Experimental study of 18F-FDG PET/CT imaging and cardiac MRI in diagnosis of radiation-induced myocardial injury in Beagle dogs

Objective To investigate the value of 18F-fluorodeoxyglucose (FDG) PET/CT imaging and cardiac MRI (CMR) in the diagnosis of radiation-induced heart disease (RIHD) in Beagle models. Methods Twenty-four normal male Beagle dogs (1-year old) were randomly divided into control group and irradiated groups (3-month, 6-month and 12-month after radiation). The left anterior myocardium of Beagle dogs in irradiated groups was irradiated locally with a single dose of 20 Gy X-ray. Cardiac 18F-FDG PET/CT imaging and CMR were performed on all dogs, and the mean standardized uptake value (SUVmean) and the area of lesions with increased 18F-FDG uptake were obtained. After imaging examinations were finished, dogs were sacrificed and their hearts were taken out to perform Masson staining and electron microcopy. One-way analysis of variance was used for data analysis. Results There was basically no uptake in myocardium in control group. The myocardium showed increased uptake of 18F-FDG in the irradiated groups. The SUVmean of myocardium in 3-month, 6-month and 12-month after radiation groups and control group were 5.90±1.31, 4.66±2.21, 3.21±0.82 and 1.13±0.21, respectively (F=11.81, P<0.05). The area with increased 18F-FDG uptake in the irradiated groups decreased progressively with the prolongation of irradiation time (F=195.74, P<0.01). The reduction in myocardial perfusion and myocardial fibrosis were observed by CMR early at 6-month after irradiation. Compared with the control group, the 6-month and 12-month after radiation groups had increased end diastolic volume (EDV) and end systolic volume (ESV; F=15.479 and 16.908, both P<0.01), and decreased left ventricular ejection fraction (LVEF; F=63.715, P<0.01). The progressive aggravation of myocardial fibrosis was displayed in irradiated groups by Masson staining. The mitochondria degeneration, swelling and the count reduction in irradiated groups were observed by electron microscopy. Conclusions The increased 18F-FDG uptake in the irradiated myocardium may predict the risk of RIHD. 18F-FDG PET/CT imaging can detect RIHD earlier than CMR. Key words: Heart; Radiation injuries, experimental; Positron emission tomography; Tomography, X-ray computed; Deoxyglucose; Magnetic resonance imaging; Dogs