Author: Phillip Cuculich, Geoffrey D. Hugo, Nels C. Knutson, Luke Christian Marut, Eric D. Morris, Stacey Rentschler, Clifford Robinson, Christian Zemlin, Brian Zenger 👨🔬
Affiliation: Washington University School of Medicine in St. Louis, WashU Medicine 🌍
Purpose: Stereotactic arrhythmia radiotherapy (STAR) is an emerging treatment for ventricular tachycardia (VT) that uses radiation to modulate cardiac electrophysiology (EP) and reduce VT. Registration of 3D imaging such as MRI and CT to excised hearts in preclinical models can inform the dose-response relationship between radiation and EP. Registering radiation planning 3D imaging to cardiac optical maps enables observation of EP’s correlation with radiation dose in a porcine STAR model.
Methods: Meshes of the left and right ventricles were created from pre-treatment MRI contours. The American Heart Association 17-segment model was fit to the left ventricle. After STAR treatment, the left ventricle was excised for optical mapping. Fluorescent dye and a high-speed camera were used to visualize and record EP. A 2D visible light image of the left ventricle was taken with the same experimental setup. The 17-segment model was mapped to the 2D surface using anatomical landmarks on the 2D visible light image. The 2D image was registered to the 3D left ventricle mesh via anatomical landmarks within the 17-segment model, allowing transfer of optical mapping data to 3D and radiation dose to 2D. Scar secondary to myocardial infarction visible on both 2D and 3D imaging was used to validate the registration.
Results: A 2D image of a porcine left ventricle was registered to a 3D left ventricle mesh using a 17-segment model framework. This 2D image was aligned with cardiac EP obtained through optical mapping. Scar is visible on the 3D MRI in segments 1,7, and 13, and on the registered mesh in segments 13, and 17. Scar on MRI extends throughout the myocardium while scar visible on the 2D image is on the surface.
Conclusion: A 17-segment model framework can be effective for registering cardiac EP data with 3D imaging for STAR research in pig models.