Quantitative assessment of proton beam dose and myocardial lesion formation detected by high-resolution, ex vivo delayed contrast-enhanced MRI for treatment of ventricular tachycardia

Proton beam therapy has the potential to non-invasively treat ventricular tachycardia (VT) by homogenizing infarct scar. It has been previously demonstrated that proton beam therapy can create lesions in healthy myocardial tissue, thereby suggesting a potential for treatment of VT. In prior work, we quantified the relationship between dose delivered to myocardial tissue with lesion formation identified with in vivo, delayed contrast-enhanced magnetic resonance imaging (DCE-MRI) scans. In the current work, we evaluate the relationship of delivered dose with lesions identified in high resolution, post-mortem DCE-MRI scans. Deformable registration is used to align the dose maps from the baseline planning CT scans to ex vivo scans following proton beam therapy in swine. The current study demonstrates that nearly 100% of tissue exposed to a dose of 30 Gy or higher developed into lesion and approximately 85% of the tissue in the 20-30 Gy interval developed into lesion. On the other hand, tissue exposed to doses of 10 Gy or less tended to remain healthy myocardium, with less than 10% of tissue in the 5-10 Gy range and almost no tissue in the 0-5 Gy range developing into lesion.