Edward G. Shapiro

Flat panel imaging system for fluoroscopy applications

This paper describes a multi-mode, digital imager for real- time x-ray applications. The imager has three modes of operation: low dose fluoroscopy, zoom fluoroscopy, and high resolution radiography. These modes trade-off resolution or field-of-view for frame rate and additionally optimize the sensitivity of the imager to match the x-ray dose used in each mode. This large area sensing technology has a form factor similar to that of a film cassette, no geometric image distortion, no sensitivity to magnetic fields, a very large dynamic range which eliminates repeat shots due to over or under exposure, 12 bit digital output and the ability to switch between operating modes in real-time. The imager, which consists of three modules: the Receptor, the Power Supply and the Command Processor, is intended as a component in a larger imaging system. Preliminary characterization of the prototype imager in fluoroscopic mode at entrance exposure rates down to 2.5 (mu) R/frame, indicates that the DQE(f), MTF and low contrast resolution are comparable to that obtained with an image intensifier tube (IIT) coupled to a video camera.

Characterization of a third-generation multimode sensor panel

This paper describes a third-generation multi-mode x-ray imager whose applications include low-dose fluoroscopy, cine, spot films, and radiography. In addition, volumetric CT and applications whose environment includes a 2 tesla magnetic field are also in development. The VIP-9 is based on an amorphous silicon TFT/Photodiode array and x-ray conversion screen, which is optionally a deposited CsI(Tl) film or a removable Gd2O2S screen. There are three primary modes of operation: RAD for high resolution radiographs and spot films; Fluoro for video rate, low dose fluoroscopy as well as cine; Zoom for high resolution, limited field of view (FOV) fluoroscopy. Through improved electronics, the imager has greater sensitivity at low doses and far better rejection of correlated line noise than its predecessors. In addition, the VIP-9 incorporates many ease-of-use features absent from earlier prototype imagers. While previous reports have primarily focused on the imager construction and noise issues in large area sensing technology, in this paper the emphasis is on features which facilitate integration into a complete imaging system and measures of image quality.

Characterization of an amorphous-silicon fluoroscopic imager

This paper describes a dual-mode, flat panel imaging system capable of both fluoroscopy and radiography. Two generations of large area sensing technology are described. The general system architecture incorporates both the high sensitivity and data throughput required for fluoroscopy with the large signal capacity, spatial resolution and form factor necessary for radiography.

Amorphous silicon dual-mode medical imaging system

An amorphous silicon medical imaging system designed to operate in both radiographic and fluoroscopic modes is described. Images of medical phantoms are presented for both modes of operation. MTF and DQE measurements are also presented. The effect of recursive filtering on the DQE performance of the system operating in fluoroscopic mode is discussed.