Heart MRI perfusion changes after chest radiation therapy in breast cancer patients
Background and Significance
Radiation therapy (RT) to the chest wall and axilla improves overall survival of patients with Stage II&III breast cancer, but inadvertent radiation exposure to the heart often occurs resulting in an increased risk for future cardiac events, especially for patients with left-sided breast cancer. While a national study is underway to determine whether proton therapy increases long-term cardiac survival, modern RT imparts a highly heterogeneous dose to the heart and we are interested in studying early sub-clinical progression of cardiac vascular and mechanical dysfunction as a function of regional dose in breast cancer patients.
Radiation is known to damage the endothelial cells of vessels leading to a cytokine-mediated inflammatory response that can lead to vessel occlusion and diminished tissue perfusion. By measuring the rate of update of an injected contrast agent into the myocardial tissue, dynamic-contrast enhanced (DCE) CMRI is able to interrogate delays in regional tissue perfusion (time to peak perfusion (TTP) and maximal slope of uptake). Our hypothesis is that radiation toxicity to the microvasculature will manifest as a decreased regional perfusion that will correlate with regional radiation dose and subsequent mechanical dysfunction.
I will analyse cardiac perfusion scans in 12-6 breast cancer patients with the technical goals to
Automatically register the heart at each of ~50 time points during the contrast uptake, to improve the ability to regionally match perfusion uptake in the same myocardial tissue over time.
Register the anatomical MRI scans upon which the heart contours will be segmented, with the perfusion scans.
Define 4-6 regions circumferentially around the LV and compute foreach region the time-to-peak uptake, maximul uptake, and slope of the uptake curve.
Align the perfusion scans to the planning CT and RT dose distribution to compute perfusion vs. dose response.