JPH10229519A - X-ray image digital processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image capable of emphasizing the fine contrast of an observation object part while suppressing halation by smoothing image data in a two-dimensional direction, performing a weighting processing and subtracting the image data after the weighting processing from original image data. SOLUTION: Analog X-ray image signals outputted from a TV camera 14 are converted to digital data in an A/D converter 21 and a smoothing circuit 22 performs the smoothing in the two-dimensional direction of the digital image data by a template processing or the like. The image data after being smoothed are sent to a weighting circuit 23 and weighted. The weighting processing is performed based on nonlinear gradation conversion characteristics. The conversion characteristics are relatively linear at a high luminance part but are suppressed at a low luminance part. The image data passed through weighting are sent to an arithmetic circuit 24 and subtracted from the original image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for converting an X-ray image signal used in medical treatment and the like into digital image data for processing.

[0002]

2. Description of the Related Art It is widely used to take an X-ray fluoroscopic image of a subject (such as a patient's body) as an electric image signal using an X-ray TV system and display it on a monitor device for observation. I have. Conventionally, smoothing is performed by an analog method, and this is subtracted from an original image signal to suppress halation and the like, so that a displayed image can be easily viewed.

[0003]

However, in the case of smoothing in the analog system as in the prior art, the configuration is complicated and difficult to realize unless the smoothing is performed only in the scanning line direction. However, there is a problem that a smooth image in both the vertical and horizontal directions cannot provide a good image.

[0004] In view of the above, the present invention provides an X-ray image which can perform a smoothing operation in two vertical and horizontal directions by a digital method, thereby suppressing halation and enhancing a delicate contrast of a portion to be observed. It is an object to provide an image digital processing device.

[0005]

In order to achieve the above object, in an X-ray image digital processing apparatus according to the present invention, A / D conversion means for A / D converting an input analog X-ray image signal; Smoothing means for smoothing the digitized image data in the two-dimensional direction; weighting means for performing weighting processing on the smoothed image data; and subtracting the weighted image data from the original digital image data. Calculation means.

[0006] Smoothing of digital image data can be easily performed in a two-dimensional direction by template processing or the like. Since the smoothed image data retains the low-frequency components of the image, the halation portion can be canceled by subtracting this image data from the original image data. In addition, by performing a weighting process on the smoothed image data, a high-luminance portion, which is a halation portion, can be selectively canceled, and an excellent image can be obtained in which a gradual contrast remains in a necessary gradation portion.

[0007]

Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, X-rays emitted from an X-ray tube 11 penetrate a subject 10 and enter an image intensifier 12, and an X-ray transmission image is converted into an optical image. A TV camera 14 is connected to the image intensifier 12 via an optical system 13, and an image signal of an output optical image of the image intensifier 12 is obtained. This image signal is sent to the TV monitor device 15 through the digital image processing device 20 to display an X-ray fluoroscopic image.

[0008] The digital image processing apparatus 20 includes an A / D converter 21, a smoothing circuit 22, and a weighting circuit 23.
, An arithmetic circuit 24, and a D / A converter 25. T
An analog X-ray image signal output from the V camera 14 is first converted into digital data by an A / D converter 21 and sent to a smoothing circuit 22. This smoothing circuit 2
Reference numeral 2 denotes smoothing of digital image data in a two-dimensional direction by template processing or the like.

The smoothed image data is sent to a weighting circuit 23 and subjected to a weighting process. This weighting process is performed based on, for example, a non-linear gradation conversion characteristic as shown in FIG. The conversion characteristic shown in FIG. 2 is relatively linear in a high luminance portion, but is suppressed in a low luminance portion.

The image data that has been subjected to the smoothing and weighting is sent to the arithmetic circuit 24 and subtracted from the original image data. Since the image data becomes only the low-frequency component of the image due to smoothing, if this is subtracted from the original image data, image data from which the low-frequency component has been removed is obtained, which is effective for suppressing halation.

However, in this case, the image data subjected to the weighting process in addition to the smoothing is subtracted from the original image data. Then, as shown in FIG. 2, the conversion characteristic of the weighting is relatively linear in the high luminance portion and is suppressed in the low luminance portion and is entirely non-linear. For this reason, in the original image data, the smoothed image data is subtracted as it is from the high luminance portion, but the suppressed luminance image data is merely subtracted from the low luminance portion.

As a result, halation occurring in a high-luminance portion is mainly subtracted from the original image data.
In the gradation range existing in the other region to be observed, the difference is not so much subtracted. Therefore, in the gradation range existing in the region to be observed, the image information (low-frequency component) that is gradually changing remains relatively, and an image with excellent image quality that is easy to see in the region to be observed is obtained. This image data is converted to an analog signal via the D / A converter 25 and
It is sent to the V monitor device 15. For this reason, an image which is easy to see at a portion to be observed is displayed as described above.

As the smoothing circuit 22, a circuit whose degree of smoothing dynamically changes according to the luminance value of each pixel may be used. This can be easily realized by monitoring each pixel value and dynamically changing the value of the template in real time. As the degree of smoothing increases, more high-frequency components remain due to subtraction from the original image data, so that an edge enhancement effect is obtained. Therefore, by increasing the smoothing degree for the gradation range that exists in the region to be observed, and decreasing the smoothing degree for the other gradation ranges, the smoothing degree is changed for each gradation so that only the region to be observed is Edge emphasis can be performed, and in other areas, it is possible to remove an image that is hard to see except for halation and high frequency components as a whole.

The frame memory 26 stores the image data after the smoothing process. One or several smoothed images are created in advance and stored, and when an image signal is sequentially output from the TV camera 14 for each frame, the smoothed images are read out from the frame memory 26 and subtracted. . In this way, the data of the background image is smoothed and stored in advance, and later read when an image is obtained in which the blood vessel is filled with the contrast agent or when an image of a catheter or the like is obtained. DSA by subtracting
(Digital subtraction angiography) can be performed.

FIG. 3 shows another example of the digital image processing apparatus 20. Here, the image data read from the frame memory 26 is passed through the smoothing circuit 22 again. By passing the image data through the smoothing circuit 22 several times in this manner, even when the smoothing circuit 22 performs processing using a small template, the same function as that performed by processing using a large template is achieved. . According to this configuration, the same function as the large-scale smoothing circuit can be obtained even with the smoothing circuit 22 having the small-scale circuit configuration. Since it takes time, when the real-time property is not required, there is an advantage in that the circuit configuration is simplified and the cost is reduced.

The above description relates to one example adopted for the sake of explanation, and the specific configuration and the like may be omitted for convenience of explanation. For example, in the case of performing the processing in real time, it is also omitted to add a delay to make the two inputs of the arithmetic circuit 24 coincide with each other. As described above, it is needless to say that the present invention is not limited to the above description, and various specific configurations can be adopted.

[0017]

As described above, the X-ray image digital processing apparatus according to the present invention is particularly effective for suppressing halation of an X-ray image during fluoroscopy. When a catheter operation is performed while performing X-ray fluoroscopy at a limited angle, a very easy-to-view image can be displayed. In this case, in the conventional case, if the contrast is enhanced to make the catheter portion easy to see, the overall contrast is also enhanced and the catheter cannot be identified, or the background can be completely canceled by DSA. In some cases, the information of the living tissue and the like that was captured as a part was lost and the positional relationship between the catheter and the living tissue became difficult to understand, but according to the present invention, in such a case, While effectively suppressing halation without completely canceling information on the living tissue as a background, it is possible to emphasize a minute contrast in a portion such as a catheter and to display the portion in a legible manner.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing an example of conversion characteristics in a weighting circuit.

FIG. 3 is a block diagram showing another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Subject 11 X-ray tube 12 Image intensifier 13 Optical system 14 TV camera 15 TV monitor device 20 Digital image processing device 21 A / D converter 22 Smoothing circuit 23 Weighting circuit 24 Arithmetic circuit 25 D / A converter 26 Frame memory

Claims (1)

[Claims] 1. An analog X-ray image signal input to
A / D conversion means for performing D conversion, smoothing means for smoothing the digitized image data in two-dimensional directions, weighting means for performing weighting processing on the smoothed image data, and image data after the weighting processing. An X-ray image digital processing apparatus comprising: an arithmetic unit for subtracting from the original digital image data.