Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
1998-04-24
2001-11-27
Jankus, Almis R. (Department: 2775)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
C345S589000, C345S601000
Reexamination Certificate
active
06323869
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to digital medical imaging, and relates more particularly to the tonal rendering of digital medical images from multiple modalities.
BACKGROUND OF THE INVENTION
The selection and application of a tone scale adjustment function is a key component to properly display multiple modalities of medical images on a common display device such as a soft copy monitor.
Current medical imaging soft copy systems implement fixed tonal processing parameters for all images. As certain modalities require different tonal processing parameters to be rendered correctly, these modalities are currently displayed with sub-optimal image quality. While DICOM (Digital Imaging and Communication in Medicine) format allows for the specification of a tonal transformation for image display, the transformation is not required and the output space of the transform is not well defined. Therefore, images from different vendors may, and typically do, require different tonal processing to achieve the desired output. For hardcopy, the tone scale may be modified by a ‘curve shape’ parameter in the printer; there is no analogous parameter for soft copy. There is a need to determine the appropriate tone scale adjustment to be applied to an image for soft copy display based upon information in the DICOM header so that the image is rendered correctly.
Muka, Blume and Daly (“Display of medical images on CRT soft-copy displays: A tutorial”, Proc. SPIE, Vol. 2431, pp. 341-359, 1995.) describe differences in tone scales between the following modalities: computed tomography (CT), magnetic resonance (MR), ultrasound (US), digitized film and computed radiography (CR). Muka, et al. states that all images of a particular modality require the same tone scale application for proper cathode ray tube (CRT) visualization. While this is true for a large number of cases, this is not true in every case. For example, the CR images of one manufacturer are processed and distributed with code value linear to density, as described. CR systems of another manufacturer process and distribute images with code values linear to CRT digital to analog converter (DAC) values.
Mills, Ingram, Spetz and Dwyer (“Suitability of non-linear display tables to clinical PACS”, Proc. SPIE, Vol. 2435, pp. 2-10, 1995.) report that applying a CRT gamma adjustment that the user can modify interactively on a soft copy workstation yield diagnostic improvements for CR images. Mills, et al. propose that similar results may be obtained for other modalities including MR, CT and digital fluoroscopy based upon results from CR. Planned research includes automation of gamma correction “based upon anatomical region, modality, acquisition device characteristics and image histogram data”. The proposed research work described in the paper indicates additional information is required to select the tone scale, namely knowledge of anatomical region and image histogram data.
Przybylowicz, et al. (U.S. Pat. No. 5,671,070, issued Sep. 23, 1997) describe a method for sending an image across a network such that the tone of the image is properly rendered on the output device. Przybylowicz et al. requires that the acquisition device generate and send, along with the image, a LUT containing information on how to tonally render the image. Various methods for creating the final LUT to be applied to the image are described. As a soft copy device may display images from various vendors, a method for proper tonal rendering of all images, regardless of source, is desired.
Hishinuma (U.S. Pat. No. 5,260,873, issued Nov. 9, 1993) describes an apparatus for applying a gradation table or tone scale to a medical image. Hishinuma does not indicate how to select the gradation table to be applied to the image.
Beaudin et al. (U.S. Pat. No. 5,250,933, Oct. 5, 1993) describes a method and apparatus for applying a different color mapping or tone scale to different images on the same system. Beaudin et al. does not claim a method for determining what LUT should be applied to the image.
SUMMARY OF THE INVENTION
This invention, in general, allows a DICOM image processed and displayed on a soft copy system to tonally match the same image printed to film. Utilizing particular DICOM elements and prior knowledge about expected output device tonal characteristics, a tone scale adjustment function is selected to be applied to an image. Therefore, the quality of the image is improved by applying the appropriate tonal processing prior to display.
According to a feature of the present invention, there is provided a method of selecting a tone scale adjustment function for displaying a medical image on a display comprising the steps of: providing a medical image object having a header with image attributes including at least modality value and manufacturer value; extracting the image attribute values from the header of the medical image object; providing a plurality of tone scale adjustment look up tables, each of which is uniquely identified by at least two image attributes; selecting a tone scale adjustment table from a tone scale selection criteria table; applying the selected tone scale adjustment table to the provided medical image; and displaying the tone scale adjusted medical image.
ADVANTAGEOUS EFFECT OF THE INVENTION
The invention has the following advantages.
1. Consistent display of various medical image types on the same display device.
2. Proper tone scale visualization of CR images produced by different manufacturers on the same display device.
3. Proper tone scale visualization of CR images and CT/MR images on the same display device.
4. User interaction in adjusting tone scale is not required. A single tone scale adjustment is identified for application to an image of a particular modality, manufacturer, etc.
5. The medical image acquisition device does not need to generate a source LUT (Look Up Table) and send the LUT along with the image. Rather, information provided with the image infers what LUT should be applied to the image.
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Edward Mika et al., Display of Medical Images on CRT Soft-Copy Displays: A Tutorial, SPIE, vol. 2431, pp. 341-359.
Stephen F. Mills et al., Suitability of Non-Linear Display Tables to Clinical PACS, SPIE, vol. 2435, pp. 2-10.
Kohm Kevin S.
VanMetter Richard L.
Awad Amr
Eastman Kodak Company
Jankus Almis R.
Noval William F.
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