Determination of the dose rate constant through Monte Carlo simulations with voxel phantoms

Assessing body dose rate constant and effective body absorption factor in Taiwanese reference phantoms

The self-attenuation of a patient's body is an important factor in nuclear medicine for designing radiation shielding. Taiwanese reference man (TRM) and Taiwanese reference woman (TRW) were constructed to simulate the body dose rate constant and the effective body absorption factor for 18F-FDG, 131I-NaI and 99mTc-MIBI using the Monte Carlo technique. For TRM, the maximum body dose rate constants for 18F-FDG, 131I-NaI and 99mTc-MIBI were 1.26 × 10-1, 4.89 × 10-2 and 1.76 × 10-2 mSv-m2/GBq-h, respectively, at heights of 110, 110 and 100 cm. For TRW, the results were 1.23 × 10-1, 4.75 × 10-2 and 1.68 × 10-2 mSv-m2/GBq-h at heights of 100, 100 and 90 cm. The effective body absorption factors were 32.6, 36.7 and 46.2% for TRM and 34.2, 38.5 and 48.6% for TRW. Regional reference phantoms along with the derived body dose rate constant and effective body absorption factor should be used for determining regulatory secondary standards in nuclear medicine.

Monte Carlo calculation of whole body counter efficiency factors for different computational phantoms

Individual monitoring can provide an estimate of the radioactivity present in the body of the exposed individuals. Periodic monitoring of occupationally exposed individuals is of great importance in case of accidental incorporation. Computational phantoms and Monte Carlo codes are often used to complement the calibration method of counting systems in internal dosimetry. Here, counting efficiency (CE) factors for a WBC system were calculated using MC simulations. The WBC system with a NaI(Tl) detector and the BOMAB phantom was modeled using three MC codes. After validation, the models were used to obtain CE values for a wide range of energies, and a CE curve was generated for the WBC system. To estimate the effects of anatomical differences on the measurement process, two anthropomorphic voxel phantoms were modeled using the VMC code. For the detector position with the highest CE value, the differences when comparing BOMAB results with the MaMP and Yale results were (-1 ± 6)% and (-1 ± 3)%, respectively. The results confirm that the use of the BOMAB phantom is a good approach for the calibration of the whole-body counter system. Measurements should be made at detector position with the highest CE values, and it is recommended to use the mean Monte Carlo CE values calculated in this work.

Shielding commissioning factors in nuclear medicine facilities

This article reviews the essential considerations in planning and designing nuclear medicine departments. There are four proposed categories to consider as 'shielding commissioning factors' (SCF). The first SCF: 'Patient flow optimisation and workload' emphasises the importance of carefully considering patient flow in the departmental design, which would impact the cost of the shielding and the management of radioactive patients. The second SCF: 'Equipment and space allocation' discusses the principles of space allocations in the department for cost-effective designs. The third SCF: 'Shielding calculation methods' reviews the methodologies of shielding calculations in nuclear medicine to offer a standardised approach. The fourth SCF: 'Shielding integrity' reviews the plan to inspect, eyewitness and verify shielding integrity. All discussions were supplemented by practical examples. Overall, this article aims to be a practical manual which health or medical physicists can use when providing counsels to the design committee.