Development of Prototype Iranian male pelvic phantom for internal dosimetry

Introduction: Existing phantoms have been constructed based on Caucasian, non-Caucasian and race-specific datasets. According to previous studies made efforts to present Korean- specific phantoms and Chinese female phantom based on CVH dataset due to compare the resulting internal dosimetry with the Caucasian based data showed possible racial difference in human anatomy between Caucasian and non- Caucasian populations. These phantoms have been used for internal radionuclide dosimetry and other nuclear-medicine applications. Specific absorbed fractions (SAF) are tools for internal dose estimation of radionuclide intake. The differences were due to the racial and anatomical differences in organ mass and inter-organ distance. Many studies have been tried to provide an accurate and reliable data for internal radiation dose calculations. Therefor we construct an Iranian computational phantom to evaluate radiation dose organs within male pelvic region based on Iranian datasets. Internal dosimetry on organ is getting more important from the viewpoint of radiation protection of organ at risk.
Materials and Methods: The first version of computational Iranian male pelvis phantom(PIPM) is provided by 5 MRI datasets of Iranian male for precise organ dose calculation, at first organs within pelvic region are segmented by enhancing their margins in each slice, determination of organs volume then, prototype Iranian male pelvis phantom was developed by modifying the equation of internal organs of the ORNL adult phantom finally, this phantom was imported to general purpose Monte Carlo code to simulate photon transport from internal radiation source.
Results: The results showed that the individual comparable phantom can be calculated with acceptable accuracy using geometric registration. Comparison of dose calculation for Iranian male pelvic, MIRD and RADAR phantoms showed that differences of self-SAF were affected by organ volume differences. The average of the percent SAF deviation was calculated in testes organ -7.73%, -5.53% for PIMP phantom into MIRD and RADAR phantoms respectively. The largest deviation was observed in urinary bladder organ follow as 37.3%, 52.3% into MIRD and RADAR phantoms and it is shown -23.5% variations in self-SAF prostate organ into MIRD phantom. This phantom could be used for absorbed dose calculation of Iranian male pelvic region with acceptable accuracy in nuclear medicine.
Conclusion: A prototype computational Iranian adult male pelvis phantom was represented from 5 Iranian adult males; the results showed that comparable phantom can be calculated internal absorbed dose with significant differences. Accurate voxel phantom is needed for dosimetric simulation in nuclear medicine for malignant tumors in male pelvic region. However, most of the existing voxel phantoms are constructed on the basis of Caucasian or non-Chinese population. It might be provided first Iranian male reference volume organ dataset for future researches.