Extracardiac findings with increased perfusion during clinical O-15-H2O PET/CT myocardial perfusion imaging: A case series

Abstract

Background: Coincidental extracardiac findings with increased perfusion were reported during myocardial perfusion imaging (MPI) with various retention radiotracers. Clinical parametric O-15-H₂O 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-H₂O.

Methods and results: All patients (2963) were scanned with O-15-H₂O PET MPI according to international guidelines and extracardiac findings were collected. In contrast to parametric O-15-H₂O 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-H₂O PET MPI. We recommend evaluating the summed O-15-H₂O PET images in addition to the low-dose CT attenuation images.

Keywords: O-15-H2O PET; cardiac PET; coincidental findings; extra cardiac; myocardial perfusion; positron emission tomography; splenic switch off.

Figure 1

A tumour in the right breast of this 71-year old woman revealed focally increased perfusion on rest O-15-H₂O PET/CT Maximum Intensity Projection (MIP), axial PET and axial PET/CT fusion image (A, broad arrows) and an axillary lymph node was even visible as well (A, thin arrow). However, the tumour was not detected until subsequent mammography and later on staged using F-18-FDG PET/CT with highly increased FDG uptake in both tumour (B, broad arrow) and lymph node (B, thin arrow)

Figure 2

Rest scan images of malignant findings. A a lung cancer with increased perfusion and FDG uptake in the periphery and without uptake in the necrotic centre. B a lung tumour with increased perfusion and FDG uptake turned out to be large-celled neuroendocrine tumour. C Mediastinal and hilar lymph node masses with increased perfusion and FDG uptake represented lymphoma. D Lung metastases from renal cell carcinoma with focally increased perfusion

Figure 3

Rest scan images of benign findings. A Highly increased perfusion on O-15-H₂O PET/CT in pneumonic infiltrate, which completely regressed on subsequent F-18-FDG PET/CT (arrow). B Patchy, ground-glass like, peripheral lung infiltrates spread in both lungs 12 days after positive COVID-19 PCR test (arrows). C Lung infiltrate with highly increased perfusion on O-15-H₂O PET/CT, and moderate FDG uptake turned out to be chronical inflammation and fibrosis on biopsy (arrow). D Pleural plaques where a part of the non-calcified plaque had increased perfusion (arrow), whereas other plaques had low perfusion. E Rib fractures a few weeks after cardiopulmonary resuscitation, where bilateral rib fractures and the sternum revealed focally increased perfusion (arrows). F Gynecomastia with increased perfusion (arrow). G Increased perfusion in atelectasis (broad arrows) in close relation to pleural effusions (thin arrows), which naturally has very low perfusion. H A lung nodule with slightly increased perfusion and no pathological FDG uptake, which turned out benign on biopsy (arrow)

Figure 4

Summed and parametric rest O-15-H₂O PET/CT images with highly increased perfusion in known pulmonary sarcoidosis lesions (arrows) diagnosed on F-18-FDG PET/CT

Figure 5

A Patient with pronounced splenic switch-off after adenosine stress. B Patient with increased muscular perfusion in the serratus anterior muscle during adenosine stress. The same phenomenon is seen in the erector spinae muscle in A. C An apparent segmental lung perfusion defect in the right lower lobe on the O-15-H₂O PET/CT early dynamic images. However, no pulmonary embolism was seen on neither conventional ventilation/perfusion scintigraphy nor CT-angiography