JPH01147619A - Graph display device and improvement in visibility thereof - Google Patents

Abstract

PURPOSE: To improve visibility by superimposing colors through the use of a window function only in an area to be considered within an image with low contrast in image displaying. CONSTITUTION: The total number of image elements in image data is displayed in a graph 30 as against a specified image having the respective considerable values of image element sizes. A part 31 in the graph is easily identified busing an image element histogram. An operator sets a window 32 and executes placement in the part desired to be identified. A queue is added to the whole image elements having the size entering a specified range by the window of the histogram. Large change in brightness, etc., exists in the queue by superimposing the colors with strong contrast. Thus, contrast is obtained in the area to be considered 55 within the image so that visibility is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to the control of electronic graphical displays, and more particularly to the superimposition of high contrast colors according to histograms in graphical images, particularly images for medical diagnostic purposes. It's about being in control.

As computer graphics capabilities improve, various applications for video display as well as hard copy display of images are increasing. In an interactive graphics system, a processor creates a display file according to instructions from an operator.

In one common configuration, the displayed image is comprised of a plurality of pixels arranged in rows and columns.

The display file consists of the brightness magnitude (and possibly color) for each pixel. When displaying an image, an operator can specify certain parameters of the image, such as image brightness and/or contrast.

In many applications, it may be important to adjust parameters to best visualize certain aspects of the data within the image. Examples include ultrasound exploration, X-rays, nuclear medicine, computed tomography (CT) and nuclear magnetic resonance (NM).
In medical diagnostic imaging modes such as R), images may have subtle tissue contrast that is difficult to see with the eye. Furthermore, optimal brightness and contrast typically vary depending on the particular parameters or objectives of the imaging experiment.

Typically, medical diagnostic equipment uses grayscale (i.e., black and white) images, so the adjustable characteristics of interest in these applications are brightness (i.e., level) and contrast (i.e., the difference from a window or level). maximum deviation). Color overlays are used to convey information in addition to the main measured quantities in medical images. For example, in Doppler ultrasound, colors superimposed on a gray scale ultrasound echo image can be used to
Indicates the direction of flow.

Still, the low contrast of clinically important tissue features reduces the effectiveness of the existing quantitative imaging modes. This is because spatially locating areas of tissue with nearly identical characteristics is important for detecting pathology, but differences in appearance between pathological and "normal" areas are important. This is because it is not easily clear.

For example, in ultrasound backscatter imaging of the heart, the signal contrast between normal myocardium and severely anemic myocardium is
Typically about 5 dB of detected backscattered signal.

A problem with real-time imaging is that the contrast of the signal changes in real time as the tissue moves. It is desirable to convert this small signal difference and real-time change into an image in which tissue type can be more easily identified.

Therefore, the main objective of this invention is to interactively improve the visibility of low contrast features in graph images.

Another object of the invention is to improve the spatial localization of tissue properties in medical diagnostic images.

Another object is to provide a method and apparatus for enhancing tissue contrast in a changing image in real time.

SUMMARY OF THE INVENTION The above and other objects are achieved according to the parameters of the image.
This is accomplished with a graphical display that assigns respective intensities to pixels of the image. Subtle contrasts between pixels are enhanced by adding color-like cues to image pixels that have intensities within a specified range. This range is specified interactively using a histogram to help identify changes in image parameters. The observer can draw a window (
For example, it is convenient to select upper and lower limits) to specify the range of pixels that receive the cue.

In one aspect of the invention, the real-time image is displayed and a histogram is also displayed corresponding to each frame of the real-time image. The real-time changes in the histogram of images for medical diagnosis are
Through the cued pixels falling within the histogram window, they provide the diagnostician with a key to characterizing the tissue.

Although the novel features of this invention are specifically described in the claims, the structure, operation, and other objects and advantages of this invention itself will be best understood from the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG.
0 includes a data collection device 11 and a processor 12. An operator interface 13 is coupled to processor 12 and allows an operator to control operation of system 10 (such as the height and width of the histogram window). A video display device 14 is provided at the output of the processor 12.
and a photographing device 15 are coupled. For medical diagnosis,
The data acquisition device 11 can be comprised of a well-known ultrasound device, NMR device or CT scanner. Such devices provide information about the object such that an image can be formed by its processing.

Video display device 14 preferably comprises a cathode ray tube (CRT) and associated files and displays images corresponding to the output signals of processor 12. Photographing device 15
may be arranged to record the image projected by the video display device 14, or may be arranged to produce a hard copy image.

In a preferred embodiment of the invention, the image displayed by the video display device 14 and the image capture device 15 consists of a plurality of pixels 21 arranged in a matrix 12 having a plurality of rows and columns, as shown in FIG. Consists of. In response to data acquisition measurements from device 11, processor 12 generates image data corresponding to the imaging experiment such that each pixel in the image has an associated size. For example, in ultrasonic exploration,
Each pixel can be assigned a size directly proportional to the backscatter cross section of the respective volume of tissue in response to an ultrasound interrogation pulse. In NMR imaging, each magnitude may represent the nuclear spin density within a particular volume;
This can be weighted according to the particular relaxation properties of the nucleus. In CT, each magnitude may represent the attenuation of x-rays in a particular part of the body.

The pixels of the video display rIi 14 or the imager 15 are capable of producing an image in which each pixel has a value directly proportional to the size of such pixel. However, better results are obtained when the operator conducting the experiment is allowed to adjust the characteristics of the displayed image to best view the structures of interest in the image. However, even with such operator adjustments, tissue features may remain blurred because the original pixel size contrast is low.

To alleviate the problems described above, the present invention provides an observer feedback mechanism that allows the observer to view the image and select portions of the image for which finer contrast data is desired. In operation, the preferred embodiment uses an image pixel histogram. An example is shown in FIG. The histogram of FIG. 3 graphs the total number of pixels in the image data for a particular image with each possible value of pixel size (referred to as a bin). That is, for each pixel size, there are a number of pixels with this size, which can be represented as line 30. By using the image pixel histogram, the swelling 31
According to histogram features such as , it becomes easy to identify vopulicidins in tissues with low contrast.

A viewer adjusts the height and width of window 32 through the operator interface. This window can be placed before or after a particular feature, such as a bulge 31, or alternatively the viewer can place the window in a histogram while watching the displayed image to see if tissue features are enhanced. The histogram can be swept by sliding across the screen. Preferably, a histogram window is displayed along with the histogram.

As shown in FIG. 4, a preferred method of the present invention includes step 4.
0 to use a static or real-time display of the histogram (depending on whether the main image is static or real-time).

At step 41, the position and width of the histogram window is set according to features of interest within the histogram or by systematic search of the image. In the example of an ultrasound scattering device used to image the heart, (1) the lesion in the image is created by a localized pocket with a different backscatter value than the surrounding tissue; (2) Both anemic and infarcted myocardium can have features in the histogram because the backscattered signal is more intense than in normal myocardium. The invention further contemplates constructing a histogram for only that region so that the viewer can identify a region of interest within the main image and see only local features.

At step 42, a cue is added to all pixels whose size falls within the range specified by the histogram window.

In a preferred embodiment, the cue is applied, for example, by an overlay of contrasting colors or by a large change in brightness. Therefore, it is possible to easily observe local pockets in the image that have the same characteristics that differ from the globally limited reference.

In real-time imaging, displaying in real time a histogram corresponding to each frame of the real-time image is particularly advantageous for identifying certain tissue properties that have such time dependence. For example, in an ultrasound examination of a normal heart, when examining tissue of a diseased heart, cyclical fluctuations may disappear in the backscattered signal.

By placing the histogram window over unexpectedly stationary areas of the histogram, the corresponding diseased tissue is highlighted.

Referring to FIG. 5, the preferred embodiment interactive display 50 includes a main image display 51. It has a histogram and window display device 52 and a window input device 53. By way of example, main display 51 shows an ultrasound sector scan image of heart 54 . The viewer can interactively highlight portions of the image using a histogram on a display 52 and an input device 53, such as a trackball. By placing the histogram window in a particular portion of the histogram, a lesion 55 within the heart 54 is highlighted by the color superimposition. Trackball 53 can be used to define a region of interest within image 51 to limit the histogram and to limit cueing to this region.

As described above, the present invention improves the visibility of low contrast features in a graph image.

In medical imaging, local regions of tissue are detected in both static and real-time images.

Although preferred embodiments of the invention have been described with reference to the drawings,
It should be understood that these examples are merely examples. Various modifications within the scope of this invention will occur to those skilled in the art. It is therefore intended that the appended claims cover all such modifications that fall within the scope of this invention.

[Brief explanation of the drawing]

FIG. 1 shows a graphic diagram suitable for implementing the invention.
A block diagram of the system, FIG. 2 is a diagram of a display device having a plurality of pixels, FIG. 3 is a graph showing an example of a histogram of an image display file, and FIG. 4 shows a method of an embodiment of the present invention. The flowchart shown in FIG. 5 is a schematic diagram of a display device that uses the present invention to generate ultrasound fan scan images of the heart and to facilitate visualization of lesions. Explanation of main symbols 51: Image display device 52: Histogram and window display device 53: Window input device

Claims (1)

[Claims] 1. Video display means for displaying an image comprising a plurality of pixels, defined by assigning respective intensities to the pixels; and while the image is being displayed, a histogram of the image; a histogram display means for displaying a histogram; a window setting means for controlling the width and height of a window to limit a range within the histogram; and queuing means for adding a cue to each pixel corresponding to the range. 2. A graph display device according to claim 1, wherein said histogram display means displays the current width and height of said window. 3. The graph display device according to claim 1, wherein the image and the histogram change temporally according to successively displayed frames. 4. The graph display device according to claim 1, wherein the cue is applied by superimposing colors superimposed on the cued pixels. 5. The graph display device according to claim 1, wherein said window setting means comprises a trackball. 6. A method for improving the visibility of low contrast features in a graph display device, comprising: displaying an image including a plurality of pixels each having an assigned intensity; and displaying a histogram corresponding to at least a portion of the image. setting a window position and width to define a range within the histogram; and adding cues to the image at each pixel location corresponding to the range. 7. The method according to claim 6, further comprising the step of displaying a window superimposed on the histogram. 8. The method of claim 6, wherein the window is swept across the histogram. 9. The method of claim 6, wherein the image and histogram vary in time according to successively displayed frames. 10. The method of claim 6, wherein the cue includes an overlay of colors superimposed on pixels corresponding to the range. 11. The method of claim 6, including the steps of: 11. defining a region of interest within the image; and limiting the histogram and adding cues to the region of interest.