Evaluation of prostate volume by transrectal ultrasonography for use in a brachytherapy program

Objectives. To evaluate two methods of measuring the prostate volume using transrectal ultrasonography. The measurements were performed in vivo at preplanning and again preoperatively in connection with brachytherapy. The accurate measurement of the prostate volume is important in a brachytherapy program for treatment planning. Methods. A total of 43 patients with biopsy-proven prostate cancer underwent prospective determination of the prostate volume, by one physician, using transrectal ultrasonography. Volume calculations were made at the preplanning and preoperative settings, both by a hand-held rectal probe using the prolate ellipsoid formula and by a mounted probe in a stepping device using the planimetric method. Results. The coefficient of variation between the preplanning and preoperative prostate volumes with the probe holder was less than 3% compared with the hand-held probe, which was greater than 10%. The difference between the median values at the preplanning and preoperative settings by serial planimetry was 2.5 cm(3) (range 0.2 to 9.4). The difference in the median volumes between the preplanning and preoperative ellipsoid calculations was 6.7 cm(3) (range 0.3 to 38.7). The difference between the median values with the ellipsoid volume was significant (P < 0.001). The Pearson correlation coefficient for all values using the planimetric method was 0.92 versus 0.58 for the ellipsoid method. The correlation coefficient was significantly greater for the planimetric method (P < 0.001). Conclusions. On the basis of these data, planimetric prostate volume determination, by a single ultrasonographer, is an accurate and reproducible method with applicability to a brachytherapy program. (C) 2001, Elsevier Science Inc.