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Using CT/MR Compatible Multichannel Vaginal Cylinder for Vaginal Cuff Treatment Can Reduce Dose to the Bladder and Rectum

M Rybak

M Rybak1*, L Huang2, H Blair1, P Xia2, (1) Cleveland Clinic Foundation, Mayfield, OH, (2) Cleveland Clinic Foundation, Cleveland, OH

WE-A-108-10 Wednesday 8:00AM - 9:55AM Room: 108

Purpose: To compare treatment plans using CT/MR multichannel vaginal cylinder (MC) with traditional plans using a single channel cylinder (SC) for vaginal cuff HDR treatment.

Methods: Seven patients with 21 clinical treatment sessions were planned and treated with 6-9 multiple channels. On the CT scan of each session, the bladder and rectum were manually contoured and the planning treatment volume (PTV) was defined as 0.5cm expansion from the cylinder surface with 4cm treatment length. The MC applicators were identified based on a reconstructed model from the treatment planning system. An inverse planning optimization (IPSA) was used for MC plans to achieve the desired objectives. For comparison, a series of corresponding SC plans were generated to achieve a similar PTV coverage as MC plans. The treatment goals were to deliver at least 95% prescription dose (Rx) to 98% (D98%) of the PTV volume for both MC and SC plans, and to limit the maximum dose (D0.1cc) and the maximum dose of 2cc volumes (D2cc) for the rectum and bladder (OARs). Descriptive statistic was used for analysis.

Results: When normalized to 95% Rx, D98% for the PTV was 97.7±1.8% and 101±2.3% for MC and SC plans, respectively. For the bladder, the average D0.1cc was significantly lower in MC plans, 88.2±11.8% versus 99.2±13.4% (P <0.05) in SC plans. The average D2cc was also significantly lower in MC plans, 67.5±12.7% versus 75.6±12.4% in SC plans. For the rectum, the average D0.1cc was significantly lower in MC plans, 99.3±3.6% versus 114.0±13.0% (P<0.05) for SC plans. The average D2cc of the rectum was 80.9±5.7% and 90.2±8.5% (p<0.05), respectively. Treatment planning time for MC plans was comparable to that of SC plans.

Conclusions: Compared to the traditional SC plans, MC plans significantly reduce the doses to the OARs with adequate dose coverage to the PTVs.

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