Active matrix X-ray imaging array

US5962856A · kind A · utility

Assignee

• Sunnybrook Hospital · CA

Inventors

• Wei Zhao · East Setauket, US
• John A. Rowlands · Toronto, CA

Key dates

• Filing date: Apr 6, 1998
• Grant date: Oct 5, 1999
• Expiry date: Apr 6, 2018

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10F39/191

Abstract

A digital detector for radiography and fluoroscopy is disclosed. The detector includes a large area, flat panel that easily fits into a conventional X-ray room bucky tray. The detector utilizes a layer of photoconductor (i.e. a-Se in the preferred embodiment) to detect X-rays and convert the X-ray energy to charge, and an active matrix TFT array in the form of a very large area integrated circuit, for readout of the charge. A dual gate structure is used for the TFT array wherein the top gate is formed as an extension of the pixel electrode, so as to provide high voltage protection of the TFT. An integrated pixel storage capacitor is provided for enhanced absorption of X-ray energy with low pixel voltage, low leakage current and a large charge leakage time constant. In a preferred embodiment, the integrated pixel storage capacitor is created by overlapping the pixel the pixel electrode with an adjacent gate line or a separate ground line of the active matrix readout array. Image charge collection efficiency is enhanced by manipulating the electric field distribution in the photoconductor layer so that image charges land on the pixel electrodes, and not on the TFT readout devices.