title: Single versus multichannel applicator in high-dose-rate vaginal brachytherapy optimized by inverse treatment planning.
abstract: OBJECTIVE
  To retrospectively compare the potential dosimetric advantages of a multichannel vaginal applicator vs. a single channel one in intracavitary vaginal high-dose-rate (HDR) brachytherapy after hysterectomy, and evaluate the dosimetric advantage of fractional re-planning.
  
  
  METHODS
  We randomly selected 12 patients with endometrial carcinoma, who received adjuvant vaginal cuff HDR brachytherapy using a multichannel applicator. For each brachytherapy fraction, two inverse treatment plans (for central channel and multichannel loadings) were performed and compared. The advantage of fractional re-planning was also investigated.
  
  
  RESULTS
  Dose-volume-histogram (DVH) analysis showed limited, but statistically significant difference (p = 0.007) regarding clinical-target-volume dose coverage between single and multichannel approaches. For the organs-at-risk rectum and bladder, the use of multichannel applicator demonstrated a noticeable dose reduction, when compared to single channel, but statistically significant for rectum only (p = 0.0001). For D2cc of rectum, an average fractional dose of 6.1 ± 0.7 Gy resulted for single channel vs. 5.1 ± 0.6 Gy for multichannel. For D2cc of bladder, an average fractional dose of 5 ± 0.9 Gy occurred for single channel vs. 4.9 ± 0.8 Gy for multichannel. The dosimetric benefit of fractional re-planning was demonstrated: DVH analysis showed large, but not statistically significant differences between first fraction plan and fractional re-planning, due to large inter-fraction variations for rectum and bladder positioning and filling.
  
  
  CONCLUSIONS
  Vaginal HDR brachytherapy using a multichannel vaginal applicator and inverse planning provides dosimetric advantages over single channel cylinder, by reducing the dose to organs at risk without compromising the target volume coverage, but at the expense of an increased vaginal mucosa dose. Due to large inter-fraction dose variations, we recommend individual fraction treatment plan optimization.
authors.affiliation: Department of Radiology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia.
authors.forename: Yasir A
authors.initials: YA
authors.lastname: Bahadur
authors.affiliation: Department of Bio-Medical Physics, King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia.
authors.forename: Camelia
authors.initials: C
authors.lastname: Constantinescu
authors.affiliation: Department of Oncology, King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia ; Department of Radiation Oncology, National Cancer Institute, Cairo University, Egypt.
authors.forename: Ashraf H
authors.initials: AH
authors.lastname: Hassouna
authors.affiliation: Department of Radiology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia ; Department of Radiation Oncology, National Cancer Institute, Cairo University, Egypt.
authors.forename: Maha M
authors.initials: MM
authors.lastname: Eltaher
authors.affiliation: Department of Bio-Medical Physics, King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia.
authors.forename: Noor M
authors.initials: NM
authors.lastname: Ghassal
authors.affiliation: Department of Radiology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia ; Department of Radiation Oncology, National Cancer Institute, Cairo University, Egypt.
authors.forename: Nesreen A
authors.initials: NA
authors.lastname: Awad
keywords: endometrial cancer; inverse planning; multichannel applicator; vaginal brachytherapy
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