Accuracy of liver puncture under US guidance: Re-evaluation by microcomputer simulation model

Objective To evaluate, using microcomputer simulation models, the degree of distortion of the puncture needle in sonograms used during a liver puncture under ultrasound guidance. Methods We made a simplified simulation model of the puncture needle passing through the abdominal wall to the target lesion in the liver (cases without ascites), and additionally through ascites between the abdominal wall and the liver (cases with ascites), to evaluate the degree of distortion of the puncture needle in the sonogram. We considered the thicknesses and sound velocities of the abdominal wall and the ascites fluid, as well as the puncture angle, on the degree of distortion. Results (1) Cases without ascites: The puncture needle displayed on sonogram shifted predominantly anteriorly with a displacement error between 6 mm forward and 1 mm backward and with an angular error between 2.2 degrees forward and 0.1 degree backward when the abdominal wall was muscular, and the pattern of distortion had an inverted S‐shape. It was displayed predominantly posteriorly with a displacement error between 14 mm backward and 2 mm forward and with an angular error between 3.7 degrees backward and 1.2 degrees forward when the abdominal wall was fatty, and the pattern was S‐shaped. Regardless of the composition of the abdominal wall, when the abdominal wall was thin, the more obtuse the puncture angle was, the larger the shift was, and when the abdominal wall was thick, the more acute the puncture angle was, the larger the shift was. (2) Cases with ascites: (a) Regardless of the quantity and sound velocity of the ascites, the puncture needle shifted predominantly anteriorly with a displacement error between 7 mm forward and 3 mm backward and with an angular error between 3.1 degrees forward and 1.9 degrees backward when the abdominal wall was muscular, and showed the inverted S‐shaped pattern. In contrast, it shifted predominantly posteriorly with a displacement error between 17 mm backward and 5 mm forward and with an angular error between 3.7 degrees backward and 3.9 degrees forward when the abdominal wall was fatty, and showed the S‐shaped pattern. (b) Regardless of the sound velocity of the ascites fluid and the composition of the abdominal wall, the shift of the puncture needle changed little with differing amounts of ascites. Conclusion It is highly recommended that a liver puncture under US guidance be performed taking into account the pattern of distortion of the puncture needle i