title: Multi-parametric MRI-guided focal tumor boost using HDR prostate brachytherapy: a feasibility study.
abstract: OBJECTIVE
  This study investigates the feasibility of delivering focal boost dose to tumor regions, identified with multi-parametric MRI, in high-dose-rate prostate brachytherapy.
  
  
  METHODS
  T2-weighted, diffusion-weighted, and dynamic-contrast-enhanced MRI were acquired the day before treatment and analyzed retrospectively for 15 patients. Twelve patients had hormone therapy before the MRI scan. The tumor was delineated on MRI by a radiologist and registered to treatment planning transrectal ultrasound images. A margin based on analysis of delineation and registration uncertainties was applied to create a focal boost planning target volume (F-PTV). Delivered treatment plans were compared with focal boost plans optimized to increase F-PTV dose as much as allowed by urethral and rectal dose constraints.
  
  
  RESULTS
  Tumors were delineated in all patients with volumes 0.4-23.0cc. The margin for tumor delineation and image registration uncertainties was estimated to be 4.5 mm. For F-PTV, the focal boost treatment plans increased median D90 from 17.6 to 20.9 Gy and median V150 from 27.3% to 75.9%.
  
  
  CONCLUSIONS
  MRI-guided high-dose-rate prostate brachytherapy focal tumor boost is feasible-tumor regions can be identified even after hormone therapy, and focal boost dose can be delivered without violating urethral and rectal dose constraints.
authors.affiliation: Medical Physics, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust; Division of Medical Physics, University of Leeds. Electronic address: Joshua.Mason@leedsth.nhs.uk.
authors.forename: Josh
authors.initials: J
authors.lastname: Mason
authors.affiliation: Medical Physics, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust.
authors.forename: Bashar
authors.initials: B
authors.lastname: Al-Qaisieh
authors.affiliation: Medical Physics, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust.
authors.forename: Peter
authors.initials: P
authors.lastname: Bownes
authors.affiliation: Medical Physics, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust.
authors.forename: Dan
authors.initials: D
authors.lastname: Wilson
authors.affiliation: Division of Medical Physics, University of Leeds.
authors.forename: David L
authors.initials: DL
authors.lastname: Buckley
authors.affiliation: Division of Medical Physics, University of Leeds; Institute of Medical Physics, School of Physics, University of Sydney, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Thwaites
authors.affiliation: Radiology, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust.
authors.forename: Brendan
authors.initials: B
authors.lastname: Carey
authors.affiliation: Clinical Oncology, St James's Institute of Oncology, Leeds Teaching Hospitals NHS Trust.
authors.forename: Ann
authors.initials: A
authors.lastname: Henry
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D012189:Retrospective Studies; D014521:Urethra
keywords: Focal boost; Multi-parametric MRI; Prostate brachytherapy