JP6277036B2 - Computer program, image processing apparatus and method - Google Patents

Description

  The present invention relates to an image processing technique.

  In conventional brain tumor examinations, in brain tomographic images such as CT (Computed Tomography) images and MRI (Magnetic Resonance Imaging) images, these images are observed and attention is paid to changes in morphology. It is done to identify the part of. However, they can only see morphological changes and cannot assess the malignancy of the tumor. In CT and MRI, an angiographic agent may be used, but in the test, tissue damage to the blood-brain barrier occurs due to the effect of the tumor, so the drug is distributed regardless of the degree of malignancy. There was a thing.

  On the other hand, in recent years, in the PET (Positron Emission Tomography) test, by utilizing the property that sugar metabolism and amino acid metabolism are enhanced in tumor cells, it is possible to use sugar analogs and amino acids labeled with radioisotopes as active ingredients. The metabolism of tumor tissue can be evaluated. As a result, tumor malignancy can be directly evaluated. The PET test is also useful for determining the effect of a cancer drug. Since cancer cells are characterized by a decrease in metabolism before they die, it is possible to evaluate the efficacy at an early stage by looking at metabolic changes in PET examination.

  The PET test includes a test performed by administering 18F-FDG (fluorodeoxyglucose) and a test performed by administering 11C-methionine. Since sugar metabolism is enhanced in tumor cells, 18F-FDG is characterized by being taken up by tumor tissues. However, similarly, since accumulation in normal brain tissue is high, accumulation may appear relatively low even at a tumor site. Complementing this drawback is methionine-PET, which is characterized by the fact that methionine accumulates in tumor tissue with active amino acid metabolism and is hardly taken up by normal brain tissue. However, since the outline of the normal gray matter region is unclear in the methionine-PET inspection image, it is desirable to perform in combination with the FDG-PET inspection.

  Both 18F-FDG and 11C-methionine PET test images are expected as biomarkers for determination of therapeutic effect and prognosis prediction, particularly in brain tumors, because the accumulation of drugs reflects tumor malignancy.

  As an index for evaluating the grade of malignancy of a tumor, it is known to use a lesion / normal brain ratio (L / N ratio) obtained by comparing a pixel value of a lesion site and a pixel value of a normal gray matter region.

  Here, in order to calculate the L / N ratio, an operator such as a doctor surrounds a tumor site and a normal site with an ROI (Region of Interest) while viewing an image. In general, the L / N ratio is calculated based on the average value of the pixel values in the ROI. In this case, whether or not the L / N ratio is obtained correctly is determined depending on whether or not the ROI setting is appropriate. That is, in the conventional method, even if the L / N ratio is obtained, individual differences among operators are likely to occur. In particular, individual differences among operators tend to occur when correctly selecting a normal brain region.

  Accordingly, an object of the present invention is to determine a normal area in a tomographic image of an organ without depending on an operator.

  Still another object of the present invention is to extract an area having a specific property using a plurality of types of images having different characteristics.

  A computer program according to an embodiment of the present invention is a computer program for an image processing apparatus having storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject, Identifying a representative value of the second image based on a step of identifying an area that is a normal tissue candidate in the first image as a first area and a pixel value of a pixel belonging to the first area in the second image And causing the image processing apparatus to execute, as a second area, an area including a pixel whose pixel value is a representative value of the second image in the second image.

  In a preferred embodiment, the image processing apparatus may further execute a step of specifying a representative value of the first image based on a pixel value of a pixel belonging to the second area in the first image.

  In a preferred embodiment, for a plurality of pixels of the first image, a step of calculating a pixel ratio between each pixel value and a representative value of the first image, and outputting according to the calculated pixel ratio is performed. And the step may be further executed by the image processing apparatus.

  In a preferred embodiment, the step of accepting designation of a region including a plurality of pixels on the first image, the step of calculating a statistical value of pixel values of a plurality of pixels included in the designated region, and the calculation The step of calculating a pixel ratio between the calculated statistical value and the representative value of the first image and the step of performing output according to the calculated pixel ratio may be further executed by the image processing apparatus.

  In a preferred embodiment, for a plurality of pixels of the second image, a step of calculating a pixel ratio between each pixel value and a representative value of the second image, and outputting according to the calculated pixel ratio is performed. And the step may be further executed by the image processing apparatus.

  In a preferred embodiment, receiving a designation of an area including a plurality of pixels on the second image, calculating a statistical value of pixel values of a plurality of pixels included in the designated area, and calculating the calculation The image processing apparatus may further execute a step of calculating a pixel ratio between the calculated statistical value and the representative value of the second image, and a step of performing output according to the calculated pixel ratio.

  In a preferred embodiment, the first image is an image obtained by administering an agent that is physiologically accumulated in normal tissue to the subject, and the second image is normal tissue for the subject. An image captured by administering a drug without physiological accumulation may also be used.

  In a preferred embodiment, the first image is a PET image obtained by administering 18F-FDG (fluorodeoxyglucose) to the subject, and the second image is obtained by administering 11C-methionine to the subject. It may be a captured PET image.

  In a preferred embodiment, the representative value of the first image is a value obtained by applying a statistical algorithm to pixel values of pixels belonging to the second area, and the representative value of the second image is It may be a value obtained by applying a statistical algorithm to pixel values of pixels belonging to the first area.

  In a preferred embodiment, the representative value of the first image is a mode value, an average value, or a median value of the pixel values belonging to the second area, and the representative value of the second image is the first value. It may be a mode value, an average value, or a median value of the pixel values belonging to the area.

  A computer program according to another embodiment of the present invention is a computer program for an image processing apparatus having storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject, A step of specifying an area composed of pixels having a pixel value equal to or greater than a predetermined threshold in the first image as the first area, and a representative value of the second image based on the pixel value of the first area in the second image And causing the image processing apparatus to execute a step of specifying, and a step of specifying, as the second area, an area including a pixel whose pixel value is a representative value of the second image in the second image.

1 is an overall configuration diagram of an image processing apparatus 1 according to an embodiment of the present invention. It is an example of the histogram of the pixel value of a pixel.

  Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an image processing apparatus 1 according to the present embodiment.

  An input device 3 and a display device 5 are connected to the image processing apparatus 1.

  The image processing apparatus 1 is configured by, for example, a general-purpose computer system, and individual components or functions in the image processing apparatus 1 described below are realized by, for example, executing a computer program. The computer program can be stored in a computer-readable recording medium.

  The image processing apparatus 1 includes an FDG-PET image data storage unit 31, a MET-PET image data storage unit 33, an alignment processing unit 11, a first area extraction unit 13, a MET representative value specifying unit 15, a first A two-area extraction unit 17, an FDG representative value specifying unit 19, a pixel ratio calculation unit 21, and a display processing unit 23 are provided.

  The image processing apparatus 1 performs a process of calculating a representative value of each image using two types of images obtained by imaging the same part (organ) of a common subject. In the present embodiment, a PET image (hereinafter referred to as FDG-PET image) imaged by administering 18F-FDG (fluorodeoxyglucose) and a PET image (hereinafter referred to as 11C-methionine) administered by administering 11C-methionine for the same subject. And MET-PET image).

  The image data of the FDG-PET image and the MET-PET image are all three-dimensional voxel data. In this embodiment, the image data is a three-dimensional image obtained by imaging the same subject's brain (head). Each of the FDG-PET image and the MET-PET image may be composed of a plurality of slice images. The pixel values (voxel values) of the FDG-PET image and the MET-PET image may both be normalized to SUV (Standardized Uptake Value).

  The FDG-PET image data storage unit 31 stores image data of an FDG-PET image. Image data of an FDG-PET image generated by a predetermined imaging device is taken into the image processing device 1 by an interface unit (not shown) and stored in the FDG-PET image data storage unit 31.

  The MET-PET image data storage unit 33 stores image data of MET-PET images. Image data of a MET-PET image generated by a predetermined imaging apparatus is taken into the image processing apparatus 1 by an interface unit (not shown) and stored in the MET-PET image data storage unit 33.

  The alignment processing unit 11 performs alignment between the FDG-PET image stored in the FDG-PET image data storage unit 31 and the MET-PET image stored in the MET-PET image data storage unit 33. The alignment is performed, for example, by a known algorithm so that the positions of the images shown in the two images are matched (the same location has the same coordinates). This alignment may be performed for each corresponding slice image. The images after alignment are stored in the FDG-PET image data storage unit 31 and the MET-PET image data storage unit 33, respectively. The following processing is performed using the FDG-PET image and the MET-PET image that are aligned with each other.

  The first area extraction unit 13 extracts an area having a predetermined feature from the FDG-PET image as the first area. For example, the first area extraction unit 13 extracts, as the first area, an area composed of pixels having pixel values equal to or greater than a predetermined threshold in the FDG-PET image (first image). The first area extraction unit 13 specifies the coordinates of the pixels included in the extracted first area.

  The threshold value is, for example, 1.0 times, 1.5 times, 2.0 times, 3.0 times the average value of the pixel values of all the pixels (whole brain) in the brain region in the FDG-PET image. Value is acceptable. The brain region may be, for example, an area having a value that is 1/8 or more of a value obtained by averaging pixel values of all the pixels of the FDG-PET image including the background. This threshold value may be set for each slice image, or one threshold value may be set for all slice images (whole brain).

  The first area may be set for a specific slice image, or may be set for all slice images (whole brain).

  From the nature of the FDG-PET image, which is a drug with physiological accumulation in normal tissue, it is considered that this first area includes a normal gray matter area and a tumor area where FDG accumulates more than a certain amount. That is, the first area extraction unit 13 extracts a first area that is a candidate for a normal gray matter region (normal tissue). Here, the physiological accumulation in the normal tissue means that there is a physiological accumulation in the normal tissue among the organs to be diagnosed.

  The MET representative value specifying unit 15 specifies the representative value of the MET-PET image based on the processing result of the first area extracting unit 13. For example, the MET representative value specifying unit 15 specifies the representative value (hereinafter, MET representative value) 51 of the MET-PET image based on the pixel values of the pixels belonging to the first area in the MET-PET image (second image). To do.

  For example, the MET representative value specifying unit 15 acquires the coordinates of the pixels included in the first area from the first area extracting unit 13, and specifies the MET representative value 51 from the pixel values of those coordinates in the MET-PET image. . The MET representative value 51 may be, for example, a value (statistical value) obtained by applying a statistical algorithm such as the mode value, average value, or median value of the pixel values of the target pixel.

  For example, the MET representative value specifying unit 15 creates a histogram of pixel values of pixels included in the first area. FIG. 2 is a diagram illustrating an example of a histogram. It is considered that the pixel values of the normal gray matter region included in the first area substantially follow a normal distribution, and one peak P1 is formed. Due to the nature of the MET-PET image, which is a drug that does not physiologically accumulate in normal tissue, when the first area includes a tumor region, it is smaller than the peak P1 in a region having a higher pixel value than the normal region. Peak P2 is formed. At this time, the mode value is the value V1 of the peak P1. The average value is a value V2 that is slightly larger than the mode value V1. Here, the absence of physiological accumulation in normal tissue means that there is no accumulation in the normal tissue among the organs to be diagnosed, or there is only accumulation to the extent that does not affect the identification of the diseased area. To do.

  The MET representative value 51 specified here is considered to be a value representative of a normal gray matter region in the MET-PET image.

  The second area extraction unit 17 extracts an area including a pixel having a pixel value of the MET representative value 51 in the MET-PET image (second image) as the second area. At this time, the second area extraction unit 17 may use only pixels having the MET representative value 51 as the second area, or define a certain value width including the MET representative value 51 and enter the width of these values. A pixel having a pixel value may be used as the second area. The second area extraction unit 17 specifies the coordinates of the pixels included in the extracted second area.

  This second area is considered to contain only normal gray matter regions.

  The first area and / or the second area may be set only in the left or right hemisphere of the brain. For example, when an operator such as a doctor designates either the left or right hemisphere, the first area extraction unit 13 may set the first area only for the designated hemisphere. Similarly, when the operator designates either the left or right hemisphere, the second area extraction unit 17 may set the second area only for the designated hemisphere. Thereby, the first area and / or the second area can be set to a hemisphere opposite to the hemisphere with the tumor.

  The FDG representative value specifying unit 19 specifies the representative value of the FDG-PET image based on the processing result of the second area extracting unit 17. For example, the FDG representative value specifying unit 19 calculates a representative value (hereinafter referred to as an FDG representative value) 53 of the FDG-PET image based on the pixel values of the pixels belonging to the second area in the FDG-PET image (first image). Identify.

  For example, the FDG representative value specifying unit 19 acquires the coordinates of the pixels included in the second area from the second area extracting unit 17, and specifies the FDG representative value 53 from the pixel values of those coordinates in the FDG-PET image. . The FDG representative value 53 may be, for example, a value (statistical value) obtained by applying a statistical algorithm such as the mode value, average value, or median value of the pixel values of the target pixel. A specific method of specifying the FDG representative value 53 may be the same as the process performed by the MET representative value specifying unit 15 to specify the MET representative value 51.

  The FDG representative value 53 specified here is considered to be a value representative of a normal gray matter region in the FDG-PET image.

  As described above, in this embodiment, in order to specify a representative value of an area having a specific property of a certain image, the area is defined by an image of a different type from that image. In particular, in this embodiment, two types of images having the same modality are used.

  The pixel ratio calculation unit 21 calculates the ratio between each pixel value and the representative values 51 and 53 of each image for a plurality of pixels of the FDG-PET image or the MET-PET image.

  For example, the pixel ratio calculation unit 21 refers to the FDG-PET image data storage unit 31 and acquires the image data of the FDG-PET image. Then, the pixel ratio calculation unit 21 calculates the pixel ratio between each pixel value and the FDG representative value 53 for an arbitrary pixel of the FDG-PET image. The pixel ratio calculation unit 21 may calculate the pixel ratio for all the pixels, may calculate the pixel ratio for the brain region, or may target the pixels in the region designated by the operator. Good. When the operator specifies an arbitrary area consisting of a plurality of pixels, the value (statistical value) obtained by applying a statistical algorithm such as the mode value, average value, or median value of the pixel values in this area The pixel ratio between this value and the FDG representative value 53 may be calculated.

  Similarly to the FDG-PET image, the pixel ratio calculation unit 21 calculates the pixel ratio with the MET representative value 51 for a plurality of pixels of the MET-PET image for the MET-PET image. That is, the pixel ratio calculation unit 21 may calculate the pixel ratio with the MET representative value 51 for each pixel for all pixels, pixels in the brain region, or pixels in the region specified by the operator, or the operator When specifying an arbitrary area consisting of multiple pixels, calculate the value (statistical value) obtained by applying a statistical algorithm such as the mode, average, or median of the pixel values in this area. The pixel ratio between this value and the MET representative value 51 may be calculated.

  Here, the representative values 51 and 53 are considered to be values representative of normal gray matter regions in the respective images. Therefore, the ratio calculated for the tumor site with the representative values 51 and 53 as the denominator corresponds to the L / N ratio that is a tumor activity index.

  The display processing unit 23 causes the display device 5 to display the FDG-PET image based on the FDG-PET image data in the FDG-PET image data storage unit 31. Similarly, the display processing unit 23 causes the display device 5 to display a MET-PET image based on the MET-PET image data in the MET-PET image data storage unit 33.

  In addition, the display processing unit 23 outputs to the display device 5 according to the ratio calculated by the pixel ratio calculation unit 21. For example, when displaying the FDG-PET image on the display device 5, the display processing unit 23 may display each pixel in a display mode corresponding to each pixel ratio, or the operator may arbitrarily select a plurality of pixels. When specifying a region of, depending on the pixel ratio calculated using a value (statistical value) obtained by applying a statistical algorithm such as the mode value, average value, or median value of the pixel values in this region It may be displayed in a different display form. Similarly, when displaying the MET-PET image on the display device 5, the display processing unit 23 may display each pixel in a display mode corresponding to the respective pixel ratio, and the operator is composed of a plurality of pixels. When specifying an arbitrary area, the pixel ratio calculated using a value (statistical value) obtained by applying a statistical algorithm such as the mode value, average value, or median value of the pixel values in this area You may display with the display form according to.

  Alternatively, the display processing unit 23 may cause the display device 5 to display the calculated pixel ratio as a numerical value.

  According to the present embodiment, the pixel value of the normal brain area in the tomographic image of the brain can be determined without depending on the operator. In particular, in the present embodiment, the representative values of the normal gray matter regions of the FDG-PET image and the MET-PET image can be specified by an objective and reproducible method.

  As a result, the L / N ratio can be calculated by an objective and reproducible method, and as long as the images are photographed under the same imaging conditions, the comparison can be made based on the same standard regardless of the operator.

  Furthermore, according to the present embodiment, an area having a specific property can be extracted using a plurality of types of images having different characteristics. In particular, in this embodiment, the candidate area of the normal gray matter region is extracted using the characteristics of one image using the two types of images having the same modalities and different characteristics, and the characteristics of the other image are used. Normal gray matter regions can be extracted.

  The above-described embodiments of the present invention are examples for explaining the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

  In the embodiment described above, the first area is specified using the FDG-PET image, but the present invention is not necessarily limited to this. For example, the first area extraction unit 13 may analyze a CT image or MRI image of the same subject and extract a first area including a normal gray matter region in the CT image or MRI image.

  An image having characteristics different from those of the above-described embodiment can also be used. For example, instead of 18F-FDG, a SPECT (Single Photon Emission Computed Tomography) image using a drug that is physiologically accumulated in other normal tissues (for example, 99mTc-ECD) may be used, or other than 11C-methionine. SPECT images or PET images using an agent having no physiological accumulation in normal tissues (for example, 201 TlCl, 18F-labeled fluorothymidine, or 18F-labeled fluorodopa) may be used.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 3 Input apparatus 5 Display apparatus 11 Position alignment process part 13 1st area extraction part 15 MET representative value specific | specification part 17 2nd area extraction part 19 FDG representative value specific | specification part 21 Pixel ratio calculation part 23 Display process part 31 FDG -PET image data storage unit 33 MET-PET image data storage unit

Claims (13)

A computer program for an image processing apparatus having storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject,
Identifying an area that is a candidate for normal tissue in the first image as a first area;
Identifying a representative value of the second image based on a pixel value of a pixel belonging to the first area in the second image;
A computer program that causes the image processing apparatus to execute, as the second area, an area that includes a pixel whose pixel value is a representative value of the second image in the second image.   The computer program according to claim 1, further causing the image processing apparatus to execute a step of specifying a representative value of the first image based on a pixel value of a pixel belonging to the second area in the first image. Calculating a pixel ratio between each pixel value and a representative value of the first image for a plurality of pixels of the first image;
The computer program according to claim 2, further causing the image processing apparatus to execute an output corresponding to the calculated pixel ratio. Receiving a designation of an area including a plurality of pixels on the first image;
Calculating a statistical value of pixel values of a plurality of pixels included in the designated region;
Calculating a pixel ratio between the calculated statistical value and the representative value of the first image;
The computer program according to claim 2, further causing the image processing apparatus to execute an output corresponding to the calculated pixel ratio. Calculating a pixel ratio between each pixel value and a representative value of the second image for a plurality of pixels of the second image;
The computer program according to claim 2, further causing the image processing apparatus to execute an output corresponding to the calculated pixel ratio. Receiving a designation of an area including a plurality of pixels on the second image;
Calculating a statistical value of pixel values of a plurality of pixels included in the designated region;
Calculating a pixel ratio between the calculated statistical value and a representative value of the second image;
The computer program according to claim 2, further causing the image processing apparatus to execute an output corresponding to the calculated pixel ratio. The first image is an image obtained by administering a drug with physiological accumulation in normal tissue to the subject,
The computer program according to any one of claims 1 to 6 , wherein the second image is an image obtained by administering a drug having no physiological accumulation in normal tissue to the subject. The first image is a PET image taken by administering 18F-FDG (fluorodeoxyglucose) to the subject,
The computer program according to claim 1, wherein the second image is a PET image imaged by administering 11C-methionine to the subject.   The computer program according to claim 1, wherein the representative value of the second image is a value obtained by applying a statistical algorithm to pixel values of pixels belonging to the first area.   The computer program according to any one of claims 1 to 8, wherein the representative value of the second image is a mode value, an average value, or a median value of pixel values belonging to the first area. A computer program for an image processing apparatus having storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject,
Identifying an area composed of pixels having a pixel value equal to or greater than a predetermined threshold in the first image as a first area;
Identifying a representative value of the second image based on a pixel value of the one area in the second image;
A computer program that causes the image processing apparatus to execute, as the second area, an area that includes a pixel whose pixel value is a representative value of the second image in the second image. Storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject;
First area specifying means for specifying a normal tissue candidate area in the first image as a first area;
Means for identifying a representative value of the second image based on a pixel value of the one area in the second image;
An image processing apparatus comprising: a second area specifying unit that specifies, as a second area, an area including a pixel whose pixel value is a representative value of the second image in the second image. Storage means for storing image data of a first image and a second image obtained by imaging the same part of the same subject;
First area specifying means for specifying, as a first area, an area composed of pixels having a pixel value equal to or greater than a predetermined threshold in the first image;
Means for identifying a representative value of the second image based on a pixel value of the one area in the second image;
An image processing apparatus comprising: a second area specifying unit that specifies, as a second area, an area including a pixel whose pixel value is a representative value of the second image in the second image.

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