Dose distribution calculation for in-vivo X-ray fluorescence scanning

R. FIGUEROA , E. LOZANO AND M. VALENTE

Guadalajara

Congreso; Seminario Latinoamericano de Tecnicas por rayos X = SARX 2010; 2010

In-vivo X-ray fluorescence constitutes a useful and accurate technique, worldwide established for constituent elementary distribution assessment. Actually, concentration distributions of arbitrary user-selected elements can be achieved along sample surface with the aim of identifying and simultaneously quantifying every constituent element. The method is based on the use of a collimated X-ray beam reaching the sample, whose characteristic fluorescence emission is recorded by a suitable detector. However, one of the more common drawbacks associated with the possibility of considering the application of this technique for routine clinical  examinations has been the supposed high dose level associated with the method. This work presents a complete study of the dose distribution resulting from a typical in-vivo X-ray fluorescence scanning devoted to identify and to quantify biohazard materials on  human hands. Absorbed dose has been estimated by means of dedicated dosimetric models specifically developed to this aim. In addition, complete dose distributions have  been obtained by means of full radiation transport calculations in based on pure stochastic Monte Carlo techniques. A dedicated subroutine has been developed using the PENELOPE 2008 main code and it has been suitably complemented and integrated by dedicated programs –MatLab® supported- capable of 2D and 3D dose distribution visualization. The obtained results show very good agreement between approximate analytical models and full descriptions by means of Monte Carlo simulations. As expected, some incident beam properties, like energy spectrum and beam flux have shown to strong determine the resulting absorbed dose. Besides, it has been found that, due to effective energy of typical incident spectrum, sample surface received almost always the main part of the total absorbed dose, which may constitute an important feature considering the analogy of skin in human hands.