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.