Determination of the primary X-ray spectrum using a PMMA wedge, a flat panel and the Monte Carlo method

Autores UPV
Revista Progress in Nuclear Science and Technology


An accurate knowledge of the photon spectra emitted by X-ray tubes in radiodiagnostic is essential to better estimate the imparted dose to patients and to improve the quality image obtained with these devices. However, it is difficult to measure the energy spectrum of these tubes due to the pile up effect produced by the high fluence of X-ray beams. In this work, it is proposed the use of a flat panel detector together with a PMMA wedge to obtain a dose distribution for different high voltages. The relation between the dose curve recorded by the flat panel and the primary beam X-ray spectrum is defined by a Response matrix. The MCNP5 code based on the Monte Carlo method has been used to simulate the actual experimental acquisition including the X-ray tube, the PMMA wedge and a flat panel. A Response matrix has been obtained by means of different monochromatic beams. Knowing the dose distribution for a given conditions and the Response matrix, the primary spectrum can be obtained. The Modified Truncated Singular Value Decomposition (MTSVD) method has been applied to unfold primary spectra using Matlab © algorithms. Unfolded spectra are compared with theoretical X-ray spectra obtained from IPEM 78 catalogue report. Results show that the hybrid technique experimental-Monte Carlo method could represent a valid tool in order to complement the Quality Control of X-ray tubes in the radiodiagnostic energy range.