Technical considerations in the performance of endoluminal ultrasonography using new catheter probes

AIM: To define technical advantages and limitations of endosonographic imaging using a new through the-scope catheter system. METHODS: Catheter based ultrasonography (C-EUS) was performed with newly developed 2.3 mm, 12 MHz (Olympus 2R) and/or 20 MHz (Olympus 3R) catheter probes introduced via accessory channel of standard diagnostic upper endoscopes or duodenoscopes. Standard endoscopic ultrasonography (S-EUS) with an ultrasound endoscope (Olympus GF-UM20) was subsequently performed on all patients. Ease of performing C-EUS (5-point scale), imaging depth, image clarity compared to S-EUS, time taken to perform C-EUS, and number of sonographic layers seen at C-EUS were all recorded. RESULTS: C-EUS was performed on 21 patients (ptsl with esophageal lesions (Gp1), 12 pts with gastric lesions (Gp2), and 6 pts with pancreaticobiliary strictures (Gp3). C-EUS was easy to perform (no or little manipulation) in 19/21 (90%) Gp1 pts, 10/12 (83%) Gp2 pts, and 5/6 (83%) Gp3 pts. Compared to S-EUS, C-EUS was rated as providing a clearer image in 6/21 (29%) Gp1 pts, 8/12 (66%) Gp2 pts, and 4/6 (66%) Gp3 patients. Lack of image clarity in Gp 1 pts was generally due to an inability to retain water in esophagus. Poor image clarity in Gp 3 pts was noted only when the catheter failed to traverse a stricture. Mean imaging depth was 2.9 cm. for 12 MHz catheter and 1.8 cm. for the 20 MHz catheter. The 12 MHz probe defined 5 sonographic layers when scanning the esophageal and gastric wall in all but one examination (7 layers seen in 1 gastric exam). The 20 MHz probe also imaged 6 sonographic layers in the esophagus and stomach except in 3 cases where 7 layers were seen. Both the 12 and 20 MHz probes demonstrated 3 layers when imaging the normal bile duct wall. Mean time for C-EUS imaging with endoscopy was 16.4 minutes (Gp1), 16.0 minutes (Gp2), and 23.7 minutes (Gp3). Catheters broke during 3 of the first 25 examinations. Following modifications to strengthen catheters, breakage occurred only in 1 of 18 examinations. CONCLUSIONS: Catheter ultrasonography with the new Olympus 2R/3R system can be performed relatively easily and quickly during diagnostic endoscopy. C-EUS provides clean sonographic images, although imaging depth is limited. Imaging in the esophagus with C-EUS is hampered by the inability to achieve good acoustical contact, but may be improved in future by development of a balloon sheath.