Investigating heterogeneous PSMA ligand uptake inside parotid glands

The purpose was to investigate the spatial heterogeneity of prostate-specificmembrane antigen (PSMA) positron emission tomography (PET) uptake withinparotid glands. We aim to quantify patterns in well-defined regions tofacilitate further investigations. Furthermore, we investigate whether uptakeis correlated with computed tomography (CT) texture features. Parotid glandsfrom [18F]DCFPyL PSMA PET/CT images of 30 prostate cancer patients wereanalyzed. Thresholding was used to define high-uptake regions, and uptakestatistics were computed within various divisions. Spearman's rank correlationcoefficient was calculated between PSMA PET uptake and the Grey Level RunLength Matrix (GLRLM) using a long and short run length emphasis (GLRLML andGLRLMS) in subregions of parotid glands. PSMA PET uptake was significantlyhigher (p < 0.001) in lateral/posterior regions of the glands thananterior/medial regions. Maximum uptake was found in the lateral half ofparotid glands in 50 out of 60 glands. The difference in SUV between parotidhalves is greatest when parotids are divided by a plane separating theanterior/medial and posterior/lateral halves symmetrically. PSMA PET uptake wassignificantly correlated with CT GLRLML (p < 0.001), and anti-correlated withCT GLRLMS (p < 0.001). Uptake of PSMA PET is heterogeneous within parotidglands, with uptake biased towards lateral and posterior regions. Uptakepatterns within parotid glands were found to be strongly correlated with CTtexture features, suggesting the possible future use of CT texture features asa proxy for inferring PSMA PET uptake in salivary glands.