Endoscopic ultrasound probes.

Ultrasound probes are being developed as alternatives to dedicated ultrasound endoscopes. These probes have been designed to pass through the instrument channel of ordinary fiberoptic or video endoscopes. We have developed a 20-MHz mechanical linear probe for use within the upper gastrointestinal tract, pancreatic duct, biliary tree, and colon. Rotational mechanical sector scanning probes as well as phased array probes are also being developed. Ultrasound probes are best used for high resolution imaging of focal endoscopically visible lesions. Endoscopic visualization enables direction of the probe to the lesion of interest. Unlike dedicated ultrasound endoscopes, ultrasound probes do not screen large areas of tissue and do not have deep penetration. Ongoing research will help define the indications for use of these probes and should lead to further refinements in their design.