Christina Hunter Chapman1, Daniel Polan2, Karen Vineberg2, Shruti Jolly2, Katherine E Maturen3, Kristy K Brock4, Joann I Prisciandaro2. 1. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI. Electronic address: chapmach@med.umich.edu. 2. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI. 3. Department of Radiology, University of Michigan, Ann Arbor, MI. 4. Department of Radiation Oncology, University of Michigan, Ann Arbor, MI; Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX.
Abstract
PURPOSE: To study the dosimetric impact of deformable image registration-based contour propagation on MRI-based cervical cancer brachytherapy planning. METHODS AND MATERIALS: High-risk clinical target volume (HRCTV) and organ-at-risk (OAR) contours were delineated on MR images of 10 patients who underwent ring and tandem brachytherapy. A second set of contours were propagated using a commercially available deformable registration algorithm. "Manual-contour" and "propagated-contour" plans were optimized to achieve a maximum dose to the most minimally exposed 90% of the volume (D90) (%) of 6 Gy/fraction, respecting minimum dose to the most exposed 2cc of the volume (D2cc) OAR constraints of 5.25 Gy and 4.2 Gy/fraction for bladder and rectum/sigmoid (86.5 and 73.4 Gy equivalent dose in 2 Gy fractions [EQD2] for external beam radiotherapy [EBRT] + brachytherapy, respectively). Plans were compared using geometric and dosimetric (total dose [EQD2] EBRT + brachytherapy) parameters. RESULTS: The differences between the manual- and propagated-contour plans with respect to the HRCTV D90 and bladder, rectum, and sigmoid D2cc were not statistically significant (per-fraction basis). For the EBRT + brachytherapy course, the D2cc delivered to the manually contoured OARs by the propagated-contour plans ranging 98-107%, 95-105%, and 92-108% of the dose delivered by the manual-contour plans (max 90.4, 70.3, and 75.4 Gy for the bladder, rectum, and sigmoid, respectively). The HRCTV dose in the propagated-contour plans was 97-103% of the dose in the manual-contour plans (maximum difference 2.92 Gy). Increased bladder filling resulted in increased bladder dose in manual- and propagated-contour plans. CONCLUSIONS: When deformable image registration-propagated contours are used for cervical brachytherapy planning, the HRCTV dose is similar to the dose delivered by manual-contour plans and the doses delivered to the OARs are clinically acceptable, suggesting that our algorithm can replace manual contouring for appropriately selected cases that lack major interfractional anatomical changes. Published by Elsevier Inc.
PURPOSE: To study the dosimetric impact of deformable image registration-based contour propagation on MRI-based cervical cancer brachytherapy planning. METHODS AND MATERIALS: High-risk clinical target volume (HRCTV) and organ-at-risk (OAR) contours were delineated on MR images of 10 patients who underwent ring and tandem brachytherapy. A second set of contours were propagated using a commercially available deformable registration algorithm. "Manual-contour" and "propagated-contour" plans were optimized to achieve a maximum dose to the most minimally exposed 90% of the volume (D90) (%) of 6 Gy/fraction, respecting minimum dose to the most exposed 2cc of the volume (D2cc) OAR constraints of 5.25 Gy and 4.2 Gy/fraction for bladder and rectum/sigmoid (86.5 and 73.4 Gy equivalent dose in 2 Gy fractions [EQD2] for external beam radiotherapy [EBRT] + brachytherapy, respectively). Plans were compared using geometric and dosimetric (total dose [EQD2] EBRT + brachytherapy) parameters. RESULTS: The differences between the manual- and propagated-contour plans with respect to the HRCTV D90 and bladder, rectum, and sigmoid D2cc were not statistically significant (per-fraction basis). For the EBRT + brachytherapy course, the D2cc delivered to the manually contoured OARs by the propagated-contour plans ranging 98-107%, 95-105%, and 92-108% of the dose delivered by the manual-contour plans (max 90.4, 70.3, and 75.4 Gy for the bladder, rectum, and sigmoid, respectively). The HRCTV dose in the propagated-contour plans was 97-103% of the dose in the manual-contour plans (maximum difference 2.92 Gy). Increased bladder filling resulted in increased bladder dose in manual- and propagated-contour plans. CONCLUSIONS: When deformable image registration-propagated contours are used for cervical brachytherapy planning, the HRCTV dose is similar to the dose delivered by manual-contour plans and the doses delivered to the OARs are clinically acceptable, suggesting that our algorithm can replace manual contouring for appropriately selected cases that lack major interfractional anatomical changes. Published by Elsevier Inc.