Click here to


Are you sure ?

Yes, do it No, cancel

Demonstration of the Need for An Air-Kerma Rate Standard for the Newest Model of the Xoft Axxent TM Source

A Walter*, D Anderson , L DeWerd, Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To provide updated air kerma rate data for the S7600 Xoft Axxent source, which is the newest model of the S700-series sources and compare to the older, S7500 Axxent model.

Methods: Charge readings for four S7600 sources were taken in two HDR 1000+ well-type ionization chambers calibrated for the older S7500 Axxent source. The air kerma rate at 50 cm from the source was calculated using S7500 calibration coefficients, and these calculated air kerma rates were compared to those measured with the Attix free-air chamber at 50 cm. The raw charge readings from each well-chamber plus the measured free-air chamber air kerma rates were then used to determine new calibration coefficients for each respective well-chamber. Air kerma rates and calibration coefficients for the S7500 and S7600 sources were compared.

Results: Applying the S7500 calibration coefficients to the well-chamber readings for the S7600 sources resulted in a calculation of air kerma rates that were, on average, 20% higher than the air kerma rates measured with the FAC for those same S7600 sources. As a result, the calculated calibration coefficients for these S7600 sources were 17% lower than those for the S7500 sources. An updated source model must be developed in EGSnrc in order to adequately compare the two sources via simulation.

Conclusion: This work provides preliminary evidence for the need of a new standard to be developed for the S7600 Axxent source. Future work will include working with NIST and Xoft to establish a new standard and dosimetrically characterize the S7600 source for clinical use. It is important that this new standard be developed prior to the source’s use in the clinic.

Funding Support, Disclosures, and Conflict of Interest: This work is funded in part by Xoft, a subsidiary of iCAD inc.


Brachytherapy, Dosimetry, HDR


TH- Brachytherapy: Dose measurement

Contact Email