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Feasibility of MR Only Intra-Operative Trans-Perineal Interstitial Gynecological HDR Brachytherapy

M Paudel1*, A Shaaer2, F Tonolete3, M Smith4,E Leung1, A Ravi1, (1) Sunnybrook Odette Cancer Center, University of Toronto, Toronto, ON, CA, (2) Ryerson University, Toronto, ON, CA, (3) Sunnybrook Odette Cancer Centre,Toronto, ON, CA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Current trans-perineal interstitial gynecological HDR brachytherapy conventionally requires an in-patient stay, adding to the trauma burden on patients. MR-only treatment planning enables an intraoperative out-patient technique that also reduces uncertainty due to registration between MR and CT. However, MR visible markers are required for reliable catheter reconstruction during planning. The purpose of this work is to evaluate our MR-only workflow for intraoperative gynecological trans-perineal interstitial high dose rate (HDR) brachytherapy.


Methods: We designed an in-house MR-line marker containing contrast media that creates positive contrast on T1W MR images. An MR-visible marker plate filled with contrast was also designed which is attached to the trans-perineal template. An MR-only workflow was developed that used both T1W and T2W images. Inter-observer variability of 5 planners to delineate catheter paths, and its dosimetric impact were evaluated as well as the time required. Average treatment planning time and time for a patient without general anesthesia were evaluated, in addition to the average pain scores for the first 3 patients.


Results: The MR-line markers provided stable contrast over time on T1W images. Complementary negative contarst from co-registered T2-3D images aided in delineation of catheters. Catheter reconstruction variation was < 2mm. There was no statistical differences in clinically relevant dosimetric parameters between MR-only and CT/MR plans. The average catheter reconstruction time was 51±10 minutes. The average procedural time for MR-only was 4.32±0.03 hrs vs. 7±2 hrs for the CT/MR workflow. Pain scores for the first 2 patients were 2/10. MR-only workflow successfully enabled a transition to an intraoperative out-patient procedure.


Conclusion: MR catheter and template markers enabled accurate and reproducible delineation of interstitial catheters. The MR-only workflow is dosimetrically equivalent to a CT based approach. An intra-operative outpatient technique is dramatically improving the patient experience during treatment.

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Keywords

Not Applicable / None Entered.

Taxonomy

TH- Brachytherapy: Development (new technology and techniques)

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