Computer-assisted analysis of transrectal ultrasound images.

We have developed a microcomputer based system with an application specific software package which permits the direct digitization and analysis of transrectal ultrasound (TRUS) images. The system is highly flexible and enables access to a wide range of image analysis tools through relatively simple software modifications, which cannot be implemented using a standard ultrasound instrument. We have demonstrated the capability of the system by an analysis of a number of morphometric parameters and by a correlation of these measurements with the presence of prostatic cancer. We found that the measurement of the ratio of the anterior-posterior axis to transverse axis and the presumed circular area ratio (PCAR) were significant predictors of prostatic cancer. The sensitivity of the PCAR measurement was 93%, the specificity was 50%, the positive predictive value was 57%, and the negative predictive value was 91%. The high negative predictive values of these parameters may provide objective criteria to allow for selective biopsy of patients. This system provides researchers with an efficient, economical, and flexible method to aid in the analysis of TRUS images in a quantitative manner.