Evaluation of the cardiac subvolume dose and myocardial perfusion in left breast cancer patients with postoperative radiotherapy: a prospective study

Figures

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  Figure 1. The flow diagram of the study. SPECT: single photon emission computed tomography. CT computed tomography. MPI myocardial perfusion imaging. AHA American heart association. SSS summed stress scores. SRS summed rest scores. SDS summed difference scores. LV left ventricle.

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  Figure 2. Demonstrations of myocardial perfusion analytic display of the study. (A) MPI SPECT multislice display of conventional qualitative interpretation, under post-stress (upper panel) and redistribution (lower panel) in the horizontal axis, respectively. The arrow shows the stress-induced perfusion defect with revere at apex. (B) Four rings display. LV myocardium was divided into four rings, namely basal, middle, apical, and apical cap. (C) Three territories display based on major coronary arteries supply. (D) Twenty segments display according to AHA’s 20-segment model. MPI myocardial perfusion imaging. SPECT single photon emission computed tomography. LV left ventricle. AHA American heart association.

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  Figure 3. Schematic diagram of isodose curve in radiation therapy plan of a left breast cancer patient. The PTV and heart are depicted in red and blue colors, respectively. The isodose curve shows relative low but inevitable heart radiation involvement (arrow). PTV planning target volume.

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  Figure 4. Workflow of generating the subvolume doses of LV: (A) To fuse SPECT MPI image with CT simulation image, with the LV as the reference for registration; (B) to rotate the images to SA view, VLA view, and HLA view, to fit the conventional MPI axes ; (C) To divided the LV into 20 segments in accordance with AHA’s 20-segment model; and (D) To input the dose distribution of radiotherapy plan to obtain the subvolume doses of the 20 segments separately. LV left ventricle. SA short axis. VLA vertical long axis. HLA horizontal long axis.

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  Figure 5. The subvolume dose distribution of 20 segments in the bull's eye plot display. (A) Using gradient rainbow color scale to show the mean subvolume dose distribution in NPD group (left), and non-NPD group (right), respectively. (B) Ischemia segments distribution of the NPD group. The numbers represents the average subvolume dose (Gy) of each segment. The orange areas display the presence of the new perfusion segments, while the green areas show the segments without perfusion decline. NPD new perfusion defect. Non-NPD non new perfusion defect.