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Rigid Registration Image Fusion for Volumetric Dose Evaluation of Gynecological Patients Treated with EBRT and HDR Brachytherapy

J Cantley

J Cantley1*, D Albani2 , R Ellis2 , T Sherertz2 , K Herrmann3 , T Podder2 , (1) Case Western Reserve University, Cleveland, OH,(2) Seidman Cancer Center University Hospitals Case Medical Center, Cleveland, OH, (3) University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, OH


SU-E-T-680 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To evaluate the effectiveness of rigid registration image fusion and dose composites in HDR brachytherapy patients who have previously undergone EBRT.

Methods: Data was collected from five randomly selected patients with cervical cancer who were treated with both EBRT (50.4Gy) and HDR brachytherapy (30Gy in 5 fractions) using a split-ring and tandem applicator. Planning CTs, contours, and dose profiles were exported from the Pinnacle and Oncentra treatment planning systems into the MIM 6.0 software tool for image fusion and dose composite generation. The planning CT for the third course of HDR brachytherapy was used as the primary image for each patient. Rigid registration image fusion was performed in two different ways: the first method used bony anatomy for initial matching and then fine tuned using surrounding OARs; the second method used the HDR applicator for matching. For EBRT CTs in which no applicator was present, images were fused using the uterus. Treatment doses were transferred to the primary image and then EQD2-BED calculations were performed using the linear quadratic model in MIM software. Results from MIM calculations were compared with the hand calculations based upon the ABS EQD2 worksheet used clinically to estimate aggregated dose to the bladder, rectum, sigmoid, and bowel.

Results: Results revealed differences in the 2cc dose between the calculation and dose composite methods for the sigmoid (mean±SD) as 7.96%±5.11% and 6.49%±3.02% for the OAR and applicator methods, respectively; bladder as 5.77%±3.28% for applicator method. No statistically significant differences (p-value >0.05) were observed for the bladder using the OAR method, or for the rectum or bowel using either method.

Conclusion: Early results suggest that current methods may be overestimating dose to the bladder while underestimating dose to sigmoid. However, more patient data needs to be collected to determine the significance of the findings and clinical implications.

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