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Po‐Thur Eve General‐31: Dosimetric Impact of Planning a Boost within a Boost in Permanent Seed Implants
Author(s) -
Beaulieu L,
Aubin S,
Varfalvy N,
Lessard E,
Pouliot J,
Vigneault E,
Martin AG
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2244658
Subject(s) - prostate , prostate cancer , urethra , medicine , nuclear medicine , urology , cancer
Purpose: To investigate the dosimetric impact on the target volume, boost volume (BV) and urethra of performing limited volume boosts in seed implants. Method and Materials: 35 localized prostate cancer patients with detailed biopsy results were treated with permanent seed implants Personalized plans in which BV corresponding to regions of positive biopsy were generated intra‐operatively based on a simulated annealing inverse planning algorithm. The dose objectives are 144 Gy to the prostate with a 3–4 mm margin, 2/3 (1/3) of the prostate covered by 150% (200%) of the prescription dose (PD), urethra V150 less than 10% and D5 should below 220 Gy. Finally, 100% of BV should receive 150% PD (or 216 Gy). Results: Comparing plans without and with BV show no significant change in the number of seeds, needles, prostate V100 and V200. Prostate V150 (D90) show significant differences increasing from 65% (187Gy) to 70% (191Gy). By forcing the coverage of the BV, the 150% isodose lines (which extend outside the prostate) shift inside of the prostate. Small increase in prostate V150 leads to significant increases of the BV V150 from 79% to 94%. BV do not translate to higher urethra doses. Thus multiple seed reconfigurations inside the prostate are achievable to cover BV. Conclusion: Specific areas within the prostate can be boost to receive 150% of the PD with no impact on the urethra. The plans lead essentially to a rearrangement of the seed positions. Potential radiobiological advantages could be obtained at no cost (procedure or time).