Table 2 - available via license: Creative Commons Attribution 3.0 Unported
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Source publication
The method defined by the IEC 60522 for determining the inherent filtration of an x-ray source device is applicable only for a limited range of tube voltage. Because the users cannot legally remove the x-ray movable diaphragm of the x-ray source device, total filtration, which is the sum of the additional filtration diaphragm movable for specific f...
Citations
A mathematical model has been developed to describe the radiation transparency of a test object with allowance for quantum noise. The technique of estimating the effective atomic number of the test object by the dual-energy method has been improved based on the analysis of radiation transparency with regard to necessary restrictions and recommendations. An algorithm is presented for the statistical evaluation of the influence of quantum noises on the quality of test-object material identification by the dual-energy method. An example is given of using the algorithm in a baggage and carryon inspection system that has the maximum X-ray energies of 80 and 160 keV and is equipped with total-absorption detectors.
Objective::
Modern image-guided small animal irradiators like the Xstrahl Small Animal Radiation Research Platform (SARRP) are designed with ultrathin 0.15 mm Cu filters, which compared with more heavily filtrated traditional cabinet-style biological irradiators, produce X-ray spectra weighted toward lower energies, impacting the dosimetric properties and the relative biological effectiveness (RBE). This study quantifies the effect of ultrathin filter design on relative depth dose profiles, absolute dose output, and RBE using Monte Carlo techniques.
Methods::
The percent depth-dose and absolute dose output are calculated using kVDoseCalc and EGSnrc, respectively, while a tally based on the induction of double-strand breaks as a function of electron spectra invoked in PENELOPE is used to estimate the RBE.
Results::
The RBE increases by > 2.4% in the ultrathin filter design compared to a traditional irradiator. Furthermore, minute variations in filter thickness have notable effects on the dosimetric properties of the X-ray beam, increasing the percent depth dose (at 2 cm in water) by + 0.4%/0.01 mm Cu and decreasing absolute dose (at 2 cm depth in water) by -1.8%/0.01 mm Cu for the SARRP.
Conclusions::
These results show that modern image-guided irradiators are quite sensitive to small manufacturing variations in filter thickness, and show a small change in RBE compared to traditional x-ray irradiators.
Advances in knowledge::
We quantify the consequences of ultrathin filter design in modern image-guided biological irradiators on relative and absolute dose, and RBE. Our results show these to be small, but not insignificant, suggesting laboratories transitioning between irradiators should carefully design their radiobiological experiments.
