Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
1997-06-26
2002-02-05
Nguyen, Chanh (Department: 2675)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
C345S670000
Reexamination Certificate
active
06344858
ABSTRACT:
FIELD OF THE INVENTION
The present invention is in the field of digital radiography. The invention more specifically relates to a method and an apparatus permitting evaluation of processing performed on the digital signal representation of a radiographic image in a most convenient way.
BACKGROUND OF THE INVENTION
In the field of digital radiography a wide variety of image acquisition techniques have been developed such as computerised tomography, nuclear magnetic resonance, ultrasound, detection of a radiation image by means of a CCD sensor or a video camera etc.
In still another technique a radiation image, for example an image of x-rays transmitted by an object, is stored in a screen comprising a photostimulable phosphor such as one of the phosphors described in European patent publication 503 702 published on Sep. 16, 1992 and U.S. Ser. No. 07/842,603. The technique for reading out the stored radiation image consists of scanning the screen with stimulating radiation, such as laser light of the appropriate wavelength, detecting the light emitted upon stimulation and converting the emitted light into an electric representation for example by means of a photomultiplier.
The signal is then digitized, processed and subsequently used to control the hard copy recording in image reproducing system such as a laser recorder. For diagnostic purposes the reproduction is viewed and analysed on an lightbox.
In an alternative image acquisition system a digital representation of a radiographic image can be obtained by scanning a radiographic film carrying a radiographic image with light, detecting the image-wise modulated light (reflected or transmitted) and converting the detected light into a digital signal representation. Likewise the digital signal can be processed and can subsequently be used for controlling hard copy recording or display of the processed image.
Previous to image reproduction, the image signal can be subjected to image processing algorithms serving various kinds of purposes and involving the selection and setting of several kinds of processing parameters depending on the specific type of examination.
The different kinds of processing methods that can be applied will be described in extenso furtheron in the application. In summary these processing methods may comprise processing for the purpose of image analysis such as a method of recognising the borders of an irradiation field in case of shielded irradiation and image enhancing processing methods such as spatial frequency processing, noise reduction, gradation correction defining the relation between signal values and corresponding density values etc.
After processing the image signal is commonly sent to an output recorder for reproduction of the radiographic image on film.
The image quality or the outlook of the reproduction does not always match with the expected quality or outlook for various causes which cannot always be assessed easily due to the wide variety of actions that were performed on the image signal prior to reproduction.
When such problems occur, a common practice among radiologists using a digital radiography system of the above-named kind is to collect unsatisfactory hard-copies and to discuss anomalies with the service-technician on his inspection tour.
However, it is sometimes difficult or even impossible to recall certain processing conditions for evaluation or to reconstruct the performed signal processing.
In U.S. Pat. No. 5,004,917 a radiation image reading apparatus has been described wherein reading conditions and/or image processing conditions are established on the basis of the radiation image information which has been read from a photostimulable phosphor plate. Whether the reading and/or image processing conditions fall outside of a predetermined range or not is determined. If the reading conditions and/or the image processing conditions fall outside a predetermined range, the radiation image information and data used to establish the reading conditions and/or the image processing conditions is held in storage.
When the system suffers a fault when it is operated on trial or in actual use it is automatically put into HALT mode, then the user attempts to switch on the apparatus to recover the fault or he calls the service man. If the fault cannot be located, the service man connects a supervising unit. This unit then determines whether established read-out and/or processing parameters fall within a given range, and if negative, the supervising unit stores the reading conditions and/or processing conditions e.g. on a magnetic tape for analysis in the laboratory, so that any fault can be located and repaired.
In this system images for which the processing and/or read-out conditions fall within the predetermined range are not stored, so that in case an anomaly appears when evaluating the hard copy reproduction of such an image there is no possibility of retrieval of the image data foreseen.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a system for reading, processing and reproducing a radiation image, said system being designed so as to provide easy evaluation of the performed processing.
A further object of the invention is to provide a system of the above-named kind wherein the performed processing can be evaluated without the need of examining a hard copy of the processed image.
Further objects will become apparent from the description hereinafter.
STATEMENT OF THE INVENTION
The objects of the invention are achieved by a method of evaluating image processing performed on a digital representation of a radiation image comprising the steps of
acquiring a digital representation of a radiation image,
producing for said radiation image an image representation of a reduced number of pixels,
storing in a storage device data identifying an image, said reduced image representation, parameters used in course of said processing and intermediate processing results.
In one embodiment a digital image representation is acquired by reading-out a radiation image that has been stored in a photostimulable phosphor screen. The read-out method comprises the steps of scanning said screen with stimulating irradiation, detecting the light emitted upon stimulation and converting the emitted light into a digital signal representation. This signal representation can then be subjected to image processing.
In an alternative embodiment of the present invention the digital signal representation is obtained by scanning a radiographic film carrying a radiation image with light, detecting image-wise modulated light and converting said detected light into a digital signal representation.
The image-wise modulation of the scanning light can be obtained through either reflection or transmission by the radiographic film. The digital signal is then processed and, in accordance with the present invention, for each read-out image an image representation of a reduced number of pixels is produced, and data identifying an image, said reduced image representation, parameters used in course of said processing and intermediate processing results are stored in a storage device for each read-out image.
Alternative systems for acquiring a digital image representation can be envisioned.
In a preferred embodiment the storage device in which the data pertaining to the radiation images are stored has a limited storage capacity and is sequentially organized so that data pertaining to N successively read-out images can be stored and that when an N+1-th image becomes available, the data pertaining to this N+1-th image are stored at the expense of the first stored image data.
The present invention provides that in case an evaluation of the processing of an image is required, the data pertaining to said image can be retrieved and transmitted to a suitable output device for evaluation. Suitable output devices are a service computer, a display monitor, a hard copy recorder etc.
The method of the present invention is advantageous for the following reasons.
It enables evaluation of the performed processing on t
Janssens Danny Jozef
Vuylsteke Pieter Paul
Agfa-Gevaert
Hoffman, Warnick & D'Alessandro LLC
Merecki John A.
Nguyen Chanh
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