Room: Exhibit Hall | Forum 1
Purpose: To quantify the impact of incorporating a detailed form of the intrinsic bremsstrahlung angular distribution in an analytical x-ray spectrum model.
Methods: Most x-ray spectrum models developed from theoretical principles assume that the angular distribution of bremsstrahlung production is uniform. This assumption stems from the rationale that electrons promptly attain a diffuse directional distribution in an x-ray target due to multiple scattering, effectively masking the intrinsic bremsstrahlung angular distribution. A more comprehensive bremsstrahlung emission model that considers in detail both the electron and the bremsstrahlung angular distributions in a tungsten target has been developed. It also includes a previously developed model for characteristic x-ray emission, to allow for direct comparison with other widely used x-ray spectrum models. The model results have been validated by Monte Carlo calculations (PENELOPE).
Results: Incorporating a detailed form of the intrinsic bremsstrahlung angular distribution can substantially improve (5-15%) predictions of the bremsstrahlung beam intensity (energy fluence) and air kerma free-in-air. Predictions of the bremsstrahlung beam quality (first and second half-value layers) are improved generally by about 2-3% and agree with Monte Carlo to within 2%. Predictions of the angular distribution of the x-ray emission are within 1% of Monte Carlo-calculated results. This is an improvement over other x-ray spectrum models whose predictions are generally within 2-10% of Monte Carlo results (depending on the emission angle and spectrum model considered).
Conclusion: More accurate analytical x-ray spectra predictions can be made by explicitly taking into account the electron and the intrinsic bremsstrahlung angular distributions in the calculation of the bremsstrahlung emission.