Physiological distribution and range of normal SUVmax values of 18F-Choline PET/CT

Introduction: 18F-Choline PET-CT is an increasingly used technique in patients with prostate cancer. The main indication is to localise the disease in patients with biochemical recurrence. To accurately interpret 18F-Choline PET, knowledge of normal tracer distribution is paramount. The aim of this study was to describe the normal distribution pattern of 18F-Choline by measuring the maximum standardized uptake values (SUVs) of various organs. Methods: 18F-Choline PET was performed in ten consecutive patients. Approximately 370 MBq of tracer was injected intravenously and a low amperage CT scan was performed for attenuation correction of PET images.Maximum SUVs were calculated on the reconstructed images for various organs. These SUVmax values depend on multiple factors and could be variable depending on the reconstruction CT methods, acquisition time and region of interest (ROI) parameters. Results: Physiologic symmetric increased tracer uptake was noted in the salivary glands and parotid glands. Intense physiological uptake was present in the liver, pancreas, duodenum, stomach, kidneys and urinary bladder and moderate to intense uptake in the sublingual glands, lacrimal glands, nasal mucosa, thyroid gland, tonsils, adrenal glands, large bowel, bone marrow and spleen. Low-grade-to-moderate uptake was present in the choroid plexus, pituitary gland, soft palate, pharynx, left myocardium, lungs, mediastinal blood pool, testicles and muscles. Prostate and prostatic beds were excluded from the volumes of interest. Conclusion: This study is the first one to describe a normal range of SUVmax values for 18F-Choline PET in various organs.