Assessment of Physiological Distribution and Normal Variants of 68Ga PSMA-I&T PET/CT

Abstract

Objective: 68Ga prostate-specific membrane antigen (PSMA) positron emission tomography/computerized tomography (PET/CT) imaging has been used efficiently in the evaluation of prostatecancer (PCa). There are three kinds of urea-based PSMA ligands labeled with 68Ga, including PSMA11, PSMA Imaging & Therapy (I&T), and PSMA 617. The aim of the present study was to investigate the in vivo distribution of the novel ligand PSMA I&T in normal tissues and to identify benignvariants.Methods: We retrospectively evaluated 34 patients with PCa who underwent 68Ga PSMA I&T PET/CT imaging in our clinic between August 2017 and December 2017. Only patients who had noevidence of recurrent disease on conventional imaging performed before the 68Ga PSMA I&T PET/CT scan were included in the study. Patients also had no 68Ga PSMA avid lesion in favor of residualdisease or recurrent disease on PET scan. The average age of the patients was 70.2±8.5 years.Results: Evaluation of the conventional maximum intensity projection images revealed uptake of 68Ga PSMA in the lacrimal, submandibular, and parotid glands; liver; spleen; kidneys; duodenum;jejunum; ileum; and urinary bladder. The radionuclide uptake of the body structures from the highest to the lowest in terms of SUVmax values was listed as kidneys, submandibular and parotidglands, urinary bladder, jejunum-ileum, lacrimal gland, duodenum, spleen, liver, and transverse colon. When SUVmean values are concerned, the list, from the highest to the lowest, was as follows:kidneys, urinary bladder, submandibular and parotid glands, duodenum, lacrimal gland, spleen,jejunum-ileum, liver, and transverse colon. We detected osteophytes in 15 patients, and 8 of themdemonstrated mild uptake. We detected mild uptake in the celiac ganglia of 4 patients. We did notobserve any physiological uptake in the surrenal glands, but there were two adenomas that showlow degree of uptake. When double organs are compared, the SUVmax values of the right lacrimal,sublingual, and parotid glands were higher than those of the left counterparts, and differenceswere statistically significant (p