13N-Ammonia PET/CT Detection of Myocardial Perfusion Abnormalities in Beagle Dogs After Local Heart Irradiation

Our objective was to determine the potential value of N-13-ammonia PET/CT myocardial perfusion imaging (MPI) for early detection of myocardial perfusion changes induced by radiation damage. Methods: Thirty-six Beagle dogs were randomly divided into a control group (n = 18) or an irradiation group (n = 18). The latter underwent local irradiation to the left ventricular anterior cardiac wall with a single dose of 20 Gy, whereas the former received sham irradiation. All dogs underwent N-13-ammonia PET/CT MPI 1 wk before irradiation and at 3, 6, and 12 mo after sham or local irradiation. One week after undergoing N-13-ammonia PET/CT MPI, the irradiation group underwent coronary angiography. Six randomly selected dogs from each group were sacrificed and used to detect pathologic cardiac injury at 3, 6, and 12 mo after irradiation. Results: Compared with the control group and baseline, the irradiation group showed significantly increased perfusion in the irradiated area of the heart at 3 mo after irradiation, perfusion reduction at 6 mo after irradiation, and a perfusion defect at 12 mo after irradiation. There was no significant difference in the left ventricular ejection fraction between the control and irradiation groups at baseline or at 3 mo after irradiation. The irradiation group showed a reduction of left ventricular ejection fraction compared with the control group at 6 mo (50.0% +/- 8.1% vs. 59.3% +/- 4.1%, P = 0.016) and 12 mo (47.2% 6.7% +/- vs. 57.4% 3.3%, P = 0.002) after irradiation. No coronary stenosis was observed in the irradiation group. Regional wall motion abnormalities appeared in the irradiated area at 6 mo after irradiation, and its extent was enlarged at 12 mo after irradiation. Pathologic changes were observed; radiation-induced myocardial tissue damage and microvascular fibrosis in the irradiated area progressively increased over time. Conclusion: N-13-ammonia PET/CT MPI can dynamically detect myocardial perfusion changes together with global and regional left ventricular dysfunction induced by irradiation and may be a valuable method for monitoring radiation-induced heart disease.