Program Information
Energy Calibration of Photon Counting Detectors Based On Measurement of X-Ray Attenuation Curve of K-Edge Materials
Y Ge , X Ji*, R Zhang , K Li , G Chen , University of Wisconsin-Madison, Madison, WI
Presentations
WE-AB-601-5 (Wednesday, August 2, 2017) 7:30 AM - 9:30 AM Room: 601
Purpose: Photon counting detectors (PCDs) use a threshold mechanism to achieve the energy-resolving imaging capability. Thresholds of PCDs are often labeled by un-specific threshold units provided by the manufacturers. For quantitative imaging applications, these threshold units need to be converted to absolute energy units, which often requires the use of radioactive isotopes with appropriate decay energy channels. Therefore, the energy calibration of the PCDs remains a challenge in practical use. The purpose of this work is to present and validate a practical solution using the k-edge energy information of the materials in imaging.
Methods: Experimental studies were performed to verify the feasibility of the proposed method. The detector used in this study is a cadmium telluride-based photon counting detector (XC-Flite X1, XCounter). The detector was operated in the anti-coincidence mode. The x-ray attenuation curve of three k-edge materials (Iodine, gadolinium, gold) were measured using the PCD. The threshold units corresponding to the position of the k-edges were recorded. The calibration relationship between the recorded nominal threshold units and the corresponding absolute energies was found using a linear regression. To validate the accuracy of the proposed calibration method, the gamma ray spectrum of an Am-241 source was measured using the PCDs and the peak position was identified based on the calibration results.
Results: The k-edges of all three materials were preserved in the measured attenuation curve. The relationship between the threshold unit and the energy is found to be 0.29/keV-2.13. Based on the calibration results and the measured gamma ray spectrum of Am-241, the estimated gamma emission energy is 61.6 keV, which is in good agreement with the ground truth (59.5 keV).
Conclusion: K-edge information of the materials provides a novel and practical approach to calibrating threshold units of PCDs. The accuracy of the method was validated using an Am-241 source.
Funding Support, Disclosures, and Conflict of Interest: The work is supported by an NIH grant R01EB020521 and a DOD Breakthrough Award W81XWH-16-1-0031.
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