Estimated radiation dose to cardiac substructures and their corresponding planning risk volumes / 中国肿瘤临床

ABSTRACT

Objective:To investigate the role of planning risk volume (PRV) in estimating the radiation dose for various cardiac substructures (CS). Methods:The CS of 23 patients with left-sided breast cancer who underwent postoperative intensity-modulated ra-diotherapy (IMRT) was delineated. PRV was expanded from CS with an additional margin determined by the mean amplitude of cardi-ac motion. Two IMRT plans were designed. The volume, mean dose, maximal dose (D2%), and standard deviation of CS and its PRV were calculated. Results:In comparison to the volume of CS, the PRV of the heart, specifically the left ventricle, increased by 50%to 80%, whereas the PRV of the main coronary arteries and sub-branches increased by 18.7 times to 42.6 times. In the two IMRT plans, the mean dose to the heart, anterior myocardial territory, anterior descending artery, and their corresponding PRVs ranged from 9.4 Gy to 11.4 Gy, 11.0 Gy to 17.5 Gy, and 22.6 Gy to 27.8 Gy, respectively. The D2%to CS and its PRV was 24.5 Gy to 36.2 Gy, 28.2 Gy to 38.8Gy, and 36 Gy to 45 Gy. The mean dose and D2%to the coronary arteries, including both left and right main coronary arteries, right marginal artery, and left circumflex artery, were 8.6 Gy to 14.9 Gy and 12.5 Gy to 23.7 Gy, respectively. The difference of the mean dose and D2%to CS and its corresponding PRVs was 2.5%to 12.5%and 8.0%to 43.1%, respectively. Compared with the stan-dard deviation of the radiation dose to CS, majority of the standard deviation to PRVs increased significantly. Conclusion:The radia-tion dose difference between CS and its corresponding PRVs is<12%.