape with respiration but do not move much.io7 Chest-wall 38

of two strongly shadowing [/?j ribs, and innermost muscle layers.

where

they

(curved the more

lie between

the

masses have smoothly tapered or rounded inner edges, and the underlying pleura/lung interface is intact, although it may be displaced inward (Fig. 54). Perhaps the most promising new use of ultrasound of the chest wall is in evaluating the ribs, costal cartilage, and sternum. Although the deep architecture of normal ribs and sternum is invisible to ultrasound, their surfaces are so close to the skin that even the most minute irregularities are easily visible. In one series of 86 patients with “hot spots” in ribs or sternum on bone scans, ultrasound detected the abnormality in all but one.‘O* In the same patients, 13 lesions were invisible at radiography. Typically, lytic lesions of the rib are characterized by interruption of the normally smooth cortical surface with hypoechoic areas underneath (Fig. 57). With larger lesions in which the soft-tissue component predominates, the rib will be completely destroyed and replaced with a heterogeneous mass (Fig. 58) that often has bright echoes within it representing residual bone fragments. lo9 The most commonly reported cause of such masses is lung cancer, either as direct spread from an underlying lesion or metastatic deposits. Other metastatic neoplasms involving ribs have been described, including breast, renal cell, gastrointestinal, prostate, and melanoma. Plasmacytoma (Fig. 59) and lymphoma are not infrequently seen, and tuberculosis and aspergillosis have been reported. lo8-11*Although lymphoma and plasmacytoma can be almost anechoic, there do not seem to be many differentiating features between these types of lesions. Acute rib fractures are seen as subtle interruptions in the cortical contour, sometimes with surrounding hypoechoic edema or hematoma and a variable amount of displacement. Eighteen reported cases of minimally Curr

Probl

Diagn

Radiol,

January/February

1997

FIG. 57. Rib metastasis (renal cell carcinoma). A, Radiograph of left chest with small lflic lesion (open arrows) in an anterior rib. B, Linear ultrasound parallel to the rib before biopsy shows subtle disruption of cortex

(open

overlying

arrow)

soft-tissue

with

hypoechoic

swelling

lesion

seen

within

the

rib

and

[arrows).

displaced fractures have been diagnosed with sonography when radiographs were negative.112,113 Sternal fractures also are easily seen, and Fenkl et a1.‘14 found 16 of them within 1 minute of starting their real-time search. The costal cartilages are hypoechoic and well defined at ultrasound with shadowing hyperechoic foci when they are calcified in older patients.l14 Costochondral dislocation is characterized by discontinuity of the junction on oblique ultrasound scans in its plane. This diagnosis has important implications in abused infants Curr

Probl

Diagn

Radiol,

January/February

1997

FIG. 58. Leukemia involving a rib.A, of lateral rib in this child with treated

Radiograph showing destruction leukemia [open arrows). B, Linear

ultrasound done in preparation for biopsy with expansile destructive soft-tissue mass replacing the rib (open arrows). Residual fragments of bone are seen within the lesion (arrows).

39

FIG. 59. Myeloma involving a rib.A, terior rib (open arrows). B, Ultrasound

Radiograph of lytic lesion in pos(before biopsy) reveals virtually

anechoic replaces

interrupts

lesion (open arrows), most of the marrow

which space.

the cortex(arrows)

and

CT scan through midthorax and is very hard to make with radiography.‘16Tietze’s FIG. 60. Local breast cancer recurrence.A, with a soft-tissue nodule in mastectomy bed (open arrows). Linear syndromeis a focal benigninflammatory processof the ultrasound over the anterior chest shows the mass (arrows). It isB, easy to costal cartilage. Ultrasound over the site of maximal measure the chest-wall thickness down to the lung - edaefopen arrows) -.. tendernessis often negative,but subtle swelling, mar- and to outline the extent of the tumor for radiation portal planning. In this case, sonographically guided FNAB confirmed the diagnosis beginal blurring, or soft-tissueedemamay be seen.115,116 fore therapy. The most important contribution of sonographyis in excluding otherpathologic conditions as a causeof the pain and swelling thesepatientsexperience. well suitedto provide suchmeasurementsandhasbeen Planningfor localizedirradiationof chest-walltumors shown to be accurateand reproducible in both situaWe use linear 5 MHz probesand make the requiresan accuratemeasurementof the distancefrom tions.118,11g skin to visceral pleura to avoid radiation pneumonitis. measurements overthesiteaftertheskin hasbeenmarked This is particularlyimportantwhenelectron-beamtherapy with indelible ink to outline the limits of the portal. A is to beusedto treatlocal breastcancerrecurrence.Addi- drawing of the site, annotatedwith the depth at several tionally, the assessmentof pulmonary plutonium levels peripheraland centrallocations,is very useful to the raby externallow-energyx-ray counting requiresknowl- diation oncologist.The depthto the outerandinner suredge of the chest-wall thicknessat the sites to be sur- face of any visible tumor, aswell asits lateral contours, veyed(usuallybilateralanteriorchest).Ultrasoundis very is also helpful andshouldbe noted(Fig. 60). 40

Curr

Probl

Diagn

Radiol,

January/February

1997

FIG. 61.

Pocket

infection

(implantable

defibrillator).

Linear

ultrasound

of anterior chest wall at the edge of defibrillator battery pack (dotted line). Small fluid collection (open arrows) was aspirated and proved to be infected.

Chest-Wall intervention Biopsy of soft-tissue masses in the chest wall is done in the same manner as has been described. The needle should be introduced in parallel with the lung edge as much as possible to avoid inadvertent pneumothorax or other complications. This also allows the needle to be almost perpendicular to the insonating beam and gives exquisite visualization during insertion and sampling. With these measures in mind, large-bore core biopsy is very safe and yields a high rate of positive diagnoses even with benign lesions. 7x31~71,73,74 We have aspirated small fluid collections in subcutaneous pockets around pacemakers, implantable defibrillators, and central venous access devices (Fig. 61). This allows Gram’s stain and culture to be performed, which is critical in differentiating between postoperative seroma and pocket infection. Drainage of larger postoperative or de novo fluid collections is also easily done with ultrasound guidance by using the standard Seldinger technique and drainage catheters (Figs. 52 and 54). Ultrasound can be used to guide biopsy of nonpalpable destructive lesions of the ribs, sternum, scapulae, and clavicles. As described previously, even subtle rib and sternal abnormalities can be seen in almost every case.‘Os Successful diagnosis with fine-needle aspiration guided by ultrasound ranges from 88% to 100% for malignant lesions.108-110~120 In a few of these cases, malignant cells were obtained by sampling subtle soft-tissue swelling around the cortical disruption when the needle could not be passed into the bone itself. As in other body reCurr

Probl

Diagn

Radiol,

January/February

1997

FIG.

62.

Healing

rib fracture.

A, Area

of increased

uptake

[open

ar-

row) in anterior right seventh rib on bone scan done for breast cancer staging. B, Ultrasound over the spot showed subtle disrupfion of cortex and a minimal hyperechoic excrescence representing callus [open arrows).19 yielding studies

A 22-gauge benign confirmed

needle

was passed

through

the defect

cytologic results. The rib was resected a healing fracture.

and

into the rib, pathologic

gions, benign lesions are somewhat harder to diagnose, with one series having 50% success.1og Six cases have been reported in which only a subtle linear disruption of the cortex without soft-tissue abnormality was seen at the site of a scintigraphic abnormality (Fig. 62). Biopsy of these areas gave negative cytologic results in all patients, and the diagnosis of nonpathologic fracture was confirmed by surgery or clinical follow-up in all but one false-negative case. 108~120 It is quite easy to gently probe a rib lesion with a 22-gauge spinal needle with real-time monitoring, during which time the needle often enters the bone even if there is no obvious soft41

FIG. 63. Diaphragm outlined lateral left thorax in a patient sion, and ture when

by fluid. Longitudinal ultrasound with severe heart failure, pleural

ascites. The diaphragm seen by itself.

(open

arrows)

is a rather

thin

of the effustruc-

tissue mass. We have performed FNAB of rib lesions in eight cases with 100% success in obtaining a diagnosis (Figs. 57-59,62). These include metastatic lung, breast, and renal cell cancer, myeloma, lymphoma, healing fracture, and aspergillus osteomyelitis. In our opinion, sonographic guidance for FNAB is the procedure of choice for diagnosing indeterminate rib lesions found with bone scan or other modalities. This method should replace the cumbersome practice of marking such lesions under the gamma camera during bone scan for subsequent surgical resection.1”1-123 Another verv useful auolication of ultrasound to cancer diagnosis and staging is in localization of nonpalpable lower cervical and supraclavicular adenopathy to guide needle aspiration or excision. We mark the skin over such lesions and carefully note the depth to the node for subsequent removal through a small incision. It is important that the patient be in the same orientation that he or she will assume during surgery to minimize error caused by differences in positioning. If the node is not quickly found, intraoperative scanning can guide the surgeon to the correct depth or direction. Overhagen et a1.124performed FNAB with sonographic guidance of supraclavicular nodes in 10 patients with esophageal carcinoma. Seven of these resulted in a positive diagnosis of metastatic adenopathy. In the three patients with negative aspirates, long-term follow-up confirmed that these were true negatives. Chang et al.125 evaluated 51 patients with non-small cell lung cancer with negative physical examinations for supraclavicuI

42

FIG.

64.

Basilar

Longitudinal (consolidated

pleural

fluid

mimicking

a subphrenic

collection.

curved-array scan posteriorly in a child with lung, C). In this case, the diaphragm (open

be seen below the fluid with no trouble. consolidation (Cl and subpulmonic fluid.

6, Another A different

causes phragm

to be brighter

A,

pneumonia arrow) can

child with lung scanning angle

LL

the lower (arrows).

lung

edge

(open

arrows)

than

the dia-

lar and cervical adenopathy. Six (12%) of these had adenopathy at ultrasound and yielded cancer on guided FNAB. Such simple procedures can both diagnose and stage intrathoracic malignancy and are much safer than thoracotomy or percutaneous lung biopsy.

Evaluation of the Diaphragm When viewed from below in normal subjects, the diaphragm has a thick bright curvilinear band on ultrasound scanning. This is made up of echoes from the peritoneum, the muscular and fibrous portions of the diaphragm itself, the pleura, and reflected air in the lung base.126-128Although this echo complex often measures as much as 10 mm, the actual thickness of the diaphragm rarely exceeds 5 mm. 127In cadaver studies, when water Curr

Probl

Diagn

Radiol,

January/February

1997

FIG. 65. Diaphragmatic reflection sector scan through the right lobe the dome

(arrow).

Its reflection

(liver hemangioma). Longitudinal of the liver with a hemangioma

(open

arrow)

is well

seen

across

at the

diaphragm.

or tissue is placed in the subpulmonic space, the diaphragm is isoechoic to mildly hyperechoic (Fig. 63) and is much thinner than in life.lz6,12* In these circumstances, the central tendon is visibly thinner than the outer muscular portion. This phenomenon must be remembered when trying to distinguish subpulmonic from subphrenic fluid. We may mistake bright echoes from the lung base for the diaphragm in patients with subpulmonic fluid and thus erroneously assume that the fluid is subphrenic.128J2g To avoid this pitfall, look above the liver or spleen for a band of echoes representing the diaphragm in its normal position (Fig. 64). This is better seen in the periphery and when the insonating beam is perpendicular to the diaphragm.lzg Another well-recognized phenomenon is that reflected features from the liver may be projected such that they seem to lie above the diaphragm (Fig. 65). This can usually be worked out by noting the mirror-image similarity across the bright interface. Thickened bands of muscle and fibrous tissue will be seen in 30% of patients during scanning of the upper abdomen.*30,*31 These bright structures may be mistaken for masses in the periphery of the liver or spleen or peritoneal implants when there is ascites. The best way to confirm that this is the case is to rotate the transducer to profile these so-called “diaphragmatic slips” in their long axis.130J31When this is done, they assume a characteristic tapered shape and can be easily recognized (Fig. 66). Another common variation is that of eventration of the diaphragm. This occurs most frequently on the right, is often anterior, and is more common in elderly patients.13’ Curr

Probl

Diagn

Radiol,

January/February

1997

FIG. lobe

66. Diaphragmatic slip.A, Longitudinal sector scan through of liver with a discrete hyperechoic structure (open arrow)

cent to the diaphragm. 9, Turning the transducer “lesion” to have a characteristic elongated shape identifies

it as a diaphragmatic

slip (open

right adia-

obliquely shows the and orientation, which

arrows).

Ultrasound can easily demonstrate the bulging liver under an intact diaphragm and thus explain the focal elevation seen on chest radiographs (Fig. 67). Inversion of the diaphragm (Fig. 68) occurs mostly with a large mass in the lung but may be seen with tense pleural fluid collections.131,132 Masses associated with the diaphragm are usually actually from the abdomen, lung, or pleura. Subphrenic masses will have a bright thick line representing diaphragm, pleura, and lung edge above them, whereas intrathoracic masses will be separated from liver or spleen by a thinner but still visible line caused by the diaphragm alone. Traumatic rupture of the diaphragm is an important diagnosis to make because if untreated, the defect usually enlarges because of differences in pressure between chest and abdomen.133 Sequelae include respiratory com43

FIG. 67. Eventration of the bulge in the right diaphragm tient. B, Longitudinal sector the liver

(L) protruding

diaphragm. A, Chest radiograph (open arrows) of this asymptomatic scan through anterior abdomen

up under

an

intact

but

displaced

with

a

pareveals

diaphragm

(arrows).

FIG. 68. Inversion

heterogeneous (open arrows)

promise, ischemia or obstruction of herniated bowel, and intrathoracic migration of solid viscera. Such injuries can occur after penetrating or blunt trauma occurring in up to 5% of multiply injured patients.134x’35Right-sided defects used to be considered rare, but recent data suggest that they are more common and may occur between 20% and 50% of the time.133,136Chest radiographs are relatively insensitive, with one report giving values of 46% for leftsided ruptures and only 17% on the right.137 CT scans interpreted by readers looking for diaphragmatic injury were positive in 63% of left-sided and 56% of right-sided cases in a recent study. 13* It is likely that these results 44

of the diaphragm

with almost complete opacification dinal curved-array scan through

(lung

cancer).

Achest

radiograph

of the right hemithorax. B, Longituthe lateral right chest shows a large

mass in the chest, causing inversion and some displacement of the liver

of the diaphragm (1).

would not be replicated in practice when the entity is not specifically sought. MRI is well suited to make this diagnosis, but most severely injured patients cannot tolerate the examination.‘39 Sonography provides an attractive alternative to other methods of diagnosing traumatic diaphragmatic rupture. Left-sided tears are evidenced by a combination of one or more of the following: discontinuity of the diaphragm, pleural or peritoneal fluid, and visualization of stomach or bowel in the chest.‘40,141Rupture of the right hemidiaphragm is also easy to diagnose Curr

Probl

Diagn

Radio],

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with longitudinal scanning, often aided by pleural fluid.136J40J42 Frequently the tom diaphragmaticleaves are seenfloating in pleural fluid or retractedagainstthe liver. The liver itself will often protrudeinto the chest, andthe bare areamay be in direct contactwith thoracic contentswithout thebrightdiaphragmaticinterface.136 We havemadethis diagnosisa few times, and in one early case,confirmedthoracoabdominalcommunicationby injecting Tc 99m sulfur colloid into the peritonealcavity (Fig. 69). Ultrasoundis themethod of choice for assessingdiaphragmatic motion. Previously, fluoroscopy in erect patients was usedto perform this task, but in addition to lack of ionizing radiationandportability, sonography is arguablymore reproducibleand can provide quantitative results of measurementof diaphragmatic excursion. For this test,the patient lies supineand a 3.5 MHz sectortransduceris placedinto a lower intercostalspace or subcostally between the midaxillary line and the midclavicular line.143-145 When patientsperform a forced expiratorymaneuver,the diaphragmbecomesobscured by air-containinglung much of the time. Thereforethe measurementof maximal excursion is made between end-tidal and maximal inspiratory capacity.143-145 One alsocanmeasurebetweentheend-tidalandend-inspiratory phasesof quiet respiration.To quantify diaphragmatic motion, we place electronic calipers on the diaphragmin the end-tidal stateandthen againat maximal inspiration. The excursion can then be simply read off the screen(Fig. 70). Experimentswith this methodin normal subjectshave shownthattheposteriorportion of thediaphragmmoves the most, followed by the dome and the anterior portion.143There is a fairly wide variability from side to sidethat canbe expressedasa right-to-left ratio. This is between0.5 and 1.6, andthe mean is >l, reflecting the fact that the right side movesmore than the left in 65% of normal subjects,whereasthe converseis true in 15%, with therestbeingequal.144 Male subjectstypically have greaterexcursionsthando femalesubjects,with population meansof 5.4 cm and4.0 cm, respectively.This can be completely explainedby a positive correlation with body weight.143 The interobservervariability of thetechnique hasbeenmeasuredat < 15%.144,145 Continuousrecording of ultrasounddiaphragmatic excursion (often with M-mode) has been correlated with pneumotachographyandinspirometry.143,145,146 There is a linear relation between diaphragm movement and inspired volume, with -60% displacementof the diaphragmoccurring at 50% of inspiratorycapacity.143J45 This method Curr

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FIG. 69. Traumatic rupture of the right diaphragm. A, Chest radiograph done -24 hours after a car accident with elevated and irregular right diaphragm (open arrow), as well as some pleural fluid (arrows). B, Longitudinal ultrasound through posterior right chest reveals the liver (1) protruding through torn diaphragm (open arrows). Pleural fluid (P) and atelectatic lung (arrow) are also seen. C, Scintigram after Tc 99m sulfur colloid injection into peritoneal the right chest (arrows) through the defect

space. Agent freely in the diaphragm.

enters

45

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FIG.

70.

subcostal

Measuring scan

with

diaphragm (arrows) during at end-tidal

diaphragmatic patient

in maximal

excursion. inspiration.

A,

Longitudinal The

dome

right of the

is marked with electronic calipers previously set volume. B, Same measurement made on the left

side.

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