Catheter-probe–assisted endoluminal US

TECHNOLOGICAL REVIEW Catheter-probe–assisted endoluminal US Gerard A. Isenberg, MD Cleveland, Ohio

EUS typically is performed with an echoendoscope. However, smaller diameter, nonoptic, catheter–based US (C-EUS) probes have been developed to expand the armamentarium for EUS imaging within the GI tract, including the pancreas and the biliary tree. These probes can be passed through the accessory channel of a gastroscope, a colonoscope, and/or a duodenoscope, providing high-resolution images of the GI wall, the ampulla, the bile duct, and the pancreatic duct. This review discusses available equipment, techniques for performing the examination, clinical applications, safety, future technical developments, and advantages and disadvantages of C-EUS. PUBLICATIONS REVIEW METHODOLOGY The Ovid database (Ovid Technologies, Inc., New York, N.Y.) was used to search publications through May 2004 related to catheter US probes by using the following keywords: ‘‘catheter ultrasound probe,’’ ‘‘intraductal ultrasound,’’ ‘‘miniprobe ultrasonography,’’ ‘‘sonoprobe,’’ ‘‘ultrasonic miniprobe,’’ ‘‘high frequency endosonography,’’ and ‘‘high frequency ultrasound probe.’’ Pertinent studies published in English were reviewed. The bibliographies of all retrieved articles were searched for further relevant references.

and transmits the signals from the transducer to the image processor, and a flexible cover for both the cable and the transducer. These probes produce a real-time, 3608 image. Most probes can be passed through the standard 2.8-mm accessory channel. The working lengths of the probes vary. Probes that are over 2 m can be used for biliary and pancreatic ductal imaging, as well as colonic EUS. The depth of penetration of the Olympus C-EUS probes has been clinically tested and averages 2.9 cm (range 1.7-4.1 cm) for the 12-MHz probe (UM-2R-3; Olympus) and 1.8 cm (range 0.9-2.7 cm) for the 20-MHz probe (UM3R-3; Olympus).1 The 30-MHz probe and the slim 20-MHz probe (UM-S30-20R and UM-S20-20R; Olympus) have the same working length as the 12- and 20-MHz probes, but the outer diameter is smaller, at 2 mm. However, the depth of penetration for the 30-MHz probe is less, at approximately 1 cm. The contact method is through either a water-filled balloon that fits over the catheter tip or water immersion. The wire-guided 20-MHz probe (UMG20-29R; Olympus), which was developed in conjunction with Dr. Amitabh Chak at Case Western Reserve University, has a monorail extension beyond the transducer that allows passage over a 0.035-inch guidewire.2 In addition, Olympus manufactures two dual-plane reconstruction C-EUS probes (UM-DP1225R, 12 MHz and UM-DP20-25R, 20 MHz; Olympus) that allow the user to simultaneously, and in real time, scan in both the sagittal (linear) and transverse (radial) planes. All of the C-EUS probes from Olympus can use a single drive unit (MAJ-935 probe driving unit; Olympus). Fujinon also manufactures 3 C-EUS probes with frequencies of 12 MHz, 15 MHz, and 20 MHz that are 2 mm in outer diameter and come in various lengths. TECHNICAL CONSIDERATIONS

EQUIPMENT The most commonly used C-EUS systems are made by Olympus America Corp. (Melville, N.Y.). Table 1 lists C-EUS probes currently available in the United States. The mechanical radial-scanning probes have a single transducer, a cable that rotates Current affiliation: Division of Gastroenterology, University Hospitals of Cleveland, Case Western Reserve University, Cleveland, Ohio. Reprint requests: Gerard A. Isenberg, MD, Division of Gastroenterology, University Hospitals of Cleveland, Case Western Reserve University, 11100 Euclid Ave., WRN5066, Cleveland OH 441065066. Copyright Ó 2004 by the American Society for Gastrointestinal Endoscopy 0016-5107/$30.00 PII: S0016-5107(04)01958-3 608

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The technique for imaging the GI tract with catheter US probes differs from that for dedicated echoendoscopes.3-10 C-EUS imaging is performed at the time of upper endoscopy, colonoscopy, flexible sigmoidoscopy, or ERCP. Patients usually are sedated to minimize movement. Intravenous glucagons or atropine can be given to decrease GI motility. Administration of mucolytics to remove superficial mucus is optional but is preferred by some endosonographers to enhance the quality of the images. Use of Pronase (Kaken Pharmaceutical Co., Ltd., Tokyo, Japan) before EUS may improve visualization by reducing sonographic artifacts.11 In general, endoscopic biopsy of lesions should be performed after C-EUS to avoid artifact related to the blood and mucosal sampling. VOLUME 60, NO. 4, 2004

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Table 1. Currently available C-EUS systems in the United States

Olympus America Corp. (Melville, N.Y.) Catheter EUS probes (mechanical radial scanning) Radial miniprobe US Slim-type and high-frequency probes

Wire-guided probe (0.035-inch guidewire) Balloon sheath probe Dual-plane reconstruction probes Drive units and processors Miniprobe dedicated processor Miniprobe drive units

Endoscopic US Center (needed in combination with MAJ-935 miniprobe drive unit for dual-plane reconstruction probes)

Model number

Frequency (MHz)

Outer diameter (mm)

Length (cm)

UM-2R-3 UM-3R-3 UM-S20-20R UM-S30-20R UM-S30-25R UM-G20-29R UM-BS20-26R UM-DP12-25R UM-DP20-25R

12 20 20 30 30 20 20 12 20

2.4 2.4 2 2 2.4 2.9 2.5 (with balloon sheath) 2.5 2.5

205 205 205 205 205 205 205 205 205

7.5 12 15 20

8 2 2 2

EU-M30S MAJ-935 MH-240 MAJ-682 EU-M60

Fujinon (Wayne, N.J.) C-EUS probes (combined mechanical radial and linear scanning) PL-1726 PL-1726 PL-1726 PL-1726 Drive unit and processor

190, 190, 190, 190,

220 220 220 220

SP-701UA

GI luminal C-EUS probe technical considerations To image within the stomach, the colon, or the rectum, the lumen is filled with deareated water to submerge the lesion and to allow transmission of the US. Approximately 300 to 500 cc water is needed for imaging within the stomach. However, lesions in the distal antrum and the angularis incisura are particularly difficult to submerge in water. Most of the water will pool in the gastric fundus. It may be necessary to turn the patient from the standard left lateral decubitus position to the supine, right oblique, or prone position to submerge the target lesion. To image within the esophagus, the head of the bed should be raised at least 308 to minimize aspiration when the water immersion method is used. Several investigators have described a balloon that occludes the distal esophagus or gastroesophageal junction to keep water within the esophageal lumen at the time of C-EUS imaging.12 Catheter balloon sheaths (UM-BS20-26R; Olympus) are available for improved acoustic coupling. These allow infusion of water into a small balloon that inflates around the transducer tip. To use the balloon sheath with the probe, a large accessory VOLUME 60, NO. 4, 2004

170, 170, 170, 170,

channel is needed. A single-channel therapeutic endoscope with the water irrigation adaptor or a two-channel therapeutic endoscope with a standard infusion adaptor enables C-EUS imaging by using both water-filled balloon and water-immersion techniques. These techniques are particularly useful in the esophagus. In two prospective studies, compared with C-EUS probes alone, catheter balloon sheaths improved image clarity and depth of esophageal lesions.13,14 An ‘‘enhanced’’ C-EUS imaging technique by using submucosal injection beneath esophageal and colorectal cancers may improve the accuracy of staging tumor depth invasion.15 With this technique, approximately 0.5 to 6 mL (average 2-3 mL) of deareated saline solution is injected with a sclerotherapy-type needle, similar to the technique performed in EMR.15 The C-EUS probe then is placed adjacent to the lesion. The submucosa is enhanced as a hyperechoic layer, and the tumor is raised with the injected saline solution. High-frequency imaging with C-EUS can lead to excellent visualization of up to 9 layers in the esophagus and in the stomach.5,16,17 Generally, more layers are seen with higher frequencies. For example, GASTROINTESTINAL ENDOSCOPY

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7 layers of the stomach wall can be seen with the 12and 20-MHz probe compared with 5 layers by using the standard 7.5-MHz echoendoscope. In the stomach, the following layers have been described (from lumen to serosa) for C-EUS: 1 + 2 hyperechoic interface echo and the hypoechoic mucosa 3 hyperechoic submucosa 4 hypoechoic inner circular muscle layer 5 hyperechoic interface echo and intermuscular connective tissue 6 hypoechoic outer longitudinal muscle layer 7 hyperechoic subserosal and serosal layer When imaging at or beyond 20 MHz, layer 2 can be occasionally visualized as 3 separate layers, corresponding to the epithelium (hypoechoic), the lamina propria (hyperechoic), and the muscularis mucosa (hypoechoic).15,18 Similarly, additional layers can be seen above and within the submucosal layer, which correspond to interface echoes and the muscularis mucosa. Visualization of the additional layers is frequency dependent, with the muscularis mucosae identified in 34% of the examinations at 20 MHz and in 87% of examinations at 30 MHz.19,20 Pancreaticobiliary C-EUS probe technical considerations Bile and pancreatic juice provide a fluid-filled lumen, allowing sonographic imaging at the time of ERCP without the need for a balloon or for water immersion.4,21 Intraductal US (IDUS) also may be performed through the percutaneous transhepatic route.22-26 If the retrograde transpapillary approach is used, ERCP is first performed to evaluate the ductal anatomy and pass a guidewire proximal to the region of interest. Wire-guided probes have a monorail configuration that allows easy passage over a guidewire under fluoroscopic assistance. The probe also can be advanced readily through tight strictures if a guidewire is in place, usually without the need for prior dilation.2 Use of a wire-guided probe generally eliminates the need for endoscopic sphincterotomy for cannulation.2 When a non-wire-guided IDUS probe is used, endoscopic sphincterotomy is needed for access in 20% of patients.27 The IDUS probe is passed through the ampulla, however, because most probes have mechanical rotating transducers, elevator use should be minimized to avoid damaging the catheter. Once the probe is advanced to the most proximal part of the duct, it can be withdrawn gradually, while imaging continuously. While imaging, the elevator should be lowered to minimize friction on the probe. 610

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In studies that have correlated IDUS images with surgical specimens, the normal bile-duct thickness measures 1.8 to 2 mm.28 The bile duct may have a 2or 3-layer appearance. The 3-layer appearance is visualized in about 80% of the cases.4 The innermost hyperechoic layer corresponds to the interface between bile-duct mucosa and bile. This layer may not always be visible. The middle hypoechoic layer corresponds to the discontinuous fibromuscular layer. The outermost hyperechoic layer corresponds to the subserosal fat tissue. The location of the transducer tip can be readily identified by fluoroscopy, and this can be correlated with the presence of structures adjacent to the extrahepatic bile duct.28 At the level of the intrahepatic duct, the portal vein is visualized as an adjacent, large, anechoic vascular structure. The liver parenchyma, with its fine reticular pattern and branching intrahepatic ducts, also is recognizable. As the probe is withdrawn, the right hepatic artery is seen as a longitudinal, vascular structure crossing behind the common hepatic duct. The larger and thinner-walled portal vein also may be visualized as a longitudinal vascular structure behind the right hepatic artery at this level. The cystic duct is seen at its takeoff from the bile duct, the level of which can vary. It is difficult to insert the IDUS probe into the gallbladder through the cystic duct, because of the tortuous nature of the cystic duct. Within the intrapancreatic common bile duct, the pancreatic parenchyma is seen with its homogenous ‘‘salt-and-pepper’’ echotexture. The main pancreatic duct also can be visualized as it travels to the major papilla alongside the distal common bile duct. The inferior vena cava also may be seen posterior to the pancreatic parenchyma at this level. IDUS of the pancreatic duct is more problematic. Advancement of the probe through the entire length of the pancreatic duct may be difficult, particularly if the main duct is not dilated or if the duct takes a tortuous route. In two different studies, catheter insertion to the pancreatic tail was achieved in only 45% of cases, compared with 89% to 90% to the body and 94% to 97% to the head.29,30 By using a wireguided EUS probe, pancreatic C-EUS imaging technically is easier to accomplish than by using a non-wire-guided probe. The main pancreatic duct is visualized with the 30-MHz probe as having 3 layers, whereas a single hyperechoic layer usually is visualized with the 20-MHz IDUS probe.31 The pancreatic parenchyma will be seen with its normal homogenous ‘‘salt-and-pepper’’ echotexture. However, the high scanning frequencies of these probes limits penetration depth, and evaluation of the entire pancreas and peripancreatic area usually is imposVOLUME 60, NO. 4, 2004

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sible with catheter EUS alone.31-35 Pancreatic cancer echo patterns are similar to that of standard EUS.36 When imaging ampullary lesions with IDUS, the probe is inserted into the bile or pancreatic duct to evaluate, for possible invasion of the ducts, the sphincter of Oddi, the adjacent duodenum, and the pancreatic parenchyma. The sphincter of Oddi will appear as a circular, hypoechoic thickening within the duodenal wall.2,37,38 The adjacent duodenal wall, with its hypoechoic mucosal and hyperechoic submucosal layers, also may be seen. An endoscopic sphincterotomy usually is necessary to allow cannulation of an obstructing lesion. Advantages and disadvantages of C-EUS C-EUS has a number of advantages over standard EUS. C-EUS probes do not require experience with passage of an oblique-viewing endoscope and technically are easier to use. C-EUS probes are much less expensive when compared with standard echoendoscopes but only if the EUS processor is readily available. C-EUS probes may be precisely placed on the target lesion that may otherwise be difficult to localize by standard EUS. C-EUS probes generally operate at higher frequencies than echoendoscopes and provide higher resolution images, which are important in the evaluation of early cancers and mucosal diseases. Up to 9 layers of the GI wall may be seen with C-EUS compared with standard EUS. Evaluation of GI-tract lesions with C-EUS may be coupled with therapy, such as EMR,39 thermal ablation, argon plasma coagulation, or photodynamic therapy immediately after EUS imaging, without the need to change endoscopes. The smaller diameter of C-EUS probes allows evaluation of stenotic lesions that are not traversable by the larger diameter echoendoscope. Because echoendoscopes may distort or compress the esophageal wall, C-EUS probes are more appropriate for evaluation of esophageal motility, achalasia, Barrett’s esophagus, and esophageal varices. C-EUS probes have several disadvantages over standard echoendoscopes. Unless a balloon sheath is used within the GI tract, the lumen needs to be filled with water for adequate C-EUS imaging. This need to use water within the lumen may increase the risk for aspiration for examinations performed in the upperGI tract. C-EUS probes are reusable but have a limited lifetime and undergo image deterioration after a certain number of cases. The number of cases per probe varies according to the indication for use. More cases can be performed per probe for GI tract lesions compared with pancreaticobiliary lesions. A continued financial investment is necessary to VOLUME 60, NO. 4, 2004

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maintain a functioning C-EUS unit. C-EUS probes have a limited depth of penetration, resulting in understaging of larger tumors. C-EUS probes also are unlikely to completely evaluate regional lymphnode metastases (particularly for gastroesophageal junction cancer and gastric cancer) and the retroperitoneal area. CLINICAL APPLICATIONS Clinical applications of C-EUS include GI tumor staging (esophageal, gastric, duodenal, colorectal, ampullary, and pancreaticobiliary neoplasms), evaluation for achalasia, esophageal varices, Barrett’s esophagus, submucosal lesions, large-fold gastropathies, indeterminate pancreaticobiliary strictures, and inflammatory bowel disease. Doppler US catheter probes have been used in the evaluation of GI bleeding, and these are discussed in a separate review. Unfortunately, few C-EUS studies are prospective, histopathologically correlated, and comparative with other imaging techniques in nature. The clinical applications of C-EUS are discussed in terms of regions of interest. Most commonly, C-EUS is used for staging of early GI cancers, particularly esophageal and gastric cancers that may be amenable to endoscopic therapy when a limited depth of penetration and absence of regional lymph node metastases are confirmed. Cancers appear hypoechoic, identical to imaging obtained with standard EUS. Visualization of the muscularis mucosa is important because absence of submucosal invasion in esophageal cancer lowers the risk of lymph node spread from 20% to 40% down to 0% to 5%. Endoscopic therapy could be offered when other imaging studies have excluded distant metastatic disease. C-EUS is the technique of choice for evaluating small, 1- to 2-cm submucosal lesions.1,40-42 The CEUS probe can be placed directly over the lesion at the time of diagnostic endoscopy. Benign and malignant submucosal tumors, such as cysts, lipomas, granular cell tumors, GI stromal cell tumors (GIST), and neuroendocrine tumors, may be imaged with excellent localization in the GI wall. The most typical appearances for lipomas are hyperechoic and homogeneous and, for GISTs, are hypoechoic and homogenous. GISTs can be identified as arising from the muscularis mucosae or from the muscularis propria (Fig. 1).41 Small tumors that are superficial can be removed by EMR.43,44 Esophageal region Esophageal cancer staging. When compared with standard EUS, C-EUS provides superior GASTROINTESTINAL ENDOSCOPY

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Figure 1. C-EUS image of a hypoechoic gastric stromal tumor characteristically arising from the 4th (muscularis propria) layer.

visualization and higher T-staging accuracy for esophageal cancer (Table 2).45-49 The highest accuracy is achieved in diagnosing muscularis mucosae (100%), submucosal (83%), and muscularis propria invasion (100%).50 When superficial cancer is present, it may appear as focal thickening located in the first two (T1m) or 3 (T1sm) layers.12 In 96 lesions, CEUS was 93% accurate in differentiating mucosal and submucosal cancers.12 As expected, in patients with early stage tumors, C-EUS provides improved T-staging accuracy and lower N-staging accuracy compared with standard EUS. Barrett’s esophagus. The appearance of Barrett’s esophagus when using high-frequency C-EUS is distinctive and can be differentiated from that of esophagitis.51,52 Barrett’s esophagus can be diagnosed if the second hypoechoic layer (deep mucosa) is thicker than the first hyperechoic layer. In contrast, esophagitis can be diagnosed if the submucosal layer (the third hyperechoic layer) is markedly increased in thickness. The sensitivity and the specificity of this model for the diagnosis of Barrett’s esophagus are 100% and 86%, respectively.51 The data on the efficacy of C-EUS in Barrett’s esophagus associated cancer and high-grade dysplasia are conflicting and limited. Most studies that used high-frequency EUS have small sample sizes. EUS may have a potential for detecting cancer in patients with Barrett’s esophagus when endoscopy does not. When performed in carefully selected patients with 612

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dysphagia, focal nodule, or stricture, with only highgrade dysplasia in biopsy specimens, C-EUS may improve the diagnosis of occult cancer.53,54 Esophageal motility disorders. In contrast to standard EUS, C-EUS probes will not compress or distort the esophageal wall.55 In patients with achalasia, the muscle layers of the lower esophageal sphincter often are thickened on C-EUS imaging.56-59 C-EUS probes have been used in imaging contraction patterns of the esophagus in correlation with manometry.60-62 C-EUS probes can accurately measure distention of the esophagus during swallows of liquid bolus and during gastroesophageal reflux in normal subjects.63 Sustained esophageal contraction may be a marker of esophageal-related chest pain, as measured by C-EUS.64 Esophageal varices. Esophageal varices, communicating vessels, and paraesophageal collateral vessels can be observed as multiple anechoic areas in the submucosal and periesophageal areas. Communicating vessels can be seen as anechoic points inside the esophageal wall. Hematocystic spots on esophageal varices, associated with a high risk of bleeding, appear as aneurysm-like echo-free projections that form on the varix wall and protrude into the esophageal lumen.65 C-EUS accurately measures esophageal variceal radius and wall thickness.66 A model using 3-dimensional (3-D) reconstruction of high-resolution C-EUS probe imaging has been developed to calculate esophageal varix volume.67 In combination with the measurement of variceal pressure,68 these parameters may identify patients at risk for variceal bleeding. One prospective study showed that the cross-sectional area of esophageal varices was predictive of future variceal bleeding.69 Disappearance of varices after ligation can be documented in follow-up endoscopic examinations.70,71 C-EUS findings have been used to predict risk for recurrence of esophageal varices after treatment.72-74 Miscellaneous uses. C-EUS may predict the likelihood of stricture formation in patients who ingest corrosive agents.75-77 C-EUS reveals diffuse thickening of the mucosa, the submucosa, and the muscularis propria in children with eosinophilic esophagitis. Gastric region C-EUS can adequately visualize gastric lymphoma and mucosa-associated lymphoid tissue lymphoma (MALToma) (thickened mucosa or submucosa and hypertrophic folds), Menetrier’s disease (marked mucosal thickening and mucosal cysts), and linitis plastica (marked thickening of the mucosa, the submucosa, and the muscularis propria).41 C-EUS also can accurately diagnose other submucosal VOLUME 60, NO. 4, 2004

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Table 2. C-EUS in the staging of esophageal cancer Percentage traversable C-EUS

T-stage accuracy (%)

N-stage accuracy (%)

Standard EUS

C-EUS standard EUS

C-EUS standard EUS

Comments

100 —

64.7 —

— —

Hasegawa45(1996)

100 100

92 76

56 67

Hunerbein46 (1998)

100 — 100 —

90 — 75 —

78 — 75 —

100 57

87 62

82 70

T-stage accuracy 80% when muscularis mucosae was visible; 16 patients Pre-operative staging of 25 superficial carcinomas (T1m and T1sm) Histopathologic correlation of C-EUS in 10 patients Histopathologic correlation: 81 patients with surgery and 32 with EMR; 95% T-stage accuracy for C-EUS in Tis-T2 cancers Histopathologic correlation in 53 patients; 46 patients with T2-T4 tumors

Investigator (y) 49

Yanai

(1996)

Murata48 (1998)

Menzel47 (1999)

abnormalities, such as extrinsic compressions, gastric varices,78 pancreatic rests,79 and hypertrophic arteries (Dieulafoy’s lesions), which suggests that it can replace standard EUS for the evaluation of submucosal lesions and large folds. Gastric cancer staging. In early gastric cancer staging, results with C-EUS are best with protruding or elevated, well-differentiated tumors (91%) and worst with depressed, poorly differentiated tumors (56%).80 Compared with standard EUS, C-EUS modestly improves overall staging accuracy (72% vs. 65% for standard EUS).80 For T stage, overall accuracy rates of about 80% are reported.5,46,80-86 CEUS is less reliable for staging of advanced cancers because of US attenuation and limited depth of penetration.46 C-EUS had the highest accuracy (85%) in staging gastric cancers that had a depth of less than 10 mm compared with 42% for gastric cancers that were greater than 30 mm in thickness.80 However, the ability of C-EUS to discriminate T1 mucosal cancer from more advanced lesions is superior to standard EUS, which may be useful in planning and performing EMR.39,81,86-91 Staging accuracy is impaired by the inherent inability of EUS to differentiate tumor from inflammation.92,93 Overstaging can occur because of inflammatory changes, edema, or scarring, which cause abnormalities in the third layer, mimicking invasion.19 Understaging is more likely with C-EUS, and overstaging is more likely with standard EUS.80 C-EUS appears to be accurate in the diagnosis of ascites associated with gastric cancer. In a study of 402 consecutive patients with confirmed gastric adenocarcinoma that did not reveal ascites on CT, C-EUS was able to detect ascites in 36 patients (9%), with a sensitivity of 60.7% and VOLUME 60, NO. 4, 2004

a specificity of 99.4%.94 The finding of ascites by CEUS was significantly related to the presence of peritoneal seeding (p < 0.001).94 Gastric lymphomas and MALTomas. When compared with standard EUS, C-EUS appeared to be inferior for locally advanced stages of MALTomas, similar to gastric cancer in that C-EUS probes have a limited depth of penetration.95 In a study of 17 patients with predominantly low-grade MALTomas, C-EUS imaging before and 6 months after Helicobacter pylori eradication was able to predict complete regression (sensitivity 90.9%, specificity 100%).96 Several case reports demonstrate that C-EUS can predict remission of MALTomas at other sites, including the duodenum97 and the colon. Miscellaneous uses. In the so-called ‘‘buried bumper syndrome’’ from percutaneous gastrostomy tubes migrating into the gastric wall, C-EUS may be beneficial in identifying the position of the internal bumper within the gastric wall to allow endoscopic extraction.98 C-EUS appears to be more accurate than standard EGD for the detection of gastric varices, and C-EUS revealed complete obliteration of the variceal vessel lumen after endoscopic treatment with Histoacryl (B. Braun, Co., Melsungen, Germany).78 Ampullary region Ampullary tumors. The combination of C-EUS of the ampullary lesion and IDUS may be important in determining the candidacy for endoscopic resection.99,100 The 5-year survival rate of patients with ampullary cancer that does not involve the sphincter of Oddi is almost 100%.101 In a prospective study of polypoid tumors of the major papilla in 27 patients, C-EUS was superior to standard EUS and GASTROINTESTINAL ENDOSCOPY

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Figure 2. Intraductal US images of invasive ampullary adenocarcinoma into the peripancreatic tissue.

CT scan for visualization and diagnosis of ampullary tumors (100% vs. 59.3% vs. 29.6%, respectively).102 Forceps biopsy specimens of these lesions diagnosed only 20% of cancers and 75% of benign adenomas.102 The accuracy rates for T staging of ampullary cancers are 88.9% for all tumors (compared with 56.3% for standard EUS)102 and 100%, 92.3%, and 100% for tumors that are limited to the sphincter of Oddi, the duodenal submucosa, or the muscularis propria, respectively, in a study of 32 patients (Fig. 2).103 The accuracy rate for nodal staging of ampullary cancers is 66.7% to 93%.102,103 Sphincter of Oddi dysfunction. There does not appear to be a correlation between sphincter muscle thickness as assessed by IDUS and basal pressure hypertension of the muscle as assessed by manometry.38 Further studies are needed to confirm this finding. Indeterminate biliary strictures. The evaluation of indeterminate biliary ductal strictures by CEUS is evolving.4,104-106 One study could not find any obvious differences in the sonographic appearance of benign vs. malignant biliary strictures.4 There was no significant difference in mean thickness or symmetry. However, other studies suggest that eccentric wall thickening with an irregular surface indicates an underlying malignancy that may direct endoscopic biopsy.23,26,28,107-110 Other findings considered diagnostic of malignancy include disruption of the normal 3-layer sonographic pattern, a hypoechoic mass with irregular margins, heterogeneous echo-poor areas invading surrounding tissue, continuation of the main hypoechoic mass into adjacent 614

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structures, presence of any lymph nodes, and vascular invasion. In two studies, IDUS diagnosed 13 and 14 additional malignancies in 60 and 56 patients that had been missed by ERCP and tissue sampling alone.104,111 In another study, IDUS had an accuracy rate of 76% in the diagnosis of cholangiocarcinoma in the evaluation of bile-duct strictures.23 IDUS criteria for malignancy in this particular study included interruption of the bile-duct wall or a tumor diameter greater than 8 mm.23 Benign strictures from cholecystectomy, Mirizzi’s syndrome, or traumatic neuroma can be differentiated from cholangiocarcinoma.30,112,113 In a retrospective blinded review, IDUS significantly increased diagnostic accuracy in 30 patients with indeterminate bile-duct strictures compared with ERCP and tissue sampling (90% vs. 67%, p = 0.04).114 When compared with standard EUS, IDUS within the bile duct stricture had greater diagnostic accuracy in 56 patients who underwent surgical resection (89.1% vs. 75.6% for standard EUS, p < 0.002).115 Primary sclerosing cholangitis (PSC) exhibits an irregularly thickened wall with a concentric, onionlike appearance on IDUS.107,116 Inhomogeneous areas that are suspicious may be localized by IDUS, allowing selective endoscopic transpapillary or cholangioscopic biopsies.27 Contrast-enhanced IDUS (discussed below as well) appears to enhance the bile-duct wall in patients with PSC as opposed to those with bile-duct cancers in which the bile-duct wall was not enhanced.117 Further investigation is warranted before conclusions regarding its use can be made. Cholangiocarcinoma. IDUS is used for staging of cholangiocarcinomas, particularly those at the hilum, which may not be well visualized by standard EUS.28,118-122 However, T-stage accuracy is limited by the US correlates to wall layers of the bile duct. Specifically, the extrahepatic bile duct is composed of an epithelial layer surrounded by dense fibrous connective tissue with scattered muscle fibers. The latter form a fibromuscular layer, but there is no definite 3-layer wall that corresponds to the TNM classification for tumor staging.107 Unfortunately, the inner hypoechoic layer on the IDUS image corresponds not only to the fibromuscular layer, but also to a part of the fibrous layer of the perimuscular loose connective tissue.119 The outer hyperechoic layer corresponds to the subserosal fat tissue. Therefore, IDUS cannot accurately distinguish T1 from T2 cholangiocarcinomas. However, IDUS may be useful in advanced disease for assessing the extension of cancer to the pancreatic parenchyma, the portal vein, and the hepatic artery.28,105,109,118,120-124 Compared with standard EUS, IDUS correctly diagnosed tumor VOLUME 60, NO. 4, 2004

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extent (76.8% vs. 53.6% for standard EUS, p < 0.001) by using operative findings.28 IDUS is particularly superior to standard EUS in the staging of cholangiocarcinomas involving the bifurcation and mid common bile duct.118 Because of the limited depth of penetration, IDUS is not useful for detecting metastatic disease. Whether IDUS improves accuracy for lymph-node invasion is uncertain.125 The utility of IDUS compared with other noninvasive imaging modalities, such as magnetic resonance cholangiopancreatography (MRCP) and CT scan (3-D spiral CT and CT angiography), needs to be further investigated. Choledocholithiasis. Cholangiography can fail to detect small stones, particularly when the bile duct is dilated or is inadequately opacified with contrast. In addition, air bubbles may be falsely identified as stones on a cholangiogram. These limitations to cholangiography may lead to prolonged fluoroscopy time, unnecessary and potentially hazardous endoscopic sphincterotomy, unnecessary manipulation of the bile duct with balloon catheters and baskets, and failure to remove small bile-duct stones. Bile-duct stones will appear on IDUS imaging as focal echogenic foci within the bile duct with or without acoustic shadowing (Fig. 3). In a study of 20 patients comparing IDUS with percutaneous transhepatic cholangioscopy in the identification of residual stones after lithotripsy, IDUS was as accurate as cholangioscopy and was superior to cholangiography.26 However, cholangiography identified stones located in ducts outside of the cannulated lobe that were missed by IDUS.26 In patients with persistent pain and dilated bile ducts after cholecystectomy, IDUS may detect bile-duct stones that were not visualized fluoroscopically.126 Many investigators have shown that IDUS is superior to ERCP (particularly when ERCP is performed with C-arm fluoroscopy) in the detection of bile-duct stones (Table 3).126-131 IDUS can detect small stones even with a dilated duct and can differentiate stones from air bubbles. In a multicenter study evaluating the clinical utility of IDUS for the detection of bile-duct stones, IDUS led to a change in management in 37% (13 of 35 patients).129 Pancreatic disease. IDUS may be useful in detecting carcinoma in situ and small tumors,132-134 in assessing the intraductal spread of the tumor and its pancreatic parenchymal invasion in mucinproducing tumors of the main duct, and in assessing the indications for surgery by revealing mural nodules in mucin-producing tumors of the distal branches.31,36,135-140 The combination of standard EUS and IDUS appears to have high sensitivity and diagnostic accuracy (80%) compared with CT (38%) VOLUME 60, NO. 4, 2004

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Figure 3. Common bile duct stone detected by intraductal US in a patient who had a negative cholangiogram.

for invasive mucin-producing tumors.137 The combination of pancreatoscopy and IDUS was highly sensitive (91%) and specific (82%) for differentiating benign from malignant mucin-producing tumors.141 Lesions that protruded more than 4 mm were considered malignant. These findings, on IDUS, influenced surgical management, resulting in 3-year cumulative survival rates and disease-free survival rates of 95% and 93%, respectively.141 IDUS also may be useful in differentiating benign from malignant strictures of the main pancreatic duct.36,142 In a series of 26 patients whose findings were confirmed on histopathology, IDUS was superior to standard EUS, CT, and ERCP in the diagnosis of strictures localized to the main pancreatic duct (14 cancers and 12 strictures from chronic pancreatitis).29 Sensitivity and specificity were IDUS (100%, 91.7%), standard EUS (92.9%, 58.3%), CT (64.3%, 66.7%), and ERCP (85.7%, 66.7%), respectively.29 The role for IDUS in the detection of small tumor foci in patients at increased risk for pancreatic cancer (e.g., familial pancreatic cancer) remains to be determined. For patients with suspected pancreatic endocrine tumors not visualized by conventional imaging, including standard EUS, IDUS may be a valuable method for pre-operative tumor localization.36,143 Colorectal region Colorectal cancer staging. C-EUS is used in many Asian countries for staging colorectal carcinomas (accuracy rates range from 82% to 92%)18,144-150 and carcinoids.151 In one study, the overall accuracy GASTROINTESTINAL ENDOSCOPY

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Table 3. IDUS in the diagnosis of choledocholithiasis

Investigator (y) 127

Ueno

(1997)

No. patients

Accuracy of IDUS (%)

Accuracy of cholangiography (%)

31

96.8

80.6

Ohashi126 (1999)

81

95

61.3

Das128 (2001)

62

97 (with dilated ducts, 95.5)

87 (with dilated ducts, 72.7)

Tseng130 (2001)

65

97

94

Kubota131 (2002)

80

100

-

Comments Presence of stones confirmed by endoscopic sphincterotomy and stone extraction in all patients; accuracy of IDUS for small stones was 100% compared with cholangiography, which had sensitivity of only 45% Accuracy of IDUS in detecting residual stones after mechanical lithotripsy was 95% compared with occlusion balloon cholangiogram 50% (p < 0.001) Presence of bile-duct stones and/or sludge confirmed by sphincterotomy and stone extraction; study compared accuracy of ERCP with C-arm fluoroscopy combined with IDUS vs. ERCP alone 59/65 patients had confirmed CBD stones; sensitivity and specificity for IDUS (100%, 67%) and cholangiography (93%, 100%) 80 consecutive patients with suspected choledocholithiasis with negative ERCP underwent IDUS; 20 patients had stones confirmed by extraction, and 37 patients had sludge

IDUS, Intraductal US; CBD, common bile duct.

for depth of invasion was relatively low, at 76%, but was higher for diagnosing T1m (83%) and T1sm (90%) lesions.145 By using a balloon-sheath C-EUS probe in 86 patients, T-stage accuracy was 85% (100% for T1, 78% for T2, 90% for T3, and 40% for T4) and N-stage accuracy was 73% with histopathologic correlation.144 C-EUS is superior to magnification colonoscopy for the determination of invasion depth in small colorectal cancers (91.8% accuracy for CEUS vs. 63.3% for magnification colonoscopy).152 Saline-solution–assisted C-EUS significantly improves the diagnosis of colon and rectal tumors compared with standard EUS by using the 7.5-MHz echoendoscope (90% vs. 50% for colonic and 92% vs. 58% for rectal, C-EUS plus injection vs. standard EUS, respectively; p < 0.01). Furthermore, the overall accuracy of T staging was improved (86% vs. 45%, C-EUS vs. standard EUS, respectively).15 Inflammatory bowel disease. Patients with Crohn’s disease (Fig. 4) and ulcerative colitis have thicker colon walls than normal individuals.153-156 The 5-layer EUS appearance may be distorted or completely lost in transmural Crohn’s disease but not in colitis limited to the mucosa.154 In patients with ulcerative colitis, investigators have described 6 types of EUS abnormalities based on 3 patterns of the boundary of each layer (smooth, irregular, or blurred).155 C-EUS can be correlated with clinical parameters and endoscopic biopsies to diagnose and to assess the severity of disease.153-156 C-EUS may be helpful in selection of therapy when biopsy specimens are indeterminate.153-156 C-EUS can also be repeated at follow-up examinations to evaluate 616

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Figure 4. Asymmetric bowel-wall thickening in a patient with Crohn’s disease (reproduced from Soweid et al.154 with permission).

response to therapy.156 Applications for C-EUS in inflammatory bowel disease need to be further evaluated and proven before widespread use. Miscellaneous uses. C-EUS can diagnose other tumors of the colon, including GISTs, lipomas,157 and lymphangiomas,158 and can determine if large colonic polyps can safely undergo endoscopic snare resection.159 VOLUME 60, NO. 4, 2004

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Safety and efficacy. There are relatively few reports on complications associated with C-EUS. No complications have been reported for C-EUS probes passed through stenotic esophageal cancers. Mild post-ERCP/IDUS pancreatitis occurred in 36 patients, all with resolution without complications.4 It is not clear if the ERCP portion of the examination or the IDUS or both contributed in equal fashion to the development of pancreatitis in these patients. Two larger studies of 204 patients and 239 paients evaluated with pancreatic IDUS reported only 3 cases and one case of pancreatitis, respectively (incidence = 0.4%–1.5%).30,36 FUTURE TECHNOLOGIC ADVANCES 3-D EUS probes are currently under development for evaluating esophageal,160-163 colorectal,163 and pancreaticobiliary164 lesions. A digital videorecording of sequential EUS images is converted into a 3-D display of the area of interest. This diagnostic modality may have clinical utility by more precisely characterizing the extent of cancer invasion and by estimating tumor volume, particularly when applied before and after multimodal adjuvant therapy.165,166 3-D EUS may be useful in the visualization of geometric changes with esophageal contractions and may allow for correlation with manometric data.62 Contrast agents for EUS may detect solid tumors earlier and may improve staging of tumors with better definition of tumor margins and its relationship to regional structures, including detection of vascular thrombosis and malignant invasion of vessels.167 Differentiation of benign from malignant bile-duct strictures may be possible with contrast agents for IDUS.117,168,169 Intra-arterial injection of carbon-dioxide microbubbles has been used in pancreaticobiliary IDUS for pancreatic-cancer evaluation.170 Air-filled albumin injected via the right cubital median vein increased T-stage accuracy from 76.7% for EUS to 90% for contrast-enhanced EUS in 30 patients.171 A major limitation to C-EUS is low depth of penetration because of the high-frequency transducers used. Adjustable multifrequency transducers or broadband technology may allow C-EUS probes to have the same depth of penetration as standard echoendoscopes.172 Existing C-EUS probes also lack color flow and Doppler capabilities. Recently, a vector phased-array C-EUS probe with these capabilities (AcuNav, Acuson, Mountain View, Calif.) designed for intracardiac and intravascular use was prospectively evaluated for use in the GI tract and found to be both feasible and safe.173,174 Further studies are VOLUME 60, NO. 4, 2004

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needed to assess its clinical utility. Another limitation of C-EUS probes is the comparatively low number of uses per probe compared with echoendoscopes. With increased durability afforded by improved materials, the cost for using C-EUS probes will decline. SUMMARY C-EUS probes are accurate in the evaluation of small mucosal and submucosal lesions of the GI and the pancreaticobiliary tract. They have a direct clinical impact on the application of endoscopic therapy, particularly for early stage cancers and in patients with suspected choledocholithiasis. Continuing improvements in technology will also further expand these capabilities. REFERENCES 1. Chak A, Canto M, Stevens PD, Lightdale CJ, Van de Mierop F, Cooper G, et al. Clinical applications of a new throughthe-scope ultrasound probe: prospective comparison with an ultrasound endoscope. Gastrointest Endosc 1997;45:291-5. 2. Chak A, Isenberg G, Kobayashi K, Wong RC, Sivak MV Jr. Prospective evaluation of an over-the-wire catheter US probe. Gastrointest Endosc 2000;51:202-5. 3. Ro¨sch T, Classen M. A new ultrasonic probe for endosonographic imaging of the upper gastrointestinal-tract. Preliminary observations. Endoscopy 1990;22:41-6. 4. Gress F, Chen YK, Sherman S, Savides T, Zaidi S, Jaffe P, et al. Experience with a catheter-based ultrasound probe in the bile duct and pancreas. Endoscopy 1995;27:178-84. 5. Maruta S, Tsukamoto Y, Niwa Y, Goto H, Hase S, Yoshikane H, et al. Evaluation of upper gastrointestinal tumors with a new endoscopic ultrasound probe. Gastrointest Endosc 1994;40:603-8. 6. Kimmey MB, Martin RW, Silverstein FE. Endoscopic ultrasound probes. Gastrointest Endosc 1990;36:S40-6. 7. Yasuda K, Mukai H, Nakajima M, Kawai K. Clinical application of ultrasonic probes in the biliary and pancreatic duct. Endoscopy 1992;24(Suppl 1):370-5. 8. Yasuda K. Development and clinical use of ultrasonic probes. Endoscopy 1994;26:816-7. 9. Saisho H, Sai K, Tsuyuguchi T, Yamaguchi T, Matsutani S, Ohto M. A new small probe for ultrasound imaging via conventional endoscope. Gastrointest Endosc 1995;41: 141-5. 10. Frank N, Grieshammer B, Zimmermann W. A new miniature ultrasonic probe for gastrointestinal scanning: feasibility and preliminary results. Endoscopy 1994; 26:603-8. 11. Sakai N, Tatsuta M, Iishi H, Nakaizumi A. Pre-medication with pronase reduces artifacts during endoscopic ultrasonography. Aliment Pharmacol Ther 2003;18:327-32. 12. Kawano T, Ohshima M, Iwai T. Early esophageal carcinoma: endoscopic ultrasonography using the Sonoprobe. Abdom Imaging 2003;28:477-85. 13. Schembre D, Chak A, Stevens P, Isenberg G, Sivak MV Jr, Lightdale CJ. Prospective evaluation of balloon-sheathed catheter US system. Gastrointest Endosc 2001;53:758-63. 14. Wallace MB, Hoffman BJ, Sahai AS, Inoue H, Van Velse A, Hawes RH. Imaging of esophageal tumors with a water-filled GASTROINTESTINAL ENDOSCOPY

617

G Isenberg

15.

16.

17.

18.

19.

20.

21.

22. 23.

24.

25.

26.

27.

28.

29.

30.

618

condom and a catheter US probe. Gastrointest Endosc 2000; 51:597-600. Watanabe H, Miwa H, Terai T, Imai Y, Ogihara T, Sato N. Endoscopic ultrasonography for colorectal cancer using submucosal saline solution injection. Gastrointest Endosc 1997;45:508-11. Miller LS, Liu JB, Klenn PJ, Dhuria M, Feld RI, Goldberg BB. High-frequency endoluminal ultrasonography of the esophagus in human autopsy specimens. J Ultrasound Med 1993;12:563-6. Wiersema MJ, Wiersema LM. High-resolution 25-megahertz ultrasonography of the gastrointestinal wall: histologic correlates. Gastrointest Endosc 1993;39:499-504. Saitoh Y, Obara T, Einami K, Nomura M, Taruishi M, Ayabe T, et al. Efficacy of high-frequency ultrasound probes for the preoperative staging of invasion depth in flat and depressed colorectal tumors. Gastrointest Endosc 1996;44: 34-9. Yanai H, Tada M, Karita M, Okita K. Diagnostic utility of 20-megahertz linear endoscopic ultrasonography in early gastric cancer. Gastrointest Endosc 1996;44:29-33. Yoshino J, Nakazawa S, Inui K, Katoh Y, Wakabayashi T, Okushima K, et al. Gastric wall structure using a 30 MHz endoscopic ultrasound probe, focusing upon delineation of the muscularis mucosae. Dig Endosc 2000;12:233-6. Cushing GL, Fitzgerald PJ, Bommer WJ, Andrews MW, Cronan MS, Martinez-Torres GG, et al. Intraluminal ultrasonography during ERCP with high-frequency ultrasound catheters. Gastrointest Endosc 1993;39:432-5. Engstrom CF, Wiechel KL. Endoluminal ultrasound of the bile ducts. Surg Endosc 1990;4:187-90. Tamada K, Ueno N, Tomiyama T, Oohashi A, Wada S, Nishizono T, et al. Characterization of biliary strictures using intraductal ultrasonography: comparison with percutaneous cholangioscopic biopsy. Gastrointest Endosc 1998; 47:341-9. Tamada K, Tomiyama T, Ichiyama M, Oohashi A, Wada S, Nishizono T, et al. Influence of biliary drainage catheter on bile duct wall thickness as measured by intraductal ultrasonography. Gastrointest Endosc 1998;47:28-32. Kuroiwa M, Goto H, Hirooka Y, Furukawa T, Hayakawa T, Naitoh Y. Intraductal ultrasonography for the diagnosis of proximal invasion in extrahepatic bile duct cancer. J Gastroenterol Hepatol 1998;13:715-9. Tamada K, Ohashi A, Tomiyama T, Wada S, Satoh Y, Higashizawa T, et al. Comparison of intraductal ultrasonography with percutaneous transhepatic cholangioscopy for the identification of residual bile duct stones during lithotripsy. J Gastroenterol Hepatol 2001;16:100-3. Menzel J, Domschke W. Gastrointestinal miniprobe sonography: the current status. Am J Gastroenterol 2000;95: 605-16. Tamada K, Ido K, Ueno N, Kimura K, Ichiyama M, Tomiyama T. Preoperative staging of extrahepatic bile duct cancer with intraductal ultrasonography. Am J Gastroenterol 1995;90:239-46. Furukawa T, Tsukamoto Y, Naitoh Y, Hirooka Y, Hayakawa T. Differential diagnosis between benign and malignant localized stenosis of the main pancreatic duct by intraductal ultrasound of the pancreas. Am J Gastroenterol 1994;89: 2038-41. Menzel J, Domschke W. Intraductal ultrasonography (IDUS) of the pancreato-biliary duct system. Personal experience and review of literature. Eur J Ultrasound 1999;10: 105-15. GASTROINTESTINAL ENDOSCOPY

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31. Yamao K, Okubo K, Sawaka A, Hara K, Nakamura T, Suzuki T, et al. Endolumenal ultrasonography in the diagnosis of pancreatic diseases. Abdom Imaging 2003;28: 545-55. 32. Menzel J, Foerster EC, Ubrig B, Keller R, Kerber S, Domschke W. Ex vivo examination of the pancreas by intraductal ultrasonography (IDUS). Endoscopy 1993;25: 571-6. 33. Furukawa T, Naitoh Y, Tsukamoto Y, Mitake M, Yamada M, Ishihara A, et al. New technique using intraductal ultrasonography for the diagnosis of diseases of the pancreatobiliary system. J Ultrasound Med 1992;11:607-12. 34. Furukawa T, Tsukamoto Y, Naitoh Y, Hirooka Y, Katoh T. Evaluation of intraductal ultrasonography in the diagnosis of pancreatic cancer. Endoscopy 1993;25:577-81. 35. Furukawa T, Tsukamoto Y, Naitoh Y, Mitake M, Hirooka Y, Hayakawa T. Differential diagnosis of pancreatic diseases with an intraductal ultrasound system. Gastrointest Endosc 1994;40:213-9. 36. Furukawa T, Oohashi K, Yamao K, Naitoh Y, Hirooka Y, Taki T, et al. Intraductal ultrasonography of the pancreas: development and clinical potential. Endoscopy 1997;29: 561-9. 37. Itoh A, Tsukamoto Y, Naitoh Y, Hirooka Y, Furukawa T, Kato T, et al. Intraductal ultrasonography for the examination of duodenal papillary region. J Ultrasound Med 1994; 13:679-84. 38. Wehrmann T, Stergiou N, Riphaus A, Lembcke B. Correlation between sphincter of Oddi manometry and intraductal ultrasound morphology in patients with suspected sphincter of Oddi dysfunction. Endoscopy 2001;33:773-7. 39. Waxman I, Saitoh Y. Clinical outcome of endoscopic mucosal resection for superficial GI lesions and the role of highfrequency US probe sonography in an American population. Gastrointest Endosc 2000;52:322-7. 40. Chak A, Soweid A, Hoffman B, Stevens P, Hawes RH, Lightdale CJ, et al. Clinical implications of endoluminal ultrasonography using through-the-scope catheter probes. Gastrointest Endosc 1998;48:485-90. 41. Buscarini E, Stasi MD, Rossi S, Silva M, Giangregorio F, Adriano Z, et al. Endosonographic diagnosis of submucosal upper gastrointestinal tract lesions and large fold gastropathies by catheter ultrasound probe. Gastrointest Endosc 1999;49:184-91. 42. Nesje LB, Laerum OD, Svanes K, Odegaard S. Subepithelial masses of the gastrointestinal tract evaluated by endoscopic ultrasonography. Eur J Ultrasound 2002;15:45-54. 43. Waxman I, Saitoh Y, Raju GS, Watari J, Yokota K, Reeves AL, et al. High-frequency probe EUS-assisted endoscopic mucosal resection: a therapeutic strategy for submucosal tumors of the GI tract. Gastrointest Endosc 2002;55:44-9. 44. Hunt GC, Smith PP, Faigel DO. Yield of tissue sampling for submucosal lesions evaluated by EUS. Gastrointest Endosc 2003;57:68-72. 45. Hasegawa N, Niwa Y, Arisawa T, Hase S, Goto H, Hayakawa T. Preoperative staging of superficial esophageal carcinoma: comparison of an ultrasound probe and standard endoscopic ultrasonography. Gastrointest Endosc 1996;44: 388-93. 46. Hunerbein M, Ghadimi BM, Haensch W, Schlag PM. Transendoscopic ultrasound of esophageal and gastric cancer using miniaturized ultrasound catheter probes. Gastrointest Endosc 1998;48:371-5. 47. Menzel J, Hoepffner N, Nottberg H, Schulz C, Senninger N, Domschke W. Preoperative staging of esophageal carciVOLUME 60, NO. 4, 2004

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48.

49.

50.

51.

52. 53.

54.

55.

56.

57.

58. 59.

60.

61.

62.

63.

64.

noma: miniprobe sonography versus conventional endoscopic ultrasound in a prospective histopathologically verified study. Endoscopy 1999;31:291-7. Murata Y, Suzuki S, Mitsunaga A, Iizuka Y, Uchiyama M, Uchida K, et al. Endoscopic ultrasonography in diagnosis and mucosal resection for early esophageal cancer. Endoscopy 1998;30(Suppl 1):A44-6. Yanai H, Yoshida T, Harada T, Matsumoto Y, Nishiaki M, Shigemitsu T, et al. Endoscopic ultrasonography of superficial esophageal cancers using a thin ultrasound probe system equipped with switchable radial and linear scanning modes. Gastrointest Endosc 1996;44:578-82. Murata Y, Suzuki S, Ohta M, Mitsunaga A, Hayashi K, Yoshida K, et al. Small ultrasonic probes for determination of the depth of superficial esophageal cancer. Gastrointest Endosc 1996;44:23-8. Adrain AL, Ter HC, Cassidy MJ, Schiano TD, Liu JB, Miller LS. High-resolution endoluminal sonography is a sensitive modality for the identification of Barrett’s metaplasia. Gastrointest Endosc 1997;46:147-51. Waxman I. Endosonography in columnar-lined esophagus. Gastroenterol Clin North Am 1997;26:607-12. Weston AP, Sharma P. Neodymium:yttrium-aluminum garnet contact laser ablation of Barrett’s high grade dysplasia and early adenocarcinoma. Am J Gastroenterol 2002; 97:2998-3006. Buttar NS, Wang KK, Lutzke LS, Krishnadath KK, Anderson MA. Combined endoscopic mucosal resection and photodynamic therapy for esophageal neoplasia within Barrett’s esophagus. Gastrointest Endosc 2001;54:682-8. Miller LS, Liu JB, Klenn PJ, Holahan MP, Varga J, Feld RI, et al. Endoluminal ultrasonography of the distal esophagus in systemic sclerosis. Gastroenterology 1993;105:31-9. Schiano TD, Fisher RS, Parkman HP, Cohen S, Dabezies M, Miller LS. Use of high-resolution endoscopic ultrasonography to assess esophageal wall damage after pneumatic dilation and botulinum toxin injection to treat achalasia. Gastrointest Endosc 1996;44:151-7. Miller LS, Liu JB, Barbarevech CA, Baranowski RJ, Dhuria M, Schiano TD, et al. High-resolution endoluminal sonography in achalasia. Gastrointest Endosc 1995;42:545-9. Van Dam J. Endosonographic evaluation of the patient with achalasia. Endoscopy 1998;30(Suppl 1):A48-50. Miller LS, Schiano TD. The use of high frequency endoscopic ultrasonography probes in the evaluation of achalasia. Gastrointest Endosc Clin N Am 1995;5:635-47. Taniguchi DK, Martin RW, Trowers EA, Dennis MB Jr, Odegaard S, Silverstein FE. Changes in esophageal wall layers during motility: measurements with a new miniature ultrasound suction device. Gastrointest Endosc 1993;39: 146-52. Miller LS, Liu JB, Colizzo FP, Ter H, Marzano J, Barbarevech C, et al. Correlation of high-frequency esophageal ultrasonography and manometry in the study of esophageal motility. Gastroenterology 1995;109:832-7. Dai Q, Liu JB, Brasseur JG, Thangada VK, Thomas B, Parkman H, et al. Volume (3-dimensional) space-time reconstruction of esophageal peristaltic contraction by using simultaneous US and manometry. Gastrointest Endosc 2003; 58:913-9. Mittal RK. Measuring esophageal distention by highfrequency intraluminal ultrasound probe. Am J Med 2003; 115(Suppl 3A):130S-6S. Balaban DH, Yamamoto Y, Liu J, Pehlivanov N, Wisniewski R, DeSilvey D, et al. Sustained esophageal contraction:

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66.

67.

68.

69.

70.

71.

72.

73.

74.

75.

76.

77.

78.

79.

80.

a marker of esophageal chest pain identified by intraluminal ultrasonography. Gastroenterology 1999;116:29-37. Schiano TD, Adrain AL, Vega KJ, Liu JB, Black M, Miller LS. High-resolution endoluminal sonography assessment of the hematocystic spots of esophageal varices. Gastrointest Endosc 1999;49:424-7. Schiano TD, Adrain AL, Cassidy MJ, McCray W, Liu JB, Baranowski RJ, et al. Use of high-resolution endoluminal sonography to measure the radius and wall thickness of esophageal varices. Gastrointest Endosc 1996;44:425-8. Chung CY, McCray WH, Dhaliwal S, Haywood T, Black M, Liu JB, et al. Three-dimensional esophageal varix model quantification of variceal volume by high-resolution endoluminal US. Gastrointest Endosc 2000;52:87-90. Miller ES, Kim JK, Gandehok J, Hara M, Dai Q, Malik A, et al. A new device for measuring esophageal variceal pressure. Gastrointest Endosc 2002;56:284-91. Miller L, Banson FL, Bazir K, Korimilli A, Liu JB, Dewan R, et al. Risk of esophageal variceal bleeding based on endoscopic ultrasound evaluation of the sum of esophageal variceal cross-sectional surface area. Am J Gastroenterol 2003;98:454-9. Kishimoto H, Sakai M, Kajiyama T, Torii A, Kin G, Tsukada H, et al. Miniature ultrasonic probe evaluation of esophageal varices after endoscopic variceal ligation. Gastrointest Endosc 1995;42:256-60. Nagamine N, Ido K, Ueno N, Kimura K, Kawamata T, Kawada H, et al. The usefulness of ultrasonic microprobe imaging for endoscopic variceal ligation. Am J Gastroenterol 1996;91:523-9. Suzuki T, Matsutani S, Umebara K, Sato G, Maruyama H, Mitsuhashi O, et al. EUS changes predictive for recurrence of esophageal varices in patients treated by combined endoscopic ligation and sclerotherapy. Gastrointest Endosc 2000;52:611-7. Konishi Y, Nakamura T, Kida H, Seno H, Okazaki K, Chiba T. Catheter US probe EUS evaluation of gastric cardia and perigastric vascular structures to predict esophageal variceal recurrence. Gastrointest Endosc 2002;55:197-203. Irisawa A, Saito A, Obara K, Shibukawa G, Takagi T, Shishido H, et al. Endoscopic recurrence of esophageal varices is associated with the specific EUS abnormalities: severe periesophageal collateral veins and large perforating veins. Gastrointest Endosc 2001;53:77-84. Kamijo Y, Kondo I, Soma K, Imaizumi H, Ohwada T. Alkaline esophagitis evaluated by endoscopic ultrasound. J Toxicol Clin Toxicol 2001;39:623-5. Kamijo Y, Kondo I, Kokuto M, Kataoka Y, Soma K. Miniprobe ultrasonography for determining prognosis in corrosive esophagitis. Am J Gastroenterol 2004;99:851-4. Bernhardt J, Ptok H, Wilhelm L, Ludwig K. Caustic acid burn of the upper gastrointestinal tract: first use of endosonography to evaluate the severity of the injury. Surg Endosc 2002;16:1004. Qi Z, Yunlin W, Jiayu X. Preliminary assessment of miniprobe sonography in the diagnosis of gastric varices and evaluation of treatment with Histoacryl. Chin J Dig Dis 2001;2:9-12. Faigel DO, Gopal D, Weeks DA, Corless C. Cap-assisted endoscopic submucosal resection of a pancreatic rest. Gastrointest Endosc 2001;54:782-4. Akahoshi K, Chijiwa Y, Hamada S, Sasaki I, Nawata H, Kabemura T, et al. Pretreatment staging of endoscopically early gastric cancer with a 15 MHz ultrasound catheter probe. Gastrointest Endosc 1998;48:470-6. GASTROINTESTINAL ENDOSCOPY

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G Isenberg

81. Okai T, Sawabu N. Miniprobe or ultrasound endoscope for gastric lesions?. Endoscopy 1998;30(Suppl 1):A60-2. 82. Kida M, Tanabe S, Watanabe M, Kokutou M, Kondou I, Yamada Y, et al. Staging of gastric cancer with endoscopic ultrasonography and endoscopic mucosal resection. Endoscopy 1998;30(Suppl 1):A64-8. 83. Akahoshi K, Chijiiwa Y, Sasaki I, Hamada S, Iwakiri Y, Nawata H, et al. Pre-operative TN staging of gastric cancer using a 15 MHz ultrasound miniprobe. Br J Radiol 1997;70: 703-7. 84. Yanai H, Noguchi T, Mizumachi S, Tokiyama H, Nakamura H, Tada M, et al. A blind comparison of the effectiveness of endoscopic ultrasonography and endoscopy in staging early gastric cancer. Gut 1999;44:361-5. 85. Yanai H, Matsumoto Y, Harada T, Nishiaki M, Tokiyama H, Shigemitsu T, et al. Endoscopic ultrasonography and endoscopy for staging depth of invasion in early gastric cancer: a pilot study. Gastrointest Endosc 1997;46:212-6. 86. Hunerbein M, Handke T, Ulmer C, Schlag PM. Impact of miniprobe ultrasonography on planning of minimally invasive surgery for gastric and colonic tumors. Surg Endosc 2004;18:601-5. 87. Akahoshi K, Chijiiwa Y, Hamada S, Sasaki I, Maruoka A, Kabemura T, et al. Endoscopic ultrasonography: a promising method for assessing the prospects of endoscopic mucosal resection in early gastric cancer. Endoscopy 1997;29:614-9. 88. Giovannini M, Bernardini D, Moutardier V, Monges G, Houvenaeghel G, Seitz JF, et al. Endoscopic mucosal resection (EMR): results and prognostic factors in 21 patients. Endoscopy 1999;31:698-701. 89. Giovannini M. Ultrasound-guided endoscopic surgery. Best Pract Res Clin Gastroenterol 2004;18:183-200. 90. Akahoshi K, Chijiiwa Y, Tanaka M, Harada N, Nawata H. Endosonography probe-guided endoscopic mucosal resection of gastric neoplasms. Gastrointest Endosc 1995;42:248-52. 91. Ohashi S, Segawa K, Okamura S, Mitake M, Urano H, Shimodaira M, et al. The utility of endoscopic ultrasonography and endoscopy in the endoscopic mucosal resection of early gastric cancer. Gut 1999;45:599-604. 92. Hizawa K, Iwai K, Esaki M, Matsumoto T, Suekane H, Iida M. Is endoscopic ultrasonography indispensable in assessing the appropriateness of endoscopic resection for gastric cancer? Endoscopy 2002;34:973-8. 93. Sabet EA, Okai T, Minamoto T, Mai M, Sawabu N. Visualizing the gastric wall with a 30-MHz ultrasonic miniprobe: ex vivo imaging of normal gastric sites and sites of early gastric cancer. Abdom Imaging 2003;28:252-6. 94. Chu KM, Kwok KF, Law S, Wong KH. A prospective evaluation of catheter probe EUS for the detection of ascites in patients with gastric carcinoma. Gastrointest Endosc 2004;59:471-4. 95. Lugering N, Menzel J, Kucharzik T, Koch P, Herbst H, Tiemann M, et al. Impact of miniprobes compared to conventional endosonography in the staging of low-grade gastric malt lymphoma. Endoscopy 2001;33:832-7. 96. Sheu BS, Shiesh SC, Wang JT, Yang HB, Lin ST, Wu JJ. Clinical application of 20 MHz endosonography and antiHelicobacter pylori immunoblots to predict regression of low-grade gastric MALToma by H. pylori eradication. Helicobacter 2003;8:36-45. 97. Nakamura S, Matsumoto T, Kusano Y, Esaki M, Kurahara K, Fukuda T. Duodenal mucosa-associated lymphoid tissue lymphoma treated by eradication of Helicobacter pylori: report of 2 cases including EUS findings. Gastrointest Endosc 2001;54:772-5. 620

GASTROINTESTINAL ENDOSCOPY

Catheter-probe–assisted endoluminal US

98. Braden B, Brandstaetter M, Caspary WF, Seifert H. Buried bumper syndrome: treatment guided by catheter probe US. Gastrointest Endosc 2003;57:747-51. 99. Aiura K, Imaeda H, Kitajima M, Kumai K. Balloon-catheterassisted endoscopic snare papillectomy for benign tumors of the major duodenal papilla. Gastrointest Endosc 2003;57: 743-7. 100. Vogt M, Jakobs R, Riemann JF. Rationale for endoscopic management of adenoma of the papilla of Vater: options and limitations. Langenbecks Arch Surg 2001;386:176-82. 101. Noda Y, Watanabe H, Iida M, Narisawa R, Kurosaki I, Iwafuchi M, et al. Histologic follow-up of ampullary adenomas in patients with familial adenomatosis coli. Cancer 1992;70:1847-56. 102. Menzel J, Hoepffner N, Sulkowski U, Reimer P, Heinecke A, Poremba C, et al. Polypoid tumors of the major duodenal papilla: preoperative staging with intraductal US, EUS, and CT—a prospective, histopathologically controlled study. Gastrointest Endosc 1999;49:349-57. 103. Itoh A, Goto H, Naitoh Y, Hirooka Y, Furukawa T, Hayakawa T. Intraductal ultrasonography in diagnosing tumor extension of cancer of the papilla of Vater. Gastrointest Endosc 1997;45:251-60. 104. Domagk D, Poremba C, Dietl KH, Senninger N, Heinecke A, Domschke W, et al. Endoscopic transpapillary biopsies and intraductal ultrasonography in the diagnostics of bile duct strictures: a prospective study. Gut 2002;51:240-4. 105. Tamada K, Tomiyama T, Wada S, Ohashi A, Satoh Y, Ido K, et al. Endoscopic transpapillary bile duct biopsy with the combination of intraductal ultrasonography in the diagnosis of biliary strictures. Gut 2002;50:326-31. 106. Waxman I. Characterization of a malignant bile duct obstruction by intraductal ultrasonography. Am J Gastroenterol 1995;90:1073-5. 107. Menzel J, Domschke W, Brambs HJ, Frank N, Hatfield A, Nattermann C, et al. Miniprobe ultrasonography in the upper gastrointestinal tract: state of the art 1995, and prospects. Endoscopy 1996;28:508-13. 108. Tamada K, Sugano K. Diagnosis and non-surgical treatment of bile duct carcinoma: developments in the past decade. J Gastroenterol 2000;35:319-25. 109. Tamada K, Kanai N, Wada S, Tomiyama T, Ohashi A, Satoh Y, et al. Utility and limitations of intraductal ultrasonography in distinguishing longitudinal cancer extension along the bile duct from inflammatory wall thickening. Abdom Imaging 2001;26:623-31. 110. Tamada K, Yasuda Y, Tomiyama T, Oohashi A, Kanai N, Aizawa T, et al. Preoperative assessment of congenital bile duct dilatation using intraductal US. Gastrointest Endosc 1999;49:488-92. 111. Farrell RJ, Agarwal B, Brandwein SL, Underhill J, Chuttani R, Pleskow DK. Intraductal US is a useful adjunct to ERCP for distinguishing malignant from benign biliary strictures. Gastrointest Endosc 2002;56:681-7. 112. Moon JH, Cho YD, Cheon YK, Ryu CB, Kim YS, Kim JO, et al. Wire-guided intraductal US in the assessment of bile duct strictures with Mirizzi syndrome-like features at ERCP. Gastrointest Endosc 2002;56:873-9. 113. Shimura K, Tamada K, Asada M, Watabiki N, Wada I, Tanaka N, et al. Intraductal ultrasonography of traumatic neuroma of the bile duct. Abdom Imaging 2001;26:632-4. 114. Vazquez-Sequeiros E, Baron TH, Clain JE, Gostout CJ, Norton ID, Petersen BT, et al. Evaluation of indeterminate bile duct strictures by intraductal US. Gastrointest Endosc 2002;56:372-9. VOLUME 60, NO. 4, 2004

Catheter-probe–assisted endoluminal US

115. Menzel J, Poremba C, Dietl KH, Domschke W. Preoperative diagnosis of bile duct strictures: comparison of intraductal ultrasonography with conventional endosonography. Scand J Gastroenterol 2000;35:77-82. 116. Tamada K, Tomiyama T, Oohashi A, Aizawa T, Nishizono T, Wada S, et al. Bile duct wall thickness measured by intraductal US in patients who have not undergone previous biliary drainage. Gastrointest Endosc 1999;49: 199-203. 117. Hyodo T, Hyodo N, Yamanaka T, Imawari M. Contrastenhanced intraductal ultrasonography for thickened bile duct wall. J Gastroenterol 2001;36:557-9. 118. Tamada K, Ido K, Ueno N, Ichiyama M, Tomiyama T, Nishizono T, et al. Assessment of portal vein invasion by bile duct cancer using intraductal ultrasonography. Endoscopy 1995;27:573-8. 119. Tamada K, Kanai N, Ueno N, Ichiyama M, Tomiyama T, Wada S, et al. Limitations of intraductal ultrasonography in differentiating between bile duct cancer in stage T1 and stage T2: in-vitro and in-vivo studies. Endoscopy 1997;29: 721-5. 120. Tamada K, Ido K, Ueno N, Ichiyama M, Tomiyama T, Nishizono T, et al. Assessment of hepatic artery invasion by bile duct cancer using intraductal ultrasonography. Endoscopy 1995;27:579-83. 121. Tamada K, Ueno N, Ichiyama M, Tomiyama T, Nishizono T, Wada S, et al. Assessment of pancreatic parenchymal invasion by bile duct cancer using intraductal ultrasonography. Endoscopy 1996;28:492-6. 122. Tamada K, Ido K, Ueno N, Ichiyama M, Tomiyama T, Nishizono T, et al. Assessment of the course and variations of the hepatic artery in bile duct cancer by intraductal ultrasonography. Gastrointest Endosc 1996;44:249-56. 123. Tamada K, Inui K, Menzel J. Intraductal ultrasonography of the bile duct system. Endoscopy 2001;33:878-85. 124. Tamada K, Nagai H, Yasuda Y, Tomiyama T, Ohashi A, Wada S, et al. Transpapillary intraductal US prior to biliary drainage in the assessment of longitudinal spread of extrahepatic bile duct carcinoma. Gastrointest Endosc 2001; 53:300-7. 125. Duda SH, Huppert PE, Schott U, Brambs HJ, Claussen CD. Percutaneous transhepatic intraductal biliary sonography for lymph node staging at 12.5 MHz in malignant bile duct obstruction: work in progress. Cardiovasc Intervent Radiol 1997;20:133-8. 126. Ohashi A, Ueno N, Tamada K, Tomiyama T, Wada S, Miyata T, et al. Assessment of residual bile duct stones with use of intraductal US during endoscopic balloon sphincteroplasty: comparison with balloon cholangiography. Gastrointest Endosc 1999;49:328-33. 127. Ueno N, Nishizono T, Tamada K, Ichiyama M, Wada S, Tomiyama T, et al. Diagnosing extrahepatic bile duct stones using intraductal ultrasonography: a case series. Endoscopy 1997;29:356-60. 128. Das A, Isenberg G, Wong RC, Sivak MV Jr, Chak A. Wireguided intraductal US: an adjunct to ERCP in the management of bile duct stones. Gastrointest Endosc 2001;54: 31-6. 129. Catanzaro A, Pfau P, Isenberg GA, Wong RC, Sivak MV Jr, Chak A. Clinical utility of intraductal US for evaluation of choledocholithiasis. Gastrointest Endosc 2003;57:648-52. 130. Tseng LJ, Jao YT, Mo LR, Lin RC. Over-the-wire US catheter probe as an adjunct to ERCP in the detection of choledocholithiasis. Gastrointest Endosc 2001;54:720-3. VOLUME 60, NO. 4, 2004

G Isenberg

131. Kubota Y, Takaoka M, Yamamoto S, Shibatani N, Shimatani M, Takamido S, et al. Diagnosis of common bile duct calculi with intraductal ultrasonography during endoscopic biliary cannulation. J Gastroenterol Hepatol 2002;17: 708-12. 132. Ariyama J, Suyama M, Satoh K, Wakabayashi K. Endoscopic ultrasound and intraductal ultrasound in the diagnosis of small pancreatic tumors. Abdom Imaging 1998; 23:380-6. 133. Inui K, Nakazawa S, Yoshino J, Okushima K, Nakamura Y, Ukai H, et al. A case of pancreatic carcinoma diagnosed by intraductal US after lithotripsy for pancreatolithiasis. Gastrointest Endosc 2000;52:418-21. 134. Itoh A, Goto H, Hirooka Y, Hashimoto S, Hirai T, Niwa K, et al. Endoscopic diagnosis of pancreatic cancer using intraductal ultrasonography. Hepatogastroenterology 2001; 48:928-32. 135. Inui K, Nakazawa S, Yoshino J, Yamachika H, Kanemaki N, Wakabayashi T, et al. Mucin-producing tumor of the pancreas: intraluminal ultrasonography. Hepatogastroenterology 1998;45:1996-2000. 136. Yamao K, Nakamura T, Suzuki T, Sawaki A, Hara K, Kato T, et al. Endoscopic diagnosis and staging of mucinous cystic neoplasms and intraductal papillary-mucinous tumors. J Hepatobiliary Pancreat Surg 2003;10:142-6. 137. Yamao K, Ohashi K, Nakamura T, Suzuki T, Watanabe Y, Shimizu Y, et al. Evaluation of various imaging methods in the differential diagnosis of intraductal papillary-mucinous tumor (IPMT) of the pancreas. Hepatogastroenterology 2001;48:962-6. 138. Igarashi Y, Tada T, Shimura J, Ukita T, Inoue H, Maetani I, et al. Endosonographic diagnosis of intraductal papillarymucinous pancreatic tumors by intraductal ultrasonography. Dig Endosc 2003;15:196-9. 139. Inui K, Nakazawa S, Yoshino J, Kanemaki N, Okushima K, Nakamura Y, et al. Endoscopy and intraductal ultrasonography. Semin Surg Oncol 1998;15:33-9. 140. Koito K, Namieno T, Nagakawa T, Hirokawa N, Ichimura T, Syonai T, et al. Pancreas: imaging diagnosis with color/ power Doppler ultrasonography, endoscopic ultrasonography, and intraductal ultrasonography. Eur J Radiol 2001; 38:94-104. 141. Hara T, Yamaguchi T, Ishihara T, Tsuyuguchi T, Kondo F, Kato K, et al. Diagnosis and patient management of intraductal papillary-mucinous tumor of the pancreas by using peroral pancreatoscopy and intraductal ultrasonography. Gastroenterology 2002;122:34-43. 142. Inui K, Nakazawa S, Yoshino J, Okushima K, Nakamura Y. Endoluminal ultrasonography for pancreatic diseases. Gastroenterol Clin North Am 1999;28:771-81. 143. Menzel J, Domschke W. Intraductal ultrasonography may localize islet cell tumours negative on endoscopic ultrasound. Scand J Gastroenterol 1998;33:109-12. 144. Tseng LJ, Jao YT, Mo LR. Preoperative staging of colorectal cancer with a balloon-sheathed miniprobe. Endoscopy 2002; 34:564-8. 145. Yoshida M, Tsukamoto Y, Niwa Y, Goto H, Hase S, Hayakawa T, et al. Endoscopic assessment of invasion of colorectal tumors with a new high-frequency ultrasound probe. Gastrointest Endosc 1995;41:587-92. 146. Hamada S, Akahoshi K, Chijiiwa Y, Sasaki I, Nawata H. Preoperative staging of colorectal cancer by a 15 MHz ultrasound miniprobe. Surgery 1998;123:264-9. 147. Harada N, Hamada S, Kubo H, Oda S, Chijiiwa Y, Kabemura T, et al. Preoperative evaluation of submucosal GASTROINTESTINAL ENDOSCOPY

621

G Isenberg

148.

149.

150.

151.

152.

153.

154.

155.

156.

157.

158.

159.

160.

161.

622

invasive colorectal cancer using a 15-MHz ultrasound miniprobe. Endoscopy 2001;33:237-40. Tsuda S, Hoashi T, Yao T. Endoscopic ultrasonography versus probe for diagnosis of depth of infiltration of colorectal cancer. Endoscopy 1998;30(Suppl 1):A85-7. Hizawa K, Suekane H, Aoyagi K, Matsumoto T, Nakamura S, Fujishima M. Use of endosonographic evaluation of colorectal tumor depth in determining the appropriateness of endoscopic mucosal resection. Am J Gastroenterol 1996; 91:768-71. Kameyama H, Niwa Y, Arisawa T, Goto H, Hayakawa T. Endoscopic ultrasonography in the diagnosis of submucosal lesions of the large intestine. Gastrointest Endosc 1997;46: 406-11. Akahoshi K, Fujimaru T, Nakanishi K, Harada N, Nawata H. Endosonography probe-guided endoscopic resection of small flat rectal carcinoid tumor using band ligation technique. Endoscopy 2001;33:471. Matsumoto T, Hizawa K, Esaki M, Kurahara K, Mizuno M, Hirakawa K, et al. Comparison of EUS and magnifying colonoscopy for assessment of small colorectal cancers. Gastrointest Endosc 2002;56:354-60. Cho E, Mochizuki N, Ashihara T, Yasuda K, Nakajima M. Endoscopic ultrasonography in the evaluation of inflammatory bowel disease. Endoscopy 1998;30(Suppl 1):A94-6. Soweid AM, Chak A, Katz JA, Sivak MV Jr. Catheter probe assisted endoluminal US in inflammatory bowel disease. Gastrointest Endosc 1999;50:41-6. Tsuga K, Haruma K, Fujimura J, Hata J, Tani H, Tanaka S, et al. Evaluation of the colorectal wall in normal subjects and patients with ulcerative colitis using an ultrasonic catheter probe. Gastrointest Endosc 1998;48:477-84. Higaki S, Nohara H, Saitoh Y, Akazawa A, Yanai H, Yoshida T, et al. Increased rectal wall thickness may predict relapse in ulcerative colitis: a pilot follow-up study by ultrasonographic colonoscopy. Endoscopy 2002;34:212-9. Kim CY, Bandres D, Tio TL, Benjamin SB, Al-Kawas FH. Endoscopic removal of large colonic lipomas. Gastrointest Endosc 2002;55:929-31. Fujimura Y, Nishishita C, Iida M, Kajihara Y. Lymphangioma of the colon diagnosed with an endoscopic ultrasound probe and dynamic CT. Gastrointest Endosc 1995;41:252-4. Stergiou N, Riphaus A, Lange P, Menke D, Kockerling F, Wehrmann T. Endoscopic snare resection of large colonic polyps: how far can we go? Int J Colorectal Dis 2003;18: 131-5. Yoshimoto K. Clinical application of ultrasound 3 D imaging system in lesions of the gastrointestinal tract. Endoscopy 1998;30(Suppl 1):A145-8. Sumiyama K, Suzuki N, Kakutani H, Hino S, Tajiri H, Suzuki H, et al. A novel 3-dimensional EUS technique for

GASTROINTESTINAL ENDOSCOPY

Catheter-probe–assisted endoluminal US

162.

163.

164.

165.

166.

167.

168.

169.

170.

171.

172.

173.

174.

real-time visualization of the volume data reconstruction process. Gastrointest Endosc 2002;55:723-8. Molin S, Nesje LB, Gilja OH, Hausken T, Martens D, Odegaard S. 3D-endosonography in gastroenterology: methodology and clinical applications. Eur J Ultrasound 1999;10: 171-7. Yoshino J, Nakazawa S, Inui K, Katoh Y, Wakabayshi T, Okushima T, et al. Surface-rendering imaging of gastrointestinal lesions by three-dimensional endoscopic ultrasonography. Endoscopy 1999;31:541-5. Kanemaki N, Nakazawa S, Inui K, Yoshino J, Yamao J, Okushima K. Three-dimensional intraductal ultrasonography: preliminary results of a new technique for the diagnosis of diseases of the pancreatobiliary system. Endoscopy 1997;29:726-31. Nishimura K, Niwa Y, Goto H, Hase S, Arisawa T, Hayakawa T. Three-dimensional endoscopic ultrasonography of gastrointestinal lesions using an ultrasound probe. Scand J Gastroenterol 1997;32:862-8. Isenberg G, Chak A, Canto MI, Levitan N, Clayman J, Pollack BJ, et al. Endoscopic ultrasound in restaging of esophageal cancer after neoadjuvant chemoradiation. Gastrointest Endosc 1998;48:158-63. Bhutani MS, Barde CJ. Contrast-enhanced gastrointestinal trans-abdominal and endoscopic ultrasonography: an idea whose time has come. Am J Gastroenterol 1997;92:1976-80. Inui K. Is contrast-enhanced intraductal ultrasonography helpful in the differential diagnosis of a thickened bile duct wall?. J Gastroenterol 2001;36:583-4. Hyodo N, Hyodo T. Ultrasonographic evaluation in patients with autoimmune-related pancreatitis. J Gastroenterol 2003; 38:1155-61. Kato T, Tsukamoto Y, Naitoh Y, Hirooka Y, Furukawa T, Hayakawa T. Ultrasonographic and endoscopic ultrasonographic angiography in pancreatic mass lesions. Acta Radiol 1995;36:381-7. Nomura N, Goto H, Niwa Y, Arisawa T, Hirooka Y, Hayakawa T. Usefulness of contrast-enhanced EUS in the diagnosis of upper GI tract diseases. Gastrointest Endosc 1999;50:555-60. Terada M, Tsukaya T, Saito Y. Technical advances and future developments in endoscopic ultrasonography. Endoscopy 1998;30(Suppl 1):A3-7. Norton ID, Bruce CJ, Seward JB, Vazquez-Sequeiros E, Affi A, Wiersema MJ. Initial experience with a steerable, phased vector array ultrasound catheter in the GI tract. Gastrointest Endosc 2001;53:496-9. Shamoun DK, Norton ID, Levy MJ, Vazquez-Sequeiros E, Wiersema MJ. Use of a phased vector array US catheter for EUS. Gastrointest Endosc 2002;56:430-5.

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