A simple technique for determining accurate urethral dosimetry after seed brachytherapy for prostate cancer

Purpose To describe a simple technique to define the anatomically accurate urethral location in the postimplant CT scans, after permanent prostate seed implants, without the discomfort associated with use of a catheter. Methods and materials We perform preplanned, preloaded transperineal transrectal ultrasound-guided permanent seed implants for men with low-risk prostate cancer. In postimplant CT scans performed 4 weeks after the procedure we previously used a catheter to identify the urethra. We now use retrograde injection of contrast, followed by the retrograde injection of a mixture of contrast and aerated sterile lubricant jelly to opacify the urethra on our CT scans. Results This technique is economical, simple, and more comfortable than the use of a catheter. It reliably allows identification of the urethra for the purposes of deriving dose–volume histogram statistics, for quality control. It provides a reference for more accurate determination of the prostate apex. Conclusions We recommend this technique to those performing prostate seed implants wishing to most accurately determine the precise urethral dose parameters in delayed postimplant CT scans, without the need for the discomfort associated with a urethral catheter.