Determination of prostate volume with transrectal US for cancer screening. Part II. Accuracy of in vitro and in vivo techniques.

Improved diagnostic information is obtained when prostate volume is correlated with results of prostate-specific antigen assays for early detection of prostate cancer. Three commonly used prostate volume measurement techniques were analyzed: planimetry, prolate ellipse volume calculation (HWL), and an ellipsoid volume measurement technique. For in vitro volume measurement, the declining order of accuracy was planimetry, HWL, and ellipsoid techniques. At the 95% confidence level, inverse prediction produced full-range values for a 40-cm3 model of 5.7, 16.0, 28.8, and 32.8 cm3 for planimetry, HWL, and the two ellipsoid techniques, respectively. Despite its superior accuracy, planimetry is not available on most ultrasound units, increases estimated clinical scanning time, requires additional equipment, and is difficult for a sole operator to perform. Although less accurate than planimetry, HWL is a rapid volume measurement technique that appears to be more accurate than ellipsoid software packages; its universal availability makes it practical for routine clinical use.