Monte Carlo-based estimation of patient absorbed dose in 99mTc-DMSA, -MAG3, and -DTPA SPECT imaging using the University of Florida (UF) phantoms

SPECT imaging is one of the common modalities used to examine kidney disease. The radiopharmaceuticals such as 99mTc-MAG3, 99mTc-DTPA, and 99mTc-DMSA are commonly employed for pediatric patients. It is generally accepted that children organs are more sensitive to radiation than adults, due to their growth rate. Therefore, evaluating the absorbed dose in children to avoid irrecoverable damage is highly crucial. In this work, absorbed dose by different organs of children within the SPECT imaging for the above-mentioned radiopharmaceuticals were estimated through the use of Monte Carlo simulation for patients at the ages of 4, 8, 11, and 14-years old. The patients absorbed dose was estimated based on the specific radiopharmaceutical uptake patterns and the age-related human body models. To this end, we used the University of Florida (UF) voxel-wise baby phantoms and the Monte Carlo simulation for the pediatric patients at 4, 8, 11, and 14 years of age. The accuracy of the dosimetric outcomes was evaluated versus the ICRP 128 data. The highest and lowest doses absorbed by the kidneys were 0.48 mGy-MBq and 0.0042 mGy-MBq obtained for 4-year-old and 14-year-old children using 99mTc-DMSA and 99mTc-MAG3 radiopharmaceuticals, respectively. Moreover, in these cases, the relative errors of simulation results compared to the reference ICRP data were 12.1% and 0.95%, respectively. The simulation results were in good agreement with the ICRP 128 data. The results showed that the highest absorbed dose was by kidneys and when 99mTc-DMSA was used. The highest and lowest absorbed dose in the organs occurs when 99mTc-DMSA and 99mTc-MAG3 (in normal renal function) are used, respectively. On the other hand, the results indicated that the dose received by the organs decreases with age.