High‐frequency Intraductal Ultrasound Images of Biliary Tract Lesions: Experimental Studies

Abstract

Abstract: To investigate the differences in images obtained with a 3.75 MHz, 7.5 MHz or 20 MHz transducer, 27 stones, five debris samples, and three cholesterol polyps were examined in a water tank. All stones showed definite acoustic shadowing on images produced with the 20 MHz transducer, although the acoustic shadowing was weak or absent on images produced by 3.75 MHz or 7.5 MHz transducers. Regarding the relation between stone size and the acoustic shadowing, this shadowing was visualized for stones as small as 1.5 mm when the 20 MHz transducer was used. The hyperechoic appearance changed to a sharp crescent shape with the high frequency transducer. Images of cholesterol polyps and debris produced by the 20 MHz transducer showed no fundamental differences when compared with conventional ultrasonographic images obtained with a 3.75 MHz transducer, and there was no accompanying acoustic shadowing. In conclusion, ultrasonic images obtained with high frequency transducers which are used in intraductal ultrasound are different from those produced with conventional ultrasound probes. These phenomena may be useful for differential diagnosis of biliary tract diseases.