JPH07210675A - Picture display device - Google Patents

Abstract

PURPOSE:To properly display the contrast of gradation in the area with high diagnosis value of the objective picture and to suppress the unevenness of brightness of pictures. CONSTITUTION:An optimal display gradation arithmetic part 3 performs the display gradation optimization processing on the picture data recorded on a picture display memory part 2 to obtain the gradation conversion curve. Further, the prescribed area is segmented and the display gradation optimization processing is performed by the boundary value of the input gradation recorded on recording parts 31 and 32. The optimization processing is performed by adjusting the output gradation value decided for the boundary value with the gradation conversion curve inputted. Thus, the display gradation optimization can be performed by using the picture information with the highest diagnosis gradation of the objective picture and the picture quality suitable for the diagnosis purpose can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display apparatus for inputting digital image data measured by, for example, a medical image photographing apparatus and converting the gradation with an optimum display gradation and displaying the image. The present invention relates to an image display device suitable for displaying optimum gradation of image data at the time of gastrointestinal examination.

[0002]

2. Description of the Related Art In a conventional image display device, when obtaining an optimum display gradation of image data, information of the entire image is uniformly used. As an example of a method of obtaining the optimum display gradation at this time, there is a histogram equalization method. This is a generally well-known method, and a method for obtaining a histogram of the entire image and performing gradation conversion to flatten the histogram to improve the contrast resolution of a frequently input gradation. Is.

That is, in the histogram equalization method, a density histogram of an input image is obtained, and an operation using a cumulative cumulative density histogram function as shown in the following equation is performed to reallocate the density value of a pixel. I = C (i) × M / N (1) In the equation, i is the density of the pixel to be converted (input gradation), I is the density of the pixel having the density i after conversion (output gradation), and C (i ) Is the cumulative density histogram function, M is the maximum value of the density to be assigned,
N indicates the number of pixels.

Further, there is a local histogram equalization method as a method for enhancing the contrast of an image. In this local histogram equalization method, a density histogram of a region (referred to as a reference region) near each pixel is obtained,
The value of that pixel is determined according to equation (1). In the local histogram equalization method, by making the reference area small, it is possible to emphasize the contrast of fine features about density, but on the other hand, the density distribution of the image as a whole changes greatly, so It is necessary to take the optimum value according to the type and purpose of use.

[0005]

By the way, in an image such as an X-ray photograph, the characteristics of the image greatly differ depending on the target portion, and the above-described method of equalizing the entire image has an optimum gradation as a whole. May not be obtained. In addition, the image may include an important region and a less important region as diagnostic information. For example, in a digestive tract examination using X-rays, a so-called double contrast method is generally used in which a contrast agent (barium) is attached to the inner wall of an organ, air is injected to inflate the organ, and contrast is obtained. According to this method, the diagnostic information is not in the gas portion or the portion in which barium is stored (barium-filled portion) but in the portion in which gas and barium are mixed (double contrast portion).

In this case, if the display gradation is optimized by utilizing the information of the entire image including the gas portion and the barium filled portion as in the conventional case, the optimum display gradation for the diagnosis is obtained. No conversion processing is performed. As a result, (1) the density varies between images, (2) the contrast is too strong,
There was such a problem. An object of the present invention is to provide an image display device capable of obtaining an optimum display gradation for an area of an image having information effective for diagnosis, and particularly for a digestive tract examination image by radiography. To obtain a display gradation with high diagnostic value.

[0007]

In order to achieve the above object, the image display device of the present invention is optimal for an image data input section for taking in measured digital image data, and for this input digital image data. In an image display device including an optimum display gradation calculation unit that obtains various display gradations and a display unit that determines and displays brightness and contrast at the time of display based on the calculated display gradation of image data. The display gradation calculation unit includes a boundary value recording unit that sets a boundary value in order to select an area surrounded by a predetermined boundary value in the image data, and calculates an optimum display gradation for the selected area. It is a thing.

As a preferred aspect of the present invention, the display gradation calculation section further includes a display gradation recording section for setting a display gradation for the boundary value, and the display gradation for the boundary value is set as image data. All input grayscales are determined from the values after the grayscale conversion.

[0009]

A desired area is selected based on the boundary value preset in the boundary value recording unit, and the optimum display gradation is calculated for the image data of this area to obtain the optimum display gradation for the desired area. be able to. In particular, it is possible to obtain a display having a high diagnostic value for a region such as a double contrast portion of a digestive tract examination image by X-ray photography. Further, by setting the display gradation for the boundary value to the display gradation set in the display gradation recording unit, it is possible to make the display gradation constant in the area outside the boundary value. Can be stabilized, and variations in brightness between images can be eliminated.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image display device of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an image display apparatus. This image display apparatus includes an image data input section 1 for taking in digital image data measured by an image pickup apparatus such as an X-ray image pickup apparatus (not shown), and the image data input section 1. An image display memory unit 2 for recording the image data read out from the data input unit 1 for display, and this image display memory unit 2
The optimum display gradation calculation unit 3 for obtaining the optimum display gradation for the image data of 1. and the display brightness and contrast of the image data read from the image display memory unit 2 are determined by the calculated display gradation. Display circuit section 5,
A display unit 6 that converts the image data from the display circuit unit 5 into an analog image and displays the image is provided, and a control unit (hereinafter, referred to as CPU) 4 that controls each of these components.

The digital image data is a digestive tract examination image by X-ray photography in this embodiment, and includes a gas portion, a barium-filled portion, and a portion where gas and barium are mixed (double contrast portion). It is input from the input unit 1 and recorded in the image display memory unit 2. The optimum display gradation calculation unit 3 includes recording units 31 and 32 that also serve as a boundary value recording unit and a display gradation recording unit, and these storage units 31 and 32 include:
Boundary values X and Y for selecting ones (areas) within a predetermined input gradation value range among the image data recorded in the image display memory unit 2, and a display floor for displaying these areas in optimum gradations. Keys x and y are set. That is, in the digestive tract examination image, the boundary value X between the gas portion and the double contrast portion and the value x after gradation conversion thereof are stored in the storage portion 31 as X, and the boundary value Y between the barium portion and the double contrast portion is represented as Y. And the value y after gradation conversion thereof are preset in the storage unit 32. The boundary values X and Y and the display gradation values x and y are set by the input device of the CPU 4 or the like. The determination of these values will be described later.

The optimum display gradation calculation unit 3 is instructed by the CPU 4 to automatically set the display gradation based on the image data of the image display memory unit 2 and the boundary values set in the recording units 31 and 32 in advance. Then, the calculated gradation conversion data is set in the lookup table of the display circuit unit 5.
The display circuit unit 5 performs gradation conversion on the image data recorded in the image display memory unit 2 based on the calculated gradation conversion data, and displays it on the display unit 6.

The processing procedure of the gradation conversion processing of the optimum display gradation calculation unit 3 having such a configuration will be described with reference to the flowchart of FIG. 2 and FIG. First, primary display gradation optimization processing is performed using all the information of the image data recorded in the image display memory unit 2 to obtain the gradation conversion curve of FIG. 3A (step of FIG. 2). 101). In this gradation conversion curve (a), the horizontal axis is the original gradation (input gradation) of the image data input to the display circuit unit 5, and the vertical axis is the floor of the image data input to the display circuit unit 5. Represents a key. In this example, the total gradation width is shown as 12 bits (0 to 4095). As a display gradation optimization processing method for obtaining such a curve, for example, a histogram equalization method or a local histogram equalization method is used.

Next, the boundary value X between the gas portion and the double contrast portion is read from the recording portion 31, and the boundary value Y between the barium portion and the double contrast portion is read from the recording portion 32, and the gradation conversion curve (a ) Is cut out from the curve (FIG. 3B) (step 102). As a result, the area containing the important diagnostic information is selected, and the optimum gradation is set for this area. Therefore, first, the value x after gradation conversion with respect to the boundary value X is read from the recording unit 31, and the recording unit 3
The value y after gradation conversion for the boundary value Y is read from 2
The cutout curve (b) is adjusted so as to pass through the coordinate points (X, x) and (Y, y) to obtain an adjustment curve (FIG. 3C) (step 103). This adjustment is performed by, for example, output values of X and Y and set values x and y for the cutout curve (b).
This is done by equally allocating the difference between and between X and Y of the cutout curve (b). As a result, the optimum gradation is set for the double contrast section.

Next, a gradation conversion curve is determined for the part other than the double contrast part, the gas part (region of gradation 0 to X) and the barium part (region of gradation Y to 4095) (step 10).
4). As these curves, a predetermined function, for example, a curve of a predetermined function such as a linear function having slopes at both ends of the adjustment curve (c) can be used. Thus
Finally, a gradation conversion curve (FIG. 3D) for the entire image data is obtained. Further, when the curves on both sides of the adjustment curve (c) change in a polygonal line shape depending on the setting method of the function, the display gradation changes discontinuously before and after the input gradation X or Y. In such a case, the entire gradation conversion curve is smoothed to obtain the final gradation conversion curve (FIG. 3 (e)) (step 105).

Next, a method of determining the boundary values X and Y and the converted output gradation values x and y will be described. Boundary values X, Y
Can be determined based on the image obtained by performing the primary display gradation optimization processing using all the information of the image data in step 101 of FIG. A region important for diagnostic information is determined based on the obtained image of the inspection image data, and an average value of pixel values (input gradation) at the boundary portion (pixel portion) is determined as a boundary value.

For example, in X-ray photography, diagnostic information is generally obtained by a contrast medium such as barium, so it is desirable to utilize barium information as much as possible. Therefore, when determining the boundary value X between the gas part and the double contrast part, the barium concentration becomes thin, and at the limit where barium information can be obtained,
That is, the gradation X until immediately before the occurrence of halation is treated as a double contrast part. On the other hand, when determining the boundary value Y between the barium portion and the double contrast portion, the gradation Y until just before the barium is filled is treated as the double contrast portion. Since the barium-filled part can be confirmed on the image, a plurality of regions of interest 13 are set at the boundary between the barium-filled part 11 and the double contrast part 12 as shown in FIG. The value on the most barium side is used as the boundary value.

Next, the values x and y after gradation conversion for these boundary values X and Y are determined. From the experience, it is possible to appropriately determine the optimum values of x and y as the gradation range of the double contrast portion, but it may be determined with reference to the density value when a film is taken. In this case, it is possible to set a plurality of regions of interest at each boundary on the film, measure the densities of the regions of interest with a densitometer, obtain the average densities of these regions, and calculate the gradation according to the following equation.

X = 4095 × (d _H −d) / d _H where d _H is the density of the halation portion, and d is the average density of each boundary value X. As described above, the boundary value X and the gradation-converted value x of the boundary value X obtained as described above are recorded in the recording unit 31, and the boundary value Y and the gradation-converted value y thereof are recorded in the recording unit 32. Are used for the processing in the optimum display gradation calculation unit 3, that is, for selecting a desired area and calculating the display optimum gradation for that area.

In the above embodiment, preliminary display is performed based on the gradation conversion curve (FIG. 3A) first obtained for the image data to be actually displayed.
Although the areas are cut out based on this display and the boundary values are set, these boundary values can also be obtained based on the inspection image data of the digestive tract or the like imaged in advance. Moreover, although two values X and Y of the upper limit and the lower limit are used as the boundary value to be set, only one boundary value may be used depending on the image.

Further, in the above embodiments, the case where the display gradation of the digestive tract image is optimized has been described, but the present invention is not limited to the digestive tract image and effective diagnosis having a characteristic input gradation. If it is image data about the area of information,
It goes without saying that the display gradation can be optimized for the image including the area.

[0022]

According to the image display device of the present invention, when optimizing the display gradation of image data such as an image of an alimentary canal taken by X-ray, only the region having the most diagnostic information, for example, only the double contrast part. Since the processing can be performed using information, the image quality after gradation conversion is better than that of the conventional method. Further, since only the gradation data having a high diagnostic value is used, it is possible to obtain a display gradation effective for diagnosis as a result. Furthermore, by appropriately adjusting the values after gradation conversion for the boundary between the region of interest and other regions, it is possible to adjust the brightness and contrast to the observer's preference.

Further, by setting the output gradation of the boundary portion, the display gradation of the portion other than the region of interest can be fixed, so that the variation in the density between the images can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image display device according to the present invention.

FIG. 2 is a flowchart showing an embodiment of processing of the image display device according to the present invention.

FIG. 3 is a diagram showing a gradation conversion curve obtained by the processing of FIG.

FIG. 4 is a diagram illustrating a method of detecting a boundary between a barium portion and a double contrast portion.

[Explanation of symbols]

 1 ... Image data input unit 3 ... Optimal display gradation calculation unit 31, 32 ... Boundary value recording unit 4 ... CPU 5 ... ..Display circuit section 6 ...

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 1/407

Claims (3)

[Claims] 1. An image data input section for taking in measured digital image data, and an optimum display gradation calculation section for obtaining an optimum display gradation for the input image data.
In an image display device including a display unit that determines and displays brightness and contrast at the time of display based on the calculated display gradation of the image data, the display gradation calculation unit is An image display device comprising: a boundary value recording unit that sets the boundary value for selecting an area surrounded by a predetermined boundary value, and calculates an optimum display gradation for the area. 2. The image display device according to claim 1, wherein the display gradation calculation section includes a display gradation recording section for setting a display gradation for the boundary value. 3. The display gradation calculation unit determines the display gradation for the boundary value from the gradation-converted values for all input gradations of the image data. Image display device.