Deformable Registration of Radiation Isodose Lines to Delayed Contrast-Enhanced Magnetic Resonance Images for Assessment of Myocardial Lesion Formation Following Proton Beam Therapy

Ventricular tachycardia is increasingly treated with ablation therapy, a technique in which catheters are guided into the ventricle and radiofrequency energy is delivered into the myocardial tissue to interrupt arrhythmic electrical pathways. Recent efforts have investigated the use of noninvasive external beam therapy for treatment of ventricular tachycardia where target regions are identified in the myocardium and treated using external beams. The relationship between the planned dose map and myocardial tissue change, however, has not yet been quantified. In this work, we use a deformable registration algorithm to align dose maps planned from baseline computed-tomography scans to delayed contrast-enhanced magnetic resonance imaging scans taken at 4 week intervals following proton beam therapy. From this data, the relationship between the planned dose and image enhancement, which serves as a surrogate for tissue change, can be quantified.