Performance of amorphous selenium-based unipolar charge sensing detector for photon counting x-ray imaging

Ahmet Camlica; Denny Lee; Hyunsuk Jang; Salman M. Arnab; Yuan Fang; M. Z. Kabir; Karim S. Karim

doi:10.1117/12.2550318

16 March 2020 Performance of amorphous selenium-based unipolar charge sensing detector for photon counting x-ray imaging

Ahmet Camlica, Denny Lee, Hyunsuk Jang, Salman M. Arnab, Yuan Fang, M. Z. Kabir, Karim S. Karim

Author Affiliations +

Proceedings Volume 11312, Medical Imaging 2020: Physics of Medical Imaging; 113120G (2020) https://doi.org/10.1117/12.2550318
Event: SPIE Medical Imaging, 2020, Houston, Texas, United States

Abstract

Practical photon counting detectors that have been adopted for commercial use are typically based on crystalline or polycrystalline materials. However, these types of materials are challenging to scale to large-area medical imaging applications because of yield and cost issues associated with the crystal growth and bonding technology required to interface the sensor with the readout IC. An alternate approach is to use a large-area-compatible, mature, direct conversion X-ray-detection sensor such as amorphous selenium (a-Se). The technical challenges for photon counting with a-Se lie in overcoming (1) the slow carrier-transport material property of a-Se, which leads to count-rate limitations due to pile-up, and (2) the lower X-ray-to-charge conversion gain, which degrades SNR and can be resolved by improved design of pixel readout circuits. In this paper, we address the a-Se material limitation by leveraging a unipolar charge sensing detector design. We demonstrate that the proposed unipolar charge sensing detector provides an effective method to detect charge of the polarity type having a higher mobility-lifetime product, obviating the need for detection of the opposite polarity slow transport charge. Transient signal measurements indicate that a quasi depth independent signal rise-time is achieved with the unipolar charge sensing detector. Moreover, two orders of magnitude improvement is observed compared to the conventional a-Se detector rise-time (0.15 μs vs. 25 μs).

Citation Download Citation

Ahmet Camlica, Denny Lee, Hyunsuk Jang, Salman M. Arnab, Yuan Fang, M. Z. Kabir, and Karim S. Karim "Performance of amorphous selenium-based unipolar charge sensing detector for photon counting x-ray imaging", Proc. SPIE 11312, Medical Imaging 2020: Physics of Medical Imaging, 113120G (16 March 2020); https://doi.org/10.1117/12.2550318

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