<title>Recent developments in a CdTe-based x-ray detector for digital radiography</title>

Abstract

The performances of a new CdTe based X-ray detector devoted to digital radiography are presented. The detectors consist of a 6 cm2 CdTe 2D-array connected to CMOS readout circuit by indium bumps. The final image has 400x600 pixels with a 50 micron pitch.This solid-state detector presents the advantages of direct (X-rays into charges) conversion, i.e. high stopping power with high spatial resolution and a significantly higher signal than commercially available scintillator/photodetector systems.The experimental results show excellent linearity, spatial resolution and detective quantum efficiency. The MTF was measured by the angled-slit method (Fourier transform of the pre-sampled Line Spread Function) : 20 to 30 % at 10 lp/mm depending on the incident X-ray energy. The measured DQE (at zero frequency) is about 0.8 at 40 KeV and 100 Gray dose.Our simulation (energy deposition by ITS Monte Carlo code) shows that these experimental results don't reach the theoretical limit. Further improvements are in progress.The first industrial application will be dental radiography (40 KeV mean energy) due to the small size and the excellent performances. We also tested the detector with X-rays from 20 KeV to 1.25 MeV. Of course the CdTe thickness should then be adapted to the incident X-ray energy.

Strategies to improve the signal and noise performance of active matrix, flat‐panel imagers for diagnostic x‐ray applications

“…An alternative approach to significantly increasing system gain would involve the utilization of an x-ray converting material offering a higher sensitivity ͑i.e., a larger number of secondary quanta per interacting x ray͒, and thus a higher gain than phosphors, CsI͑TI͒, or a-Se. While a wide variety of candidate radiation detection materials exist, including TlBr, HgI 2 , CdTe, and CdZnTe, 8,29 one particularly promising material which has recently been under considerable investigation for use in active matrix imagers is lead iodide, PbI 2 . 8,[30][31][32] Table II contains a comparison of properties for PbI 2 with those for other detection materials which are already used in AMFPI devices.…”

Image quality of scintillator-based x-ray electronic imagers

“…The ultimate spatial resolution is then essentially dependent on the charge reading mechanism, e.g. pixel size and fill factor in a digital image [5,6,7], or distance from the sensor to the photoconductor plate in the case of capacitive readout L8].…”