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Dosimetric Implications of the Organs at Risk in Vaginal Cuff Brachytherapy with Multi-Lumen Cylinder

N Dumitru

N Dumitru1*, M Shojaei1 , S Pella1, 2, 3 , T Leventouri1 , (1) Florida Atlantic University, Boca Raton, Florida, (2) 21st Center Oncology, (3) Advanced Radiation Physic, Boca Raton, Florida


SU-I-GPD-T-37 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To develop a method to evaluate the cumulative dose when using the Multi-Lumen Cylinder applicator in vaginal cuff brachytherapy.

Methods: A retrospective analysis of 30 patients treated in 2015 with the MLC applicator with 3 cm diameter, were considered for this study. All patients received 5 fractions with 5 Gy each delivered twice a week and prescribed to the applicator’s surface for 2/3 of the vaginal length. The CT scans of these patients, taken for treatment plan were separately imported into the treatment planning system and paired with the initial CT scan after completing the contouring and fused using mutual registration. The maximum doses received by the rectum wall, bladder wall and bowels and PTV were analyzed and traced over the five fractions to determine the total dose distribution over the entire prescribed treatment.

Results: No contour of any of the OAR was exactly similar when CT images were fused to each other. Each plan was performed independently and cumulated 2 at a time until all 5 fractions were added to the initial fraction. There is a difference between the doses received by the OARs between treatments and between the points of maximum does. The maximum dose varied between 15% and 25% in rectum wall and bladder neck. The minimum dose varied between 3% and 6% in rectum wall and bladder neck. The average dose varied between 10% and 22% in rectum and bladder. The cumulative treatment does not indicate a total maximum dose exceeding the tolerances for the rectum and bladder.

Conclusion: The variation in volumes of the PTVs and isodoses are minor indicating that the desired area receives the entire prescribed treatment. Rectum wall will not exceed 85% of the prescribed cumulative dose and the bladder neck will not exceed 75% of the prescribed dose.

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