Case series of extra cardiac findings with increased perfusion during clinical 15O-H2O PET myocardial perfusion imaging

ABSTRACT

Aim/Introduction: Multiple extra cardiac findings with increased perfusion have been reported as coincidental findings during myocardial perfusion imaging (MPI) with various radiotracers. At our facility, 15O-H2O-PET MPI was implemented in daily clinical routine in May 2020, and we therefore anticipated similar findings using this radiotracer. The aim of this is therefore to share a case series of our initial experience regarding extra cardiac findings characterized by increased blood flow on 15O-H2O-PET. Material(s) and Method(s) Patient cases with extra cardiac findings observed during clinical 15O-H2O PET MPI scans were collected. All patients were scanned according to facility standards and international guidelines on a GE Discovery MI Digital Ready PET/CT (GE Healthcare, Waukesha, Wisconsin, USA). In contrast to the parametric myocardial 15O-H2O images, summed and gated retention images were used for assessment of extra cardiac perfusion. Biopsy histopathological diagnosis was used as reference standard in all malignant lesions and in some benign lesions. In the remaining patients, other imaging modalities were used as reference standard. Result(s) A variety of malignant lesions with increased perfusion appeared during the scans, including primary tumours of breast cancer, lung cancers, large-celled neuroendocrine tumours, lymphomas and metastases from colonic carcinomas and renal cell carcinomas. Furthermore, a number of benign conditions with increased perfusion were observed Healing rib fractures, gynecomastia, atelectasis, acute pneumonia (disappeared on subsequent FDG-PET/CT), lung infiltrate with biopsy-verified chronic inflammation and fibrosis (FDG-positive), biopsy-verified benign lung nodulus, chronic diffuse lung infiltrates, pleural plaques and sequelae after recent COVID-19 infection (scan 12 days after positive test). In general, the benign findings were either inflammation or hyperplastic tissue, which are conditions known to be characterized by increased perfusion. Conclusion(s) Both malignant and benign extra cardiac coincidental findings with increased perfusion are readily visible and frequently encountered on 15O-H2O-PET MPI. In most cases, the coincidental findings are also visible on the low-dose attenuation correction CTscan. However, we did observe a 15O-H2O avid breast cancer tumour located outside the CT field of view, underlining the importance of evaluating the entire field of view of the retention 15O-H2O-PET and not just the reconstructed parametric myocardial images.