Timing of postseed imaging influences rectal dose-volume parameters for cesium-131 prostate seed implants

Ravindra Yaparpalvi, Raquibul Hannan, Evan Landau, Norman Kahan, William Bodner, Hsiang Chi Kuo, Lloyd Minsky, Keyur J. Mehta, Madhur K. Garg, Shalom Kalnicki, Chandan Guha

Research output: Contribution to journalArticlepeer-review


Purpose: To study the influence of timing of postseed implant imaging on rectal dose-volume parameters for cesium-131 (131Cs) seed prostate implants. Methods and Materials: Fifteen patients were treated in our institution with combination 131Cs brachytherapy followed by pelvic external beam radiation therapy for intermediate to high-risk prostate cancers. For all patients, CT scans were scheduled at 7 days (CT7) and again at 2 months for external beam radiation therapy simulation purpose (CT60) postseed implantation. Comprehensive postseed implant dosimetry was performed for both CT7 and CT60 scans. In each case, dose-volume histogram parameters, rectal separation (the distance between the center of posterior most seed and most anterior rectal wall), and posterior row activity (the total activity implanted within 2-4mm anterior to the posterior wall of the prostate) data were collected. The absolute rectal volumes receiving 100% and 110% prescription dose were also collected. Results: Rectal dose correlated strongly with rectal separation (p<0.001). The mean change in rectal separation between CT7 and CT60 scans was 1.1 (±1.7) mm, and the corresponding change in 0.1-cc rectal dose was 18 (±26.5) Gy. Posterior row activity did not correlate with rectal dose (p=0.51). The mean volume of rectum that receives between 100% and 110% of the prescription dose (RV100 and RV110) increased twofold, between CT7 and CT60 evaluations (0.03 [±0.06] cc vs. 0.07 (±0.05) cc, respectively, p=0.06). Conclusions: Our study has demonstrated that rectal doses after 131Cs seed implants are influenced by the timing of postseed imaging. This may be a consequence of prostatic and periprostatic edema resolution.

Original languageEnglish (US)
Pages (from-to)489-494
Number of pages6
Issue number6
StatePublished - Nov 2012


  • Cs
  • Imaging
  • Post-seed
  • Rectum

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging


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