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

Abstract

Our objective was to determine the potential value of ¹³N-ammonia PET/CT myocardial perfusion imaging (MPI) for early detection of myocardial perfusion changes induced by radiation damage. <b>Methods:</b> Thirty-six Beagle dogs were randomly divided into a control group (<i>n</i> = 18) or an irradiation group (<i>n</i> = 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 ¹³N-ammonia PET/CT MPI 1 wk before irradiation and at 3, 6, and 12 mo after sham or local irradiation. One week after undergoing ¹³N-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. <b>Results:</b> 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%, <i>P</i> = 0.016) and 12 mo (47.2% ± 6.7% vs. 57.4% ± 3.3%, <i>P =</i> 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. <b>Conclusion:</b>¹³N-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.