JP2005136594A - Image processing apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for generating a difference image in which aging of an object is clearly recognized from a first image and a second image indicating the object picked up at different times. <P>SOLUTION: When a portion region is designated from the difference image because the difference image is not clear, a first parameter for coordinate conversion for solving positional deviation or distortion of the second image from the first image which is previously stored is used to match the positions between the images, and then a first portion image of the first image and a second portion image of the second image with respect to the portion image are extracted. For the first portion image and the second portion image which are extracted, a second parameter for coordinate conversion for solving the positional deviation or distortion between the images is calculated, the positions between the images are matched using this second parameter before generating the first portion image and the second portion image, and the generated images are displayed so as to be overlapped on the difference image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus, a control method thereof, a control program, and a storage medium, and more specifically, can display changes with time of a subject in a medical image such as a simple X-ray image with high accuracy and effectively. The present invention relates to an image processing apparatus, a control method thereof, and a storage medium.

  In the medical imaging field, CAD (Computer Aided Diagnosis) has been actively researched in recent years, and images of simple X-rays, CT (Computerized Tomography), etc. are analyzed by a computer, and lesions are analyzed. It is expected to contribute to early detection of diseases by detecting suspicious parts.

  Various types of CAD are conceivable depending on the target image and the detection target. By taking a difference between images obtained by photographing the same part in the CAD, a CAD based on a time-difference method that obtains an image that emphasizes temporal changes is obtained. (Time difference CAD) is attracting attention.

  In the temporal difference CAD, for example, a set of chest X-ray images taken at different points in time are input, and image analysis is performed to obtain anatomically identical positions in the respective images. Alternatively, any one of the past images is deformed, and the difference processing for each pixel is performed.

  Such a temporal difference CAD method is disclosed in, for example, US Pat. No. 5,982,915 (for example, Patent Document 1). According to this document, an image to be subjected to difference processing is reduced so as to have a predetermined resolution, difference processing is performed between the reduced images, and a result is output. For example, an image having the number of pixels of 2048 × 2048 is subjected to differential processing after being reduced to a resolution of 512 × 512. This is because the processing speed is increased by reducing the number of processed pixels and the required image quality in the difference image. Is determined in relation to.

  By the way, it is desirable that the difference image is extracted as a difference signal only from a portion where a normal anatomical structure is sufficiently removed and a change with time is generated. For this purpose, the posture of the subject and the state of exhalation need to be as identical as possible between the pair of images to be subjected to the difference processing. However, there is a limit to performing imaging with these items being the same in normal clinical settings.

  Therefore, as disclosed in the above-mentioned documents, a plurality of ROIs (Region of Interest) are set in an image to obtain a plurality of shift vector amounts, and they are nonlinearly interpolated to form a deformed image. And a method of performing difference processing based on this. However, even if this difference processing is performed, the alignment between the two images may not be performed completely, and artifacts (shadows) due to misalignment may occur.

In such a case, when a minute change occurs between two images, it is discriminated whether the changed part is a part that has changed over time or is caused by an artifact. The problem that it is difficult to stick occurs. Therefore, if it is difficult to distinguish the above, for example, when a difference image is observed, a detailed difference image is displayed using a function such as a magnifying glass. Even if the resolution is lowered before the difference processing, sufficient image quality may not be obtained.
US Pat. No. 5,982,915

  The present invention has been made starting from solving the above-described problems of the prior art, and an object of the present invention is to provide a high-accuracy differential image that eliminates the influence of artifacts when observing the differential image. It is providing a processing apparatus and its control method.

  In order to achieve the above object, an image forming apparatus according to an embodiment of the present invention has the following arrangement. That is, an image processing device that generates a difference image from a first image and a second image of an object captured at different times, wherein the first image, the second image, the first image, and the second image A first parameter for coordinate conversion that eliminates a positional shift or distortion between the first image and a difference image between the first image and the second image generated after matching the positions between the images using the first parameter; Is stored in advance, a display means for displaying the difference image stored in the storage means, and a partial area in the difference image displayed on the display means is designated, the first parameter The first partial image and the second image in the first image corresponding to the partial area after the positional deviation or distortion between the first image and the second image is eliminated by using To determine the second partial image And a second parameter for coordinate conversion that eliminates displacement or distortion between the first partial image and the second partial image determined by the determination unit, and using the second parameter, the position between the images is calculated. And generating means for generating a partial difference image between the first partial image and the second partial image after matching.

  Here, for example, the first parameter is obtained by changing the point coordinate of one image to the other point based on a predetermined conversion formula with respect to the coordinate of the reference point indicating the characteristic position of the object between the two images. It is preferable to include a parameter used when converting the coordinates to coordinates.

  Here, for example, it is preferable that the first image and the second image are images taken by simple X-ray or computed tomography, and the reference point is a position of an anatomically characteristic part.

  Here, for example, the generating means sets the setting position of the second setting area to be set in the second partial image using the predetermined conversion formula, corresponding to the second setting area. It is preferable that conversion means for converting into a setting position of the first setting area set in the partial image is included.

  Here, for example, it is preferable that the display unit displays the first image and the second image stored in the storage unit side by side with the difference image.

  Here, for example, the generation unit reads out the data of the first image and the second image corresponding to the partial area from the selection unit that selects the resolution of the image of the partial area and reads the data. And changing means for changing the pixel size of the data to the resolution selected by the selecting means.

  Here, for example, the data of the first image and the second image stored in the storage unit is preferably compression-coded data.

  In order to achieve the above object, an image processing apparatus control method according to an embodiment of the present invention has the following arrangement. That is, the first image and the second image of the object imaged at different times, the first parameter for coordinate conversion for eliminating the displacement or distortion between the first image and the second image, and the first A control method for an image processing apparatus comprising storage means for storing in advance a difference image between the first image and the second image generated after matching positions between images using parameters, the storage means When the display step for displaying the difference image stored in the image and the partial area in the difference image displayed by the display step are designated, the first image and the second image are used using the first parameter. Deciding to determine a first partial image in the first image and a second partial image in the second image corresponding to the partial region after eliminating the positional deviation or distortion between them and matching the positions between the images Process and the decision process After calculating the second parameter for coordinate conversion that eliminates the positional deviation or distortion between the first partial image and the second partial image determined in this way, and using the second parameter to match the positions between the images A generating step of generating a difference image between the first partial image and the second partial image. In order to achieve the above object, a control program according to an embodiment of the present invention has the following arrangement. That is, the first image and the second image of the object imaged at different times, the first parameter for coordinate conversion for eliminating the displacement or distortion between the first image and the second image, and the first A control program for controlling an image processing apparatus comprising storage means for storing in advance a difference image between the first image and the second image generated after matching positions between images using a parameter, When the program code of the display step for displaying the difference image stored in the storage means and the partial area in the difference image displayed by the display step are specified, the first parameter is used to specify the first parameter. The first partial image in the first image and the second partial image in the second image corresponding to the partial area after eliminating the positional deviation or distortion between the image and the second image and matching the position between the images. Decided And calculating a second parameter for coordinate conversion that eliminates a positional shift or distortion between the first partial image and the second partial image determined by the determination step, and using the second parameter And a program code of a generating step for generating a difference image between the first partial image and the second partial image after matching the positions between the images.

  In order to achieve the above object, an image processing apparatus according to an embodiment of the present invention has the following arrangement. That is, an image processing apparatus that generates a difference image from a first image and a second image of an object captured at different times, a reduction unit that reduces the image size of the first image and the second image, A first difference image generation means for generating a difference image from the first image and the second image reduced by the reduction means, and a specific area on the difference image generated by the first difference image generation means. A region designating unit for designating, an extracting unit for extracting a region corresponding to the specific region from the first image and the second image, a region extracted from the first image by the extracting unit, and the second image And a second difference image generating means for generating a difference image from the region extracted from.

  In order to achieve the above object, an image processing apparatus according to an embodiment of the present invention has the following arrangement. That is, an image processing apparatus that generates a difference image from a first image and a second image of an object captured at different times, a reduction unit that reduces the image size of the first image and the second image, A first difference image generation means for generating a difference image from the first image and the second image reduced by the reduction means, and a specific area on the difference image generated by the first difference image generation means. An area designating unit for designating, an image size designating unit for designating an image size of the first image and the second image, and changing the first image and the second image to an image size designated by the image size designating unit. Extraction means for extracting the area corresponding to the specific area from the first image and the second image whose image size has been changed, the area extracted from the first image by the extraction means, and the second And having a second difference image generating means for generating a difference image from the extracted region from the image, a.

  In order to achieve the above object, an image processing method according to an embodiment of the present invention has the following arrangement. That is, an image processing method for generating a difference image from a first image and a second image of an object captured at different times, a reduction step of reducing the image sizes of the first image and the second image; A first difference image generation step for generating a difference image from the first image and the second image reduced in the reduction step, and a specific region on the difference image generated by the first difference image generation step. A region designating step, an extracting step for extracting a region corresponding to the specific region from the first image and the second image, a region extracted from the first image by the extracting step, and the second image And a second difference image generation step of generating a difference image from the region extracted from

  In order to achieve the above object, an image processing method according to an embodiment of the present invention has the following arrangement. That is, an image processing method for generating a difference image from a first image and a second image of an object captured at different times, a reduction step of reducing the image sizes of the first image and the second image; A first difference image generation step for generating a difference image from the first image and the second image reduced by the reduction means, and a specific area on the difference image generated by the first difference image generation means. An area designating step for designating, an image size designating step for designating image sizes of the first image and the second image, and changing the first image and the second image to the image size designated by the image size designating step. An extraction step of extracting a region corresponding to the specific region from the first image and the second image whose image size has been changed, and the region extracted from the first image by the extraction step and the second And having a second difference image generation step of generating a difference image from the extracted region from the image.

  According to the present invention, it is possible to provide an image processing apparatus that can provide a high-accuracy difference image that eliminates the influence of artifacts and a control method thereof even when the displayed difference image is unclear when the difference image is observed.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
[Configuration of Image Processing Device: FIG. 1]
FIG. 1 is a diagram showing a configuration of an image processing apparatus according to the present invention. The operation of the image processing apparatus according to the present embodiment will be described below with reference to FIG.

  The imaging unit 1 is a modality such as an imaging device that newly generates a medical image used for diagnosis, such as an X-ray imaging device. In the present embodiment, the simple X-ray imaging apparatus is intended for the chest, but the present invention can be applied to other imaging apparatuses such as CT (Computer Tomography).

  The image generated by the imaging unit 1 is output to the storage unit 2 and stored. The storage unit 2 is a storage device such as a hard disk drive or a magneto-optical disk drive, and has a general function as a medical image storage system, and will not be described in detail in the present embodiment. A series of images of a patient are stored in association with each other together with additional information such as imaging date / time and conditions.

  The image stored in the storage unit 2 is read by the image input unit 3 as necessary, and is output to the difference processing unit 4. Here, since the read image is a target of the difference process, it is a pair of images obtained by imaging the same patient's part at different times (a first image and a second image of the target imaged at different times). However, when two or more images are stored, two are selected according to a predetermined selection criterion. For example, the latest image (hereinafter referred to as the current image) and the image captured immediately before (hereinafter referred to as the past image) are read out, but this selection criterion is not directly related to the present invention. Therefore, detailed description is omitted.

  Here, the image read by the image input unit 3 is not necessarily the same as the resolution at the time of imaging. In the present embodiment, the resolution is a predetermined resolution with respect to the resolution of the original image (image at the time of imaging). Assume that a reduced image is read out. The condition for which resolution is reduced may be set in advance, or may be interactively given by the user from the control unit 5.

  Here, it is assumed that an input device (input unit) for inputting parameters for display, such as a mouse and a keyboard, is connected to the control unit 5.

  The processing for reducing an image is performed in the image input unit 3, but the reduction processing can be performed by a known technique. As the reduction processing, for example, a combination of a Gaussian filter and sub-sampling can be considered.

  In the following description, it is assumed that the resolution of the original image is, for example, 2048 × 2048, and the resolution of the image reduced for difference processing is 512 × 512. The resolution here means the size of the photographed image.

  The difference processing unit 4 performs difference processing on the two input images, and outputs the difference image and parameters in the difference processing process to the storage unit 2.

  The control unit 5 shown in FIG. 2 and FIG. 8B while controlling each unit such as the image input unit 3, the difference processing unit 4, and the display control unit 6 while using the RAM based on various control programs stored in the ROM. Execute the process.

[Difference Processing Unit Processing: FIG. 2]
FIG. 2 is a flowchart showing the operation of the difference processing unit 4, and the operation of the difference processing unit 4 will be described with reference to FIG.

(Step S401: Whole matching)
In step S401, detection of the reference position of the current image (first image) and past image (past image) and global matching parameters are calculated according to the following procedure.

  A predetermined reference position is detected with respect to two input images (one is a current image and the other is a past image captured at a predetermined past time point), and an overall shift of the subject is obtained. As the reference position, a reference position representing the reference of the position of the organ to be a difference target is preferable. For example, in the case of a chest X-ray image, the characteristic features of the target part such as the bottom of the right lung and the bottom of the left lung, the midpoint of the right lung and the left lung apex This is suitable for specifying the approximate position of the target lung.

  FIG. 3A is an example of detecting the reference position. In the figure, for example, (a) is a current image and (b) is a past image. In each image, three reference points (P1, P1 ′ to P3, P3) of one midpoint of lung apex and two lung bottoms are shown. ') Is detected. As for the detection method of the reference point, a known method (for example, “Image feature analysis of computer-aided diagnosis: Accurate determination of ribcage boundary in chest radiographs”, Xin-Wei Xu and Kunio Doi, Med. Phys. 22 (5), May 1995).

  Next, based on the detected three pairs of reference points, parameters for correcting the positional deviation between the two images (coordinate conversion parameters for eliminating the positional deviation and matching the corresponding positions between the images) are calculated. As a correction method, for example, affine transformation shown in (Expression 1) can be used.

u = ax + by + c
v = dx + ey + f (Formula 1)
In the above equation, x and y are the reference point coordinate values of the past image, u and v are the reference point coordinate values of the current image, a to d are rotation and enlargement between two images, and e and f are parallel movements. If the parameters of the above equation are determined based on the coordinates of the three reference points described above, the overall positional deviation between the two images can be determined and coordinate conversion between corresponding points can be performed. I can do it.

  That is, the point (x, y) of the past image can be converted into the corresponding point (u, v) in the current image. The parameter determination method is described in, for example, (“Image Analysis Handbook”, supervised by Mikio Takagi, The University of Tokyo Press, 1991), and detailed description thereof is omitted. The obtained parameters are stored in a memory (not shown). In the following description, these parameters are referred to as global matching parameters.

(Step S402: ROI setting)
In step S402, the setting position of the ROI on the current image corresponding to the setting position of the ROI (Region of Interest) set in the past image is set by the following procedure using the global matching parameter.

  The difference processing unit 4 sets a plurality of ROIs in the past and current images. At this time, the ROIs corresponding to each other in the two images are determined based on the overall coordinate transformation parameters (af) obtained in step S401.

  First, a plurality of ROIs are set in the past image. As shown in FIG. 3B, each ROI is set on the matrix in the horizontal and vertical directions at predetermined intervals with reference to the position of the characteristic part of the target region. That is, the ROI may be evenly arranged in a range surrounded by the lung apex midpoint P1 and the lung bottoms P2 and P3.

  Next, the ROI setting position of the current image corresponding to the ROI set in the past image is determined by the following procedure. That is, the setting position (u, v) of the current image corresponding to one ROI setting position (x, y) in the past image is calculated by (Equation 1). As a result, when the subsequent detailed matching is performed, the two corresponding ROIs are set at substantially the same anatomical positions. In the present embodiment, the ROI size is determined in advance, and the ROI size of the past image is set smaller than the ROI size of the current image.

(Step S403: Detailed matching)
In step S403, coordinates indicating the maximum matching degree are calculated for each ROI pair set as described above according to the following procedure, and shift vectors (Δxi, Δyi) between two images as shown in FIG. Desired.

  In step S402, matching is performed between the corresponding ROIs set in the past image and the current image, and coordinates indicating the maximum matching degree are calculated for each pair of ROIs. Here, the matching is performed while shifting the position of the ROI of the past image with respect to the ROI of the corresponding current image.

  As a matching method, for example, a measure such as a cross-correlation or a maximum difference value can be used. Here, by obtaining a difference between coordinate values indicating the maximum degree of matching, a shift vector (Δxi, Δyi) between two images can be obtained for each pair of ROIs as shown in FIG.

(Step S404: Shift vector interpolation)
In step S404, parameters for coordinate conversion to the set position (u, v) of the current image corresponding to an arbitrary position (x, y) of the past image are obtained based on the plurality of shift vectors obtained in step S403. .

  Here, in this step, it is desirable that the alignment method of the two images is a method capable of correcting more local distortion than that in step S402. Therefore, in this embodiment, it is assumed that a high-order polynomial is used as the coordinate conversion method. In this case, the parameters aij and bij in the conversion equation shown in (Equation 2) may be obtained by a known technique such as the least square method as described above.

In the following description, these parameters are called detailed matching parameters. This detailed matching parameter is stored in a memory (not shown) in the same manner as the previous global matching parameter.
(Step S405: One image deformation)
Using the detailed matching parameters obtained in step S404, a modified image is generated by converting the coordinates of the past image into the coordinates of the current image.

(Step S406: Difference processing)
A difference for each pixel between the image obtained by deforming the past image generated in step S405 and the current image is calculated, and a difference image having the calculation result as a pixel value is generated. Note that step S405 and step S406 may perform difference processing while directly converting the coordinates without distinction. In this case, it is not necessary to generate an image obtained by deforming the past image.

(Step S407: difference image and parameter output)
The difference image generated in step S406 and the global matching parameter and the detailed matching parameter stored in the memory (not shown) are output to the storage unit 2.

  With the above processing, the difference processing of a pair of images (current image and past image) is performed. In this way, the current image, the past image, the difference image, the global matching parameter, and the detailed matching parameter are stored in the storage unit 2 in advance.

[Difference image display: FIG. 5]
Next, various operations in displaying a stored difference image or the like will be described. This process is a process performed by the control unit while controlling each unit based on the control program according to the doctor's instruction, for example, when the doctor displays a difference image on the display screen and observes the change in the chest over time.

  In FIG. 1, the control unit 5 controls various modes in reading and displaying an image from the storage unit 2.

  When displaying the difference image, the control unit 5 instructs the image input unit 3 to output the difference image and the two images used when generating the difference image from the storage unit 2. The image read by the image input unit 3 is output to the display unit 7 via the display control unit 6 and is interpreted by a doctor. The display unit 7 is an image display device such as a CRT monitor, and the display control unit 6 converts and arranges the read image into a form suitable for interpretation. For example, the image is displayed according to the size of the monitor. It is arranged and converted to pixel accuracy according to the display capability of the monitor.

  FIG. 5 is a schematic diagram of an image display form on the display unit 7 composed of two monitors. Two images used to generate the difference image are displayed on the monitor 1 and the difference image is displayed on the monitor 2. However, the present invention is not necessarily limited to this configuration. Any one of the past images may be displayed. These display methods can be changed by the user giving an instruction to the display control unit 5 from an input device such as a mouse.

[Processing when the difference image is unclear: FIG. 6]
Next, when the doctor displayed the difference image on the display screen and observed changes in the chest over time, he found that the difference image could be identified, that is, that a minute change occurred between the two images. In this case, a process will be described in which it is difficult to distinguish whether the difference image is unclear and whether the change portion is a change portion with time or is caused by an artifact.

  FIG. 6 is an enlarged view of the display on the monitor 2. In the figure, it is assumed that there is a shadow N in the right lung of the difference image, but the shadow is small and unclear. At this time, the doctor designates a partial area R (an area including the shadow N) in the image from the screen, and starts a process of generating a more detailed difference image.

[Partial Difference Image Generation Processing: FIG. 8B]
That is, C in FIG. 6 is a mouse cursor, and a region R including a shadow N is set by a doctor by using the mouse as shown in FIG. When the region R is determined, the doctor (user) clicks the difference processing execution button B with the mouse. Then, the difference process shown in FIG. 8B is executed while the control unit controls the five units based on the control program.

  First, in step S501, when it is detected that the difference processing execution button B is pressed, information on the current image, the past image, and the matching parameter corresponding to the difference image displayed on the monitor 2 is acquired.

  Next, in step S502, the position and size of the region R (partial region in the difference image) set on the monitor 2 are detected, and the position and size of the detected region R are output to the image input unit 3. The

  Next, in step S503, the image input unit 3 stores the partial image data of the current image and the partial image data of the past image corresponding to the region R set in the difference image displayed on the monitor 2. 2 is extracted from the current image (FIG. 7A) and the past image (FIG. 7B) stored in 2 and output to the difference processing unit 4. At this time, the global matching parameter stored in the storage unit 2 is stored. The partial image from the current image stored in the storage unit 2 and the partial image from the past image are extracted using either or both of the detailed matching parameters and both.

  That is, in the previous difference processing (FIG. 2), for example, in step S401 or step S403, the past image is used by using the global matching parameter or the detailed matching parameter in order to eliminate the positional deviation or distortion between the past image and the current image. Has been transformed to overlap the current image. Accordingly, since the region R designated in the difference image is based on the coordinate system of the current image, the position and size of the region R designated in the difference image are determined when partially extracting image data from the current image. The image data area (FIG. 7A) (partial image) that is partially extracted from the current image is used as it is. However, when image data is partially extracted from the past image, misalignment or distortion between images. In order to eliminate the above and match the positions of the images, the coordinate value of the region R must be converted from the coordinate system of the current image to the coordinate system of the past image using the matching parameter. In this way, a region (partial image) of image data partially extracted corresponding to the region R designated from the past image is obtained.

  At this time, even if the extracted region R has a rectangular shape in the current image, the extracted region R does not necessarily have a rectangular shape in the past image. Therefore, in the following description, as shown in FIG. 7B, regarding the image data of the past image, it is assumed that a rectangular region R ′ including a region occupied by the region R in the past image is extracted.

  Next, in step S504, the image data of the current image and the past image thus extracted is subjected to the difference processing of the region R in the difference processing unit 4, and a difference image SI 'is generated. This process is the same as the process of steps S402 to S407 of the difference process of FIG. In step S504, since the correspondence between the reference points (P to Q and P ′ to Q ′) of the two regions R and R ′ is already known, it is not necessary to perform the process of step S401 in FIG. Only steps S402 to S407 in FIG. 2 are performed. Also, as shown in FIG. 7, when the sizes of the regions R and R ′ are not equal, it is possible to apply the same processing described above by assuming that all of the missing image data is zero.

  In step S505, the obtained difference image SI 'is output to the display unit 7 via the direct display control unit 6. Here, in the present embodiment, the display control unit 6 displays the newly generated difference image SI ′ superimposed on the original difference image as shown in FIG. 8A, but the image size is different. 6 is displayed larger than the area R specified in FIG. The newly generated difference image SI 'can be displayed on a different screen (a different window) from the original difference image. Here, since the difference image SI 'is a part extracted from the original image (before being reduced), it has the same image size (resolution) as the original image. Therefore, it is possible to obtain a differential signal with higher definition than the original differential image.

  In the above description, the past image is modified to be superimposed on the current image using the global matching parameter or the detailed matching parameter in order to eliminate the positional deviation or distortion between the past image and the current image. However, this is an example, and when the above-described method is used, the current image can be modified to be superimposed on the past image in order to eliminate the positional shift or distortion between the past image and the current image.

  The newly generated difference image of the partial area may be stored in the storage unit 2 as necessary.

  As explained above, even when the difference image displayed is unclear when observing the difference image, it uses the parameter for matching the positions between the images obtained and stored in advance by the difference image processing. It is possible to generate and display a detailed partial difference image by performing again the difference processing of only the area designated based on the resolution of the image that has not been reduced.

Second Embodiment
In the first embodiment, when the displayed difference image is unclear, when the difference image is generated again, processing is performed with the same image size (resolution) as the original image. However, the pixel size (resolution) in the partial area may be specified when the partial area is specified. Such a function is effective when the shadow for performing the detailed display in the difference image is relatively large. This process will be described below.

  FIG. 9 shows an example of a screen for designating an enlarged display area in the present embodiment. Similar to the first embodiment, the region R is selected on the difference image, and at the same time, the display resolution is designated by the pop-up menu P displayed by right-clicking the mouse.

When the image size (resolution) of the original image is 2048 × 2048, as shown in the figure, a combination of resolutions of (1/2) ⁿ (n = 1, 2, 3) is displayed in both horizontal and vertical directions. The pixel size corresponding to the resolution when the user performs display is determined. For example, when 1024 × 1024 is selected as the image size (resolution), a size that is ½ of the original pixel size is designated. The image size here means not the image size of the region R on the difference image but the size (resolution) of the entire image.

  The position / size and resolution of the partial region R in the difference image determined by the above operation are output to the image input unit 3 via the control unit 5. The image input unit 3 reads the portion corresponding to the designated area R of the current and past images stored in the storage unit 2, further reduces the image size (resolution) to a specified size, and outputs the reduced size to the difference processing unit 4. . Here, regarding the extraction of the designated region R, the same processing method as that described in the first embodiment can be used, and therefore a detailed description thereof is omitted. Moreover, since the difference process in the difference process part 4 can also take the same processing method as demonstrated in 1st Embodiment, the overlapping detailed description is abbreviate | omitted.

  The newly generated reduced image is the same as the display form in the first embodiment shown in FIG. 8A, but the difference image of the enlarged display part in this embodiment is half the size both horizontally and vertically. .

<Third Embodiment>
In the first embodiment, the image data stored in the storage unit 2 is not compression-encoded image data. However, when the image stored in the storage unit 2 is compression-encoded, more efficient processing can be performed.

  Therefore, in the present embodiment, processing when the image storage format in the storage unit 2 is compressed data using wavelet transform will be described below. Further, various forms can be applied as a compression encoding method. In the present embodiment, it is assumed that image data is compressed by ISO / IEC15444 (hereinafter referred to as JPEG2000).

  FIG. 10 shows an example of a form when the image IM is compressed by JPEG2000. In FIG. 5A, the image IM is divided into tiles T and is compressed and encoded independently for each tile.

  Here, when the current image and the past image are compressed and encoded by JPEG2000 and stored in the storage unit 2, and the partial enlarged display area of the difference image is included in the shaded tile in FIG. The input unit 3 reads only the encoded data of the tile from the storage unit and performs a decoding process. Further, when the designated pixel size is 1/2 in both the horizontal and vertical directions, a decoding operation is performed on the subband codes hatched in FIG. As a result, the restored image has a size 1/2 that of the original size.

  This process is performed for both the current and past images, and the restored image is output to the difference processing unit 4 to generate and display a difference image in the same manner as described in the first embodiment. However, since the description overlaps, detailed description here is abbreviate | omitted.

<Other embodiments>
Furthermore, the present invention is not limited to only the apparatus and method for realizing the above-described embodiment, but software for realizing the above-described embodiment on a computer (CPU or MPU) in the system or apparatus. A case in which the above-described embodiment is realized by supplying a software program code and causing the system or apparatus computer to operate the various devices according to the program code is also included in the scope of the present invention.

  In this case, the program code of the software itself realizes the function of the above embodiment, and the program code itself and means for supplying the program code to the computer, specifically, the program code Is included in the scope of the present invention.

  As a storage medium for storing such a program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  The computer controls various devices according to only the supplied program code so that the functions of the above-described embodiments are realized, and the OS (operating system) on which the program code is running on the computer is also provided. Such program code is also included in the scope of the present invention when the above embodiment is realized in cooperation with a system) or other application software.

  Further, after the supplied program code is stored in the memory of the function expansion board of the computer or the function expansion unit connected to the computer, the program code is stored in the function expansion board or function storage unit based on the instruction of the program code. The case where the above-described embodiment is realized by performing a part or all of the actual processing and the processing is included in the scope of the present invention.

  When the present invention is applied to the above storage medium, the storage medium stores a program that realizes the processing shown in FIGS. 2 and 8B described above.

  As described above, according to the present embodiment, the first parameter and the first parameter for coordinate conversion for eliminating the positional deviation or distortion between the first image and the second image and between the first image and the second image in advance. The difference image between the first image and the second image generated after matching the positions between the images using is stored in a memory in advance, and the difference image is displayed on the display screen and is a partial area in the difference image. Is specified, the first parameter is used to match the positions of the images, the first partial image in the first image and the second partial image in the second image corresponding to the partial region are determined, and the first A second parameter for coordinate conversion that eliminates a positional shift or distortion between the partial image and the second partial image is calculated, and after the positions of the images are matched using the second parameter, the first partial image and the second partial image A partial difference image between images can be generated.

  Therefore, even if the displayed difference image is ambiguous (when the user cannot identify whether the difference image is due to changes in the object over time or due to artifacts), the displayed partial difference image is displayed first. Since the image is clearer than the difference image, the user can identify the change of the object with time with higher accuracy.

1 is an overall configuration diagram of an image processing apparatus according to the present invention. It is a flowchart of a difference image generation process. It is an example of the reference point detection at the time of global matching. It is a figure explaining the example which sets several ROI in the past image. It is an example of a shift vector. It is a structure of a display apparatus. It is an example of designation | designated of the shadow part shown with the difference image. It is a figure explaining the partial area | region where the present image and the past image were extracted. It is a figure explaining the example which superimposes and displays a re-difference image on a difference image. It is a flowchart of a re-difference image generation process. It is area | region specification explanatory drawing in 2nd Embodiment. It is tile division explanatory drawing of an image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up part 2 Storage part 3 Image input part 4 Difference processing part 5 Control part 6 Display control part 7 Display part

Claims (14)

An image processing device that generates a difference image from a first image and a second image of an object imaged at different times,
The first image and the second image, the first parameter for coordinate conversion that eliminates the displacement or distortion between the first image and the second image, and the position between the images are matched using the first parameter. Storage means for storing in advance a difference image between the first image and the second image generated after
Display means for displaying the difference image stored in the storage means;
When a partial area in the difference image displayed on the display means is designated, the first parameter is used to eliminate positional deviation or distortion between the first image and the second image, and to match the positions between the images. And determining means for determining a first partial image in the first image and a second partial image in the second image corresponding to the partial area,
A second parameter for coordinate conversion that eliminates a positional shift or distortion between the first partial image and the second partial image determined by the determining means is calculated, and the position between the images is matched using the second parameter. Generating means for generating a partial difference image between the first partial image and the second partial image after,
An image processing apparatus comprising:   The first parameter is a coordinate conversion of the point coordinate of one image to the other point coordinate based on a predetermined conversion formula with respect to the coordinate of the reference point indicating the characteristic position of the object between the two images. The image processing apparatus according to claim 1, further comprising parameters used at times.   The first image and the second image are images obtained by simple X-ray or computed tomography, and the reference point is a position of an anatomically characteristic part. The image processing apparatus described.   The generation unit sets a setting position of a second setting area set in the second partial image using the predetermined conversion formula in the first partial image set corresponding to the second setting area. The image processing apparatus according to claim 2, further comprising conversion means for converting into a setting position of the first setting area.   The image processing apparatus according to claim 1, wherein the display unit displays the first image and the second image stored in the storage unit side by side with the difference image. The generating means is a selecting means for selecting the resolution of the image of the partial area;
Changing means for reading the data of the first image and the second image corresponding to the partial area from the storage means and changing the pixel size of the read data to the resolution selected by the selection means;
The image processing apparatus according to claim 5, further comprising:   The image processing apparatus according to claim 1, wherein the data of the first image and the second image stored in the storage unit is compression-coded data. The first image and the second image of the object imaged at different times, the first parameter for coordinate conversion for eliminating the positional deviation or distortion between the first image and the second image, and the first parameter A method for controlling an image processing apparatus comprising storage means for preliminarily storing a difference image between the first image and the second image generated after matching positions between images using the method,
A display step of displaying the difference image stored in the storage means;
When a partial area in the difference image displayed in the display step is specified, the first parameter is used to eliminate positional deviation or distortion between the first image and the second image, and to match the positions between the images. A determination step of determining a first partial image in the first image and a second partial image in the second image corresponding to the partial region;
A second parameter for coordinate conversion that eliminates a positional shift or distortion between the first partial image and the second partial image determined in the determining step is calculated, and the position between the images is matched using the second parameter. Generating a difference image between the first partial image and the second partial image after,
A control method for an image processing apparatus, comprising: The first image and the second image of the object imaged at different times, the first parameter for coordinate conversion for eliminating the positional deviation or distortion between the first image and the second image, and the first parameter A control program for controlling an image processing apparatus comprising storage means for preliminarily storing a difference image between the first image and the second image generated after matching the positions between the images,
A program code of a display step for displaying the difference image stored in the storage means;
When a partial area in the difference image displayed in the display step is specified, the first parameter is used to eliminate positional deviation or distortion between the first image and the second image, and to match the positions between the images. And a program code of a determining step for determining a first partial image in the first image and a second partial image in the second image corresponding to the partial region,
A second parameter for coordinate conversion that eliminates a positional shift or distortion between the first partial image and the second partial image determined in the determining step is calculated, and the position between the images is matched using the second parameter. A program code of a generating step for generating a difference image between the first partial image and the second partial image after
A control program for controlling an image processing apparatus.   A computer-readable recording medium storing the computer program according to claim 9. An image processing device that generates a difference image from a first image and a second image of an object imaged at different times,
Reduction means for reducing the image size of the first image and the second image;
First difference image generation means for generating a difference image from the first image and the second image reduced by the reduction means;
Area specifying means for specifying a specific area on the difference image generated by the first difference image generating means;
Extraction means for extracting a region corresponding to the specific region from the first image and the second image;
Second difference image generation means for generating a difference image from the area extracted from the first image and the area extracted from the second image by the extraction means;
An image processing apparatus comprising: An image processing device that generates a difference image from a first image and a second image of an object imaged at different times,
Reduction means for reducing the image size of the first image and the second image;
First difference image generation means for generating a difference image from the first image and the second image reduced by the reduction means;
Area specifying means for specifying a specific area on the difference image generated by the first difference image generating means;
Image size designating means for designating image sizes of the first image and the second image;
Extracting the first image and the second image to an image size designated by the image size designation means, and extracting an area corresponding to the specific area from the first image and the second image having the changed image size Means,
Second difference image generation means for generating a difference image from the area extracted from the first image and the area extracted from the second image by the extraction means;
An image processing apparatus comprising: An image processing method for generating a difference image from a first image and a second image of an object imaged at different times,
A reduction step of reducing the image size of the first image and the second image;
A first difference image generation step of generating a difference image from the first image and the second image reduced in the reduction step;
An area designating process for designating a specific area on the differential image generated by the first differential image generating process;
An extraction step of extracting an area corresponding to the specific area from the first image and the second image;
A second difference image generation step of generating a difference image from the region extracted from the first image and the region extracted from the second image by the extraction step;
An image processing method comprising: An image processing method for generating a difference image from a first image and a second image of an object imaged at different times,
A reduction step of reducing the image size of the first image and the second image;
A first difference image generation step of generating a difference image from the first image and the second image reduced by the reduction means;
An area designating step of designating a specific area on the differential image generated by the first differential image generating means;
An image size designation step for designating image sizes of the first image and the second image;
Extracting the first image and the second image to an image size designated by the image size designation step, and extracting an area corresponding to the specific area from the first image and the second image whose image size has been changed Process,
A second difference image generation step of generating a difference image from the region extracted from the first image and the region extracted from the second image by the extraction step;
An image processing method comprising:

Images