Can the HVL help the mechanical X-ray tube characterization?

Abstract

High-intensity X-ray beams are usually characterized by their kVp (kilovoltage peak) value and half-value layer (HVL). While the first parameter is reasonably well known (apart from accelerating potential fluctuations), on the second, there is a greater deal of uncertainty. The HVL depends on the used filtration, the effective kVp value and on some of the X-ray tube mechanical features, such as the anode angle. This last parameter is not always provided by the tube manufacturer, so we may question if the HVL dependence on the anode angle can be used to extract information on this angle. We tried to give an answer to this question using two different numerical models and a full Monte Carlo (MC) program to simulate the photon field produced by the X-ray tube for several anode angles. One of the numerical models was developed by the Institute of Physics and Engineering in Medicine and gives X-ray spectra and HVL values for a wide range of kVp values and anode angles. The other model, named SpekCalc, is based on a theoretical work developed by Gavin Poludniowski and Phil Evans. The MC simulation was done using the PENELOPE code for coupled electron-photon transport. Using the computed photon spectra, HVLs were obtained and compared with experimental HVL values obtained with a Philips PW 2184/00 X-ray tube with a 26° tungsten anode and accelerating potentials in the range of 40–90 kVp. We are now able to show the PENELOPE simulation can deliver the correct anode angle value. Copyright © 2011 John Wiley & Sons, Ltd.