VMC dose calculation was validated through the 2018 international intercomparison organized by EURADOS. Three geometries and sources were simulated.

(1) Ground contamination with ²⁴¹Am

The results of this part of the intercomparison were published in the paper “Monte Carlo calculation of organ and effective dose rates from ground contaminated by ²⁴¹Am: Results of an international intercomparison exercise”. Figure 1 shows the ground contamination geometry.

The problem was to calculate the organ and effective doses from an exposure of one hour to a simulated ground source of 10 MBq per square meter of a gamma emitter of 60 keV (²⁴¹Am). The VMC dose calculation result for the effective dose was 6.20 E-08 Sv/s and the “reference” effective dose was 6.29 E-08 Sv/s.

Figure 1. Screen shot of VMC dose calculation for the ground geometry showing the female voxel phantom. Dose values given in the figure were divided by 3600 to convert from Sv/h to Sv/s.

(2) Exposure to a point source

A 10 minute exposure to a 10 GBq ⁶⁰Co source at a distance of 125 cm from the ground and 100 cm from the chest was simulated. VMC dose calculation result for the effective dose was 4.2 E-04 Sv, and the reference effective dose calculation was also 4.2 E-04 Sv.

The results of this part of the intercomparison were published in the paper "Monte Carlo calculation of organ and effective doses due to photon and neutron point sources and typical X-ray examinations: Results of an international intercomparison exercise"

Figure 2.Screen shot of VMC dose calculation for this geometry showing the male voxel phantom. The phantom has been placed in a rectangular room and the red circles and blue lines represent the exit point and direction of each photon from the 4 room walls, roof and ceiling.

(3) Exposure to typical X-ray examinations

Two exposure situations were simulated; the first was an abdomen AP with 115 cm between the anode and the image receptor with a 10 cm distance between the skin and the receptor of size 45 cm × 35 cm, see Figure 3.

Figure 3. 90 kV abdomen AP examination with 115 cm between the anode and the image receptor with a 10 cm distance between the skin and the receptor of size 45 cm × 35 cm.

VMC dose calculation results for this geometry showed values of absorbed doses per entrance air kerma free in air and per Kerma-Area-Product for 7 tissues and organs lower than the reference values by 10%.

The second exposure situation was a 125 kV chest PA of the female phantom with 180 cm between the anode and the image receptor with a 10 cm distance between the skin. The receptor size was 35 cm × 35 cm. VMC results for this geometry showed values of absorbed doses per entrance air kerma free in air and per Kerma-Area-Product for 7 tissues and organs lower than the reference values by 40% - still work in progress! Figure 4 shows the geometry.

Figure 4. 125 kV chest PA of the female phantom with 180 cm between the anode and the image receptor with a 10 cm distance between the skin.

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