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Xeroradiographic evaluation of obstructive lesions of the larynx and trachea
Xeroradiographic Evaluation of Obstructive Lesions of the Larynx and Trachea By Richard M. Heller, Sandra G. Kirchner, and James A. O'Neill, Jr. Nashville, Tennessee 9 Xeroradiography is a useful technique to evaluate the larynx and trachea for masses, granulation tissue, and, in general, to separate normal from a b n o r m a l m o r p h o l o g y . B e c a u s e of t h e e d g e enhancement effect, there is more information on the xeroradiograph than on the conventional radiograph, but the radiation exposure is 8 - 1 0 times greater. Thus, xeroradiography should be reserved for the evaluation of the airway in a child with respiratory difficulty w h e r e conventional imaging modalities have been unsuccessful. INDEX W O R D S : Upper airway obstruction; xeroradiography.
ERORADIOGRAPHY
is an imaging
X method that clarifies the appearance of soft tissues according to the edge enhancement effect and, at the same time, permits detailed study of osseous structures. ~-4 The increased information contained on the xeroradiograph has been found to be especially important in the evaluation of the trachea. 5-7 The technology used in xeroradiography of the trachea is identical to that used in xeromammography; therefore, equipment is readily available. This report includes experience with three children with upper airway obstruction in order to demonstrate the usefulness of xeroradiography in patients with this problem. CASE REPORTS Case L B.S., a 4-yr-old neurosurgical patient, had had two unsuccessful attempts to remove his tracheostomy tube. A xeroradiogram was obtained to evaluate the cervical trachea (Fig. 1), and a mass was detected just superior to the tracheostomy tube. This mass was shown to be granulation tissue at bronchoscopy. Case 11. M.G., a 4-yr-old boy, developed symptoms of severe " a s t h m a " 12 hr after removal of an endotracheal tube. Since it was felt that the child had developed upper airway obstruction, a xeroradiogram was obtained, and it showed an irregular mass projecting below the true vocal cords (Fig. 2). At bronchoscopy this mass consisted of adherent inspissated mucous that had become attached to the inferior surface of the true vocal cords. The mucous plug was removed and the child's symptoms disappeared. Case IlL
R.L., an 8-wk-old baby girl, was evaluated
Journal of Pediatric Surgery, Vol. 16, No. 5 (October), 1981
because of almost total upper airway obstruction. The anteroposterior and lateral xeroradiographs show an eccentric intramural mass in the subglottic region, a subglottic hemangioma (Fig. 3).
DISCUSSION
Xeroradiography was developed in 1937. It is a technique whereby an electrostatic image is formed on a photoconductor when it is exposed to conventional x-rays. A permanent image is obtained by dusting a cloud of charged particles over the electrostatic image and then transferring this image to paper. The advantage of xeroradiography over conventional radiography rests in the "edge enhancement" concept, whereby boundaries between tissues of different density have an exaggerated appearance. This allows for more reliable recognition of alterations in soft tissue planes than does conventional radiography. Consequently, regions of edema, hemorrhage, or infection are more readily detected using xeroradiography, even though conventional radiographs depict similar but more subtle abnormalities. What produces the "edge enhancement effect?" An electrostatic field is first induced in the selenium photoconductor. When an x-ray beam passes through a patient, it is attenuated according to the differences in tissue densities. When this attenuated beam strikes the photoconductor, an electrostatic image is created which reflects these alterations in the x-ray beam. However, exaggerated electrostatic charges build up at tissue density interfaces.
From the Departments o f Radiology and Radiological Sciences, Pediatric Surgery, and Pediatrics, Vanderbilt University Medical Center, Nashville, Tenn. Address reprint requests to Richard M. Heller, M.D., Department o f Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn. 37232. 9 1981 by Grune & Stratton, Inc. 0022-3468/81/1605-0009501.00/0
691
692
HELLER, KIRCHNER, AND O'NEILL
Fig. 1. Note the mass just superior to th e tracheostomy. Upon decannulation this mass obstructed the airway, Bronchoscopy showed this to be granulation tissue.
These are reflected in the final image as "edge enhancement" after powder has been applied. Xeroradiography is used commonly only for evaluating thin parts such as the neck, hands, or feet because of radiation dosage considerations. 8 For a xeroradiograph of the trachea the radia-
Fig. 3. An eccentric subglottic mass is seen to project into the a i r w a y on both frontal and lateral projections. This demonstrates the value of obtaining both views in some instances. This mass is a subglottic hemangioma.
Fig. 2. The oblong mass in the cervical trachea just inferior to the larynx consists of an adherent mucous plug, It was removed at bronchoscopy w i t h relief of symptoms.
tion exposure to the thyroid gland is reported in the range of 140 mR per exposure, which is about 8-10 x greater than in conventional radiography. However, this figure is much less than the amount of radiation accrued by fluoroscopy (fluoroscopes generally produce 1000-5000 mR at the x-ray table top), a technique used in many institutions to evaluate obstructive syndromes of the larynx and trachea. Fluoroscopy and xeroradiography are not the
XERORADIOGRAPHY OF THE LARYNX AND TRACHEA
693
only ways to evaluate the pediatric larynx and trachea. High kilovoltage images obtained by using filters to absorb lower kilovoltage radiation have been used very successfully. 9 However, when conventional radiographs fail to yield diag
nostic information, and when filters are not available, xeroradiography is one way to gain additional information about tracheal and laryngeal morphology, but at increased radiation burden.
REFERENCES
I. Oliphant WE: Xeroradiography. I. Apparatus and method of use. Br J Radio| 28:543-544, 1955 2. Roach JF, Hilleboe HE: Xeroradiography. Am J Roentgenol 73:5-9, 1955 3. Roach JF, Hilleboe HE: Xeroradiography. JAMA 157:899-901, 1955 4. Otto RC, Pouliadis GP, Kumpe DA: The evaluation of pathologic alterations of juxtaosseous soft tissue by xeroradiography. Radiology 120:297-302, 1976 5. Scott JR, Kramer SS, Griscom NT: The pediatric tracheostomy. Ill. An appraisal of xeroradiography. Invest Radiol 13:279-285, 1978 6. Scott JR, Kramer SS: The pediatric tracheostomy. I.
Roentgen feature of normal healing~ Am J Roentgenol 130887-891, 1978 7. Scott JR, Kramer SS: The pediatric tracheostomy. II. The difficult decannulation. Am J Roentgenol 130:893-898, 1978 8. Rotherberg LN, Kirch RLA, Snyder RE: Patient exposures from film and xeroradiographic mammographic techniques. Radiology 117:701 703, 1975 9. Joseph PM, Berdon WE, Baker DH, et al: Upper airway obstruction in infants and small children. Improved radiographic diagnosis by combining filtration, high kilovoltage, and magnifications. Radiology 121 : 143-148, 1976
ERORADIOGRAPHY
is an imaging
X method that clarifies the appearance of soft tissues according to the edge enhancement effect and, at the same time, permits detailed study of osseous structures. ~-4 The increased information contained on the xeroradiograph has been found to be especially important in the evaluation of the trachea. 5-7 The technology used in xeroradiography of the trachea is identical to that used in xeromammography; therefore, equipment is readily available. This report includes experience with three children with upper airway obstruction in order to demonstrate the usefulness of xeroradiography in patients with this problem. CASE REPORTS Case L B.S., a 4-yr-old neurosurgical patient, had had two unsuccessful attempts to remove his tracheostomy tube. A xeroradiogram was obtained to evaluate the cervical trachea (Fig. 1), and a mass was detected just superior to the tracheostomy tube. This mass was shown to be granulation tissue at bronchoscopy. Case 11. M.G., a 4-yr-old boy, developed symptoms of severe " a s t h m a " 12 hr after removal of an endotracheal tube. Since it was felt that the child had developed upper airway obstruction, a xeroradiogram was obtained, and it showed an irregular mass projecting below the true vocal cords (Fig. 2). At bronchoscopy this mass consisted of adherent inspissated mucous that had become attached to the inferior surface of the true vocal cords. The mucous plug was removed and the child's symptoms disappeared. Case IlL
R.L., an 8-wk-old baby girl, was evaluated
Journal of Pediatric Surgery, Vol. 16, No. 5 (October), 1981
because of almost total upper airway obstruction. The anteroposterior and lateral xeroradiographs show an eccentric intramural mass in the subglottic region, a subglottic hemangioma (Fig. 3).
DISCUSSION
Xeroradiography was developed in 1937. It is a technique whereby an electrostatic image is formed on a photoconductor when it is exposed to conventional x-rays. A permanent image is obtained by dusting a cloud of charged particles over the electrostatic image and then transferring this image to paper. The advantage of xeroradiography over conventional radiography rests in the "edge enhancement" concept, whereby boundaries between tissues of different density have an exaggerated appearance. This allows for more reliable recognition of alterations in soft tissue planes than does conventional radiography. Consequently, regions of edema, hemorrhage, or infection are more readily detected using xeroradiography, even though conventional radiographs depict similar but more subtle abnormalities. What produces the "edge enhancement effect?" An electrostatic field is first induced in the selenium photoconductor. When an x-ray beam passes through a patient, it is attenuated according to the differences in tissue densities. When this attenuated beam strikes the photoconductor, an electrostatic image is created which reflects these alterations in the x-ray beam. However, exaggerated electrostatic charges build up at tissue density interfaces.
From the Departments o f Radiology and Radiological Sciences, Pediatric Surgery, and Pediatrics, Vanderbilt University Medical Center, Nashville, Tenn. Address reprint requests to Richard M. Heller, M.D., Department o f Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tenn. 37232. 9 1981 by Grune & Stratton, Inc. 0022-3468/81/1605-0009501.00/0
691
692
HELLER, KIRCHNER, AND O'NEILL
Fig. 1. Note the mass just superior to th e tracheostomy. Upon decannulation this mass obstructed the airway, Bronchoscopy showed this to be granulation tissue.
These are reflected in the final image as "edge enhancement" after powder has been applied. Xeroradiography is used commonly only for evaluating thin parts such as the neck, hands, or feet because of radiation dosage considerations. 8 For a xeroradiograph of the trachea the radia-
Fig. 3. An eccentric subglottic mass is seen to project into the a i r w a y on both frontal and lateral projections. This demonstrates the value of obtaining both views in some instances. This mass is a subglottic hemangioma.
Fig. 2. The oblong mass in the cervical trachea just inferior to the larynx consists of an adherent mucous plug, It was removed at bronchoscopy w i t h relief of symptoms.
tion exposure to the thyroid gland is reported in the range of 140 mR per exposure, which is about 8-10 x greater than in conventional radiography. However, this figure is much less than the amount of radiation accrued by fluoroscopy (fluoroscopes generally produce 1000-5000 mR at the x-ray table top), a technique used in many institutions to evaluate obstructive syndromes of the larynx and trachea. Fluoroscopy and xeroradiography are not the
XERORADIOGRAPHY OF THE LARYNX AND TRACHEA
693
only ways to evaluate the pediatric larynx and trachea. High kilovoltage images obtained by using filters to absorb lower kilovoltage radiation have been used very successfully. 9 However, when conventional radiographs fail to yield diag
nostic information, and when filters are not available, xeroradiography is one way to gain additional information about tracheal and laryngeal morphology, but at increased radiation burden.
REFERENCES
I. Oliphant WE: Xeroradiography. I. Apparatus and method of use. Br J Radio| 28:543-544, 1955 2. Roach JF, Hilleboe HE: Xeroradiography. Am J Roentgenol 73:5-9, 1955 3. Roach JF, Hilleboe HE: Xeroradiography. JAMA 157:899-901, 1955 4. Otto RC, Pouliadis GP, Kumpe DA: The evaluation of pathologic alterations of juxtaosseous soft tissue by xeroradiography. Radiology 120:297-302, 1976 5. Scott JR, Kramer SS, Griscom NT: The pediatric tracheostomy. Ill. An appraisal of xeroradiography. Invest Radiol 13:279-285, 1978 6. Scott JR, Kramer SS: The pediatric tracheostomy. I.
Roentgen feature of normal healing~ Am J Roentgenol 130887-891, 1978 7. Scott JR, Kramer SS: The pediatric tracheostomy. II. The difficult decannulation. Am J Roentgenol 130:893-898, 1978 8. Rotherberg LN, Kirch RLA, Snyder RE: Patient exposures from film and xeroradiographic mammographic techniques. Radiology 117:701 703, 1975 9. Joseph PM, Berdon WE, Baker DH, et al: Upper airway obstruction in infants and small children. Improved radiographic diagnosis by combining filtration, high kilovoltage, and magnifications. Radiology 121 : 143-148, 1976