Dental Imaging with a Quantum-dot-based Direct Conversion X-ray Image Sensor
No Thumbnail Available
Author
Zhang, Chun-Min
Quaglia, Riccardo
Shulga, Artem
Goossens, Vincent
Hussain, Adib Al-Haj
Stadlinger, Bernd
Rüedi, Pierre-François
DOI
10.1109/NSS/MIC/RTSD57108.2024.10654883
Abstract
X-ray imaging has been extensively used in medical diagnosis thanks to the ability of X-rays to
penetrate through our body or a part for non-invasive imaging of internal structures. Nowadays,
most commercial X-ray detectors including dental imaging instruments rely on a cesium iodide
(CsI) scintillator to convert X-rays into visible light. However, they normally suffer from a low
spatial resolution due to optical crosstalk among neighboring pixels. Pixelated detectors made of
cadmium telluride (CdTe) or cadmium zinc telluride (CdZnTe) have shown excellent performance
for X-ray imaging. Nevertheless, they require flip-chip hybridization to connect to silicon readout,
adding assembly complexity, increasing fabrication cost, and restricting achievable pixel
resolution. We have developed a direct conversion X-ray imager with a high-Z lead-sulfide (PbS)
quantum-dot (QD) based photon absorber monolithically and directly deposited on a CMOS
readout chip. The silicon readout has been designed with a standard 180-nm CMOS process and
the photon absorber with a 120-μm layer of PbS QDs has been deposited from solutions at low
temperature. This approach takes advantages of CMOS technologies for a high pixel resolution,
low-power consumption, and complex readout electronics. It also benefits from high X-ray
absorption efficiency and low-temperature solution-based fabrication of PbS QDs. To our
knowledge, this is the first direct conversion X-ray imager with an absorber stack of PbS QDs on
silicon readout. Following an introduction to sensor design and fabrication, this paper
demonstrates the potential use of this imager in medical imaging particularly dental imaging. This
novel radiation detector has been used to produce high-quality tooth images while presenting a
low dark current, high linearity, a low noise equivalent dose, and a high spatial resolution. The
validation of this solution-based monolithic approach benefits realization of low-cost high performance X-ray imagers.
Publication Reference
2024 IEEE Nuclear Science Symposium (NSS), Medical Imaging Conference (MIC) and Room Temperature Semiconductor Detector Conference (RTSD), October 2024, Tampa, USA
Year
2024-07-16
Sponsors
This work was supported by the Clean Sky 2 Joint Undertaking under the European Unions Horizon 2020 research and innovation program under Grant 887192 and the Swiss State Secretariat for Education, Research, and Innovation (SERI) under the SwissChips initiative.