title: Calcifications in low-dose rate prostate seed brachytherapy treatment: post-planning dosimetry and predictive factors.
abstract: OBJECTIVE
  The brachytherapy dose algorithm of the American Association of Physicists in Medicine Task Group (TG) Report 43 overrides all tissue materials with water. In reality, dose discrepancies will occur around tissue calcifications. This study investigates these perturbations in low dose rate prostate brachytherapy dosimetry.
  
  
  METHODS
  43 cancer patients with prostatic calcifications are identified. Geant4 Monte Carlo (MC) simulations are made with materials assigned based on TG186 recommendations. Five dose calculation scenarios are presented: MC in water (MCW), MCW with calcifications, (MCCA), MCCA with seeds (MCCASEED) and full tissue definition and seeds with dose to medium in medium (FMC) and dose to water in medium (FMC-Dw,m).
  
  
  RESULTS
  The mean FMC prostate D90 (V100) difference relative to TG43 is -6.4% (range [-1.8, -14.1]) (-2.6% [-0.3, -6.7]). For MCCA we obtained -3.9% [-1.0, -8.7] (-1.5% [-0.2, -4.1]). The mean urethra D10 difference is -4.5% [-1.3, -9.9] for FMC, -2.4% [-0.7, -5.1] with MCCA. FMC-Dw,m D90 has a -0.45% smaller dose difference than FMC on average. The calcification/prostate volume ratio is a good predictor of dose perturbation (R(2)=0.75).
  
  
  CONCLUSIONS
  Based on these results, calcifications alter the dose coverage and may have severe dose perturbation that requires recalculation.
authors.affiliation: Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada. Electronic address: charles-antoine.collins-fekete.1@ulaval.ca.
authors.forename: Charles-Antoine
authors.initials: CA
authors.lastname: Collins Fekete
authors.affiliation: Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada. Electronic address: mathieu.plamondon.2@ulaval.ca.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Plamondon
authors.affiliation: Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada. Electronic address: andre-guy.martin@mail.chuq.qc.ca.
authors.forename: André-Guy
authors.initials: AG
authors.lastname: Martin
authors.affiliation: Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada. Electronic address: Eric.Vigneault@mail.chuq.qc.ca.
authors.forename: Éric
authors.initials: É
authors.lastname: Vigneault
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW - School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht, The Netherlands; Medical Physics Unit, McGill University Health Centre and Department of Oncology, McGill University, Montréal, Québec, Canada. Electronic address: Frank.Verhaegen@maastro.nl.
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
authors.affiliation: Département de physique, de génie physique et d'optique et Centre de recherche sur le cancer, Université Laval, Québec, Canada; Département de radio-oncologie et CRCHU de Québec, CHU de Québec, Québec, Canada. Electronic address: Luc.Beaulieu@phy.ulaval.ca.
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D002114:Calcinosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D015331:Cohort Studies; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D009010:Monte Carlo Method; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies
keywords: Calcifications; Low-dose rate brachytherapy; Monte Carlo; Tissue heterogeneities