Extracardiac findings with increased perfusion during clinical O-15-HO PET/CT myocardial perfusion imaging: A case series

Background: Coincidental extracardiac findings with increased perfusion were reported during myocardial perfusion imaging (MPI) with various retention radiotracers. Clinical parametric O-15-HO PET MPI yielding quantitative measures of myocardial blood flow (MBF) was recently implemented at our facility. We aim to explore whether similar extracardiac findings are observed using O-15-HO. Methods and results: All patients (2963) were scanned with O-15-HO PET MPI according to international guidelines and extracardiac findings were collected. In contrast to parametric O-15-HO MBF images, extracardiac perfusion was assessed using summed images. Biopsy histopathology and other imaging modalities served as reference standards. Various malignant lesions with increased perfusion were detected, including lymphomas, large-celled neuroendocrine tumour, breast, and lung cancer plus metastases from colonic and renal cell carcinomas. Furthermore, inflammatory and hyperplastic benign conditions with increased perfusion were observed: rib fractures, gynecomastia, atelectasis, sarcoidosis, pneumonia, chronic lung inflammation and fibrosis, benign lung nodule, chronic diffuse lung infiltrates, pleural plaques and COVID-19 infiltrates. Conclusions: Malignant and benign extracardiac coincidental findings with increased perfusion are readily visible and frequently seen on O-15-HO PET MPI. We recommend evaluating the summed O-15-HO PET images in addition to the low-dose CT attenuation images.