Akihito Takahashi

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

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 inches X 14 inches 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 inches X 9 inches presented last year based on a TFT array with 150 um x 150 um pixel and a 1000 mm thick a-Se PIN structure operated at 10V/um. 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 inches X 14 inches chest image is presented.

Performance of a real-time selenium-based x-ray detector for fluoroscopy

As amorphous selenium based flat panel detectors gain more interest for direct, real-time x-ray imaging, we report in this paper the performance of such a detector by ANRAD Corporation. This new detector is based on a 1536 X 1536 array of amorphous silicon TFT pixels coupled with a 1000 micrometers selenium converter biased at 10 V/micrometers . Each 150 micrometers X 150 micrometers pixel is made of a thin film transistor, a storage capacitor and a collecting electrode having a geometrical fill factor of 77% and an effective fill factor of nearby 100%.

Image quality evaluation of a selenium-based flat-panel digital x-ray detector system based on animal studies

The x-ray flat-panel detector (FPD) will be a key component of the coming generation of x-ray imaging systems. FPD systems applicable to both fluoroscopy and radiography especially, will be the prime candidate to replace current image intensifier x-ray (IIXR-TV) systems. Nevertheless, IIXR-TV systems which have recently been improved by the addition of CCD cameras, have established themselves over time by offering good image quality which in most cases clinicians appear to be satisfied with. It will thus take a substantial improvement in image quality combined with a new ease of use due to reduced physical size for new FPDs to replace those systems that have evolved over many decades. Our group has been developing a selenium-based FPD which has superior spatial resolution characteristics. The purpose of this research is to elucidate the FPDs potential to replace IIXR-TV systems by offering improved image quality. Detailed measurements of physical characteristics were made and extensive in vivo animal studies were conducted. It can be concluded that the FPDs demonstrated superior image quality appears to have the potential to improve clinical performance.

Clinical performance of a 14-in. x 14-in. real-time amorphous selenium flat-panel detector

Clinical evaluation results are presented using a large area, real time, amorphous selenium (a:Se), flat panel detector (FPD). The detector comprises of 1 mm thick amorphous selenium layer deposited onto a TFT panel that has a pixel pitch of .15 mm. The field of view of the detector is about 14” x 14” that is large enough to be used in R/F as well as general angiography application including digital subtraction angiography (DSA). Due to its high spatial resolution and low noise performance, it is shown that the detector is well suited to replace conventional image intensifier systems as well as film-screen systems.