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TH‐AB‐BRA‐04: Dosimetric Evaluation of MR‐Guided HDR Brachytherapy Planning for Cervical Cancer
Author(s) -
Kamio Y,
Barkati M,
BeliveauNadeau D
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4958055
Subject(s) - contouring , brachytherapy , nuclear medicine , radiation treatment planning , medicine , rectum , computer science , radiology , radiation therapy , surgery , computer graphics (images)
Purpose: To perform a retrospective study on 16 patients that had both CT and T2‐weighted MR scans done at first fraction using the Utrecht CT/MR applicator (Elekta Brachytherapy) in order to evaluate uncertainties associated with an MR‐only planning workflow. Methods: MR‐workflow uncertainties were classified in three categories: reconstruction, registration and contouring. A systematic comparison of the CT and MR contouring, manual reconstruction and optimization process was performed to evaluate the impact of these uncertainties on the recommended GEC ESTRO DVH parameters: D90% and V100% for HR‐CTV as well as D2cc for bladder, rectum, sigmoid colon and small bowel. This comparison was done using the following four steps: 1. Catheter reconstruction done on MR images with original CT‐plan contours and dwell times. 2. OAR contours adjusted on MR images with original CT‐plan reconstruction and dwell times. 3. Both reconstruction and contours done on MR images with original CT‐plan dwell times. 4. Entire MR‐based workflow optimized dwell times reimported to the original CT‐plan. Results: The MR‐based reconstruction process showed average D2cc deviations of 4.5 ± 3.0%, 1.5 ± 2.0%, 2.5 ± 2.0% and 2.0 ± 1.0% for the bladder, rectum, sigmoid colon and small bowels respectively with a maximum of 10%, 6%, 6% and 4%. The HR‐CTV's D90% and V100% average deviations was found to be 4.0 ± 3.0%, and 2.0 ± 2.0% respectively with a maximum of 10% and 6%. Adjusting contours on MR‐images was found to have a similar impact. Finally, the optimized MR‐based workflow dwell times were found to still give acceptable plans when re‐imported to the original CT‐plan which validated the entire workflow. Conclusion: This work illustrates a systematic validation method for centers wanting to move towards an MR‐only workflow. This work will be expanded to model based reconstruction, PD‐weighted images and other types of applicators.