Department of Radiology, College of Medicine Yonsei University
ABSTRACT
The ultrasonic diagnosis of bile duct stone is still difficult and disappointing, espicially compared with the diagnostic accuracy of gall stone. We analized ultrasonic findings of the relationship between bile duct stone and posterior acoustic shadow under different conditions in vitro real time scans of bile duct stones using human liver tissue phantom.
The results were as follows:
1. In vitro real time scans of each 1to 6mm sized 23 stones, even the detection of the 1mm sized stones were possible in 3 cases among 5 cases when using 5MHz transducer, however there shows no definite posterior acoustic shadow in all cases of 1mm sized stones when using 2.4 MHz probe.
2. The posterior acoustic shadows were demonstrated in almost all the stones more than 2mm size except two stones, each 2mm and 4mm stones, among 13 stones, and the reflected echoes from the stones and posterior acoustic shadows were more evident when using higher frequency probe.
3. In real time scans of 4 to 6 mm sized 3 stones using 3.5MHz probe at different depth, only faint posterior acoustic shadows were noted when the stones were placed deeper than the focal range of the probe, while dense posterior acoustic shadows were identified when the stones were placed within the focal range of the probe.
4. When 7 to 9 mm sized stones were scanned in different tubes, posterior acoustic shadows were not dense in thick rubber tuber as in condom or thin rubber tube. After pulling of thick rubber tube for the purpose of reducing fluid-stone interface, previous posterior acoustic shadows were no more identified.
5 When the 1 to 3 mm sized multiple stones were evenly distributed in rubber tube, multiple dense acoustic shadows were demonstrated, while there shows no definite posterior acoustic shadows after impaction of these stones by inclining the phantom box.
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