VMC dose calculation was applied to the 2018 EURADOS internal dosimetry intercomparison. The objectives of the intercomparison were to evaluate absorbed fractions (AF) and specific absorbed fractions (SAF) in specified “target” organs for monoenergetic photons emitted in specific “source” organs of both ICRP reference adult phantoms, and also to calculate S-values for the same source and target organ combinations for specific radionuclides, see ICRP 133 "The ICRP Computational Framework for Internal Dose Assessment for Reference Adults: Specific Absorbed Fractions" for the definition of SAFs.

The results of the intercomparison were reported in the paper “Monte Carlo calculation of organ dose coefficients for internal dosimetry: Results of an international intercomparison exercise”. VMC DC was participant “e”.

A number of absorbed fraction AF(target ← source) calculations were required in the intercomparison. Figure 1 shows the screenshot of the VMC dose calculation with the liver as the source.

Figure 1. 50 keV photons being emitted from all points inside the liver in all directions.

For the photons that interact in the thyroid, the total interaction energy is binned and the AF calculated. The results for the AF(thyroid ← liver) calculation by VMC were compared with the results from the other participants, see Figure 2.

Figure 2. Comparison of intercomparison participants’ AF(thyroid ← liver) calculations, normalized by the "Master solution" calculations. VMC is dark blue, participant "e".

It may be necessary to zoom into Figure 2; the VMC dose calculation and “master solution” values are almost equal.

Figure 3. "S" values normalized by the “master solution” for photons from ¹⁸F deposited in the liver.

The implementation of the dose calculation for red bone marrow and bone surface in VMC is not fully in accordance with the ICRP recommendation, however the algorithm will be modified to improve the agreement.

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