Masayuki Nishiki

Development of a selenium-based flat-panel detector for real-time radiography and fluoroscopy

Flat-panel detector (FPD) is the driving force for realizing the next generation of x-ray systems. The purpose of this study was to develop a selenium-based FPD for both radiography and fluoroscopy. The detector uses amorphous selenium (a-Se) and a thin-film transistor (TFT) array. The simple construction of the a-Se layer permits real-time readout. The unique response characteristics of the FPD, which can be saturated over permitted x-ray doses, are provided by the TFT structure. Our prototype FPD was designed to acquire images at 30 frames per second (fps). A high modulation transfer factor was obtained: 0.63 at 2.0 Lp/mm. Sequential fluoroscopic images were acquired at up to 30 fps. The linear characteristics of the detector covered the commonly employed range of clinical exposure dose. Less than 1.5% image lag was measured at 30 fps.

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.

Stereo fluoroscopy-assisted distal interlocking of intramedullary nails

A simulation study of distal interlocking of an intramedullary nail was performed using newly devised, portable stereo fluoroscopy. Two intramedullary nails in which ten holes were drilled perpendicular to the long axis and at various angles to the diameter were inserted into a femoral and a tibial bone model. Ten drill bits were drilled freehand into the holes in the nail with the aid of the stereo fluoroscope. All twenty drill bits were seated in the holes in the first attempt. This instrument provides a three-dimensional view in real time, which enables the surgeon to appreciate the three-dimensional relationship between the drill bit and the hole in the nail in the bone model. Distal interlocking of the intramedullary nail is facilitated with the aid of this stereo fluoroscope.

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.

Reconstruction of Pediatric 3D Blood Vessel Images from Biplane Angiograms

In pediatric cardiac angiography, there are several peculiarities such as limitation of both x-ray dose and the amount of contrast medium in comparison with conventional angiography. Due to these peculiarities, the catheter examinations are accomplished in a short time with biplane x- ray apparatus. Thus, it is often difficult to determine 3D structures of blood vessels, especially those of pediatric anomalies. Then a new 3D reconstruction method based on selective biplane angiography was developed in order to support diagnosis and surgical planning. The method was composed of particular reconstruction and composition. Individual 3D image is reconstructed with the particular reconstruction, and all 3D images are composed into standard coordinate system in the composition. This method was applied to phantom images and clinical images for evaluation of the method. The 3D image of the clinical data was reconstructed accurately as its structures were compared with the real structures described in the operative findings. The 3D visualization based on the method is helpful for diagnosis and surgical planning of complicated anomalies in pediatric cardiology.