JP4777456B2 - X-ray diagnostic equipment - Google Patents

Description

  The present invention relates to an X-ray diagnostic apparatus.

As conventional technology, various image processing has been applied to image data obtained when imaged or transmitted by an X-ray diagnostic apparatus or the like in order to display it effectively as diagnostic information with contrast. . For example, recent image processing such as digital signal processing is applied to these image processing, and window processing and gamma curve processing are known as effective image processing means. These image processing techniques are uniformly applied to the entire range of the entire image on which the image processing target is displayed.

However, not only a target that needs to be subjected to image processing on all display images, but, for example, a portion of an imaging target portion of a subject that has a high X-ray transmission and a low X-ray absorption has a contrast. Hateful. However, if an attempt is made to add contrast to the entire image, a contrast that is more than necessary is added even to a well-displayed portion. There is also a method of placing an actual compensation filter in order to give contrast only to a portion requiring contrast. This compensation filter is performed using, for example, lead clay. By placing this lead clay in the lower part of the imaging target region of the subject to be contrasted, the amount of X-ray transmission can be physically adjusted to provide contrast. In this case, the compensation filter is installed under the imaging target portion of the subject by hand or by machine.

JP-A-5-168614

However, the image compensation means for providing contrast according to the above-described conventional technique has the following problems.

Image processing such as window processing and gamma curve processing described above is uniformly applied to the entire range of the image, and in the case of an image including both a region with a high pixel value and a region with a low pixel value, there is a limit to the density region that can be used. For this reason, if the contrast is increased, the contrast of either or both of the high and low pixel values must be lowered, and an appropriate contrast cannot be obtained, so that fine information in this region cannot be expressed well. .

Conversely, if the overall contrast is lowered, a wide range can be observed, but the image becomes difficult to observe due to the low contrast. Even if a technique for placing a compensation filter is applied, it is difficult to specify the position depending on the imaging target region of the subject, or a region with a high pixel value is partially in the subject due to gas in the small intestine. When this occurs, an actual compensation filter cannot adequately cope with it.

The problem to be solved by the present invention is to provide an X-ray diagnostic apparatus capable of obtaining a medical image capable of expressing fine information with good contrast even in image data in which both a region having a high pixel value and a region having a low pixel value are mixed.

In order to solve the above problems, in the present invention, in an X-ray diagnostic apparatus capable of obtaining image data based on X-rays transmitted through a subject, image processing means for performing image processing on the image data; , in conjunction with the image processing, the dynamic range of the image remain contrast necessary part maintaining a fine image information data and image compensation processing means for image compensation processing, the image compensation processing unit, the Image compensation processing suitable for image data after image processing is performed .

According to the present invention, there is provided an X-ray diagnostic apparatus comprising an image processing apparatus capable of obtaining a medical image capable of expressing fine information with good contrast even in image data in which both a region having a high pixel value and a region having a low pixel value are mixed. can do.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic for demonstrating the structure of the image compensation filter by the 1st Embodiment of this invention is shown. BRIEF DESCRIPTION OF THE DRAWINGS The schematic for demonstrating the structure of the image compensation filter by the 1st Embodiment of this invention is shown. BRIEF DESCRIPTION OF THE DRAWINGS The schematic for demonstrating the X-ray diagnostic apparatus with which the image compensation filter by the 1st Embodiment of this invention is applied is shown. FIG. 5 is a schematic diagram for explaining a configuration of an image compensation filter according to a second embodiment of the present invention. The schematic for demonstrating the X-ray diagnostic apparatus with which the image filter by the 3rd Embodiment of this invention is applied is shown.

FIG. 1 is a schematic diagram for explaining an image compensation filter according to a first embodiment of the present invention.

The image compensation filter 16 includes a logarithmic conversion unit 1 for performing logarithmic conversion processing on image data obtained by transmission or photographing, and a filter for removing fine information from the output from the logarithmic conversion unit 1 2, a compensation value calculation unit 3 that performs a predetermined calculation process on the output from which fine information output from the filter 2 is removed, and a compensation value output from the compensation value calculation unit from the output of the logarithmic conversion unit 1 It comprises subtracting means 4 for subtracting.

In FIG. 1, a is input image data, and b is compensated image data after a predetermined image compensation is performed. The image data input from a is first input to the logarithmic conversion unit 1 which is an original data creation means. The logarithmic conversion unit 1 performs logarithmic conversion on the input image data to create logarithmically converted image data. This image data is proportional to the product of the X-ray absorption coefficient and the thickness of the subject through which X-rays pass. Therefore, even if the background pixel value is changed by subsequent processing, the fine unevenness information included in the image data subjected to the logarithmic conversion processing remains correct information and does not change. The logarithmically converted image data is shown as original data.
Image processing is performed on the original data by the image compensation filter according to the first embodiment of the present invention.

Next, this original data is input to the filter 2 which is outline information extraction means. Logarithmic converter 1
The image data obtained by applying a predetermined filter to extract rough density information is generated from the original data generated by logarithmic conversion at, and outline information extraction data is generated. The filter 2 is set to have a predetermined characteristic so that the outline information extraction data does not include fine unevenness information included in the original data.

Next, the outline information extraction data is calculated by the compensation value calculation unit 3 which is a compensation processing value calculation means. The compensation value calculation unit 3 performs linear or non-linear conversion based on the density extraction data output from the filter 2, and calculates and obtains a target range and a compensation amount for image compensation. Compensation processing value data is created based on the calculation result. In this data, a portion of the display image based on the image data that is subject to image compensation processing is extracted and included as target range data. It also includes data representing the compensation amount from the range data.

The compensation value calculation unit 3 can perform the same conversion process for lookup table conversion without using linear or non-linear conversion. In the case of lookup table conversion, a plurality of pieces of conversion information stored in advance corresponding to the value of the input outline information extraction data is selected and output. This conversion information may be appropriately selected from a plurality of predetermined conversion information according to the outline information extraction data, or may be selected and applied from a plurality of predetermined arithmetic expressions instead of the conversion information. Also good.

Next, the compensated image data is generated by subtracting the compensation processing value data from the original data created by the logarithmic conversion unit 1. This subtraction processing is performed by subtraction means 4 which is compensation processing means. Compared with the image data input to a, the generated compensated image data is compressed only in the dynamic range while retaining fine unevenness information necessary for diagnosis. The part of the dynamic range to be compressed is only the part on the image extracted by the previous compensation value calculation unit 3,
Only this portion is subjected to image compensation processing in which the dynamic range is compressed. The other portions are not subjected to any image processing, and therefore maintain good contrast information based on the original image data.

Note that the main image processing is not limited to only a portion on the image extracted by the compensation value calculation unit 3 in the original image data, but it is also possible to perform image processing on the entire original image data. is there. The original image data may be subjected to image processing with a uniform value, or image processing with a predetermined weight applied to each part so that intended image processing can be performed.

FIG. 2 is a schematic diagram for explaining the signal flow of the image compensation filter according to the first embodiment of the present invention.

The image compensation filter 19 shown in FIG. 2 is equivalent to the configuration of the image compensation filter 16 shown in FIG. 1, and shows one example for more specifically explaining the configuration of the image compensation filter 16. .

First, X-rays output from the X-ray high voltage generator pass through the subject, and image data having a pixel value proportional to the dose incident on the detector (image intensifier and camera, flat detector, etc.) is output. The An image compensation filter configured by hardware and / or software is provided for monochrome medical image data collected by such fluoroscopy and imaging, or already collected, and is necessary for image display. A predetermined image compensation process is performed for each correct image frame.

First, original data (A) is generated by performing logarithmic conversion for holding fine unevenness information on the image data input by the logarithmic conversion unit 1. This original data (A) shows, for example, a distribution diagram as shown in the figure, and of course varies depending on the displayed image. In this distribution diagram, the vertical axis L indicates the pixel value, and the horizontal axis S indicates the coordinate position on the image. This logarithmic transformation is
If the input image data is proportional to the product of the absorption coefficient and thickness of the subject through which X-rays pass, logarithmic conversion is not performed.

Next, an extraction process is performed on the original data (A) by the filter 2 in order to extract rough density information. For example, image data obtained by applying a low-pass filter to the original data (A) is created. This image data is light and shade extraction data (b) and shows a distribution diagram as shown. The fine unevenness information held in the original data (A) is deleted, and only rough gray values are represented. This is a result of preventing the fine unevenness information from being present for subsequent processing, and for example, an equivalent method other than the low-pass filter can be used.

Next, a predetermined calculation process is performed on the density extraction data (b). The compensation value calculation unit 3 for this calculation processing is applied with a non-linear processing method that exhibits an effect of lowering only a region having a certain pixel value or more according to the pixel value, such as lookup table conversion. . Here, compensation processing value data (c) for determining the processing target range and compensation amount of the image compensation filter is created.
Compensation processing value data (c) shows a distribution diagram shown in the figure, a portion where image compensation is performed at a position on the horizontal axis S of this distribution is specified, and a value on the vertical axis L indicates an image compensation amount. Of course, the conversion may be performed by a predetermined arithmetic expression regardless of the lookup table conversion, and can be set according to the design intention.

With this compensation processing value data (c), the image processing by the image compensation filter can be partially applied to the display image, not necessarily the entire range. It is also possible to use linear transformation instead of nonlinear transformation. Furthermore, by changing the data and coefficients of linear or non-linear transformation as appropriate, the effect of changing the image processing target range and compensation amount of the image compensation filter, or the dynamic range not only for regions with high pixel values but also for low regions It is also possible to operate.

Next, the subtraction means subtracts the compensation processing value data (C) from the original data (A) generated by the previous logarithmic conversion unit 1. The compensated image data (d) is generated by subtracting the compensation processing value data (c) from the original data (a). As shown in the figure, this compensated image data (d)
By subtracting the data of the pixel value reduction width, it is possible to compensate data only for the dynamic range of the portion where contrast is desired while maintaining the fine image information necessary for diagnosis. The compensated image data (d) is converted back to image data by the inverse logarithmic conversion unit 5 and output.

FIG. 3 is a schematic configuration diagram for explaining an X-ray diagnostic apparatus including an image compensation filter according to the first embodiment of the present invention.

The configuration of the X-ray diagnostic apparatus includes an X-ray diagnostic imaging apparatus body 15 that performs image processing and operation control,
An X-ray tube 6 for generating and exposing X-rays, a detector 8 for detecting X-rays transmitted through the subject 7 and outputting them as electrical signals, and receiving the output of the detector 8 for analog An A / D converter 9 for converting electrical signals into digitized image data, a storage device 10 for storing image data, an image compensation filter 16 for performing image compensation processing on the image data,
An image processor 11 for performing various image processing on the entire image, a D / A converter 12 for converting image data output from the image processor 11 into an analog electrical signal, and the D / A An image monitor 13 for displaying image data from the converter 12 and an image printer 14 for printing and outputting the image data are provided.

X-rays are exposed to the subject 7 by the X-ray tube 6, and X-rays transmitted through the subject by this exposure are detected by the detector 8 and converted into electrical signals. The converted electric signal is converted into an A / D converter 9
The image data is converted into a digital signal in step S2. This image data is input to the X-ray image diagnostic apparatus main body 15 and after predetermined image processing is performed, the image monitor 13 and the image printer 1
It becomes useful diagnostic image information by being output to 4 or the like.

The X-ray image diagnostic apparatus main body 15 includes a storage device 10 for storing input image data. For example, the storage device 10 is used under such a usage condition that a large amount of image data is captured at a time. It is also possible to store all image data regardless of the amount of image data and create a database to be used later.

Next, the image data is input to the image compensation filter 16 or the image processor 11.
Is selected. The selection of this process is performed by the process selection means 21, and the determination criterion for this selection may be an arbitrary input from the outside (not shown), or a value of a predetermined selection criterion is input in advance and the value is determined according to this value. A process selection may be made.

The image data input to the image compensation filter 16 is subjected to a predetermined image compensation process as described with reference to FIGS. By this image compensation processing, the dynamic range compression is performed on the image data, for example, only on the part where the contrast is unclear on the image. The image data subjected to the image compensation processing is input to the image processor 11 and, for example, inverse logarithmic conversion processing or other image processing as necessary is performed based on the image data obtained by this processing. Therefore, it is possible to display an image with good contrast with accurate unevenness information. Further, image data determined not to be input to the image compensation filter 16 by the processing selection unit 21 is also input to the image processor 11.

The image processor 11 performs predetermined image processing regardless of whether the input image data that has undergone image compensation or image data that has not undergone image compensation processing is input. This image processing is widely performed, and for example, gamma curve processing, window processing, and the like are performed. The contrast and brightness of the entire screen displayed by these image processes are set to predetermined values.

After this image processing, the image data is sent to various displays or recording media connected to the outside of the X-ray diagnostic imaging apparatus main body 15. For example, to display an image on the image monitor 13, D / A
The image data once converted into a digital signal by the converter 12 is converted back into an analog image signal. Thereafter, a desired image can be displayed by being input to the image monitor 13. Since the image data can be output as an analog signal, it can be displayed on almost all general image monitors, or can be stored in a video recording device, and versatility is enhanced.

Further, the image data can be output as it is as a digital signal, and input to the image printer 14, for example, to print out the image. Further, the present invention is not limited to the image printer 14, and other digital signals can be stored in a recordable medium or apparatus so that image data having a good contrast subjected to image compensation processing can be used more effectively. it can. By using a digital signal, image communication using a digital line or the like as a medium becomes possible.

FIG. 4 is a schematic diagram for explaining the configuration of the image compensation filter according to the second embodiment of the present invention.

The image compensation filter 18 is different from the image compensation filter 16 described above in that an instruction input unit 17 is connected to the compensation value calculation unit 3. According to this configuration, for example, a specific location in the display image can be designated by the operator arbitrarily, and image processing by the image compensation filter 18 can be performed only on that portion. For example, the operator can specify a portion and an amount to be subjected to image processing by operating an input unit such as a trackball (not shown) provided in the instruction input unit 17 while viewing an image displayed on the image monitor.

FIG. 5 is a schematic diagram for explaining a configuration of an X-ray diagnostic apparatus and an image compensation filter according to the third embodiment of the present invention.

The X-ray diagnostic apparatus shown in FIG. 5 differs from the X-ray diagnostic apparatus and the image compensation filter already described with reference to FIG. 3 in that an instruction input unit 20 is provided. The instruction input unit 20 is connected to the image processor 11, the filter 2, and the compensation value calculation unit 3. The instruction input means 20 can input an image processing instruction for image processing in the image processor 11 in addition to the image compensation processing in the image compensation filter 16 of the present invention.

The image compensation filter 16 can also perform image compensation processing linked to the image processing according to image processing such as window processing and gamma curve processing separately performed in the image processor 11. Based on the image processing data such as the window value in the window processing and the gamma curve data of the gamma curve processing, the image data processing method in the filter 2 and the compensation value calculation unit 3 constituting the image compensation filter may be determined. Is possible.

For example, when the gamma curve is changed by the image processor 11 in accordance with an instruction from the instruction input unit 20, the conversion process in the image compensation filter 16 is correspondingly changed based on the gamma curve and the set value obtained therefrom. Image compensation filter 1 optimal for the gamma curve after this change
6 is performed. Similarly, when the window value is changed, the conversion processing of the digital compensation filter is changed by calculation based on the window value, and the processing by the image compensation filter 16 suitable for the window value after the change is performed.

It should be noted that not only the image processing in the image processor 11 but also the image compensation processing of the image compensation filter 16 may be changed in accordance with, for example, the conditions at the time of fluoroscopy or photographing collection. In this case, the operation of each X-ray diagnostic apparatus is performed by switching the image data processing method or the set value in the filter 2 or the compensation value calculation unit 3 according to the examination name, the size or magnification of the image intensifier, and the like. It is possible to perform a good image compensation process that closely corresponds to the conditions and states.

The first, second, and third embodiments of the present invention described above can be configured by software, and of course are not limited to the control method by software, for example, signals by hardware Even if a processing circuit is used, sufficient implementation is possible.

The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit the present invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Logarithmic conversion part 2 ... Filter 3 ... Compensation value calculating part 4 ... Subtraction means 5 ... Reverse log conversion means 6 ... X-ray tube 7 ... Subject 8 ... Detector 9 ... A / D converter 10 ... External storage device 13 Image monitor 14 Image printer 16 Image compensation filter

Claims (4)

In an X-ray diagnostic apparatus capable of obtaining image data based on X-rays transmitted through a subject,
Image processing means for performing image processing on the image data;
In association with the image processing, image compensation processing means for performing image compensation processing on a dynamic range of a portion requiring contrast while maintaining fine image information of the image data ,
The X-ray diagnostic apparatus, wherein the image compensation processing means performs image compensation processing suitable for the image data after the image processing . The image compensation processing means includes
A logarithmic conversion unit that performs logarithmic conversion processing on the image data;
Rough shape information extracting means for calculating rough shape information by calculating the logarithmically transformed image data;
Compensation processing value computing means for computing the extracted outline information to obtain a compensation processing value for image compensation;
The X-ray diagnostic apparatus according to claim 1, further comprising compensation processing means for subtracting the compensation processing value from the logarithmically transformed image data and outputting an image subjected to image compensation. An instruction input unit connected to the image compensation processing unit and the image processing unit and configured to input an image processing instruction for image processing of the image processing unit;
The said image compensation process means performs the said compensation process in connection with the image process of the said image process means by the image process instruction | indication of the said instruction | indication input means, The said compensation process is characterized by the above-mentioned. X-ray diagnostic equipment.   The X-ray diagnostic apparatus according to any one of claims 1 to 3, wherein the image processing in the image processing means is window processing or gamma curve processing.

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