Application of an automatic segmentation method for evaluating cardiac structure doses received by breast radiotherapy patients

• Published in: Physics and imaging in radiation oncology 2021-07, Vol.19, p.138-144
• Main Authors: Jung, Jae Won, Mille, Matthew M., Ky, Bonnie, Kenworthy, Walter, Lee, Choonik, Yeom, Yeon Soo, Kwag, Aaron, Bosch, Walter, MacDonald, Shannon, Cahlon, Oren, Bekelman, Justin E., Lee, Choonsik
• Format: Article
• Language: English
• Subjects: Automatic segmentation; Breast cancer; Cardiac structures; Late effects; Original; Radiotherapy
• ISSN: 2405-6316; 2405-6316
• DOI: 10.1016/j.phro.2021.08.005

•Atlas-based method for contouring heart substructures on breast radiotherapy CT.•Excellent agreement between automatic and manual contours for most patients.•Dice similarity coefficient for LAD was low (0.06) because a narrow, long structure.•Doses derived from automatic and manual contours agree within observer variability.•For left breast treatment, right ventricle and LAD dose most senstive to contour shift. Quantifying radiation dose to cardiac substructures is important for research on the etiology and prevention of complications following radiotherapy; however, segmentation of substructures is challenging. In this study we demonstrate the application of our atlas-based automatic segmentation method to breast cancer radiotherapy plans for generating radiation doses in support of late effects research. We applied our segmentation method to contour heart substructures on the computed tomography (CT) images of 70 breast cancer patients who received external photon radiotherapy. Two cardiologists provided manual segmentation of the whole heart (WH), left/right atria, left/right ventricles, and left anterior descending artery (LAD). The automatically contours were compared with manual delineations to evaluate similarity in terms of geometry and dose. The mean Dice similarity coefficient between manual and automatic segmentations was 0.96 for the WH, 0.65 to 0.82 for the atria and ventricles, and 0.06 for the LAD. The mean average surface distance was 1.2 mm for the WH, 3.4 to 4.1 mm for the atria and ventricles, and 6.4 mm for the LAD. We found the dose to the cardiac substructures based on our automatic segmentation agrees with manual segmentation within expected observer variability. For left breast patients, the mean absolute difference in mean dose was 0.1 Gy for the WH, 0.2 to 0.7 Gy for the atria and ventricles, and 1.8 Gy for the LAD. For right breast patients, these values were 0.0 Gy, 0.1 to 0.4 Gy, and 0.4 Gy, respectively. Our automatic segmentation method will facilitate the development of radiotherapy prescriptive criteria for mitigating cardiovascular complications.