Author: Wesley S. Culberson, Ryan Gardner, John Thomas Stasko 👨🔬
Affiliation: Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin - Madison, University of Wisconsin 🌍
Purpose: X-ray tube voltage is a critical parameter in influencing an X-ray tube’s beam quality. The endpoint tube potential, the potential difference between the X-ray tube’s cathode and anode, is particularly important as it defines the maximum energy of primary photons. Differences between the nominal tube potential and the endpoint tube potential can result in significant changes in beam quality. International standards require the use of high-voltage dividers for an accurate, invasive measurement. However, high-voltage dividers are expensive, nontrivial to maintain, and incapable of measuring the actual electric potential between cathode and anode, prompting the exploration of more cost-effective and direct alternatives. This study presents an alternate method to determine the endpoint tube potential with a spectrometry-based approach.
Methods: Tube voltage measurements were conducted for an ADCL's M-series beam qualities, including M60, M80, M100, and M120, using a cadmium telluride (CdTe) x-ray spectrometer. The spectrometer was calibrated for energy with well-characterized Co-57, Cd-109, Am-241, and Pb-210 check sources. The endpoint tube potential was determined by two methods: (1) it was determined as the minimum difference between the energy of a spectrum bin and the energy at which a tangent line to the spectrum at that bin intersects the x-axis; and (2) it was defined as the intersection of a linear fit to the spectrum's terminal segment and a constant fit to the background.
Results: Methods 1 and 2 agreed with nominal tube potential displayed on the generator to within 0.22% and 0.42%, respectively. Averaging the results of the two methods agreed with the nominal tube potential to within 0.17%.
Conclusion: Cost-effective spectrometric techniques, such as CdTe X-ray spectrometers, offer viable alternatives for determining tube potentials. The results show low uncertainties across different fitting procedures, highlighting the precision of spectrometry-based methods for measuring endpoint tube potential.