Program Information
Energy Spectra Measurements with a CdTe-Based Imaging Photon Counting Detector (PCD)
A Shankar*, J Krebs , M Russ , D Bednarek , S Rudin , Toshiba Stroke and Vascular Research Center , University at Buffalo , Buffalo, NY
Presentations
WE-RAM1-GePD-I-6 (Wednesday, August 2, 2017) 9:30 AM - 10:00 AM Room: Imaging ePoster Lounge
Purpose: Perform a preliminary evaluation using four operational modes in XCounter’s Actaeon PCD for x-ray spectrum measurements.
Methods: In contrast to energy integration, a PCD involves counting individual photons above a fixed threshold. XCounter AB’s Actaeon imager is based on direct detection with 0.75 mm thick CdTe, 100 µm pixel pitch, and 256 x 256 pixels. X-ray spectra at 70 kVp from a Toshiba Rotanode DRX T744GFS tube were measured by summing 150 individual frames to find total counts at varying threshold settings. Differential counts were obtained to plot the x-ray spectra. Initially dark field measurements were taken to check for background/scatter counts as a function of threshold settings up to 70 keV.
Results: High Sensitivity with Anti-Coincidence On (HS-On) mode outperformed the other modes in giving the spectrum with greatest counts for thresholds above 20 keV probably because the charge sharing circuit enables counts in adjacent pixels that would have had values below the threshold, now to be able to contribute to more accurate values above the threshold and hence counted unlike for other modes. At lower energies where there is greater flux, however, pulse pile up may contribute to lower spectrum values. This was evidenced when the charge sharing was turned off but high sensitivity maintained (HS - Off). The High Flux (HF) mode does produce higher counts at lower threshold energies but drops down more rapidly at higher keVs. The dark field/scatter counts were significant only up to a 4 keV threshold after which instrumentation noise appears to be negligible.
Conclusion: For higher thresholds and where instrumentation noise was negligible, energy spectra were greatest in magnitude for the HS-ON PCD mode indicating the most potential for dual energy applications of the four available modes.
Funding Support, Disclosures, and Conflict of Interest: This research was supported in part by Toshiba Medical Systems Corporation and NIH Grant R01EB002873
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