2213 - Utilizing in-Room Cone-Beam CT to Streamline Gynecological Brachytherapy Workflow
Presenter(s)
S. Samanta1, J. S. Cordova2, R. J. Megahed3, and F. Kalantari4; 1Department of Radiation Oncology, UAMS Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR, 2Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, 3Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, 4University of Texas, Dallas, TX
Purpose/Objective(s): Gynecologic brachytherapy demands precise, timely imaging to optimize target delineation and treatment delivery. However, the utilization of standard CT simulation for treatment planning is cumbersome, requiring multiple patient transfers, coordinating brachytherapy with external radiotherapy simulations, and prolonged patient wait times. Recently, in-room cone-beam CT imaging rings have been developed that offer potential advantages for brachytherapy including real-time CT guidance and planning, fewer patient transfers, and abbreviated treatment workflows. In this study, we evaluated the feasibility of using a robotic, in-room CBCT imaging ring (irCT) as an alternative imaging modality for gynecologic brachytherapy treatment planning
Materials/Methods: Patients receiving intracavitary (IC) or interstitial (ISI) brachytherapy for gynecologic malignancies at a single academic institution were scanned using irCT prior to standard CT for brachytherapy planning. irCT image quality was compared to standard CT in terms of image contrast, and organs at risk (OARs), including rectum, bladder, and sigmoid colon were contoured by a radiation oncologist blinded to preimplantation anatomy using only irCT images. The physician's confidence in the accuracy of each contour was recorded on a 1 to 5 scale. The time required to complete each contour as well as the time interval between irCT and CT simulation were also recorded.
Results: Seventeen patients were scanned with irCT following brachytherapy applicator implantation. This included 4 patients treated with vaginal cylinder, 7 treated with tandem and ovoid, 2 treated with ISI alone, and 4 treated with hybrid IC + ISI. Contrast values were comparable for the low contrast slice of a Catphan imaged with both CT and the irCT (0.187 and 0.181, respectively). The average confidence score rated by the contouring physician was 4, 3.9, and 3.7 for rectum, bladder, and sigmoid colon, respectively. Of the OARs completed using irCT, confidence scores of 3 or greater were identified in 94.1%, 76.5%, and 80% of rectal, bladder, and sigmoid contours, respectively. Average time to contour each OAR using irCT was 3 min (range: 2 – 5 min), 4 min (range: 2 – 8 min), and 4 min (range: 2 – 8 min), respectively. The average time between acquisition of irCT and acquisition of CT simulation scan was 2 hrs (range: 1 hr 1 min – 3 hr 9 min).
Conclusion:: irCT demonstrated acceptable image quality and reliable delineation of critical OARs, supporting its feasibility for treatment planning in gynecologic brachytherapy. This approach offers a streamlined workflow by reducing patient transfers and expediting treatment planning without compromising physician confidence. Further studies are warranted to optimize irCT protocols and validate these findings in a larger cohort.