Numerous studies reveal that the rate of uptake and elimination of radionuclides is greatly influenced by the age of the subject. This is also true for strontium as witnessed from the examination of thousands of human skeletons. Adults have high chances of exposure to strontium because of occupational hazards. Therefore, there are more dosimetry replicas for adults than for young people. However, with more prominence being given to the possible exposure of the public to radiations, it is essential to develop dosimetric models that include the relationship between age and the uptake of radionuclides. This paper looks at the possibility of developing an age-dependent dosimetric model for strontium by utilizing fundamental human anatomical and physiological data.
The study of strontium is similar to calcium because the two elements undergo similar metabolism. The bone, which is the main calcium store, is partitioned into two key sections. These are the structural bone that carries out motorized roles and the metabolic bone that controls calcium quantities in the extracellular fluids. This model relies on the fact that the skeleton comprises three compartments, two of which are coupled with the structural bone (bone volume) and the other compartment that is connected to metabolic processes (surface bone). The bone volume further consists of three vast parts that are soft, compact and hard bone. This model assumes that these three compartments are present during all life stages, but their metabolism differs at various life stages.
Increases and reductions of calcium by the bone volume significantly affect the metabolism of Sr. The cortical bones (compartment 1) and the cancellous bones (compartment 2) have little differentiation in terms of structure and function in young people. Therefore, there are no disparities in their uptake and retention of Sr. However, as a person grows old, there are distinct dissimilarities between these two compartments in terms of their Sr uptake and retention. It is thought that the body cannot distinguish between Ca and Sr during metabolism due to their similarities. However, there is a facet of discrimination of Sr before it reaches the skeleton, which is accounted for by the formula k (t) =0.7 exp (-1.2t) +0.2 where ‘t’ is age, and ‘k’ is the bias aspect.
Skeleton age greatly affects its reactivity. Young bones have a rich blood and water supply that makes them extremely active. Old bones, on the other hand, are the least reactive because of complete mineralization. However, the bone proportion available for exchange of calcium remains constant throughout the developmental process. Strontium elimination from bones is the same as calcium removal, which increases with increasing age due to the natural aging process that causes bone loss. The radioactive decay process of about 0.025 annually also contributes to Sr loss. Compact bone and cancellous bones show different Sr removal rates with cancellous bone having a lower rate than compact bone. The product of the discrimination factor and the fraction of calcium that is absorbed by the bones is the proportion of Sr that is ultimately retained by bones.
It is possible to develop age-specific human models of various nuclides by using compartments that match up to physically identifiable processes in various organs. In addition, experimentally appropriate methods can establish age trends of the absorption and retention of radionuclides in various compartments. It is also crucial to account for the relationships between various physiological processes during the development of such models to ensure the accuracy of the models.