Exploring the diagnostic potential of 68Ga DOTA-TOC PET/CT for quantification of myocardial inflammation

Abstract

Cardiovascular diseases represent the leading cause of mortality on a global basis. These diseases can range from ischemic heart diseases, stroke, heart failure, myocarditis, and other vascular conditions. Inflammation is an immune response to harmful stimuli. It is a consequence of infections, exposure to toxic substances, autoimmune diseases, irradiation, and in some cases post-myocardial infarction. Somatostatin receptor (SSTR) is known to be expressed during an inflammation. The increasing availability of PET cameras and improved accessibility to the tracer opens the door to a new way of utilizing the method. Macrophages and other proinflammatory cells express SSTR, allowing the SSTR tracers to provide insight into the progression of inflammation in the heart, as well as treatment response. This study aims to establish, describe and quantify left ventricle (LV) myocardial uptake of 68GA DOTA-TOC in a heterogenous population and correlate it with risk factors for cardiac disease. Material and Methods: A patient population of 314 patients diagnosed or with the suspicion of neuroendocrine tumors (NETs) imaged by 68Ga DOTA-TOC between 2019 and 2021 were included. All patients had signed to be included in the PET registry at Oslo university hospital (OUS). The SUV window used for image analysis was 0-3 SUV for 68Ga DOTA-TOC. A banana-shaped region of interest was drawn around the LV wall on the axial PET slice where the ventricle had the largest volume. Clinical information regarding diagnosis and medication was collected from the patient record. Results: SUVmax myocardium in the study population was 1.65 (0.77 – 4.92). SUVmax myocardium in positive uptake score was 1.92 (1.37 – 4.92) compared to 1.61 (0.77 – 3.21) in the negative uptake score. TBR myocardium in the positive uptake score was 2.52 (1.67 – 5.46) and in the negative uptake score 1.49 (0.75 – 3.18). BMI showed a moderate significant correlation with SUV quantifications and calculations. Hypercholesterolemia showed a significant association with uptake score. Hypertension showed higher SUVmax myocardium values compared to non-hypertensive patients. An association was found between uptake score and NET and SUVmax myocardium was significantly different between the NET stages. Conclusion: Myocardial uptake of 68Ga DOTA-TOC can be found in several conditions affecting the heart. This is relevant both for the interpretation of findings when this tracer is used for diagnosis and follow up of established inflammatory heart diseases like cardiac sarcoidosis. But it also opens up new possibilities for imaging in the understanding of the interplay between inflammation and fibrosis development in the heart.