Abnormal Fluorodeoxyglucose Uptake in Lung without Structural Abnormality on Computed Tomography

Hot Embolus Artifact Mimicking Disease Progression in Post-therapy 177Lu-DOTATATE Scan: Incremental Value of SPECT/CT

Peptide receptor radionuclide therapy (PRRT) has become an established treatment for patients with inoperable and/or metastatic, well-differentiated neuroendocrine tumors with overexpression of somatostatin receptor type 2 (SSTR-2). The post-therapy 177Lu-DOTATATE whole-body scan not only assesses the biodistribution of the lesions seen on pre-therapy 68 Ga-SSTR PET/CT scan but also provides a quick assessment of disease status and dosimetry during treatment. Like any other radionuclide scan, the whole-body 177Lu-DOTATATE scan may also show abnormal radiotracer uptake, which may require further imaging to establish its exact etiology. Though radiotracer emboli mimicking focal pulmonary lesions have been described with 18F-FDG and 68 Ga-DOTANOC PET/CT scans, similar artifacts with post-therapy 177Lu-DOTATATE scans have not been described. Herein, we report two cases of hot emboli in the post-therapy 177Lu-DOTATATE scans.

The hot embolus of 18F-fluorodeoxyglucose

Scanning oncological patients with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) for their disease staging, evaluation of treatment response, and monitoring/management has become a standard of care. The use of the radioactive fluorine in the FDG molecule helps establish cell/tissue lines high on glucose consumption and hence metabolically active. Abnormalities are detected on the scan as areas of increased uptake. However, these areas of increased (hot) uptakes do not necessarily translate into a pathological finding. A comprehensive knowledge of the uptakes of the tracer and the potential "pitfalls" that may be associated with them should be known and kept in mind during scan reading. One such pitfall is the "hot clot" or "pulmonary emboli," and we report two such cases encountered at our setup and discuss their causes and how they should be identified and avoided.

Iatrogenic Lung Microembolism Resulted in Extraosseous Uptake of 99mTc-MDP

A 61-year-old woman diagnosed with left breast cancer underwent a bone scan for the evaluation of possible bone metastases. Multiple foci of elevated activity were noticed in the spine and pelvis. In addition, a focus of intense activity was observed in the right lung on the SPECT/CT images without corresponding anatomic abnormality.