Course Description:

In medical imaging, dual energy x-ray imaging and in particular Dual Energy Computed Tomography (DE-CT) [1] have raised expectations about the clinical benefits that energy resolving x-ray detectors could provide. With the first Photon Counting CT (PC-CT) systems now in clinical use, researchers and clinicians start to prove those expectations in particular by demonstrating improved spatial resolution [2], reduced radiation doses [3] and better contrast and tissue separation [4]. The promising initial results lead to the proclamation of not less but “a quantum leap in computed tomography” [5].

Consequently, Varex Imaging Corp., as the largest provider of x-ray imaging components and detectors in the world, has been investing in the technology of photon counting x-ray detectors through its acquisition of Direct Conversion [6], a developer of such technology for over 20 years. With this step, Varex positions itself as an independent supplier of this next generation technology and makes it available to all manufacturers of medical imaging devices without them having to bear large and long term investments in the technology. In addition, due to its unique position, Varex is able to offer components and subsystems that are matched and synced to the challenges of this new technology such has high power small focal spot x-ray tubes in conjunction with small pixel PC detectors.

Varex photon counting detectors already today are widely used in industrial [7], but also medical imaging [8] and CT [9, 10]. Based on a wealth of experience and with implemented necessary correction algorithms [11], recent developments are focusing on a new generation detector platform [12] that overcomes the size and flexibility limitations of current PC technology. The new platform provides new features such as design flexibility, medical CT compatible high count rates, ultra-high frame rates, on chip binning and enhanced spectral capabilities. The design of the new platform is versatile such that potential integrators and OEMs can develop and realize their own detector concepts.
Initial results of physical performance of the new platform and first images will be presented.
Clinical imaging examples from medical imaging devices based on Varex photon counting technology that are already on the market will complement the presentation.

[1] Flohr TG, et.al.: “First performance evaluation of a dual-source CT (DSCT) system”. Eur Radiol 16(2) (2007): 256

[2] Leng S, et. al.: “Ultra-High Spatial Resolution, Multi-Energy CT using Photon Counting Detector Technology.” Proc SPIE IntSocOpt Eng. (2017) Feb 11;10132.

[3] Rajagopal JR, et. al.: “Comparison of Low Dose Performance of Photon-Counting and Energy Integrating CT.” Academic Radiology (202): 1–7 (2021)

[4] Sawall S, et.al.: “Threshold-dependent iodine imaging and spectral separation in a whole-body photon-counting CT system”. Eur Radiol 31(9) (2021): 6631-6639.

[5] https://www.siemens-healthineers.com/de/computed-tomography/technologies-and-innovations/photon-counting-ct

[6] Varex Completes Acquisition Of Direct Conversion (prnewswire.com)

[7] Ullberg C, et.al. (PDF) Evaluation of the performance of a novel CdTe based photon counting detector for NDT applications (researchgate.net)

[8] EOSedgeTM: Dose Optimization Technology Insights in Musculoskeletal Imaging”, White Paper, EOS Imaging S.A, Paris (2021)

[9] Bader AM, et.al.: ''Development of a benchtop photon counting cone-beam CT system with a translate-rotate geometry,'' Proc. SPIE 11312, Medical Imaging 2020: Physics of Medical Imaging, 113124Y (2020)

[10] “Breast CT - a ground-breaking innovation”, Interview in Diagnostic Imaging Europe, (Nov. 2020): 18ff.

[11] Ullberg C, et al. “Photon counting, dual energy X-ray imaging at CT count rates: measurements and implications of in-pixel charge sharing correction” Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging; 1057319 (2018)

[12] Ullberg C, et al. “Measurements on a novel 4-side buttable photon counting ASIC with integrating charge sharing correction.” Proc. SPIE. 12031, Medical Imaging 2022: Physics of Medical Imaging (2022)