High energy, real time capable, direct radiation conversion X-ray imaging system for Cd-Te and Cd-Zn-Te based cameras

Abstract

A calibrated real-time, high energy X-ray imaging system is disclosed which incorporates a direct radiation conversion, X-ray imaging camera and a high speed image processing module. The high energy imaging camera utilizes a Cd—Te or a Cd—Zn—Te direct conversion detector substrate. The image processor includes a software driven calibration module that uses an algorithm to analyze time dependent raw digital pixel data to provide a time related series of correction factors for each pixel in an image frame. Additionally, the image processor includes a high speed image frame processing module capable of generating image frames at frame readout rates of greater than ten frames per second to over 100 frames per second. The image processor can provide normalized image frames in real-time or can accumulate static frame data for substantially very long periods of time without the typical concomitant degradation of the signal-to-noise ratio.

Description

FIELD OF THE INVENTION [0001] The present invention is in the field of semiconductor imaging systems for imaging x-ray and gamma ray radiant energy. More specifically, the invention relates to a high energy charge-integrating imaging devices utilizing Cd—Te or Cd—Zn—Te based detector substrates in combination with CMOS readout substrates. Additionally, the invention relates to a process for calibrating such high energy radiation imaging systems. BACKGROUND OF THE INVENTION [0002] Over the past ten years digital radiation imaging has gradually been replacing conventional radiation imaging for certain applications. In conventional radiation imaging applications, the detecting or recording means is a photosensitive film or an analog device such as an Image Intensifier. Digital radiation imaging is performed by converting radiation impinging on the imaging device (or camera) to an electronic signal and subsequently digitizing the electronic signal to produce a digital image. [0003] Digi...

AI Technical Summary

Benefits of technology

[0012] The present invention is a high energy, direct radiation conversion, real time X-ray imaging system. More specifically, the present real time X-ray imaging system is in tended for use with Cd—Te and Cd—Zn—Te based cameras. The present invention is particularly useful in X-ray imaging systems requiring high image frame acquisitions rates in the presence of non linear pixel performance. The present invention is “high energy” in that it is intended for use with X-ray and gamma ray radiation imaging systems having a

Problems solved by technology

Therefore, in these current imaging systems, increasing accuracy requires increasing the pixel charge integration time.

Unfortunately, errors inherent in current imaging systems limit the length of a charge integration cycle to just a few seconds at most, before the signal-to-noise ratio first “saturates” and then becomes so bad as to preclude any increase in accuracy with increasing charge integration time.

Designing and manufacturing a sensitive, high energy radiation-imaging device is a very complex task.

Although great progress has been made in the research and development of semiconductor radiation imaging devices, a large number of old performance issues remain and certain new performance issues have developed.

Some of the new performance issues result from solving other even more severe performance problems, while some are intrinsic to the operating principle of such devices.

On the other hand, current methods of producing Cd—Te and Cd—Zn—Te flat panel substrates limits their uniformity and impacts the crystal defect rate of these materials, which as can cause some of the problems mentioned above.

In addition, due to the use of an electric field of the order of 100V / mm or higher, a considerable leakage current (or dark current) results, causing image degradation.

However, these documents make no mention of and do not address the issues arising when a device of this type operates at high frame rates exceeding 10 fps, or how to calibrate, or even the need to calibrate in the case of such an application.

However the issue of operating the device at high rates and how to compose an image from many uncorrected individual frames is not addressed.

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