Endoluminal US: experiments with nonvascular uses in animals

Catheters containing miniature ultrasound (US) transducers, originally developed for intravascular evaluation of plaque, were used in a series of in vivo and in vitro animal experiments to image a variety of nonvascular lumina. Measurements of the wall thickness and echotexture of the urethra, urinary bladder, ureter, renal pelvis, bile ducts, small bowel, fallopian tubes, and uterus were carried out. Close correlation between the US images and actual anatomic specimens was obtained. Structures outside of the lumen were identified and confirmed with both direct visualization and radiographic localization. Two small stones artificially inserted into the renal pelvis and a polyp-like projection artificially created within the fallopian tube were clearly identified by using the US probe. These initial US studies demonstrate the potential feasibility of these miniature transducers contained within catheters for intraluminal analysis in humans.