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Location: Marriott Marquis
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Main Session

QP 17 - Phys 10: Imaging for Treatment Monitoring

1099 - The Novel Assessment of Stereotactic Body Radiotherapy (SBRT) for Cardiac Radioablation to the Cavotricuspid Isthmus by 13C Pyruvate Metabolic Imaging and Redox Reaction Imaging Using Dynamic Nuclear

Tuesday, October 1, 2024
5:40 PM – 5:45 PM ET
Location: Room 147
M. Matsuo1, T. Mori1, A. Kobori1, H. Kawada1, S. Nagata1, K. Fujimoto1, T. Mori2, N. Takasugi3, T. Hiroyuki4, and F. Hyodo5; 1Department of Radiology, Graduate School of Medicine, Gifu University, Gifu, Japan, 2Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan, 3Department of Cardiology, Gifu University, Gifu, Japan, 4Department of Tumor Pathology, Graduate School of Medicine, Gifu University, Gifu, Japan, 5Department of Pharmacology, Graduate School of Medicine, Gifu University, Gifu, Japan

Purpose/Objective(s): We examined the role of spatiotemporal visualization of stereotactic body radiotherapy (SBRT) for cardiac radioablation to the cavotricuspid isthmus (CTI) based on both 13C labeled pyruvate metabolic imaging by Dynamic Nuclear Polarized (DNP) and redox reaction by in vivo DNP MRI compared with routine MRI. Materials/

Methods: First, four mini pigs underwent electrophysiology assessment using electroanatomical mapping (EAM) before and 3 months after SBRT with single-fraction doses of 25Gy. Routine MR examination, including diffusion-weighted, dynamic Gd-enhanced, spectroscopy, and T2-weighted images were performed before and 3 months after SBRT. Second, the dynamics of 13C compound pyruvate for metabolic imaging by DNP MRI (SpinAligner), free radical imaging by low filed type of in vivo DNP MRI and routine MR (1.5T) were performed on the four mice before and 3 days and 7 days after single-fraction doses of 25Gy and 10Gy to whole heart.
Results: EAM visualized the irradiated site and confirmed clockwise conduction block across the CTI after SBRT. Both Abnormal signals which reflect the damaged myocardium on T2WI and DWI images and late gadolinium enhancement which reflects fibrosis could not be detected by routine MRI in four mini pigs. Pyruvate metabolic imaging by DNP MRI showed a significant increase in 13C lactate/pyruvate ratio after SBRT at all time points compared to before SBRT. In vivo DNP MRI signals were decreased depending on prescribed irradiation dose and days after SBRT. The mice treated by 10Gy irradiation showed a decrease on day 3 in whole heart. The mice treated by 25Gy irradiation showed a marked decrease on day 3 and a further decrease on day 7 in whole heart.
Conclusion: Pyruvate metabolic imaging by DNP and redox reaction by in vivo DNP MRI could be useful for the evaluation of early response to the cardiac damaged after SBRT for cardiac radioablation to CTI.