Initial experience with a steerable, phased vector array ultrasound catheter in the GI tract

Background: EUS requires a significant capital outlay. The ability to perfo rm high-resolution phased array scanning and Doppler interrogation by using a catheter that interfaces with a standard US console could increase the a ccessibility of EUS, Recently, an electronic phased-array US catheter was d eveloped for intracardiac use,To date, this technology has not been applied to the GI tract. The aim of this study is to determine the feasibility and imaging characteristics of a new phased array scanning US catheter in the GI tract. Methods: Swine were placed under general anesthesia. This study used a 100 cm, 10F, torquable catheter with 4-way tip deflection to greater than 90 de grees. The catheter tip houses a phased vector array transducer with variab le frequency (5.5-10 MHz) and variable focal distance. It has pulsed/color and power Doppler capability. The probe was passed through a therapeutic fl exible sigmoidoscope into the upper GI tract. Acoustic coupling was achieve d via a condom filled with water or by gastric water infusion. Needle visua lization experiments were performed with a second endoscope (also passed pe r oral) with a standard BUS-guided fine needle aspiration needle. Results: Acoustic coupling was easily achieved. Resolution of the GI wall i nto characteristic layers (esophagus 5, stomach 7) was demonstrated. At 5.5 MHz, tissue resolution and Doppler imaging were excellent to greater than 10 cm from the transducer. A 22-gauge EUS-guided fine needle aspiration nee dle was easily visualized at depth greater than 4 cm, Flow in gastric, hepa tic, and pancreatic parenchymal vessels approximately 1 mm diameter was vis ualized by using power and color Doppler. Conclusions: This 10F array US catheter is capable of high-resolution two-d imensional imaging of the gut wall as well as high-quality Doppler imaging. The Doppler capabilities of this equipment may have new GI applications.