Abstract
460
Objectives: 68Ga-DOTANOC is a 68Ga-labelled DOTA-derivatised peptide ligand, somatostatin analogue, that could be used to study neuroendocrine tumors (NET). Aim of this work is whole-body radiation dosimetry and biodistribution study of 68Ga-DOTANOC. Methods: We enrolled 8 subjects, 5 males and 3 females. Patients were administered with about 200 MBq of 68Ga-DOTANOC. 6-7 beds acquisitions were performed 5, 20, 60 and 120 minutes after injection. All acquisitions have been performed using a PET/CT scanner (Discovery LS, GE) and attenuation correction was obtaind using CT data and 2D OSEM reconstruction algorithm. Regions of interest (ROI) were placed over all visually identifiable organs and the time-activity curves were computed. The system was calibrated in order to obtain KBq/cc values in each ROI. The time-activity curves were normalized to the injected activity and the area under the curves provided the residences times for the different organs. Blood and urinary samples were collected at different time intervals and measured using a Germanium solid state detector coupled to a multichannel spectrum analyzer. Blood residence time was used to calculate the residence time of the red marrow. Absorbed doses were calculated following the MIRD scheme by using the Olinda software. Residence time of urinary bladder was calculated by applying the dynamic bladder model included in Olinda. Results: As many other peptides 68Ga-DOTANOC presented a very fast clearance from the blood and tumor masses appeared clearly also in early acquisitions. Organs which presented a high affinity with 68Ga-DOTANOC and which were included in ROIs analysis were: heart wall, liver, lungs, spleen, kidneys, urinary bladder and pituitary gland. Organs with the highest radiation burden were urinary bladder wall (1.01x10-1 mSv/MBq), kidneys (8.97x10-2 mSv/MBq), spleen (6.56x10-2 mSv/MBq) and liver (3.38x10-2 mSv/MBq). The average effective dose equivalent delivered to the patient is 2.61x10-2 mSv/MBq. Conclusions: The 68Ga-DOTANOC is a safe tracer with high desirable pharmacokinetics properties for the imaging of NET. All organs and total body absorbed doses associated are well below the limits established by CFR for research subjects.
- Society of Nuclear Medicine, Inc.