Establishing cutoff values for a quality assurance test using an ultrasound phantom in screening ultrasound examinations for hepatocellular carcinoma: An initial report of a nationwide survey in Korea

Objectives-The purpose of this study was to evaluate the results of ultrasound (US) device testing using a US phantom and to determine cutoff values for phantom quality assurance tests in US examinations for the screening of hepatocellular carcinoma in Korea. Methods-Ultrasound phantom images were acquired from the general hospitals in Korea that participated in the National Cancer Screening Program for hepatocellular carcinoma. Ultrasound images of the phantom were acquired with a 3.0- to 5.0-MHz convex transducer and evaluated in terms of the dead zone, vertical and horizontal measurement, axial and lateral resolution, sensitivity, and gray scale/dynamic range. Appropriate cutoff values were determined to guarantee minimal qualifications for the performance of the US scanners. Results-Three hundred fifty-seven US scanners were tested using the following cutoff values: less than 2 mm for the dead zone, 5% discrepancy in the vertical measurement, 7.5% discrepancy in the horizontal measurement, all 11 identifiable line targets for axial and lateral resolution, more than 14 cm for sensitivity, and more than 4 cylindrical structures for gray scale/dynamic range. With these criteria, 283 US scanners (79.3%) passed the tests. The most common cause of disqualification was the dynamic range/gray scale. No statistical difference was observed in the disqualification rate between 3 groups based on different years of manufacture. Conclusions-Through this study, we have defined cutoff values for phantom images acquired with US scanners. These will be used in performing screening US examinations for hepatocellular carcinoma in Korea.