Comparability of CT-based and TRUS-based prostate volumes

Purpose: To compare the prostate volumes defined by transrectal ultrasound (TRUS) versus computed tomographic (CT) scans used for brachytherapy planni ng. Methods and Materials: Ten unselected patients underwent evaluation for pro state brachytherapy with TRUS and CT imaging. Axial prostate contours were obtained at 5-mm intervals in both studies. The CT images were photographed , scanned into a commercial software program, and reprinted from a laser pr inter at 600 dots per inch to provide individual images that were interpret ed independently by the three physician authors (BK, KW, and JB). An effort was made to exclude pelvic floor muscles from the defined prostate contour . Volumes were calculated in cubic centimeters. The prostate volume and max imum dimension in each plane were compared for each imaging modality. Results: The CT-based prostate volumes ranged from 31.1 cc to 48.1 cc. The TRUS-based volumes ranged from 26.6 cc to 46.4 cc. There was close agreemen t between imaging modalities (r = 0.9). The anterior-posterior, lateral, an d craniocaudal prostatic dimensions were similar between modalities. To tes t for consistency between observers, the CT volumes were drawn independentl y by KB, KW, and JB. The prostatic measurements were consistent in all dime nsions between observers. Conclusion: CT scan volumes and measurements correlate well with those obta ined by TRUS, and are appropriate for pre- or postimplant dosimetry. (C) 19 99 Elsevier Science Inc.