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New National Air-Kerma Standard for Low-Energy Electronic Brachytherapy Sources



Stephen M. Seltzer, C M. O'Brien, Michael G. Mitch


The purpose of this report is to document the NIST air-kerma measurement standard for the electronic brachytherapy sources, i.e., the Axxent sources of Xoft, Inc., which operate at tube potentials of 50 kV and anode currents of 300 μA. The use of such sources requires basic dosimetry to ensure the delivery of the desired absorbed dose in the target. Details of the identification of a NIST standard and the required development of the instrument’s corrections factors are provided in this report. Results of the air-kerma comparison between two primary NIST x-ray standards that validates the corrections are provided, as well as the acceptance of a transfer instrument that can be used by secondary calibration facilities or users of the Axxent sources to provide traceability of the measurement of air kerma.
Journal of Research (NIST JRES) - 119.022
Report Number


electronic brachytherapy sources, air-kerma standard, low-energy x-rays, free-air ionization chamber, correction factors, dosimetry


Seltzer, S. , O'Brien, C. and Mitch, M. (2014), New National Air-Kerma Standard for Low-Energy Electronic Brachytherapy Sources, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 12, 2024)
Created October 6, 2014, Updated November 10, 2018