Intense focal Fluoro-deoxyglucose uptake in the lungs with no corresponding computed tomography abnormality
A 66-year-old man was referred for a PET/CT study to assess response to external beam radiotherapy given about 12 weeks back for a primary hypopharyngeal cancer. The maximum intensity projection (MIP) image [] revealed an intense focus of increased tracer uptake (maximum standardized uptake value (max SUV) 8.9) in the right lung (arrow) against a background multiple heterogeneous foci of low-grade uptake in both the lungs. No abnormal increased tracer uptake was seen at the primary site or in the neck. On axial images, foci of low-grade uptake [] coincided with tree-in-bud opacities [, arrowhead], which were considered infective. The focus of intense uptake in the right lung [, arrowhead] on the other hand was thought to be a metastatic nodule; however, inspection of the CT image [] surprisingly did not show any corresponding morphologic abnormality. The expected nodule (morphologic abnormality) was not visible on both the lung and mediastinal window settings. In view of the discordance between the CT and PET findings, the focal uptake in the lungs was considered artifactual.