JP4404291B2 - Image processing apparatus and method and system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing technique, and more particularly to an image processing technique suitable for processing radiographic images in the medical field.
[0002]
[Prior art]
A technique for imaging the transmission intensity distribution using the substance transmission ability of radiation typified by X-rays is fundamental to the development of modern medical technology. Since the discovery of X-rays, the intensity distribution has been imaged by converting the X-ray intensity distribution into visible light with a phosphor and then developing a latent image with a silver salt film. In recent years, photostimulable phosphors are used when digitizing X-ray images, and a latent image as a stored energy distribution on the photostimulable phosphor by X-ray irradiation is read out by excitation with a laser beam and converted into a digital image. A method using a so-called imaging plate has also been generalized. In addition, large solid-state image sensors that can cover the size of the human body due to advances in semiconductor technology, so-called flat panel detectors, have also been developed so that X-ray images can be digitized directly without making latent images so that efficient diagnosis can be performed. Came.
[0003]
On the other hand, it is possible to image the fluorescence of weak X-rays with a high-sensitivity imaging device represented by a photomultiplier tube (image intensifier), and observe the dynamics inside the human body, which has been generally used. ing. Modern flat panel detectors have sensitivity comparable to such image intensifiers, and it has become possible to capture dynamics over a wide range of the human body.
[0004]
In general, the most effective X-ray imaging for medical use is chest imaging of a human body. Taking a wide area of the chest, including the abdomen, can help discover many diseases, including lung disease, so chest X-ray imaging is indispensable for normal health examinations. Also, in recent years, in order to efficiently diagnose a huge amount of chest X-ray images taken for medical examinations, image analysis is performed on the chest digital X-ray images using a computer to assist the initial diagnosis of the doctor. The so-called computer aided diagnosis (CAD) is also being put into practical use.
In addition, the abnormal shadow detection apparatus which detects the abnormal shadow which appears in a radiographic image is known in patent document 1 and patent document 2.
[0005]
[Patent Document 1]
Japanese Patent No. 2582665 [Patent Document 2]
Japanese Patent No. 2582666 [0006]
[Problems to be solved by the invention]
Now, when a finding that there is some suspicion of a disease is obtained by a chest X-ray or the like in a health check, a definitive diagnosis is performed by a so-called precise diagnosis. In such precise diagnosis, CT and MR scans are often performed. The CT scan and MR scan require several times the diagnostic cost as compared with normal X-ray imaging. Although there are many cases where the initial diagnosis is misdiagnosis and there is no illness due to such a precise diagnosis, such misdiagnosis consumes unnecessary medical expenses and contributes to an increase in medical expenses. . In order to prevent this, it is important to improve the accuracy of the initial medical examination.
[0007]
As a method of suppressing the cost increase and improving the accuracy of diagnosis, it is effective to obtain a chest moving image showing dynamics by breathing or the like and to perform dynamic observation using the above-described large flat panel detector. In the dynamic observation, unlike the case of observing a conventional still image, the images are observed by switching in time series. However, such dynamic observations often depend on the subjectivity of the observer compared to still image observations, and ambiguous points tend to remain. In addition, since a great amount of observation time is consumed, the diagnostic efficiency is poor.
[0008]
The present invention has been made in view of the above problems, and an object thereof is to generate an image effective for diagnosis based on a dynamic image.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, an image processing apparatus according to the present invention comprises the following arrangement. That is,
Difference means for generating a plurality of difference images by taking a difference between two temporally adjacent images of the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated by the difference means, a pixel value for each pixel group is selected from a maximum value, a minimum value, an average value, and an intermediate value for each pixel group. Analyzing means for generating an image as a value.
An image processing apparatus according to another aspect of the present invention has the following configuration. That is,
For each corresponding pixel group from a plurality of dynamic images, a reference image is generated using any one of the maximum value, minimum value, average value, and intermediate value of the pixel value of the pixel group as a reference pixel value corresponding to the pixel group. Differential means for generating a plurality of difference images by taking a difference between the reference image and the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated by the difference means, one of the maximum value, the minimum value, the average value, and the intermediate value of the pixel value for each pixel group corresponds to the pixel group. Analyzing means for generating an image as a pixel value.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0011]
[First Embodiment]
In this embodiment, an inter-frame difference image of the acquired respiratory dynamic image is created, and the differential moving image is displayed. Further, each difference image is analyzed, a difference pixel having the maximum absolute value is obtained for each corresponding pixel group, a maximum value image including the difference pixels is created, and the maximum value image is placed on an image of a specific respiratory phase. It is possible to determine the presence or absence of a disease by creating a single image by superimposing and observing and analyzing the image.
[0012]
FIG. 1 is a block diagram schematically showing the configuration of the respiratory dynamic imaging apparatus according to the first embodiment. In FIG. 1, reference numeral 1 denotes an X-ray image sensor that images X-ray intensity, and continuous image acquisition is possible. As the X-ray image sensor 1, a flat panel detector can be used. An X-ray generator 2 generates X-rays and irradiates the subject. Reference numeral 3 denotes a control device that controls the X-ray image sensor 1 and the X-ray generation device 2 to appropriately synchronize X-ray generation and image acquisition. Reference numeral 4 denotes a human body as a subject (subject).
[0013]
Reference numeral 5 denotes a continuous image acquisition unit that continuously acquires image data output from the X-ray image sensor 1. Reference numeral 6 denotes a moving image display unit which displays a human chest image continuously acquired by the continuous image acquisition unit 5 on the display in real time. Reference numeral 7 denotes a storage device that stores images acquired by the continuous image acquisition unit 5. The moving image display unit 6 can pull out data from the storage device 7 as needed and refer to it sequentially. That is, the moving image display unit 6 can display a continuously acquired image such as a moving image display in real time or recording and reproduction later as a moving image.
[0014]
Reference numeral 9 denotes an inter-frame difference calculation unit, which performs the inter-frame difference calculation of the time-series X-ray images acquired continuously by the continuous image acquisition unit 5 and stored in the storage device 7. Reference numeral 8 denotes an inter-frame difference moving image display unit which displays a plurality of created inter-frame difference images as moving images on a display. A difference image analysis unit 10 analyzes a plurality of difference images obtained from the inter-frame difference calculation unit 9. Specifically, in this embodiment, one image composed of pixels indicating the maximum pixel value for each corresponding pixel group in a plurality of difference images is created. A difference analysis result display unit 11 displays a difference analysis result (specifically, one image composed of difference pixels having the largest absolute value of the difference pixel value) on the display.
[0015]
FIG. 2 is a diagram showing how the difference image is created by the inter-frame difference calculation unit 9. In FIG. 2, reference numeral 21 denotes a plurality of frame images representing respiratory dynamics acquired by the continuous image acquisition unit 5 and stored in the storage device 7. A result obtained by calculating the difference between adjacent images of the plurality of frame images is 22 and is referred to as an inter-frame difference image.
[0016]
Now, assuming that the pixel value range of the original respiratory dynamic image is 0 to A, the pixel value range of the inter-frame difference image theoretically extends to the range of -A to A. However, since each frame image is a substantially similar image, the pixel value range of the difference image is considerably narrowed. Further, since a normal display targets only positive pixel values, in order to display the above-described difference image, all pixel values must be set to positive values. As a method for realizing this, there are methods such as adding an offset to each pixel value to make all the values positive, and taking an absolute value for each pixel. In this embodiment, in order to display the difference image on the display in the inter-frame difference moving image display unit 8, A / 2 is added to each pixel of the difference image as an offset, and as a result, a value less than 0 is clipped to 0. Then, a value exceeding A is clipped to A, thereby realizing a stable inter-frame difference image display.
[0017]
FIG. 3 is a flowchart for explaining the difference image analysis processing by the difference image analysis unit 10. FIG. 4 is a diagram for explaining processing by the inter-frame difference calculation unit 8 and the difference image analysis unit 10.
[0018]
In FIG. 4, it is assumed that the time-series images representing the respiratory dynamics are five images T1 to T5, but in reality, the time-series images are composed of more images (for example, 30 images or more). As described above, the difference for each pixel between the adjacent images T1 and T2 is calculated, and the difference image D1 is generated. Similarly, the difference image D2 is calculated from the images T2 and T3, the difference image D3 is calculated from the images T3 and T4, and the difference image D4 is calculated from the images T4 and T5. These difference images are provided to the difference image analysis unit 10. The difference image analysis unit 10 obtains a maximum value for each pixel from the provided plurality of difference images, and generates a result image (also referred to as an integrated image) C using the maximum value. Hereinafter, the process of acquiring the result image C will be described with reference to the flowchart of FIG.
[0019]
First, each pixel value of the result image C is set to 0 in step S11. In step S12, it is determined whether or not all inter-frame difference images (all difference images D1 to D4 in FIG. 4) have been processed. If the processing has been completed for all the difference images, the result image C has been obtained, and thus this processing ends.
[0020]
If there is an unprocessed difference image, the process proceeds from step S12 to step S13, the difference image to be processed is selected, and this is designated as B. In the first process, for example, D1 is selected. In step S14, the processing address x indicating the pixel of the selected difference image and the corresponding pixel of the result image C is initialized to zero.
[0021]
In step S15, it is determined whether or not x exceeds the image size of the difference image (which is also the image size of the result image C). If it exceeds, the processing has been completed for all the pixels of the difference image. The process returns to step S12. If x does not exceed the image size, the process proceeds to step S16, and the absolute value (| B (x) |) of the pixel value in the processing target difference image indicated by x and the corresponding pixel in the result image C are currently displayed. The set pixel value (C (x)) is compared. If | B (x) | is larger than C (x), the process proceeds to step S17, and the pixel (C (x)) of the result image C is updated with B (x). Then, the processing address x is incremented by 1, and the process returns to step S15. On the other hand, when | B (x) | is equal to or less than C (x), it is not necessary to update C (x), so step S17 is skipped and the process continues to the next processing address.
[0022]
With the above-described processing of FIG. 3, a result image C composed of difference pixels having the maximum absolute value of the difference pixel value is obtained. The difference analysis result display unit 11 displays this result image. In displaying the result image, addition of an offset value and clipping are performed on each pixel value of the result image in the same manner as described above. By observing such a result image, it is possible to clearly understand a portion where the movement due to breathing of the chest is large and a portion where the movement is small. Therefore, for example, when the lung function is damaged due to the influence of a chest disease or the like, the movement of the damaged portion is reduced, so that the observer clearly shows the damaged portion of the lung function by the image displayed according to the present embodiment. Can be recognized.
[0023]
[Second Embodiment]
In the first embodiment, a difference image is generated from adjacent frames. In the second embodiment, one reference image integrated from a plurality of images (a plurality of frame images) is created, a difference image is generated from the reference image and each frame, and displayed and analyzed.
[0024]
FIG. 5 is a block diagram schematically showing the configuration of the respiratory dynamic imaging device according to the second embodiment. Parts similar to those in FIG. 1 are denoted by the same reference numerals. In FIG. 5, reference numeral 31 denotes a frame image integration processing unit, which integrates a plurality of frame images acquired by the continuous image acquisition unit 5 and stored in the storage device 7 into one image. Hereinafter, an image obtained by integrating a plurality of frame images by the frame image integration processing unit 31 is referred to as a reference image. Reference numeral 32 denotes a storage device that stores the reference image obtained by the frame image integration processing 31 and can be replaced by means such as a semiconductor memory. A difference calculation unit 33 calculates a difference between the reference image and each frame image. Reference numeral 34 denotes a difference image moving image display unit, which displays a plurality of difference images calculated by the difference calculation unit 33 as moving images.
[0025]
The integration of a plurality of images by the frame image integration processing 31 means, for example, the following image processing.
Maximum value projection image: A plurality of images are integrated by holding the maximum value in the corresponding pixel of each of the plurality of images.
Minimum value projection image: A plurality of images are integrated by holding a minimum value in a corresponding pixel of each of the plurality of images.
Average image: A plurality of images are integrated by holding an average value of corresponding pixels of the plurality of images.
Intermediate value image: A plurality of images are integrated by holding intermediate values of corresponding pixel values of a plurality of images.
In this embodiment, it is assumed that each integration method can be selected according to the purpose.
[0026]
According to the second embodiment, the difference calculation unit 33 calculates the difference between the integrated image (reference image) and each frame image and displays the difference image by the difference image moving image display unit 34. An image in which the amount of variation is emphasized can be displayed. Note that offset processing and clipping processing for display are the same as in the first embodiment.
[0027]
Similarly to the first embodiment, the difference image analysis unit 10 generates and displays an image composed of pixels indicating the maximum absolute value in the corresponding pixel group from all the difference images. FIG. 6 is a diagram illustrating generation of a difference image and generation of a result image C according to the second embodiment. The difference image analysis unit 10 uses a difference image (D1 to D5) that is a difference between the integrated image (reference image R) and each of the frame images (T1 to T5), and uses the maximum absolute value in the corresponding pixel group. Is generated as a result image C. For this reason, according to the second embodiment, it is possible to obtain a clearer image of a portion having a large fluctuation amount.
Note that the result image C can be generated using various statistics such as the minimum value, the average value, and the intermediate value instead of the above-described maximum absolute value, and the same effect can be obtained.
[0028]
[Third Embodiment]
In the third embodiment, as the analysis result display by the difference analysis result display unit 11, the result image obtained in the first embodiment or the second embodiment is used as a specific image among a plurality of images stored in the storage device 7. It is displayed superimposed on the image. By observing such an image, the observer can easily grasp the anatomical position of the abnormal part. In addition, as the specific one image, when the plurality of images represent respiratory dynamics, it is desirable to use an image during maximum inspiration. In the case of superimposing, it is more desirable to change the color between the specific image and the result image.
[0029]
[Fourth Embodiment]
In the fourth embodiment, as the analysis result display by the difference analysis result display unit 11, the result image C obtained by the above procedure is further analyzed by a computer, and an area showing an abnormal value is detected and displayed in an identifiable manner. . This is realized, for example, by the following processing. That is, first, each pixel value of the result image C obtained in the difference image analysis unit 10 is compared with a fluctuation value known from normal medical knowledge or experience, and an abnormal value (such as an abnormally large difference value) is obtained. The indicated area is detected. Then, a mark is applied to the area of the pixel value detected as an abnormal value, and the result image C is displayed. Such a display further improves the diagnostic efficiency.
[0030]
The mark is attached to the result image C. However, the mark may be attached to a specific image among a plurality of images representing respiratory dynamics stored in the storage device 7. Alternatively, the result image C or the specific image may be selected to be marked. When a plurality of images represent respiratory dynamics, it is desirable to use an image during maximum inspiration as the specific one image. Furthermore, the magnitude of the fluctuation amount may be divided into a plurality of ranks, and the color of the mark attached according to the rank may be changed. By providing such an image display to a doctor as a primary detection result (disease candidate) of a disease, diagnosis by the doctor can be supported.
[0031]
An object of the present invention is to supply a storage medium that records a program code of software that realizes the functions of the above-described embodiments to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0032]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.
[0033]
As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0034]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing and the processing is included in the embodiment of the present invention.
[0035]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. Needless to say, the embodiment of the present invention also includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.
[0036]
【The invention's effect】
As described above, according to the present invention, an image effective for diagnosis can be generated based on a dynamic image.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a configuration of a respiratory dynamic imaging device according to a first embodiment.
FIG. 2 is a diagram showing how a difference image is created by an inter-frame difference calculation unit 9;
FIG. 3 is a flowchart for explaining difference image analysis processing by the difference image analysis unit 10;
FIG. 4 is a diagram illustrating processing by an inter-frame difference calculation unit 8 and a difference image analysis unit 10 according to the first embodiment.
FIG. 5 is a block diagram schematically showing a configuration of a respiratory dynamic imaging device according to a second embodiment.
FIG. 6 is a diagram illustrating generation of a difference image and generation of a result image C according to the second embodiment.

Claims (11)

Difference means for generating a plurality of difference images by taking a difference between two temporally adjacent images of the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated by the difference means, a pixel value for each pixel group is selected from a maximum value, a minimum value, an average value, and an intermediate value for each pixel group. An image processing apparatus comprising: an analysis unit that generates an image as a value. For each corresponding pixel group from a plurality of dynamic images, a reference image is generated using any one of the maximum value, minimum value, average value, and intermediate value of the pixel value of the pixel group as a reference pixel value corresponding to the pixel group. Differential means for generating a plurality of difference images by taking a difference between the reference image and the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated by the difference means, one of the maximum value, the minimum value, the average value, and the intermediate value of the pixel value for each pixel group corresponds to the pixel group. An image processing apparatus comprising: an analysis unit that generates an image as a pixel value.   The image processing apparatus according to claim 1, further comprising display means for displaying the image generated by the analysis means.   The image processing apparatus according to claim 3, wherein the display unit displays the generated image superimposed on a predetermined image of the plurality of images. The image processing apparatus according to claim 4 , wherein a color of the generated image displayed in a superimposed manner is different from a color of the predetermined image. The dynamic image, the image processing apparatus according to any one of claims 1 to 5, characterized in that the one that was generated based on the intensity distribution of radiation transmitted through the object. System comprising: the image processing device according to any one of claims 1 to 6, and an image capturing apparatus for capturing a dynamic object. A difference step for generating a plurality of difference images by taking a difference between two temporally adjacent images of the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated in the difference step, any one of the maximum value, minimum value, average value, and intermediate value of the pixel value for each pixel group is determined for each pixel group. An image processing method comprising: an analysis step of generating an image as a value. For each corresponding pixel group from a plurality of dynamic images, a reference image is generated using any one of the maximum value, minimum value, average value, and intermediate value of the pixel value of the pixel group as a reference pixel value corresponding to the pixel group. A difference step for generating a plurality of difference images by taking a difference between the reference image and the plurality of dynamic images;
For each corresponding pixel group from the plurality of difference images generated in the difference step, a pixel corresponding to the pixel group is one of the maximum value, minimum value, average value, and intermediate value of the pixel value of the pixel group An image processing method comprising: an analysis step of generating an image as a value. A program for causing a computer to execute the method according to claim 8 or 9 .   A computer-readable storage medium storing the program according to claim 10.

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