PET/ MR CRITICAL ORGAN DOSIMETRY

Abstract

Aim: Comparison of calculated radiation doses, obtained from different imaging methods, (whole body PET/MR and PET/CT) of the organs (bladder, brain, liver, kidneys and spleen) and the whole body of the patients coming to the clinic with different types of a cancer diagnosis.
Material and Method: In this study, radionuclide dosimetry was performed in 10 patients who underwent F-18 FDG injection for PET / MR imaging for the diagnosis of the primary tumour, determination of metastatic foci or response to treatment. F-18 FDG IV was administered to patients in the amount of 185-259 MBq activity. PET / MR images were taken at the 20th, 40th, 60th and 240th minutes after radiopharmaceutical injection. Time-activity changes were obtained by drawing ROIs over the images Organ doses were calculated according to the MIRD method by using OLINDA / EXM software.
Results: Patients received an average of 182 ± 32.5 MBq of F-18 FDG radiopharmaceuticals. Percentages of involvement at the 20th, 40th, 60th and 240th minutes in the organs are 8.89, 8.94, 8.55, 2.27 for the brain, 1.59, 1.22, 0.91, 0.12 for the kidney, 0.73, 0.65, 0.60, 0.095 for the spleen, 7.02 for the liver, 5.57, 4.18, 0.99, 4.92, 5.37, 3.25, 0.18 for bladder wall, respectively. Effective doses (Mean ± SD) 5.7 ± 1.90 mSv for the brain, 3.37 ± 1.34 mSv for kidney, 2.64 ± 1.51 mSv for kidney, liver 3.29 ± 1.67mSv was found to be 8.21 ± 2.13mSvo for the bladder wall.
Conclusion: In PET / MR imaging, the highest calculated absorbed organ dose from was in the bladder wall and the lowest calculated absorbed organ dose was in the spleen.