JPS63115542A - Gradation converting circuit of x-ray imaging apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an X-ray imaging apparatus that digitally processes a video signal of an X-ray transmission image, and more particularly to a circuit that converts the contrast (contrast) of the image.

[Conventional technology]

Traditional X-ray imaging devices print X-rays that have passed through a subject onto film, producing analog images. In contrast, in recent years, digital X-ray imaging devices have begun to be used, which convert X-ray transmitted images into electrical video signals using an image intensifier and television camera, and then perform various digital processing on the signals. There is. In a digital X-ray imaging device, for example, a digital subl-
processing is performed. This is mainly for extracting blood vessel images.First, before injecting the contrast agent, an X-ray transmission image is taken and this is stored as a mask image.
Next, a contrast medium is injected into the blood vessel, and the above-mentioned mask image is digitally subtracted from the resulting X-ray image to extract an image of only the contrast medium, that is, an image of only the blood vessel. The gradation conversion circuit performs enhancement by converting the brightness/darkness or light/dark gradation of the digital subtraction image obtained in this way, and adjusts the contrast I. That is, window processing is performed to enlarge or reduce only a part of the dynamic range of each pixel value (representing gradation).

[Problems to be solved by the invention]

However, in the conventional gradation conversion circuit, window processing for each pixel value is uniformly performed on the entire screen. Therefore, problems have arisen regarding blood vessel images obtained by digital subtraction processing. To be more specific, digital subtraction processing extracts a large blood vessel @11 and a peripheral thin blood vessel image 12, as shown in FIG. 3, and creates an image in which these are represented in one image. There are things you can get. In this case, a large amount of contrast medium flows into large blood vessels, so blood vessel image 11 has strong contrast and is easy to see as it is, but contrast medium does not flow into small blood vessels very much, so the image of blood vessel @12 is faint. The Con I last is weak and it is difficult to identify blood vessels. Therefore, we darkened the blood vessel image 12 and contrasted it with
It is possible to perform enhancement to increase the However, since it is enhanced like a full screen,
As shown in FIG. 4, although the peripheral blood vessel image 12 has just the right contrast, the thick blood vessel image 11 has too strong a contrast and becomes black, making diagnosis impossible. In this way, in the past, it was not possible to perform different enhancements depending on the contrast of each part.
It was not possible to make all screens easy to see. Therefore, conventionally, when printing and saving this image on film, multiple images were created by performing enhancements according to the contrast of each part, and each of these images was printed on film individually, which was extremely cumbersome. It has become. This invention makes it possible to perform the most appropriate enhancement I for each arbitrarily set area of a single image, thereby making it possible to obtain an image in which the entire screen is easier to see. , an object of the present invention is to provide a gradation conversion circuit for an X-ray imaging apparatus.

[Means to solve the problem]

The gradation conversion circuit of the X-ray imaging apparatus according to the present invention includes an area setting circuit that arbitrarily sets an area within one image;
An input/output conversion circuit whose input/output characteristics can be set arbitrarily, and when a signal from a certain pixel is sent, it determines whether the position of that pixel is within the above set area and performs the above input/output. and a circuit for selecting a conversion circuit.

[For production]

When it is desired to perform gradation conversion on only a certain area, the area is set and the input/output conversion circuit is set depending on how the gradation is to be converted. Then, when the signals of each pixel of one image are sent sequentially, it is automatically determined whether the position of that pixel is within the set area, and if it is within that area, one input/output is performed. It is output through a conversion circuit, and if it is outside the area, it is output through another input/output conversion circuit. Therefore, signals of pixels inside and outside the area are converted according to separately set characteristics, and a certain part of the dynamic range is emphasized and output. Since the desired gradation conversion is performed inside and outside of the set area in this way, the entire screen becomes extremely easy to see, and recording this one image tS is sufficient, and multiple There is no need to record multiple images that have been subjected to Enhancement I.

【Example】

In FIG. 1, each time an address is specified by an address control circuit 2, a signal of a pixel at that address is read out from an original image memory 1 in which an original image of an X-ray transmission image is stored, and sent to a switching circuit 3. input/output conversion circuit 41.4
2 is selected and sent to the display image memory 7. The region of interest setting circuit 5 is a circuit for setting a region of interest (ROI). The address of the pixel just read out from the original image memory 1 is the address of this region of interest setting circuit 5.
Based on the address signal from the address control circuit 2, the address determination circuit 6 determines whether or not the area is within the area set by the address control circuit 2.
It is judged by. The signal of each pixel that has passed through the input/output conversion circuit 41 or 42 is read into the display image memory 7 at the same address as the original image memory 1 based on the address signal sent from the address control circuit 2. The region of interest setting circuit 5 sets a region of interest 13, for example as shown in FIG.
2 should be included. And input/output conversion circuit 41
For example, as shown by the dotted line 21 in FIG.
Set the characteristics to enlarge and output. In addition, the input/output characteristics of the input/output conversion circuit 42 are as shown by the one-dot chain line 22 in FIG.
It is set to the characteristic that the image is enlarged and output. In addition, in this figure 2, the solid line does not perform any input/output conversion,
This is a characteristic when outputting input as is. In this case, if the position of the pixel read from the original image memory 1 is within the region of interest 13, the address determination circuit 6 determines this and switches the switching circuit 3 to the input/output conversion circuit 41 side. Therefore, only the signal of the pixel located within the region of interest 13 is converted according to the characteristic shown by the dotted line 21 in FIG. 2, and a portion of the signal is enlarged. Therefore,
Within this region of interest 13, the con I and lath I of the peripheral blood vessel image 12, which was originally an image with low density and weak con I and lath I, are emphasized. On the other hand, in the case of a signal from a pixel located outside the region of interest 13, the address determination circuit 6 determines this and switches the switching circuit 3 to the input/output conversion circuit 4.
2 side, and signal conversion is performed according to the characteristics indicated by the dashed-dotted line 22 in FIG. Therefore, signals outside the region of interest 13 are subjected to weaker contrast I, laser I, and emphasis, and are displayed in the display image memory 7.
will be sent to. Therefore, both the thick blood vessel image 11 and the thin peripheral blood vessel image 12 have appropriate contrast I.
・Can be displayed in an easy-to-read format. Note that depending on the settings of the conversion characteristics of the input/output conversion circuits 41 and 42, all the signals within the region of interest may be set to O or a very small value, and the image inside the region may be erased and not displayed. Even if it is displayed, it can be made so that it is a very faint image so that it is not noticeable. therefore,
For example, if unnecessary images (artifacts, etc.) appear in the background of a blood vessel image, this can be erased. Further, in the above, only two input/output conversion circuits 41 and 42 are provided, but a large number of them are provided, and different input/output conversion characteristics are set for each of them. By setting a large number of different areas in the region of interest setting circuit 5 and performing different gradation transformations on each area, it is also possible to perform arbitrary enhancement 1- for each of the large number of areas. good. Furthermore, it is also possible to automatically set the enhancer 1- by using the dispersion within the set region of interest. The above explanation assumes that the original image is stored in the memory, and after converting the contrasts 1 to 1, it is stored again in the memory of the pond.
It goes without saying that the present invention can be similarly applied to the case where a video signal obtained from a television camera or the like is directly subjected to contrast/last conversion and displayed.

【Effect of the invention】

According to the gradation conversion circuit of the X-ray imaging apparatus of this invention, arbitrary enhancement can be selectively performed only in an arbitrarily set area, so that all parts of the X-ray image can be easily seen in one image. Linear imaging images can be obtained.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an embodiment of this invention, Figure 2 is a graph showing input/output characteristics, Figure 3 is a diagram showing the original image, and Figure 4 is when the same enhancement is applied to the entire screen. Figure 5 is a diagram showing the set area, Figure 6 is a diagram showing an image of
The figure shows an image when selective enhancement is performed. 1... Original image memory, 2... Address control circuit, 3
...Switching circuit, 41.42...Input/output conversion circuit, 5
. . . region of interest setting circuit, 6 . . . address determination circuit,
7...Display image memory.

Claims (1)

[Claims] (1) A region setting circuit that arbitrarily sets an area within one image, an input/output conversion circuit that arbitrarily sets input/output characteristics, and a position of a pixel when a signal of that pixel is sent. a gradation conversion circuit for an X-ray imaging apparatus, comprising: a circuit for determining whether or not the input/output conversion circuit is within the set area and selecting the input/output conversion circuit;