title: Customized vaginal vault brachytherapy with computed tomography imaging-derived applicator prototyping.
abstract: OBJECTIVE
  A novel customized vaginal brachytherapy mould technique has been developed for clinical use. This image-guided technique provides a brachytherapy applicator solution for irregular vaginal vault configuration and/or a wide vaginal apex relative to the vaginal introitus that would be sub-optimally treated with standard cylinders.
  
  
  METHODS
  The customized vaginal applicator is generated by the following process: CT images are obtained with contrast-soaked vaginal packing in situ to highlight unique anatomical detail. A 3-dimensional digital model is developed from the images and subsequently converted into a custom applicator with the use of stereolithography, which is an additive manufacturing technique whereby layers 50-100 μm thick of resin are deposited and polymerized using a laser to create intricate 3-dimensional objects. The density of the applicator and the dose delivered using the custom applicator were both measured to ensure accurate dosimetry.
  
  
  RESULTS
  The CT-based densities of a clinical vaginal cylinder and the cylinder generated using stereolithography were 1.29 ± 0.06 g/cm(3) vs 1.28 ± 0.01 g/cm(3), respectively. The mean measured dose from a representative stereolithographed applicator normalized to dose measured for a single plastic catheter was 99.8 ± 4.2%. In patient dosimetric results indicate improved coverage of the lateral aspect of vaginal vault with the custom cylinder relative to the standard cylinder; 700 cGy vs 328 cGy, respectively, at a representative lateral vaginal dose point, while simultaneously achieving relatively narrow dose distribution in the anterior/posterior direction.
  
  
  CONCLUSIONS
  Stereolithographic applicator production was available within a clinically acceptable timeframe, and its clinical feasibility and utility has been demonstrated.
authors: Department of Radiation Oncology, Cross Cancer Institute, Edmonton, AB, Canada.
authors: Ericka
authors: E
authors: Wiebe
authors: Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors: Harry
authors: H
authors: Easton
authors: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors: Gillian
authors: G
authors: Thomas
authors: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors: Lisa
authors: L
authors: Barbera
authors: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors: Laura
authors: L
authors: D'Alimonte
authors: Department of Medical Physics, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada. Electronic address: Ananth.Ravi@sunnybrook.ca.
authors: Ananth
authors: A
authors: Ravi
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods*; D016889:Endometrial Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D014621:Vagina / Q000033:anatomy & histology / Q000000981:diagnostic imaging
keywords: Custom applicator; Image-derived prototyping; Stereolithography; Vaginal brachytherapy