The impact of heartbeat on the left ventricular myocardial and the left anterior descending coronary arterial dosimetry following intensity modulated radiotherapy for left-sided breast cancer

Abstract

Objective To study the impact of heartbeat on the left ventricular myocardial (mLV) and the left anterior descending (LAD) coronary arterial dosimetry following intensity modulated radiotherapy (IMRT) for left-sided breast carcinoma. Methods A total of 15 female patients who received electrocardiography gated 4D-CT scan in inspiratory breathing-holding were enrolled. According to cardiac cycle, 20 time-phase images were reconstructed from 0 to 95% at 5% interval. Then, the mLV and the LAD were delineated respectively and the IMRT plans of the left breast carcinoma were generated based on 0% phase CT images. The volume and dice similarity coefficient (DSC) of the mLV were calculated, and the variation range of the mLV and the LAD dose-volume indexes were compared among different phases. Results The average rate of DSC variation of mLV was eightfold of volume, which reached to 472.07%, and the average change rate of mLV (Dmean) was up to 41.95%. The difference of the mLV′ s volume and DSC was statistically significant between the maximum and minimum(t=-6.585, -28.870, P<0.05), as well as the Dmean, V10, V20, V30 and V40(t=-5.260, -4.084, -3.592, -3.273, -2.566, P<0.05). The average change rate of the LAD′ s Dmean was up to 130.14%. The difference of Dmean, V10, V20, V30 and V40 of LAD was statistically significant between the maximum and minimum(t=-9.758, -8.810, -8.682, -7.853, -6.205, P<0.05). Conclusions The dosimetry impact of heartbeat on mLV and LAD should not be ignored. Key words: Breast carcinoma; Intensity modulated radiotherapy; Left ventricular myocardial; Left anterior descending; Dose evaluation