title: Dosimetric comparison of optimization methods for multichannel intracavitary brachytherapy for superficial vaginal tumors.
abstract: OBJECTIVE
  Multichannel vaginal applicators allow treatment of a more conformal volume compared with a single, central vaginal channel. There are several optimization methods available for use with multichannel applicators, but no previous comparison of these has been performed in the treatment of superficial vaginal tumors. Accordingly, a feasibility study was completed to compare inverse planning by simulated annealing (IPSA), dose point optimization (DPO), and graphical optimization for high-dose-rate brachytherapy using a multichannel, intracavitary vaginal cylinder.
  
  
  METHODS
  This comparative study used CT data sets from five patients with superficial vaginal recurrences of endometrial cancer treated with multichannel intracavitary high-dose-rate brachytherapy. Treatment plans were generated using DPO, graphical optimization, surface optimization with IPSA (surf IPSA), and two plans using volume optimization with IPSA. The plans were evaluated for target coverage, conformal index, dose homogeneity index, and dose to organs at risk.
  
  
  RESULTS
  Best target coverage was achieved by volume optimization with IPSA 2 and surf IPSA with mean V100 values of 93.89% and 91.87%, respectively. Doses for the most exposed 2-cm(3) of the bladder (bladder D2cc) was within tolerance for all optimization methods. Rectal D2cc was above tolerance for one DPO plan. All volume optimization with IPSA plans resulted in higher vaginal mucosa doses for all patients. Greatest homogeneity within the target volume was seen with surf IPSA and DPO. Highest conformal indices were seen with surf IPSA and graphical optimization.
  
  
  CONCLUSIONS
  Optimization with surf IPSA was user friendly for the generation of treatment plans and achieved good target coverage, conformity, and homogeneity with acceptable doses to organs at risk.
authors.affiliation: Department of Radiation Oncology, Calvary Mater Newcastle, Newcastle, New South Wales, Australia; Division of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia. Electronic address: carminia.lapuz@petermac.org.
authors.forename: Carminia
authors.initials: C
authors.lastname: Lapuz
authors.forename: Claire
authors.initials: C
authors.lastname: Dempsey
authors.forename: Anne
authors.initials: A
authors.lastname: Capp
authors.forename: Peter C
authors.initials: PC
authors.lastname: O'Brien
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation*; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D005260:Female; D006801:Humans; D008875:Middle Aged; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy; D016896:Treatment Outcome; D014621:Vagina; D014625:Vaginal Neoplasms / Q000532:radiotherapy*
keywords: Brachytherapy; IPSA; Intracavitary; Optimization; Vagina