JPH04129538A - Output of image - Google Patents

Abstract

PURPOSE:To obtain the image output method for easily obtaining the change of the abnormal shadow represented in the radioactive ray images of a same inspected body by outputting the information which represents the difference between the abnormal shadow which are shown on a regenerated image, based on the image data, and a radioactive ray image which is taken up in the past, and the abnormal shadow on a radioactive ray image which is taken up at present. CONSTITUTION:When a tumor image is extracted, the information such as the position on an X-ray image and the dimension of the tumor shadow and the image data SD which are related to the extracted tumor shadow are sent into an image memory device 50, and memorized in an optical disc 51 installed in an image memory device 50. When an operator operates a keyboard 43 for the input of the ID information, the image data SD1 which represents the X-ray images obtained for a same inspected body in the past, information related to the abnormal shadow of the X-ray image, and the image data SD2 which represents the X-rays image obtained at present and the information related to the abnormal shadow of the X-ray image which correspond to the inputted ID information, are read out from the image memory device 50 and inputted into a computer system 40. The tumor shadow which are shown at the corresponding positions on two X-ray images are comparsed, and the difference between the image in the past and at present is judged.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention detects an abnormal shadow that does not appear in a radiographic image of a normal subject based on image data representing a radiographic image of the subject, and detects an abnormal shadow that does not appear in a radiographic image of a normal subject. This relates to an image output method for outputting a reproduced image, etc. (prior art) Reading a recorded radiation image to obtain image data, performing appropriate image processing on this image data, and then reproducing and recording the image. is being carried out in various fields. For example, an X-ray image is recorded using an X-ray film with a low gamma value designed to be compatible with subsequent image processing, and the electrical signal ( Contrast and sharpness can be improved by converting to image data), performing image processing on this image data, and then reproducing it as a visible image in a copy photograph, etc.

Efforts have been made to obtain reproduced images with good image quality such as graininess (see Japanese Patent Publication No. 81-5193).

The applicant has also proposed radiation (X-rays, α-rays).

When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when irradiated with excitation light such as visible light, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. Using a stimulable phosphor, radiation image information of a subject such as a human body is recorded on a sheet of stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. The resulting stimulated luminescence is read photoelectrically to obtain image data, and based on this image data, a radiation image of the subject is made visible on a recording material such as a photographic material, a CRT, etc. Radiation image recording and reproducing systems that output images as images have already been proposed (Japanese Patent Application Laid-open Nos. 12429-12429, 11395-1980, 11395-1980, and 55-1988).
No. 163472, No. 5B-104645, No. 55-1
16340 etc.).

This system has the practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiation image into an electric signal and using this electric signal to output the radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. be able to.

In recent years, systems using the above-mentioned X-ray films, stimulable phosphor sheets, etc., especially systems configured for medical diagnosis of the human body, have been used to obtain reproduced images with good image quality suitable for simple observation (diagnosis). In addition, automatic recognition of images has been carried out (for example, Japanese Patent Laid-Open No. 2002-12
No. 5481, Japanese Patent Application No. 1-162904, t-t62
No. 905 and No. 1-162909).

Automatic image recognition here refers to the operation of extracting a desired pattern from a complex radiographic image by performing various processes on the image data. This refers to the operation of extracting, for example, a shadow corresponding to a tumor from a very complex image containing a mixture of circular patterns.

A target pattern (for example, a tumor shadow) in such a complex radiographic image (for example, a chest X-ray image of a human body)
By extracting the pattern and reproducing and displaying a visible image clearly showing the extracted pattern, it is possible to assist the observer in observation (for example, assist the doctor in diagnosis).

(Problem to be Solved by the Invention) For example, in a system that recognizes an abnormal shadow such as a tumor shadow from an X-ray image of a human body and outputs the recognized abnormal shadow, it is necessary to Compare this with the current X-ray image to determine what changes in abnormal shadows (
For example, it may be necessary to know whether there is a lesion). In such a case, when displaying each X-ray image, the recognized abnormal shadow is clearly displayed on each X-ray image, and the doctor etc. It was common to judge changes by comparing them.

Furthermore, in order to assist in this comparative observation, a method has been considered in which a difference image corresponding to the difference between two X-ray images is generated and the difference between the two X-ray images is extracted based on this difference image. However, with this method, it is difficult to align the two X-ray images due to slight positional shifts of the subject during imaging, and therefore it is not possible to successfully extract the differences between the two X-ray images. The problem is that it is not the target.

In view of the above circumstances, it is an object of the present invention to provide an image output method that can easily detect changes in abnormal shadows appearing in radiation images of the same subject between the past and the present, or at two points in the past. It is something to do.

(Means for Solving the Problems) The image output method of the present invention for achieving the above object detects abnormalities based on a plurality of image data representing each of a plurality of radiographic images of the same subject taken over time. By scanning the plurality of radiographic images using a shadow extraction filter, abnormal shadows appearing in the plurality of radiographic images are detected, and the abnormal shadows appearing in the radiographic images taken earlier are compared over time with the abnormal shadows appearing in the radiographic images taken earlier. The present invention is characterized in that it recognizes a difference from an abnormal shadow that appears in a radiation image taken later, and outputs a reproduced image based on the image data and information representing the difference.

Here, the detection of abnormal shadows appearing in the plurality of radiographic images does not need to be performed simultaneously on the plurality of radiographic images, and may be performed at each time point when each radiographic image is obtained.

Furthermore, in the present invention, the "reproduced image based on the image data" and the "information representing the difference" are, for example, CR
They may be displayed using a device that displays them on a display screen, such as a T-display, or they may be displayed using a device that outputs them on film, paper, etc., such as a laser printer.

(Function) The image output method of the present invention is different from the conventional two-way image output method.
Unlike the method of calculating a difference image corresponding to the difference between two images, first, abnormal shadows are detected in each radiation image, and then, for example, the size of abnormal shadows located in similar positions on multiple radiation images and the detected By recognizing differences in the probability that an abnormal shadow is truly an abnormal shadow,
It is only necessary that the rough positions of the multiple radiographic images match, and there is no need for strict alignment of these multiple radiographic images. Changes in abnormal shadows can be easily detected by displaying information representing the recognized differences. This means that you can do it.

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

FIG. 1 is a perspective view of an X-ray image reading device 5, a computer system using an example of the image output method of the present invention, and an example of an image storage device.

Here, an example will be described in which the above-mentioned stimulable phosphor sheet is used to detect a tumor shadow, which typically occurs in the lungs of a human body in a substantially spherical shape, as an abnormal shadow. This tumor appears as a whitish (lower density) approximately circular pattern than the surrounding area on a visible image reproduced based on image data.

After an X-ray image of the chest of a human body is accumulated and recorded on a stimulable phosphor sheet in an X-ray imaging device (not shown), the stimulable phosphor sheet 14 is set at a predetermined position of the X-ray image reading device 20.

The stimulable phosphor sheet 14 set at a predetermined position is conveyed (sub-scanning) in the direction of arrow Y by a sheet conveying means 22 such as an endless belt driven by a motor 21.
be done. On the other hand, the light beam 24 emitted from the laser light source 23 is reflected and deflected by the rotating polygon v12B driven by the motor 25 and rotates at high speed in the direction of the arrow, passes through a focusing lens 27 such as an fθ lens, and then changes its optical path by a mirror 28. enters the sheet 5 and performs main scanning in the direction of arrow X, which is substantially perpendicular to the direction of sub-scanning (direction of arrow Y). The stimulable luminescent light 29 is emitted from the part of the stimulable phosphor sheet 14 that is irradiated with the light beam 24, and the amount of stimulated luminescent light 29 corresponds to the accumulated and recorded X-ray image information. 30 and photoelectrically detected by a photomultiplier 31. The light guide 30 is made by molding a light-guiding material such as an acrylic plate, and is arranged in such a way that a linear entrance end surface 30a extends along the main scanning line, and is formed in an annular shape. A light receiving surface of a photomultiplier 31 is coupled to the exit end surface 30b. The stimulated luminescent light 29 that enters the light guide 30 from the entrance end surface 30a travels through the interior of the light guide 30 through repeated total reflection, exits from the exit end surface 30b, and is received by the photomultiplier 31, forming an X-ray image. The photomultiplier 31 converts the stimulated luminescent light 29 into an electrical signal.

The analog output signal S^ outputted from the photomultiplier 31 is logarithmically amplified by the logarithmic amplifier 32, and the A/D
The image data SO is digitized by a converter 33 and obtained as an electrical signal.

The image data SO obtained in this way is transmitted to a computer system 4 using an example of the image output method of the present invention.
It is input to 0. This computer system 40 is a CP
U, main body part 41 in which internal memory etc. are built-in. A drive unit 42 into which a floppy disk as auxiliary memory is inserted and driven. The operator uses this computer system 4
Keyboard 43 for inputting necessary instructions etc. X
It consists of a CRT display 44 for displaying line images and necessary information.

At the same time as reading the X-ray image, ID information for identifying the subject of the X-ray image, such as name, gender, body part, etc., is input from the keyboard 43 provided in the computer system 40. The X-ray image that is to be read or has been read is specified by the ID information.

When the image data SD is input to this computer system 40, within this computer system 40, the following calculation is executed based on the image data SO, and as a result, the X carried by the image data SD is
The tumor shadow appearing in the line image is extracted. Here, an example of this tumor shadow extraction will be explained.

In order to explain an example of a real space filter for extracting a tumor shadow, FIG.
It is a diagram virtually drawn on a line image. Here, a calculation is performed to obtain a large characteristic value C when a predetermined pixel PO is a pixel within the tumor shadow, and this calculation is performed sequentially for each pixel of the X-ray image, that is, as shown here. By scanning the X-ray image using a filter, a tumor shadow appearing on the X-ray image is determined. The filter described here is the filter described in the aforementioned Japanese Patent Application No. 1-182904.

FIG. 3 shows the above-mentioned predetermined pixel P. FIG. 3 is a diagram showing an example of the profile of an X-ray image in the direction (X direction) in which line segments L1 and L5 in FIG. 2 extend, centered on . Here, it is assumed that the predetermined pixel Po is located at a position where a density gradient (change in value of image data SD) exists. The tumor shadow 57 typically appears as a nearly bilaterally symmetrical profile, but if the tumor shadow 57 is located at a position where there is a concentration gradient as in this example, the profile may not be bilaterally symmetrical on the X-ray image. There is also. It is important to be able to extract this tumor shadow 57 even in such a case. Note that the broken line 58 in FIG. 3 is an example of a profile when there is no tumor.

As shown in FIG. 2, a plurality of (eight lines in this case) line segments Lt (1-1, 2,... , 8),
Furthermore, each radius '1 is centered at a predetermined pixel Po.
+ '2+ '3 circle R+ (j -1,2,3
) is assumed. The image data of a predetermined pixel Po is f. Each pixel P located at each intersection of the binding, each line segment, and each day R0
z (Figure 2 shows PIl+ P 12+ P13+ P5
Symbols are shown for 1+P 52+ P 53. ) is assumed to be fl.

Here, image data fo of a predetermined pixel Po and each pixel P,
The difference between the image data f and the image data f is Δ6. is obtained according to the following equation (1).

Δ1− f lr f o =・(ll
(+ −1, 2, ..., 8, j −1
, 2, 3) Next, for each line segment, the maximum value of the difference Δ1 determined by equation (1) is determined. That is, line segment L1°L5
For example, for line segment Ll, pixel PII
+ Each difference Δ11” corresponding to P12+ P13
f II fO Δ12” f 12 fO Δ13−f 13 f.

The maximum value of these is calculated. In this example, as shown in FIG. <Δ1□×Δ,×0, so Δ is the maximum value.

Here, typically, a circular pattern in which the central image data has a smaller value than the surrounding image data is obtained (<U tumor shadow), whereas for the line segment L1, Δ
13. Δ1□, Δ1. Both are negative, so the formally determined maximum value Δ1. is a valid maximum value, so here 0.0 is for each difference Δ18. with respect to line segment L1.
Δ, 2. This value is used as an alternative to the maximum value of Δ13. however,
The maximum value formally determined as described above may be used as is.

Also, regarding line segment L5, pixels P, 1+ P5□, P,
Each difference Δ51""f51 f corresponding to 3.

Δ52”f52 f.

Δ53”f53 f.

The maximum value Δ5. is required.

In this way, the maximum value of the difference Δ between a predetermined pixel Po and a plurality of pixels P is determined for each line segment, and if this determined maximum value is a valid maximum value, that maximum value is used. , if it is not a valid maximum value, use 0.0 as a value in place of the maximum value (hereinafter, this is also referred to as the maximum value).Next, two line segments extending in opposite directions from a predetermined pixel Po are As a set, that is, line segment and line segment L5, line segment L2 and line segment L6% line segment L3 and line segment L7, and line segment L4
and line segment L6 as one set, and the average value of the two maximum values (Mis, M26, M37, respectively) for each set of weights.
．． M4g) is required.

For the set of line segment L1 and line segment L5, the average value M1
5 is found as .

By treating the two line segments extending in opposite directions from a predetermined pixel Po as a set, the tumor shadow 7 is located at a position with a density gradient and its image data is distributed as shown in FIG. It is possible to reliably detect tumor shadows even if they are asymmetric.

Average value M15. M26. M
When 37°M4H is determined, these average values M 15
．． Based on M26°M3□1M48, a characteristic value corresponding to a predetermined pixel P0 is determined as follows. These average values M15. M26. M37. M4
Although the method for determining the characteristic value based on B is not limited to a specific method, for example, the following method may be adopted.

FIG. 4 is a diagram for explaining an example of how to obtain characteristic values. The horizontal axis is the average value M obtained as described above, 6.
M26. M, , M48, the vertical axis is the average value M,
,, M26. M, 7. M4. 〇Average value M which is each evaluation value CI5, C26, C37, C48 corresponding to 15. M26. M 3□5M48 value M
If it is smaller than 1, the evaluation value is 0. If it is larger than a certain value M2, the evaluation value is 1.0. In the middle between M1 and M2, the evaluation value is between 0.0 and 1.0 depending on the size of the value. value. In this way, each average value M15. M 26゜M
,7. Evaluation value C+ S+ corresponding to M48 respectively
C261C17+C48 are calculated, and their evaluation values C8,.

Sum of C26・C37+C48 C-CI, 10C26+C37+ Cas...
A31 is taken as a characteristic value. That is, this characteristic value C has any value between the minimum value 0.0 and the maximum value 4.0. In this embodiment, this characteristic value is compared with a predetermined threshold Thl, and it is determined that C≧Thl. It is determined whether each predetermined pixel Po is a pixel within the tumor shadow, depending on whether C<Thl.

Each evaluation value above CI S+ C26+ C37+ C4
8, if the above evaluation values Cl5I C261C37, C411 are calculated using a conversion formula that saturates at a small value M2' as shown by the dashed line in FIG. The characteristic value C is
In the case of a tumor shadow that is more circular, the characteristic value C has a large value, and conversely, as shown by the two-dot chain line in Fig. 4, the characteristic value C is determined using a conversion formula that does not saturate up to a large value M2'. Then, this characteristic value C has a large value for a tumor shadow with a large contrast with the surroundings. Therefore, an appropriate conversion formula is selected depending on the purpose.

Scanning the X-ray image using the real space filter as described above, that is, sequentially scanning each pixel of the X-ray image to a predetermined pixel P,
The tumor shadow is extracted by repeating the calculations described above.

When the tumor shadow is extracted in this way, information regarding the extracted tumor shadow, such as the position on the X-ray image and the size of the tumor shadow, and the image data SO are stored in the image storage shown in FIG. The image is sent to the image storage device 50 and stored on the optical disk 51 loaded in the image storage device 50.

Note that the filter algorithm for extracting tumor shadows is not limited to the above-mentioned algorithm, and may be any one of the algorithms described in the several documents mentioned above, other known algorithms, or a combination thereof. It is something that can be done.

Next, based on the image data SD, the CRT display 44
A case where a visible image is reproduced and displayed on the top will be explained.

When the operator inputs ID information by operating the keyboard 43, image data SDI representing a previously obtained X-ray image of the same subject corresponding to the input ID information and abnormal shadows in this X-ray image are displayed. information, image data SD2 representing a recently obtained X-ray image, and information regarding abnormal shadows in this X-ray image are stored in the image storage device 5.
0 and input into the computer system 40.

FIG. 5 is a diagram schematically representing two X-ray images based on each of the two image data SDt and SD2 input to the computer system 40 in this manner. FIGS. 5(a) and 5(b) are an X-ray image obtained in the past and an X-ray image currently obtained, respectively, and the black circles represent the position and size of the tumor shadow.

Here, tumor shadows appearing at mutually corresponding positions in these two X-ray images are compared.

Whether the tumor shadows are located at corresponding positions can be determined by, for example, determining the center coordinates of the tumor shadow A in FIG. 5(a) by (xt).

yl), and the center coordinates of the tumor shadow A' in FIG. 5(b) are (Xz
, )'z), prepare a predetermined threshold value Δ8゜Δ in advance, and calculate
If l≦Δ, (5) is satisfied, it is determined that the two tumor shadows are located at positions corresponding to each other. In this way, in the present invention, for example, Δ8. A permissible width of Δ can be provided, and the alignment of the two X-ray images can be done roughly so that there is almost no need to be conscious of it, compared to the case of obtaining the difference image described above.

Comparison between corresponding tumor shadows is performed in the manner described above. In the example of FIG. 5, tumor shadow A and tumor shadow A' appear as shadows of almost the same size at mutually corresponding positions, and therefore it is determined that there is no difference between the past and the present. Also, the past X in Figure 5(a)
Tumor shadow B does not appear in the X-ray image, but tumor shadow B' appears in the recent X-ray image shown in FIG. 5(b). This determines that this tumor is a newly generated tumor.

Furthermore, the tumor shadow C appearing in the past X-ray image in FIG. 5(a) and the tumor shadow C' appearing in the recent X-ray image in FIG. 5(b) are at positions corresponding to each other. However, tumor shadow C
The area of the tumor shadow C' is larger than that of the tumor shadow C'.

This indicates that the tumor has grown.

In this way, the differences in whether tumor shadows exist at mutually corresponding positions and whether there is a change in size when tumor shadows exist at mutually corresponding positions are automatically recognized. After that, mainly the most recently obtained X-ray image is displayed as a visible image on the CRT display 44, and information representing the above-mentioned differences is displayed superimposed or juxtaposed with this visible image.

The method of displaying information representing this difference is not limited to a specific method, but for example, only tumor shadows that are different between two X-ray images are displayed surrounded by an O. How to display only.

Tumor shadows with differences are circled with ◎, tumor shadows with no differences are circled with O, etc. The method of indicating the difference depending on whether there is a difference or not, and the presence or absence of difference and the degree of difference, etc., separately from the visible image, etc. It is possible to adopt a method of displaying.

This allows the observer to easily recognize the difference between the past and the present.

Although the above embodiment describes an example in which a tumor shadow is detected as an abnormal shadow, the abnormal shadow referred to in the present invention is not limited to a tumor shadow, and may include, for example, a shadow of a calcified part that occurs within the breast, a shadow of pneumoconiosis, etc. or a combination thereof.

Furthermore, although the above embodiments have been described using stimulable phosphors, the present invention is not limited to systems using stimulable phosphors, but can also be applied to systems using X-ray films, etc. It is.

(Effects of the Invention) As explained in detail above, the image output method of the present invention has the following features:
First, abnormal shadows are detected in each of a plurality of radiographic images of the same subject taken over time, and then differences in these abnormal shadows are recognized by comparing the abnormal shadows that appear in these multiple radiographic images, Since information representing this difference is output, the difference can be automatically recognized with high precision, and thereby the observer can easily grasp the changes in the abnormal shadow.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of an X-ray image reading device, a computer system using an example of the image output method of the present invention, and an image storage device, and FIG. 2 is a perspective view of a real space filter for extracting a tumor shadow. To explain an example, FIG. 3 is a diagram virtually drawn on an X-ray image centering on a predetermined pixel Po on the X-ray image. A diagram showing an example of the profile of an X-ray image in the extending direction (X direction) of line segments Ll and L5 in FIG. FIG. 5 is a diagram schematically representing two X-ray images based on each of the two image data S DI + S D2 input to the computer system shown in FIG. 1. 14...Stormative phosphor sheet 20...X-ray image reading device 31...Photo multiplier 40...Computer system 50...Image storage device 5■...Optical disk 57...Tumor shadow f Fig. 2 Fig. 3 Fig. 4 Funeral map

Claims (1)

[Claims] (1) Based on a plurality of image data representing each of a plurality of radiographic images of the same subject taken over time, the plurality of radiographic images are scanned using an abnormal shadow extraction filter. Detecting an abnormal shadow appearing in a radiographic image, recognizing a difference between an abnormal shadow appearing in a radiographic image taken earlier over time and an abnormal shadow appearing in a radiation image taken later over time, and collecting the image data. An image output method characterized by outputting a reproduced image based on the above and information representing the difference.