A NEW PROSTATE VOLUME CALCULATION METHOD: NON-ELIPSOIDAL MODEL BASED ON THE SAGITTAL CONTOUR.

A. Kimura, M. Yoshida, I. Saito

Department of Urology, Tokyo Kyosai Hospital, Japan

A common prostatic volume calculation method; height times width times length times pi/6 has three problems; First, reproducibility is poor, since the prostatic apex is frequently poorly visualized. Second, errors increase as the angle between the height and the length moves out of perpendicular. Third, there is a risk of increasing false positives of PSA density in prostatic hypertrophy because of its tendency to underestimate the volume in prostatic hypertrophy. These problems arise because only 3 diameters are measured in this method, which means only 6 points of the prostatic contours are used for the calculation. Recently, we proposed a new method of calculation that we termed "biplane planimetry". By this new method, the prostatic contours of both cross- and sagittal sections are traced. Based on the cross and sagittal contours, a non-ellipsoidal model is created. The model is composed of sequentially arranged copies of the cross-section, which are reduced so as to fit the sagittal contour. Using full information obtained from biplane sections, the new method is resistant to the errors mentioned above.

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