title: Effects of prescription depth, cylinder size, treatment length, tip space, and curved end on doses in high-dose-rate vaginal brachytherapy.
abstract: OBJECTIVE
  To determine the effects of the prescription depth, cylinder size, treatment length, tip space, and curved end on high-dose-rate vaginal brachytherapy (HDR-VBT) of endometrial cancer.
  
  
  METHODS
  Treatment plans were prescribed and optimized based on points at the cylinder surface or at 0.5-cm depth. Cylinder sizes ranging from 2 to 4 cm in diameter, and treatment lengths ranging from 3 to 8 cm were used. Dose points in various depths were precisely defined along the cylinder dome. The given dose and dose uniformity to a depth of interest were measured by the mean dose (MD) and standard deviation (SD), respectively, among the dose points belonging to the depth. Dose fall-off beyond the 0.5 cm treatment depth was determined by the ratio of MD at 0.75-cm depth to MD at 0.5-cm depth.
  
  
  RESULTS
  Dose distribution varies significantly with different prescriptions. The surface prescription provides more uniform doses at all depths in the target volume, whereas the 0.5-cm depth prescription creates larger dose variations at the cylinder surface. Dosimetric uncertainty increases significantly (>30%) with shorter tip space. Extreme hot (>150%) and cold spots (<60%) occur if no optimization points were placed at the curved end.
  
  
  CONCLUSIONS
  Instead of prescribing to a depth of 0.5 cm, increasing the dose per fraction and prescribing to the surface with the exact surface points around the cylinder dome appears to be the optimal approach.
authors.affiliation: Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan 48202, USA. sli1@hfhs.org
authors.forename: Shidong
authors.initials: S
authors.lastname: Li
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Aref
authors.forename: Eleanor
authors.initials: E
authors.lastname: Walker
authors.forename: Benjamin
authors.initials: B
authors.lastname: Movsas
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D016889:Endometrial Neoplasms / Q000532:radiotherapy*; D004867:Equipment Design; D005260:Female; D006801:Humans; D011879:Radiotherapy Dosage; D014621:Vagina