title: Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior.
abstract: Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components.
authors.affiliation: Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea. js900331@gmail.com.|Department of Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi 17104, Korea. js900331@gmail.com.
authors.forename: Jeong Seok
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea. dgkang@keri.re.kr.
authors.forename: Dong-Goo
authors.initials: DG
authors.lastname: Kang
authors.affiliation: Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea. sojin@keri.re.kr.
authors.forename: Seung Oh
authors.initials: SO
authors.lastname: Jin
authors.affiliation: Korea Electrotechnology Research Institute, Ansan, Gyeonggi 15588, Korea. iskim@keri.re.kr.
authors.forename: Insoo
authors.initials: I
authors.lastname: Kim
authors.affiliation: Department of Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi 17104, Korea. sylee01@khu.ac.kr.
authors.forename: Soo Yeol
authors.initials: SY
authors.lastname: Lee
keywords: CdTe; Medipix-2; photon counting spectral detector; spectral x-ray imaging; tube voltage