Physiologic prostate-specific membrane antigen-targeted 18F-DCFPyL uptake in the epididymis head newly appreciated on digital PET/CT.

Purpose: The published physiological distribution of prostate specific membrane antigen (PSMA) PET ligands includes normal uptake in the lacrimal glands, salivary glands, bowel, liver, spleen, kidneys and parasympathetic ganglia but does not include the epididymis.
Methods: Retrospective review of 134 PSMA-targeted 2-(3-(1-carboxy-5-[(6-[18F]fluoropyridine-3-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid (18F-DCFPyL) PET/CT scans performed on a latest generation digital scanner for radiotracer uptake in the epididymal head region was correlated with multiple clinical and laboratory factors.
Results: Physiologic PSMA radiotracer uptake in the epididymal head region was present in 57% of all subjects, including 29% in those with a total serum testosterone ≤ 5 nmol/L and 65% of patients with serum testosterone > 5 nmol/L, odds ratio of 0.21 (P < 0.01).
Conclusion: Epididymal head uptake is physiologic and very common on digital PSMA PET/CT and is more frequent in patients with higher serum testosterone levels. The enhanced small structure detection of digital PET/CT is the most likely explanation for the novel visualization of this normal variant.
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