JPS62286445A - Radiation image processor - Google Patents

Abstract

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

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention is effective for medical diagnosis by processing radiographic images formed by radiation transmitted through a subject. The present invention relates to a radiation image processing device for obtaining images.

(Prior Art) Conventionally, in a radiographic image processing apparatus, at least one integrated image (mask image) taken before a contrast medium is injected into the imaging target region of a subject, and the ↑most contrast target region At least one integrated image (contrast image) obtained after a contrast medium was injected into the region of interest (hereinafter also referred to as the diagnostic target region) is input to a subtracter, and the subtracter calculates each of the above-mentioned images. By subtracting (subtracting) the density value of each pixel in , an image (subtract image) of only the region where the contrast agent is present is extracted. However, the subject often moves in a complicated manner while collecting the two images used for this process, and in such cases, in addition to the image of the contrast-enhanced blood vessel or organ, the image between the mask image and the contrast image is This method has the disadvantage that artifacts (false images) due to positional deviations overlap, making diagnosis impossible.

(Problems to be Solved by the Invention) In order to solve the above-mentioned drawbacks, a plurality of subtract images obtained by calculating a plurality of mask images and a contrast image are sequentially displayed, and the displayed plurality of subtract images are A so-called remasking method is used in which an operator looks at the image and selects a mask image that provides a subtract image with the least amount of artifacts.

However, it is very difficult for the operator to view the images and select the image with the least amount of artifacts, resulting in a problem of heavy burden on the operator.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a radiation image processing apparatus that can automatically select an image with the least artifacts.

[Structure of the invention]

(Means for Solving the Problems) The radiation image processing device of the present invention includes an arithmetic unit that obtains the sum of pixel data of a specific region of each of a plurality of subtract images, and obtains a subtract image that minimizes the sum of the pixel data. The mask image selection section selects a mask image.

(Function) The radiation image processing device of the present invention uses the size of the sum of each pixel data of a plurality of subtract images obtained in the hearing section as an index, and uses the mask image selection section to provide a subtract image with the least false images. A mask image is automatically selected.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

First, with reference to FIGS. 2 and 3, the appropriateness of using the sum of pixel data of a specific area of a subtract image as an index in remasking will be explained. Here, density is used as pixel data.

Now, if we cut out the one-dimensional data within the region of interest,
It is assumed that a certain degree of positional deviation occurs between the mask image and the contrast image in the cutting direction. Then, the image density profile of the mask image a and the contrast image in that case becomes, for example, as shown in Fig. 2 fal, and the density profile of the subtract image C is shown in Fig. 2 fb).
become that way.

Here, in FIG. 2 (bl), M1 and M2 reflect the positional deviation between the mask image a and the contrast image.

In order to select a mask image that gives a subtract image in which the M and M2 portions are the minimum from FIG. is preferred.

Then, the sum of the negative component data including the M1 part is shown in Figure 2 (
a) If the density level of the contrast image is higher than the density level of the mask image a as shown in (b), it corresponds to the area of the shaded part d in Figure 2 (bl). When the area of d is calculated as the sum of negative component data, there is a problem that even if the sum of the negative components of the part of Ml that reflects the positional shift becomes smaller, the sum of the negative components of the entire region of interest does not necessarily become smaller. be.

Therefore, considering the case where the density level of mask image a is higher than the density level of contrast image as shown in FIG. 3 (al (b)), the image density profile of mask image a and contrast image is as shown in FIG. a),
The density profile for subtract image C is as shown in Figure 3 (bl).As is clear from Figure 3 (b), the sum of negative components in subtract image C is
The diagonally shaded area d' in FIG.

From the above, it is important that the density level of the mask image is higher than the density level of the contrast image, and it is necessary to correct the density difference between the mask image and the contrast image to the above state by performing density conversion of the mask image or contrast image. be. Note that the above explanation was about the case where a subtract image is obtained by subtracting a contrast image from a mask image, but conversely, when subtracting a mask image from a contrast image to obtain a subtract image, the index for remasking is the sum of distortion components. Therefore, it is necessary to correct the density level of the contrast image to be higher than the density level of the mask image.

Next, based on the above considerations, an embodiment of a radiation image processing apparatus that performs remasking using the sum of pixel densities in a specific density region of a subtract image as an I target will be described with reference to FIG. In the figure, reference numeral 1 denotes an arithmetic/control section which mainly controls the operations of a computing section and a storage section, which will be described later, and also has a mask image selection function, and is mainly composed of, for example, a CPU (central processing unit). 2 is a calculation unit that performs subtraction processing between the captured mask image and the contrast image; 3 is a calculation unit that performs density conversion on the captured image to correct the density difference between the mask image and the contrast image; 4 is a calculation unit that performs a subtraction process between the captured mask image and the contrast image; A calculation unit that calculates the sum of pixel densities in the region of interest based on information indicating the region of interest, 5a, 5b, . . . , 5n a storage unit that stores a plurality of mask image data, and 6 a storage unit that stores a contrast image. , 7 is a storage unit that stores image data subjected to density conversion processing, 8 is a storage unit that stores subtract images,
9 is information indicating the set region of interest and the calculation unit 4;
This is a storage unit that stores the sum of negative components within the region of interest of the image obtained. Next, the operation will be described. First, under the control of the arithmetic/control section 1, a plurality of mask images are written into the storage sections 5a, 5b, . . . , 5n, and a contrast image is written into the storage section 6, respectively. Next, under the control of the arithmetic/control unit 1, a region of interest for calculating the sum of negative component data for the subtract image is set, and the set region of interest is written into the storage unit 9. In this case, it is preferable that the region of interest be as large as possible for reasons described later. Next, the mask image is read out from the storage section 5a under the control of the calculation/control section 1, and the read mask image is subjected to density conversion processing by the calculation section 3 (density conversion step). (Hereafter, the density-converted image is
In this case, the density conversion process takes into account the X-ray exposure conditions when collecting the mask image and contrast image and the amount of noise in both images, so that the density level of the contrast image changes to the density level of the mask image. It is preferable to perform conversion so that the amount of noise is reduced. The density conversion processing data in the calculation section 3 is written into the storage section 7.

Next, under the control of the calculation/control unit 1, the G-mask image in the storage unit 7 and the contrast image in the storage unit 6 are read out and input to the calculation unit 2, where the contrast image is subtracted from the G-mask image. A subtract image is obtained (
subtraction step). The obtained subtract image is written into the storage section 8.

Thereafter, under the control of the calculation/control unit 1, the subtract image in the storage unit 8 is read out and input to the calculation unit 4.
In step, the sum of negative components within the region of interest is calculated based on the information of the region of interest stored in the storage section 9 (index calculation step), and the result is written into the storage section 9.

Similarly, the density conversion step, subtraction step, and index calculation step are performed for the mask images stored in the storage units 5b, . . . , 5n. As a result, the storage unit 9 stores index values corresponding to all mask images, that is, the sum of negative component data within the region of interest of the subtract image.

Thereafter, under the control of the arithmetic/control unit 1, a mask image that provides a subtract image corresponding to the minimum value among all the index values stored in the storage unit 9 is selected.

Next, the reason why it is preferable to set the above-mentioned region of interest as large as possible will be explained.

In the method of using the sum of the negative components of the subtract image as a remasses; 1 Jung's gist, it is important that the edges of structures such as bones be included in a large amount within the region of interest.

This is because, for example, if the region of interest is within the range indicated by R in FIG. It is a condition for correct remasking that all of the applied portion d' is included in the R region. Therefore, the area of interest to be set is, for example, as shown in Figure 3(b).
It is preferable to set the value as large as possible so that the entire d' portion is included. According to experimental results of various examples, it is sufficient to set this setting range to an area of A or more of the entire image.

In this way, in the apparatus of this embodiment, by performing density conversion on the mask image, the density level of the contrast image is corrected to be lower than that of the mask image by the amount of noise, and then remasking is performed. Therefore, this remasking can be performed accurately, and in the subsequent subtract processing, it is possible to obtain a subtract image with few artifacts and excellent diagnostic performance. Furthermore, if the region of interest in which the sum of the negative components is to be calculated is about A of the entire image on the subtract image, the operator's manual setting effort can be saved and completely automatic remasking becomes possible.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment and includes various modifications.

For example, in the above embodiment, the contrast image is subjected to density conversion. However, conversely, the mask image may be subjected to density conversion. In this density conversion, in the above embodiment, the ? The 14 degree level was converted to be about a noise level lower than that of the mask image, but this is because the subtract image is obtained by subtracting the contrast image from the mask image, and conversely, the subtract image is obtained by subtracting the contrast image from the mask image. It goes without saying that when obtaining a subtract image by reducing the contrast image, the density of the contrast image or mask image is converted so that the density level of the contrast image is higher than that of the mask image by the amount of noise. .

In the above embodiment, density values were used as the pixel data to be handled, but the processing is not limited to this, and image pixels can be used as the pixel data.
The sum of image pixels that become negative may be minimized.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to provide a radiation image processing apparatus that can perform remasking accurately and automatically and can obtain subtract images with few artifacts and excellent diagnostic performance. Can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a radiation image processing apparatus showing an embodiment of the present invention, and FIG. Figure 2 (fl) is a characteristic diagram showing the density distribution of the mask image and contrast image, Figure 2 (b) is a characteristic diagram showing the density distribution of the subtract image, and Figure 3 (ill (b)
3 shows the density distribution when the density level of the mask image is higher than the density level of the contrast image, and FIG.
bl is a characteristic diagram showing the density distribution of a subtract image. 1... Arithmetic/control unit 1.2... Arithmetic unit for subtraction processing,
3... Correction calculation unit, 4... Pixel density sum calculation unit,
5a, 5b...5n...Mask image storage section, 6...
・Storage unit for contrast image, 8...Storage unit for subtract image, (G) (b) Fig. 2 Fig. 3

Claims (3)

[Claims] (1) A plurality of mask images obtained before the contrast medium is injected into the diagnostic target region of the subject and a contrast image obtained after the contrast medium is injected are stored, and one of the plurality of mask images is stored. A radiation image processing device that sequentially selects a plurality of subtract images and obtains a plurality of subtract images by calculating the selected mask image and the contrast image includes a calculation unit that calculates the sum of pixel data of a specific region of each of the plurality of subtract images; A radiation image processing apparatus comprising: a mask image selection section that selects a mask image that obtains a subtract image with a minimum sum of pixel data. (2) The radiation image processing apparatus according to claim 1, wherein the pixel data is a density value. (3) The radiation image processing apparatus according to claim 1, wherein the pixel data is the number of image pixels.