In a Heartbeat: An Assessment of Dynamic Dose Variation to Cardiac Structures using Dual Source Computed Tomography

Publication date: Available online 31 January 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Houda Bahig, Jacques de Guise, Toni Vu, Danis Blais, Carl Chartrand-Lefebvre, Nhu Tram Nguyen, Sophie Lavertu, Jean-Pierre Guay, David Roberge
PurposeTo assess radiation dose variation to the left anterior descending artery (LAD), left main coronary artery (LMCA), left ventricle (LV) and whole heart (WH) during the cardiac cycle using dual source computed tomography (DSCT).MethodsThis prospective study included patients with left breast cancer planned for tangential radiotherapy. An electrocardiogram-synchronized contrast-injected DSCT was obtained in treatment position, in deep-inspiration breath-hold (DIBH), using retrospective sequential acquisition. WH, LV, LMCA as well as proximal, middle and distal LAD segments were contoured on each phase of the cardiac cycle. Maximum, minimum and mean Hausdorff distance between each structure and the tangential fields was assessed in ventricular systole vs. diastole. Four-dimensional dose-volume histograms were used to compare systolic vs. diastolic dosimetries.ResultsTen patients were enrolled. Average maximum, minimum and mean Hausdorff distance variation from systole to diastole was ≤4 mm for LV and LMCA, and ≤3 mm for the heart and LAD segments. WH maximum dose and volume receiving 5Gy were decreased in systole vs. diastole (42.9 Gy vs. 44.5 Gy, p=0.03 and 21.7 cm3 vs. 27.7 cm3, p=0.01), but mean dose remained similar throughout the cycle. Maximum and mean dose to distal LAD was 21.2 Gy vs. 26.6 Gy (p=0.005) and 8.6 Gy vs. 13.2 Gy (p=0.006), in systole vs. diastole, respectively. Maximum and mean dose to middle LAD was 18.4 Gy vs. 25.1 Gy (p=0.005) and 8.5 Gy vs. 10.2 Gy, in systole vs. diastole (p=0.005). Maximum dose to LV was lower in systole vs. diastole (21.5 Gy vs. 26.7 Gy, p=0.005).ConclusionBeyond DIBH, systolic irradiation would be associated with decrease in dose to LAD, LV and WH. In addition to potential use in planning for cardiac gating, DSCT imaging can be used to help define a planning organ at risk volume for clinically important cardiac sub-structures.

Teaser

Dynamic dose variation to cardiac substructures was assessed in left breast tangential irradiation using dual-source computed tomography. Maximum and mean dose to left anterior descending artery and maximum dose to whole heart and left ventricle were significantly decreased in systole vs. diastole. The described method allows for precise segmentation of cardiac substructures and can be used for definition of a planning organ at risk volume for clinically important cardiac substructures.


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