Catalog of x-ray spectra of Mo-, Rh-, and W-anode-based x-ray tubes from 10 to 50 kV

• Published in: Physics in medicine & biology 2021-06, Vol.66 (11), p.115013
• Main Authors: Ketelhut, Steffen, Büermann, Ludwig, Hilgers, Gerhard
• Format: Article
• Language: English
• Subjects: high-purity germanium detector; mammography; x-ray spectrometry
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/1361-6560/abfbb2

This work presents a comprehensive catalog of x-ray spectra measured from x-ray tubes with tungsten, molybdenum, and rhodium anodes generated at tube potentials between 10 and 50 kV in steps of 1 kV. They can serve as an input for dose calculations, image quality calculations, investigations of detector features, and validations of computational spectral models, among other things. The measurements are performed by means of a high-purity germanium detector-based spectrometer 1 m from the x-ray sources without any added filtration. The x-ray tubes are characterized by thin beryllium exit windows (0.15−4 mm); thus, for energies above 15 keV, the spectra recorded can be considered approximately unfiltered. This allows potential users of the catalog to computationally add any filter to the spectra in order to create special radiation qualities of their choice. To validate this option, a small number of spectra are recorded with filter materials in place whose purity and thickness are known with high precision. These spectra are compared to the corresponding spectra from the catalog obtained by means of computationally added filters. The two types of spectra agree extremely well. Several typical mammographic radiation qualities are selected to compare the spectra obtained from the catalog presented here with corresponding spectra obtained from other catalogs published by Boone et al (1997 Med. Phys. 24 1863–74) and Hernandez et al (2017 Med. Phys. 44 2148–60). In contrast to the work presented here, those spectra rely partly or fully on calculations. A quantitative comparison is made by means of typical x-ray quality descriptors such as the mean energy and the first and second half-value layer. The results obtained from the Boone catalog match those of the current catalog sufficiently well for the Mo- and Rh-anode-based spectra. However, significant differences up to 10 times the estimated uncertainties are found for the quality descriptors evaluated from the spectra of Hernandez et al and the W-anode based spectra of Boone et al.