Detection of Myocardial Metabolic Abnormalities by 18F-FDG PET/CT and Corresponding Pathological Changes in Beagles with Local Heart Irradiation

Abstract

ObjectiveTo determine the efficacy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the detection of radiation-induced myocardial damage in beagles by comparing two pre-scan preparation protocols as well as to determine the correlation between abnormal myocardial FDG uptake and pathological findings.Materials and MethodsThe anterior myocardium of 12 beagles received radiotherapy locally with a single X-ray dose of 20 Gy. 18F-FDG cardiac PET/CT was performed at baseline and 3 months after radiation. Twelve beagles underwent two protocols before PET/CT: 12 hours of fasting (12H-F), 12H-F followed by a high-fat diet (F-HFD). Regions of interest were drawn on the irradiation and the non-irradiation fields to obtain their maximal standardized uptake values (SUVmax). Then the ratio of the SUV of the irradiation to the non-irradiation fields (INR) was computed. Histopathological changes were identified by light and electron microscopy.ResultsUsing the 12H-F protocol, the average INRs were 1.18 ± 0.10 and 1.41 ± 0.18 before and after irradiation, respectively (p = 0.021). Using the F-HFD protocol, the average INRs were 0.99 ± 0.15 and 2.54 ± 0.43, respectively (p < 0.001). High FDG uptake in irradiation field was detected in 33.3% (4/12) of 12H-F protocol and 83.3% (10/12) of F-HFD protocol in visual analysis, respectively (p = 0.031). The pathology of the irradiated myocardium showed obvious perivascular fibrosis and changes in mitochondrial vacuoles.ConclusionHigh FDG uptake in an irradiated field may be related with radiation-induced myocardial damage resulting from microvascular damage and mitochondrial injury. An F-HFD preparation protocol used before obtaining PET/CT can improve the sensitivity of the detection of cardiotoxicity associated with radiotherapy.

Relationship between Changes in Myocardial F-18 Fluorodeoxyglucose Uptake and Radiation Dose after Adjuvant Three-Dimensional Conformal Radiotherapy in Patients with Breast Cancer

“…It has been already found that radiation can cause damage to the myocardial microvascular tissue and myocardial metabolism [21,24,28]. In previous studies with animal models, radiation directly affected endothelial capillary cells within the myocardium, resulting in capillary swelling, obstruction of vascular lumens, and perivascular fibrosis [28,29].…”

“…In previous studies with animal models, radiation directly affected endothelial capillary cells within the myocardium, resulting in capillary swelling, obstruction of vascular lumens, and perivascular fibrosis [28,29]. These microvascular damages lead to ischemic conditions and fibrotic changes in the myocardium [27][28][29]. Under ischemic conditions, the myocardium switches its main energy source from free fatty acid to glucose and lactate [21,28].…”

“…These microvascular damages lead to ischemic conditions and fibrotic changes in the myocardium [27][28][29]. Under ischemic conditions, the myocardium switches its main energy source from free fatty acid to glucose and lactate [21,28]. Furthermore, high-dose irradiation to the myocardium also causes degeneration and deregulation of proteins in the myocardial mitochondria, especially for mitochondrial oxidative phosphorylation, pyruvate metabolism, and cytoskeletal structure [28,30,31].…”

18FDG PET-CT standardized uptake value for the prediction of radiation pneumonitis in patients with lung cancer receiving radiotherapy

“…In particular, PET-CT is superior to CT for the formation of precise radiotherapy plans, reducing the development of radiation injury, evaluating the therapeutic effect, and identifying residual tumors and fibrosis subsequent to chemotherapy. Furthermore, 18 F-FDG PET-CT is able to detect the inflammation and fibrosis caused by radiotherapy (9)(10)(11).…”

Radiation-Induced Cardiomyopathy Incidentally Detected on Oncology ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography

“…7 Yan et al investigated RTx-induced microvascular damage and mitochondrial injury in an experimental study. 8 These alternations may cause ischemia and diminished energy production, resulting in regional metabolic shift from FFA to glucose and contractile dysfunction. It is well known, however, that non-specific FDG uptake is occasionally observed even under fasting conditions, leading to misinterpretation.…”