<title>Progress report on the performance of real-time selenium flat-panel detectors for direct x-ray imaging</title>

Abstract

Real time flat panel detectors based on amorphous selenium (a-Se) have demonstrated to be the most advanced technology for direct conversion X-ray imaging in various medical applications. In continuation of real time detector development, ANRAD Corporation introduce in this paper a large size 14" x 14" active area detector built with an amorphous selenium (a-Se) converter coated on a TFT array. This new detector is a scaled up version of the 9" x 9" presented last year based on a TFT array with 150 µm x 150 µm pixel and a 1000 µm thick a-Se PIN structure operated at 10V/µm. DQE(f=0) measurements were performed in low dose range and demonstrated to be in agreement with a linear model including 2500e of electronic noise. It is also shown that the spatial resolution (MTF) could be controlled by selenium coating process and can almost reach the theoretical limit defined by the pixel pitch. Finally, the first 14" x 14" chest image is presented.

Reduction of the dark current in stabilized a-Se based X-ray detectors

“…Typically the dark current density for detector applications should be smaller than $10 À10 A cm À2 [3] at operating fields of 5-10 V lm À1 . In commercialized a-Se detectors, the structure is a 'p-i-n'-like multilayer [4], where an intrinsic-like (i-layer) thick aSe (with both hole and electron transport) is sandwiched between two thin layers of p-type (doped a-Se that has good hole transport but no electron transport) and n-type a-Se (doped material that has good electron transport but no hole transport) as illustrated Fig. 1.…”

Photoconductor Digital X‐Ray Imaging

“…Such reset cycles decrease the maximum imaging frame rate. Anrad developed a rectifying p -i -n diode structure in a -Se [4] that was further modifi ed jointly with Toshiba [5] . It requires no special reset sequences.…”

Pixel detectors for tracking and their spin-off in imaging applications

“…A challenge for counting pixel detectors in radiology is to build large area detectors. Commercially available integrating pixellated systems such as flat panel imagers [28,29,30,31,32] set the competition level.…”