Application of the MTSVD method in the experimental x-ray spectrum unfolding in the diagnostic energy range using CR film and Plexiglas wedge

Obtaining the quality of the beam is considered one of the most important quality control issues for X-ray tubes. X-ray spectrum is a very important aspect of quality control of medical imaging devices. However it may not be measured directly due to the very high photon flux, increasing the problems of the dead time and the Pile-up effect. The purpose of this study is to use a simple, and indirect method to unfold the primary X-ray spectrum. In this investigation, a system composing of a PMMA wedge, and a CR film was designed and constructed. The absorbed dose by the film is related to the primary spectrum by response matrix which was obtained using the MCNP Monte Carlo code exactly. The response matrix was used to unfold the spectrum, from the reading of the CR film. However, as the response matrix is ill-conditioned, it is not possible to solve the equation system in the normal way. Therefore the MTSVD regularization method in MATLAB software was used for unfolding the primary spectrum. The shape of the spectrum and the beam quality was compared with the IPEM 78 report catalog. The results indicate that the X-ray spectrum may be unfolded using this indirect method with sufficient accuracy.