title: Dosimetric comparison of 3-dimensional planning techniques using an intravaginal multichannel balloon applicator for high-dose-rate gynecologic brachytherapy.
abstract: OBJECTIVE
  To study the dosimetric differences of various channel combinations of the Capri vaginal applicator.
  
  
  METHODS
  The Capri consists of a single central channel (R1), an inner array of 6 channels (R2), and an outer array of 6 channels (R3). Three-dimensional plans were simulated for 6 channel arrangements (R1, R2, R12, R13, R23, and R123). Treatment plans were optimized to the applicator surface or 5-mm depth while minimizing dose to organs at risk (OARs: bladder, rectum, sigmoid, and urethra). The clinical target volume (CTV) was defined as a 5-mm circumferential shell extending 4 cm in length around the applicator. Clinical target volume coverage (Dmean, D90, V100, and V150) and OAR doses (D0.1 cm3, D1 cm3, D2 cm3, and Dmean) were compared. A comparison between the Capri (R123) and a conventional single-channel applicator was also done. Statistical significance (P value<.05) was evaluated with a 2-tailed t test.
  
  
  RESULTS
  When prescribing to 5-mm depth, CTV coverage using all 13 channels (R123) versus a single channel (R1) was similar; however, when prescribing to the surface there were differences (P<.0001) in all CTV metrics except for the V150. The R1 plans had higher doses to all OARs compared with R123 plans (P<.007). Doses to OARs were not significantly different between R23 and R123 plans (P=.05-.95), and CTV coverage differences were on the order of 1%. Capri R123 plans provided slightly lower CTV D90 and Dmean but equivalent OAR doses with smaller standard deviations compared with conventional cylinder plans for both prescriptions.
  
  
  CONCLUSIONS
  The Capri multichannel applicator provides equivalent target coverage at 5-mm depth, with significantly reduced dose to OARs relative to using a single channel. Optimal plans can be achieved using R12 (lowest V150) or R123 or R23 (lowest OAR doses).
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California. Electronic address: spark@mednet.ucla.edu.
authors.forename: Sang-June
authors.initials: SJ
authors.lastname: Park
authors.forename: Melody
authors.initials: M
authors.lastname: Chung
authors.forename: D Jeffrey
authors.initials: DJ
authors.lastname: Demanes
authors.forename: Robyn
authors.initials: R
authors.lastname: Banerjee
authors.forename: Michael
authors.initials: M
authors.lastname: Steinberg
authors.forename: Mitchell
authors.initials: M
authors.lastname: Kamrava
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D012809:Colon, Sigmoid / Q000528:radiation effects; D016889:Endometrial Neoplasms / Q000532:radiotherapy; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D009929:Organ Size; D058958:Organs at Risk / Q000000981:diagnostic imaging*; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D014521:Urethra / Q000000981:diagnostic imaging; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy; D014621:Vagina / Q000033:anatomy & histology