Measured low-energy x-ray spectra of interest in diagnostic radiology and mammography

Abstract

Objective. In cities situated at high-altitude, the measured x-ray spectra are required to calculate the absorbed dose to water in radiobiology and medical dosimetry because of the air-density effect. This work aims to measure, in a high-altitude city, a set of x-ray spectra from an x-ray tube with tungsten anode generated at potentials of the M-series x-ray beams from NIST in the range of 20 and 150 kV as well as other beam qualities that have been characterized and used for dosimetry study in our group called W-series. To also measure some spectra of mammography interest in the energy range of 25 and 35 kV using additional filtration of rhodium (Rh), molybdenum (Mo) and silver (Ag). Approach. A tungsten anode x-ray tube with potential between 10 to and 160 kV was used. A high-purity germanium (HPGe) detector associated with a DSPEC Jr 2.0TM digital signal processing module has been used for the spectra measurements. Prior the spectra measurements, the HPGe detector has been characterized and calibrated using several radioactive sources. Main results. The M80 spectrum was compared to a mathematically filtered beam from Physicalisch Technische Bundesanstalt corresponding to the same potential finding a difference of 0.7% in the average energy. So, the mathematically filtered beam from PTB matches very well our M80 beam. The beams M80, M100 and M120 were also compared with calculations for the corresponding kilovoltage from an executable that calculates x-ray spectra from tungsten anode x-ray tubes in the energy range between 40 to 300 kV called SpekCalc. The SpekCalc reproduces qualitatively the experimental spectra, but not quantitatively, mainly for M100 and M120 beams. Significance. These spectra can be used to simulate the patient dose as well as image quality using Monte Carlo (MC) codes or to evaluate the absorbed dose in dosimetry studies