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Assessment of absorbed dose in the hematopoietic stem cell layer of the bone marrow, assuming non-uniform distribution around the vascular endothelium of the bone marrow
Background:
Recent studies have shown that hematopoietic stem cells (HSCs) are concentrated around the endothelium of the sinusoidal capillaries. However, the current International Commission on Radiological Protection (ICRP) dosimetry model does not take into account the heterogeneity of the bone marrow tissue and stem cell distribution. If the location of the hematopoietic stem cell layer differs from previous assumptions, it is necessary to re-evaluate the dose. It is especially important for short-range alpha particles, the energy deposited in the target HSC layer can vary greatly depending on the distance from the source region.
Objective:
The objective of this study is to evaluate of red bone marrow doses assuming that the hematopoietic stem cell layer of the bone marrow is localized in the vascular endothelium.
Methods:
A model of the trabecular bone tissues in cervical vertebrae was created using PHITS(Particle and Heavy Ion Transport System) code. Radiation transport simulations were performed for beta and alpha radionuclides and noble gases and the absorbed doses to the stem cell layer in the perivascular HSC layer in the bone marrow from radionuclides inhaled into the body were estimated. These results were then compared with the absorbed dose based on the ICRP 60 and ICRP 103 recommendations.
Results:
The absorbed doses to the bone marrow obtained from the model calculations were not significantly different from ICRP60 and ICRP103 for beta-nuclides. However, they were much lower than previously estimated for alpha-nuclides, and the contribution of red bone marrow and blood sources was greater than that of trabecular bone for alpha-nuclides. Noble gases in the red bone marrow may also affect the bone marrow stem cell layer.
Conclusions:
The bone marrow dose assessment for alpha nuclides and noble gases should be re-examined using a precise model based on CT images from the perspective of occupational and public radiation protection.
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