A new miniature ultrasonic probe for gastrointestinal scanning: feasibility and preliminary results

A prototype of a new miniature ultrasonic probe (Aloka) was clinically evaluated in 37 patients with a variety of gastrointestinal lesions. The probe's diameter of 2.0 mm allowed passage through the working channel of conventional endoscopes; the ultrasonic frequencies used were 15 and 20 MHz. Fourteen patients with benign and malignant gastrointestinal tumors, and thirteen patients with a variety of benign conditions, were examined, 12 of whom also underwent conventional endoscopic ultrasonography with side-viewing echoendoscopes. The image quality of the two systems was well comparable, but the ultrasonic penetration depth of the miniprobes was inferior to that of conventional endoscopic ultrasonography (EUS). All but three lesions were adequately visualized by the ultrasonic probe, whereas conventional EUS failed to completely visualize four cases. Of the two ultrasonic frequencies used, we found 15 MHz to be superior, since it provided good image quality and adequate penetration depth. In conclusion, we feel that the probe can be used for EUS indications in the gastrointestinal tract, whereas further technical improvements, such as increasing the penetration depth, are necessary before pancreatobiliary EUS can be carried out.