Comparison of Urethral Diameters for Calculating the Urethral Dose After Permanent Prostate Brachytherapy

Overview

Journal Radiat Med

Specialties Nuclear Medicine
Oncology
Radiology

Date 2007 Aug 21

PMID 17705002

Authors

Osamu Tanaka

Shinya Hayashi

Masayuki Matsuo

Masahiro Nakano

Yasuaki Kubota

Sunaho Maeda

Kazuhiro Ohtakara

Takashi Deguchi

Hiroaki Hoshi

Affiliations

Soon will be listed here.

Abstract

Purpose: No studies have yet evaluated the effects of a dosimetric analysis for different urethral volumes. We therefore evaluated the effects of a dosimetric analysis to determine the different urethral volumes.

Methods: This study was based on computed tomography/magnetic resonance imaging (CT/MRI) combined findings in 30 patients who had undergone prostate brachytherapy. Postimplant CT/MRI scans were performed 30 days after the implant. The urethra was contoured based on its diameter (8, 6, 4, 2, and 0 mm). The total urethral volume-in cubic centimeters [UrV150/200(cc)] and percent (UrV150%/200%), of the urethra receiving 150% or 200% of the prescribed dose-and the doses (UrD90/30/5) in Grays to 90%, 30%, and 5% of the urethral volume were measured based on the urethral diameters.

Results: The UrV150(cc) and UrD30 were statistically different between the of 8-, 6-, 4-, 2-, and 0-mm diameters, whereas the UrD5 was statistically different only between the 8-, 6-, and 4-mm diameters. Especially for UrD5, there was an approximately 40-Gy difference between the mean values for the 8- and 0-mm diameters.

Conclusion: We recommend that the urethra should be contoured as a 4- to 6-mm diameter circle or one side of a triangle of 5-7 mm. By standardizing the urethral diameter, the urethral dose will be less affected by the total urethral volume.

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