JP3793137B2 - Image processing apparatus, image processing method, program, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing device, an image processing method, a program, and a storage medium.
[0002]
[Prior art]
In recent years, in response to the international standard DICOM (digital information and communication in medicine) related to the digitization of medical images, the Japan Radiation Equipment Industry Association (JIRA) has established the MIPS (medical image processing system) standard in Japan. Digitization is in progress.
[0003]
In the field of medical images, the use of CAD (Computer Aided Diagnosis) that analyzes medical X-ray images, CT scan images, MRI images, etc. with a computer is progressing. A time-difference type CAD is attracting attention.
[0004]
For example, the time-difference CAD is obtained by inputting a film of a set of chest X-ray images taken at different points in time with a scanner to generate a digital image, performing image analysis, and analyzing each image anatomically. The same position is obtained, one of the current image and the past image is deformed, and the difference processing is performed for each pixel. In this specification, among images taken at different points in time, an image taken earlier in time is referred to as a past image, and an image taken more recently in time is referred to as a current image for convenience. To do.
[0005]
The density value of the difference image corresponds to the change in the image signal between the current and past images.
That is, when there is no change between the past image and the current image, the difference value is 0, but when any change occurs, a change in the luminance level corresponding to the change appears.
[0006]
FIG. 11 is a one-dimensional display of the past and present image signals and the difference image signals obtained thereby. If a signal representing a shadow appears in the portion of the past image shown in FIG. 6A that is a substantially flat profile, as shown by A in FIG. 4B, the difference between the current image and the past image is obtained. When an image is generated, a profile as shown in FIG.
[0007]
[Problems to be solved by the invention]
In a radiographic image, whether a large pixel value corresponds to high luminance or low luminance on display may differ depending on the image generation apparatus. For example, an apparatus that generates a digital image by directly or indirectly converting an X-ray transmitted through a subject into an electric signal, such as an FPD (Flat Panel Detector), which has been practically used in recent years, displays a large pixel value. Image data is generated as a positive image corresponding to high brightness. For this reason, for example, in the chest X-ray image, the value of the pixel corresponding to the lung field becomes large.
[0008]
On the other hand, since a normal radiographic image is observed as a negative image, the image data obtained by digitizing an X-ray film with a film scanner or the like has a smaller pixel value corresponding to the lung field.
[0009]
Therefore, when the difference process is performed by mixing the negative image and the positive image, the appearance of the shadow in the difference image is not unified, and it is extremely difficult to discriminate.
[0010]
The present invention provides a method and apparatus for generating a differential image that is consistent even when differential images are generated from images that are not unified in the positive / negative of the image. It is an object of the present invention to provide a method and an apparatus capable of outputting a difference image that is consistent in the display form.
[0011]
[Means for Solving the Problems]
According to the present invention, in an image processing apparatus that generates a difference image from a first image and a second image, an image attribute acquisition unit that acquires image attributes of the first image and the second image, and the first image And / or image processing means for performing predetermined image processing on the second image, shadow definition means for defining how to express a change in shadow in the difference image, and acquisition by the image attribute acquisition means The image processing means applies the first image and / or the second image to the first image and / or the second image according to the image attributes of the first image and the second image and the shadow definition defined by the shadow definition means. Control means for changing image processing to be performed, and calculation means for calculating a difference image from the first image and the second image processed by the image processing means. This makes it possible to generate a consistent differential image for differential images generated from images whose image positive / negative is not unified, and output a consistent differential image in the display form of the shadow on the differential image It is.
[0012]
Alternatively, the present invention provides an image attribute acquisition unit that acquires an image attribute of the first image and the second image in an image processing device that generates a difference image from the first image and the second image; A shadow defining means for defining how to express a change in shadow in the difference image, a first gradation inversion means for performing gradation inversion processing on the first image, and a second image A second gradation inversion unit for performing gradation inversion processing on the output, an arithmetic unit for calculating a difference image from the output of the first gradation inversion unit and the output of the second gradation inversion unit, and the image According to the image attribute of the first image and the second image acquired by the attribute acquisition means and the shadow definition defined by the shadow definition means, the first gradation inversion means and / or Gradation inversion processing by the second gradation inversion means Control means for controlling whether or not to perform.
[0013]
Alternatively, the present invention provides an image attribute acquisition unit that acquires an image attribute of the first image and the second image in an image processing device that generates a difference image from the first image and the second image; A shadow defining means for defining how to express a change in shadow in the difference image, a first gradation inversion means for performing gradation inversion processing on the first image, and a second image Second gradation inversion means for performing gradation inversion processing on the output, computing means for computing a difference image from the output of the first gradation inversion means and the output of the second gradation inversion means, and the difference In accordance with the image attribute information adding means for adding image attribute information to the image, the image attribute acquired by the image attribute acquisition means and the shadow definition defined by the shadow definition means, the first image and Image processing for the second image As well as change, and a control means for determining information to be added by the image attribute information adding unit.
[0014]
The present invention provides an image processing method for generating a difference image from a first image and a second image, an image attribute acquisition step of acquiring image attributes of the first image and the second image, and the first An image processing step for performing predetermined image processing on the image and / or the second image, a shadow definition step for defining how to express a change in shadow in the difference image, and the image attribute acquisition According to the image attributes of the first image and the second image acquired by the step and the shadow definition defined by the shadow definition step, the first image and / or Or a control step for changing image processing performed on the second image, and the first image and the second image processed by the image processing step. And a calculation step of calculating an amount image. This makes it possible to generate a consistent differential image for differential images generated from images whose image positive / negative is not unified, and output a consistent differential image in the display form of the shadow on the differential image It is.
[0015]
The image processing method according to the present invention may further include an image attribute information adding step for adding image attribute information to the difference image.
[0016]
In the image processing method according to the present invention, in the image processing step, gradation inversion image processing is performed on the first image and / or the second image, and the control step is performed by the image processing step. It may be configured to control whether or not to perform gradation inversion image processing on one image and / or the second image.
[0017]
In the image processing method according to the present invention, the image processing step performs sign-inversion image processing on the first image or the second image, and the control step performs the first image by the image processing step. Alternatively, it may be controlled whether or not to perform image inversion on the second image.
[0018]
In the image processing method according to the present invention, in the image processing step, gradation inversion image processing is performed on the first image and / or the second image, and the first image or the second image is processed. The image is subjected to sign inversion, and the control step controls whether the image processing step performs gradation inversion image processing on the first image and / or the second image, and Control may be made as to whether or not sign inversion is performed on the first image or the second image.
[0019]
In the image processing method according to the present invention, the first image and the second image are, for example, images obtained by photographing the same part of the human body at different times.
[0020]
In the image processing method according to the present invention, the shading definition step defines, for example, whether to express an increase or decrease in shading in the difference image as a high brightness area or a low brightness area.
[0021]
In the image processing method according to the present invention, the image attribute information adding step adds, for example, image attribute information representing the gradation of the difference image.
[0022]
The present invention relates to an image for acquiring image attributes of the first image and the second image in a computer-executable program for image processing for generating a difference image from the first image and the second image. An attribute acquisition step, an image processing step for performing predetermined image processing on the first image and / or the second image, and a shadow definition that defines how to express a change in shadow in the difference image In the image processing step according to the step, the image attributes of the first image and the second image acquired in the image attribute acquisition step, and the shadow definition defined in the shadow definition step. A control step of changing an image process performed on the image and / or the second image, the first image processed by the image processing step, and Having a program code for performing the serial second image and computing step of computing a difference image, to the computer.
[0023]
The storage medium according to the present invention stores the program and is readable by a computer.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
In FIG. 1, a medical image processing apparatus 110 according to the first embodiment of the present invention is connected to medical image generation apparatuses 130, 140, 150 and a medical data server 160 via a local area network (LAN) 100. Yes. The medical image generation apparatuses 130 and 140 are, for example, CT scan apparatuses and MRI apparatuses, and the medical image generation apparatus 150 is, for example, an X-ray imaging apparatus.
[0025]
The medical images generated by the medical image generation apparatuses 130, 140, and 150 are directly transmitted to the medical image processing apparatus 110, or once stored in the medical data server 160 and then transmitted to the medical image processing apparatus 110. The medical image directly transmitted to the medical image processing apparatus 110 is stored in a storage medium of the medical image processing apparatus 110.
[0026]
The medical image processing apparatus 110 includes a high-definition monitor 120 for medical images, and can display medical images with high definition. In addition, a medical image processing apparatus 1800 provided with a cheaper PC monitor 170 can also be used.
[0027]
In FIG. 2, a medical image processing apparatus 110 is formed by connecting a CPU 210, a RAM 220, a ROM 230, a communication interface 240, and an input means 260 to a bus 200, and an output device such as a medical image high-definition monitor 120 or a printer 250 is suitable. It is connected to the bus 200 via an interface. The input means includes a keyboard, a pointing device, and the like.
[0028]
The CPU 210 is used to control the entire medical image processing apparatus 110 and the output apparatus, and the control program is stored in the ROM 230. The communication interface 240 controls communication via the LAN 100, and appropriately transmits and receives medical images and other data to and from the medical image generation apparatuses 130, 140, and 150 and the medical data server 160.
[0029]
FIG. 3 is a block diagram illustrating a functional configuration of the medical image processing apparatus, and FIG. 4 is a graph illustrating characteristics of a lookup table used in the medical image processing apparatus of FIG. FIG. 5 is a table showing combinations of lookup tables used in the medical image processing apparatus of FIG.
[0030]
In FIG. 3, a current image file and a past image file, which are a set of images obtained by photographing the same part of the human body at different times, are input to the image input unit 1 from the medical data server 160 via the local area network 100. . Here, each image file is composed of radiation image data and tag information for holding incidental information, and the incidental information includes information indicating whether the image data is a positive image or a negative image.
[0031]
Information indicating whether the image data is a positive image or a negative image is, for example, a DICOM format file, which is a standard medical image file. It is defined to indicate a positive image when “is.
[0032]
The image input unit 1 outputs the image data to the difference processing unit 2, extracts information indicating whether the past image and the current image output to the difference processing unit 2 are negative images or positive images, and sends them to the control unit 3. The determination signal S0 is input.
[0033]
On the other hand, the shadow definition input unit 4 inputs the correspondence between the shadow on the difference image and the determination criterion for diagnosis in response to an external input (not shown), for example, a direct instruction from a computer external storage device or user. The shadow definition specifies whether the lesion corresponds to a high density (high luminance level) or a low density (low luminance level) on the difference image with respect to the exacerbation or lightness of the lesion in image diagnosis.
[0034]
FIG. 6 is a diagram showing an example of shadow definition. In FIG. 6, type A expresses an increase in shadow as a low density (black) area and a decrease in shadow as a high density (white) area on the difference image. Defined. On the other hand, type B is defined to express an increase in shadow as a high density (white) area and a decrease in shadow as a low density (black) area on the difference image. Here, the low density or the high density represents a low value or a high value with respect to the reference level when the luminance level of a portion where no change occurs on the difference image is used as a reference.
[0035]
The difference processing unit 2 has lookup tables LUT1 and LUT2 into which past and current images are input from the image input unit 1, and necessary conversion processing is performed in these lookup tables LUT1 and LUT2. The outputs of the lookup tables LUT1 and LUT2 are input to the level correction unit 203, and the density of one image is shifted so that the histogram center of the previous or current image matches the histogram center of the other image. Thus, if alignment is performed using the level-corrected image, the alignment accuracy can be improved.
[0036]
The output of the level correction unit 203 is input to the alignment unit 20, and coordinate conversion is performed so that the coordinates of the corresponding pixels match.
[0037]
In the alignment unit 20, the following steps shown in the flowchart of FIG. 7 are executed in order to perform alignment so that the anatomical corresponding points coincide with the current and past images.
[0038]
Step S201: The position of the subject in the current and past images is detected, and the process proceeds to step S202.
[0039]
Step S202: A plurality of regions of interest ROI are set at substantially corresponding positions in the current and past images, and the process proceeds to step S203.
[0040]
Step S203: Perform matching processing of current and past images for each ROI. In the matching process, for example, a cross-correlation coefficient is calculated, and a position with the highest degree of matching is obtained as a shift vector.
[0041]
Step S204: The shift vector obtained in step S203 is two-dimensionally interpolated to calculate parameters for coordinate conversion for matching the corresponding coordinates of both images.
[0042]
Step S205: Coordinate-transform the current or past image based on the parameter obtained in step S204.
[0043]
Step S206: An image that has not undergone coordinate transformation and an image that has undergone coordinate transformation are output.
[0044]
Next, outputs corresponding to the past image and the current image of the alignment unit 20 are input to the lookup table LUT3 and the lookup table LUT4, respectively, and necessary conversion is performed.
[0045]
The outputs of the look-up table LUT3 and the look-up table LU4 are input to the adder 202, and addition for the difference is executed.
[0046]
A control unit 3 is connected to the lookup tables LUT1 to LUT4, and an image input unit 1 and a shadow definition input unit 4 are connected to the control unit 3. The control unit 3 receives a determination signal S0 indicating whether the past and current images are negative images or positive images from the image input unit 1, and whether the determination method is type A or type B from the shadow definition input unit 4. The information indicating whether or not it is input.
[0047]
The look-up table LUT1 and the look-up table LUT2 unify both images as negative or positive, and the look-up table LUT3 and the look-up table LUT4 code either one of the images so that the difference is executed by addition in the adder 202. Invert.
[0048]
The adding unit 202 generates a difference image and inputs it to the image output unit 5.
[0049]
The lookup table LUT1 to lookup table LUT4 can freely select three types of characteristics as shown in (a), (b), and (c) of FIG. 4A is a non-conversion lookup table (Type I) that outputs the input as it is, and FIG. 4B is a lookup table (Type II) that inverts the input (negative / positive conversion). FIG. 4C is a look-up table (Type III) for inverting the sign of the input.
[0050]
In Table A of FIG. 5, when the determination method is set to type A and the past image is a negative image and the current image is a positive image, look-up table LUT1, look-up table LUT2, look-up table Type I, Type II, Type I, and Type III are set in the up table LUT3 and the lookup table LUT4, respectively.
[0051]
How the image data of the past and current images changes will be described with reference to FIG. As shown in FIG. 8A, in this example, in the current image that is a positive image, there is a lesion shadow that did not exist in the past image of the negative image. When the determination method is type A, since Type II is set in the lookup table LUT2, the gradation of the current image is inverted, and the average value is corrected as shown in FIG. 8B.
[0052]
Further, when addition is performed after alignment, since the sign inversion is performed on the current image in the LUT 4, the data profile of the current image is as shown in FIG. 8C, and the difference is calculated by the addition. become.
[0053]
That is, the current image that has been tone-reversed from a positive image to a negative image is subtracted from the past image of the negative image, so that when the shadow increases on the difference image, it appears as a low density (black) region, and the shadow is When it decreases, it appears as a high density (white) area.
[0054]
When the determination method is set to type A and the past image and the current image are negative images, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table LUT4 Type I, Type I, Type I, and Type III are set, respectively. Therefore, in the look-up table LUT1 and the look-up table LUT2, the gradation of the current image and the past image is not reversed, and in the look-up table LUT3 and the look-up table LUT4, the sign of the image signal is reversed with respect to the current image. Therefore, the adding unit 202 substantially subtracts the current negative image from the negative past image, and as a result, when the shadow increases, it appears as a low density (black) area on the difference image, and the shadow decreases. In some cases, it appears as a high density (white) region on the difference image.
[0055]
When the determination method is set to type A and the past image is a positive image and the current image is a negative image, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table LUT4 Type II, Type I, Type I, and Type III are respectively set in. Therefore, after the gradation of the past image is inverted from the positive image to the negative image, the current image is subtracted. Therefore, on the difference image, when the shadow increases, it appears as a low density (black) area, and when the shadow decreases, it appears as a high density (white) area.
[0056]
When the determination method is set to type A and the past image and the current image are positive images, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table LUT4 Type I, Type I, Type III, and Type I are set, respectively. Therefore, since the past image of the positive image is subtracted from the current image of the positive image, when the shadow increases on the difference image, it appears as a low density (black) region, and when the shadow decreases, the high density ( Appears as white) area.
[0057]
When the past image and the current image are both negative images, a difference image is formed by subtracting the current image from the past image. When both the past image and the current image are positive images, the past image is obtained from the current image. By subtracting, a difference image is formed. In both cases, when the shadow increases on the difference image, it appears as a low density (black) area, and when the shadow decreases, the density is high (white ) Appears as a region.
[0058]
In Table B of FIG. 5, when the determination method is set to type B and the past image and the current image are negative images, look-up table LUT1, look-up table LUT2, look-up table LUT3 In the lookup table LUT4, TypeI, TypeI, TypeIII, and TypeI are set, respectively. Therefore, the past image of the negative image is subtracted from the current image of the negative image, and when the shadow increases on the difference image, it appears as a high density (white) region, and when the shadow decreases, the low density (black) ) Appears as a region.
[0059]
When the determination method is set to type B and the past image is a positive image and the current image is a negative image, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table Type I, Type II, Type I, and Type III are set in LUT4, respectively. Therefore, to subtract the current image that is tone-reversed from the negative image to the positive image from the past image of the positive image, if the shadow increases on the difference image, it appears as a high density (white) area and the shadow decreases In this case, it appears as a low density (black) area.
[0060]
When the determination method is set to type B and the past image is a negative image and the current image is a positive image, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table Type II, Type I, Type I, and Type III are set in LUT4, respectively. As a result, the current image of the positive image is subtracted from the past image that has been tone-reversed from the negative image to the positive image, and when the shadow increases on the difference image, it appears as a high density (white) region, When shading decreases, it appears as a low density (black) area.
[0061]
When the determination method is set to type B and the past image and the current image are positive images, the lookup table LUT1, the lookup table LUT2, the lookup table LUT3, and the lookup table LUT4 include Type I, Type I, Type I, and Type III are set, respectively. Therefore, the current image of the positive image is subtracted from the past image of the positive image.When the shadow increases on the difference image, it appears as a high density (white) area, and when the shadow decreases, the low density Appears as a black area.
[0062]
When the past image and the current image are both negative images, a difference image is formed by subtracting the past image from the current image. When both the past image and the current image are positive images, the current image is obtained from the past image. By subtracting, when the shadow increases on the difference image, it appears as a high density (white) area, and when the shadow decreases, it appears as a low density (black) area.
[0063]
As described above, according to the present embodiment, an increase and a decrease in shadow can be expressed in a predetermined form regardless of the combination of the attributes of the current and past images.
[0064]
[Second Embodiment]
In a display device capable of displaying a DICOM format image, gradation inversion is displayed for image data having a Photometric Interpretation value of “MONOCHROME I”, and gradation inversion is displayed for image data having a Photometric Interpretation value of “MONOCHROME II”. It is supposed to be displayed as it is without.
[0065]
In the medical image processing apparatus shown in the first embodiment, when the past image and the current image have the same image characteristics, the order of subtraction is changed by changing the image to be subjected to the sign inversion of the image signal. In the embodiment, a similar result is obtained by fixing the order of subtraction and changing the value of Photometric Interpretation given to the difference image.
[0066]
FIG. 9 is a block diagram illustrating a functional configuration of a medical image processing apparatus according to the second embodiment of the present invention. Since the configuration of the medical image processing apparatus is the same as that shown in FIGS. 1 and 2, the description thereof is omitted.
[0067]
In FIG. 7, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The look-up table LUT3 and the look-up table LUT4 included in the difference processing unit 2 are not changed in characteristic by the control unit 3, and are set invariable. The tag generation unit 8 generates incidental information attached to the difference image data output from the difference processing unit 2. The accompanying information includes tag information indicating whether the difference image data output from the difference processing unit 2 is a positive image or a negative image.
[0068]
In the tag generation unit 8, a difference processing unit according to a combination of the incidental information of the past image data and the incidental information of the current image data input from the image input unit 1 and the shadow definition input to the shadow definition input unit 4. Attached information attached to the difference image data output from 2 is generated. Therefore, the difference image output from the difference processing unit 2 is output to the image output unit 5 as an image file to which additional information generated by the tag generation unit 8 is added.
[0069]
In the second embodiment, a case where the lookup table LUT3 is fixed to Type I and the lookup table LUT4 is fixed to Type III will be described as an example.
[0070]
When the determination method is set to type A and the past image and the current image are negative images, Type I is set in the lookup table LUT1 and the lookup table LUT2 by the control unit 3. . Therefore, in the look-up table LUT1 and the look-up table LUT2, neither the current image nor the past image is inverted in gradation. The sign of the image signal is inverted with respect to the current image by the look-up table LUT3 fixed to Type I and the look-up table LUT4 fixed to Type III. The current image of the negative is subtracted. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0071]
Therefore, when this difference image is displayed on a display device capable of displaying an image in the DICOM format, when the shadow increases, it appears as a low density (black) region on the difference image, and when the shadow decreases, the difference image Appears as a high density (white) area above.
[0072]
When the determination method is set to type A and the past image is a negative image and the current image is a positive image, Type I and Type II are set in the lookup table LUT1 and the lookup table LUT2, respectively. The
Since Type II is set in the lookup table LUT2, the gradation of the current image is inverted. The sign of the image signal is inverted with respect to the current image by the look-up table LUT3 fixed to Type I and the look-up table LUT4 fixed to Type III. The current image of the negative is subtracted. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0073]
Therefore, when this difference image is displayed on a display device capable of displaying an image in the DICOM format, when the shadow increases, it appears as a low density (black) region on the difference image, and when the shadow decreases, the difference image Appears as a high density (white) area above.
[0074]
When the determination method is set to type A and the past image is a positive image and the current image is a negative image, Type II and Type I are set in the lookup table LUT1 and the lookup table LUT2, respectively. The
Since Type II is set in the lookup table LUT1, the gradation of the past image is inverted. The sign of the image signal is inverted with respect to the current image by the look-up table LUT3 fixed to Type I and the look-up table LUT4 fixed to Type III. The current image of is subtracted. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0075]
Therefore, when this difference image is displayed on a display device capable of displaying an image in DICOM format, when the shadow increases, it appears as a low density (black) region on the difference image, and when the shadow decreases, the difference image Appears as a high density (white) area above.
[0076]
On the other hand, when the determination method is set to type B and the past image is a positive image and the current image is a negative image, Type I and Type II are stored in the lookup table LUT1 and the lookup table LUT2, respectively. Set. Since Type II is set in the lookup table LUT2, the gradation of the current image is inverted. Since the sign of the image signal is inverted with respect to the current image by the look-up table LUT3 fixed to Type I and the look-up table LUT4 fixed to Type III, the adder 202 converts the positive image from the positive past image. The current image of is subtracted. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0077]
Therefore, when this difference image is displayed on a display device capable of displaying an image in DICOM format, it appears as a high density (white) area when the shadow increases, and when the shadow decreases, the density is low (black). Appears as an area.
[0078]
When the determination method is set to type B and the past image is a negative image and the current image is a positive image, Type II and Type I are set in the lookup table LUT1 and the lookup table LUT2, respectively. The
Since the sign inversion of the image signal is performed on the current image in the look-up table LUT3 fixed to Type I and the look-up table LUT4 fixed to Type III, from the past image in which the tone is inverted from the negative image to the positive image The current image of the positive image is subtracted. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0079]
Therefore, when this difference image is displayed on a display device capable of displaying an image in DICOM format, it appears as a high density (white) area when the shadow increases, and when the shadow decreases, the density is low (black). Appears as an area.
[0080]
Similarly, when the determination method is set to type B, when the past image and the current image are positive images, Type I is set in both the lookup table LUT1 and the lookup table LUT2. The sign of the image signal is inverted with respect to the current image in the lookup table LUT3 fixed to Type I and the lookup table LUT4 fixed to Type III, so the current image of the positive image is subtracted from the past image of the positive image. It will be. The control unit 3 controls the tag generation unit 8 to give “MONOCHROME II” to the value of Photometric Interpretation for this difference image.
[0081]
Therefore, when this difference image is displayed on a display device capable of displaying an image in DICOM format, it appears as a high density (white) area when the shadow increases, and when the shadow decreases, the density is low (black). Appears as an area.
[0082]
When the determination method is set to type A, when the past image and the current image are positive images, Type I is set for both lookup table LUT1 and lookup table LUT2. Since the sign inversion of the image signal is performed on the current image in the lookup table LUT3 fixed to Type I and the lookup table LUT4 fixed to Type III, the adder 202 substantially changes the positive image from the positive past image. The current image is subtracted. The control unit 3 controls the tag generation unit 8 so as to give “MONOCHROME I” to the value of Photometric Interpretation for this difference image.
[0083]
By giving “MONOCHROME I” to the value of Photometric Interpretation, a display device capable of displaying an image in DICOM format displays a difference image with gradation reversed.
[0084]
Therefore, when this difference image is displayed on a display device capable of displaying an image in the DICOM format, when the shadow increases, it appears as a low density (black) region on the difference image, and when the shadow decreases, the difference image Appears as a high density (white) area above.
[0085]
When the determination method is set to type B and Type I is set in both the look-up table LUT1 and the look-up table LUT2 when the past image and the current image are negative images, the negative image is changed from the past image of the negative image. The current image of the image is subtracted. The control unit 3 controls the tag generation unit 8 so as to give “MONOCHROME I” to the value of Photometric Interpretation for this difference image.
[0086]
Therefore, when this difference image is displayed on a display device capable of displaying an image in the DICOM format, when the shadow increases, it appears as a low density (black) region on the difference image, and when the shadow decreases, the difference image Appears as a high density (white) area above.
[0087]
In the present embodiment, a method has been described in which the output of the alignment unit 201 is subjected to code conversion using the fixed lookup tables LUT3 and LUT4, and the conversion result is added by the addition unit 202. However, as illustrated in FIG. The same applies to a subtracting unit 205 that subtracts the current image from the past image with respect to the output of the combining unit 201.
[0088]
As described above, in this embodiment, the subtraction order is fixed, and DICOM given to the difference image based on the shadow definition input from the shadow definition input unit 4 and the positive / negative information of the past image and the current image. By changing the value of Photometric Interpretation in the format, it is possible to unify the meaning of shadows even in a difference image between images in which a positive image and a negative image are mixed.
[0089]
The present invention can be applied to apparatuses other than the image processing apparatus of the above-described embodiment, and may be applied to, for example, a system composed of a plurality of devices or an apparatus composed of one device.
[0090]
A method for realizing the functions of the above-described embodiments by an arbitrary apparatus or system constitutes the present invention, and a software program that causes a general-purpose computer to execute such a method constitutes the present invention.
[0091]
Furthermore, the present invention supplies a storage medium storing the program code of the software to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. But it goes without saying that this is achieved.
[0092]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0093]
As a storage medium for supplying the program code, for example, a floppy 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.
[0094]
Further, by executing the program code read out by the computer, not only the functions of the above-described embodiments are realized, but also the OS operating on the computer based on the instruction of the program code performs the actual processing. Needless to say, a case where the function of the above-described embodiment is realized by performing part or all of the processing is also included.
[0095]
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. It goes without saying that 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.
[0096]
【The invention's effect】
According to the present invention, it is possible to generate a consistent difference image for a difference image generated from images whose image positive / negative is not unified, and a difference image having a consistent shade display form on the difference image. Can be output.
[0097]
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a medical image processing apparatus as a first embodiment.
FIG. 2 is a block diagram showing an internal configuration of the medical image processing apparatus as the first embodiment.
FIG. 3 is a block diagram illustrating a functional configuration of the medical image processing apparatus according to the first embodiment.
FIG. 4 is a diagram illustrating characteristics of a lookup table.
FIG. 5 is a diagram illustrating combinations of lookup tables.
FIG. 6 is a diagram illustrating shadow definition in a difference image.
FIG. 7 is a flowchart illustrating the operation of the alignment unit.
FIG. 8 is an explanatory diagram of a profile change of an image signal.
FIG. 9 is a block diagram illustrating a functional configuration of a medical image processing apparatus as a second embodiment.
FIG. 10 is a block diagram illustrating a functional configuration of a modified example of the second embodiment.
FIG. 11 is a diagram for explaining a profile change of an image signal when a difference image is created.
[Explanation of symbols]
1 Image input section
2 Difference processing part
3 Control unit
4 Shadow definition input part

Claims (13)

In an image processing apparatus that generates a difference image from a first image and a second image,
Image attribute acquisition means for acquiring image attributes of the first image and the second image;
Image processing means for performing predetermined image processing on the first image and / or the second image;
A shadow definition means for defining how to express a change in shadow in the difference image;
In accordance with the image attributes of the first image and the second image acquired by the image attribute acquisition unit and the shadow definition defined by the shadow definition unit, the image processing unit performs the first image and / or the Control means for changing image processing performed on the second image;
Computing means for computing a difference image from the first image and the second image processed by the image processing means;
An image processing apparatus comprising: In an image processing apparatus that generates a difference image from a first image and a second image,
Image attribute acquisition means for acquiring image attributes of the first image and the second image;
A shadow defining means for defining how to represent a change in shadow in the difference image;
First gradation inversion means for performing gradation inversion processing on the first image;
Second gradation inversion means for performing gradation inversion processing on the second image;
Computing means for computing a difference image from the output of the first gradation inversion means and the output of the second gradation inversion means;
According to the image attributes of the first image and the second image acquired by the image attribute acquisition means and the shadow definition defined by the shadow definition means,
Control means for controlling whether or not gradation inversion processing is performed in the first gradation inversion means and / or the second gradation inversion means;
An image processing apparatus comprising: In an image processing apparatus that generates a difference image from a first image and a second image,
Image attribute acquisition means for acquiring image attributes of the first image and the second image;
A shadow defining means for defining how to represent a change in shadow in the difference image;
First gradation inversion means for performing gradation inversion processing on the first image;
Second gradation inversion means for performing gradation inversion processing on the second image;
Computing means for computing a difference image from the output of the first gradation inversion means and the output of the second gradation inversion means;
According to the image attribute information adding means for adding image attribute information to the difference image and the image attribute acquired by the image attribute acquisition means and the shadow definition defined by the shadow definition means, the first image And control means for changing the image processing for the second image and determining information added by the image attribute information adding means,
An image processing apparatus comprising: In an image processing method for generating a difference image from a first image and a second image,
An image attribute acquisition step of acquiring image attributes of the first image and the second image;
An image processing step for performing predetermined image processing on the first image and / or the second image;
A shadow definition step for defining how to express a change in shadow in the difference image;
According to the image attributes of the first image and the second image acquired by the image attribute acquisition step and the shadow definition defined by the shadow definition step, the image processing step includes the first image processing step. A control step of changing image processing performed on the image and / or the second image;
A calculation step of calculating a difference image from the first image and the second image processed by the image processing step;
An image processing method. The image processing method according to claim 4, further comprising an image attribute information adding step of adding image attribute information to the difference image. In the image processing step, gradation inversion image processing is performed on the first image and / or the second image, and the control step includes the first image and / or the second image by the image processing step. 6. The image processing method according to claim 4, further comprising: controlling whether or not to perform tone reversal image processing on the image. In the image processing step, sign inversion image processing is performed on the first image or the second image, and the control step is performed on the first image or the second image by the image processing step. 6. The image processing method according to claim 4, wherein whether or not to perform image processing for sign inversion is controlled. The image processing step performs gradation inversion image processing on the first image and / or the second image, and performs sign inversion on the first image or the second image, The control step controls whether or not gradation-inversion image processing is performed on the first image and / or the second image by the image processing step, and the first image or the second image is processed. 6. The image processing method according to claim 4 or 5, wherein whether or not the sign inversion is performed is controlled. 9. The image processing method according to claim 4, wherein the first image and the second image are images obtained by photographing the same part of the human body at different times. 10. The method according to claim 4, wherein the shading definition step defines whether to express an increase or decrease in shading in the difference image as a high brightness area or a low brightness area. The image processing method as described. 9. The image processing method according to claim 4, wherein the image attribute information adding step adds image attribute information representing a gradation of a difference image. In a computer-executable program for image processing for generating a difference image from a first image and a second image,
An image attribute acquisition step of acquiring image attributes of the first image and the second image;
An image processing step for performing predetermined image processing on the first image and / or the second image;
A shadow definition step for defining how to express a change in shadow in the difference image;
According to the image attributes of the first image and the second image acquired by the image attribute acquisition step and the shadow definition defined by the shadow definition step, the first image and / or the image processing step Or a control step for changing image processing to be performed on the second image;
A calculation step of calculating a difference image from the first image and the second image processed by the image processing step;
A computer-executable program having program code for causing a computer to execute the program. A computer-readable storage medium in which the program according to claim 12 is stored.

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