JP5280058B2 - Diagnostic imaging support system - Google Patents

Description

  The present invention relates to an image diagnosis support system that performs image processing on information relating to the degree of progression of osteoporosis based on medical images.

  Diagnosis of osteoporosis using a medical image diagnostic apparatus such as a conventional X-ray CT apparatus is performed according to the following procedure. A feature value for performing predetermined threshold processing on the bone region of the subject image is set. Read the image from the storage means for storing the image of the subject, extract a diagnostic area including a bone area from the read image according to the feature amount set by the input means, and about the extracted diagnostic area Bone structure analysis information is calculated from the component identification information of the bone component and components other than the bone component. The calculated bone structure analysis information is displayed in association with the image of the subject. (For example, see [Patent Document 1].)

WO2006 / 085525 publication.

  Recently, it has been found that structural analysis of the bone interior depends on the three-dimensional structure of the cancellous beam.

  However, the above prior art does not mention that the analysis of the internal structure of the bone depends on the structure of the trabecular bone, and the analysis of the internal structure of the bone in consideration of the dependence on the trabecular structure of the cancellous bone. Remained an open issue.

  Therefore, an object of the present invention is to provide an image diagnosis support system capable of quantifying the characteristics of the three-dimensional structure of the beam in the cancellous bone.

The object is to extract a cancellous bone region from an image of a subject, a means for separating the cancellous bone region into a beam region and a gap region between the beams, a ratio of the gap region to the cancellous bone region, and the cancellous bone. This is achieved by including means for calculating the degree of progression of osteoporosis based on the pixel value of the region, and means for displaying the degree of progression .

  ADVANTAGE OF THE INVENTION According to this invention, the diagnostic imaging support system which can quantify the characteristic of the three-dimensional structure of the beam in cancellous bone can be provided.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.

  FIG. 1 is a block diagram showing the hardware configuration of the entire diagnostic imaging support system to which the present invention is applied. This diagnostic imaging support system quantifies and displays the structure of the trabecular bone of the spine based on a plurality of tomographic images (CT images, etc.) collected for the target region of the subject with an X-ray CT apparatus or the like, for example. Is.

  This diagnostic imaging support system includes a central processing unit (CPU) 10 that controls the operation of each component, a main memory 11 that stores a control program for the device, and a magnetic memory that stores a plurality of tomographic image data, programs, and the like. A disk 12, a display memory 13 for temporarily storing image data for display, a CRT display 14 as a display device for displaying an image based on the image data from the display memory 13, and a soft switch on the screen are operated. The mouse 15 and its controller 16, a keyboard 17 having keys and switches for setting various parameters, a speaker 18, and a common bus 19 for connecting the above components.

  In this embodiment, a case where only the magnetic disk 12 is connected as a storage device other than the main memory 11 is shown, but in addition to this, a floppy disk drive, a hard disk drive, a CD-ROM drive, a magneto-optical disk ( MO) drive, ZIP drive, PD drive, DVD drive, USB memory, etc. may be connected. Furthermore, it can be connected to various communication networks 1a such as a LAN (local area network), the Internet, a telephone line, etc. via a communication interface (not shown), and other computers, CT devices / MR devices / US devices 1b, etc. The image data may be transmitted and received between the two. Further, image data can be transmitted and received by connecting a medical image diagnostic apparatus capable of collecting tomographic images of a subject such as an X-ray CT apparatus, MRI apparatus, and ultrasonic diagnostic apparatus to the communication network 1a such as the LAN. Good.

  First, a case where the structure of the trabecular bone is quantified and displayed will be described. As the first method. FIG. 2 is a diagram showing an example of a case where the structure of the trabecular bone is quantified and displayed using left-right asymmetry when the shape of the spinal cancellous bone is divided line-symmetrically. FIG. 3 is a diagram showing an example of CT images in a normal case and an osteoporosis case. FIG. 3 (a) shows normal cancellous bone 21 and cortical bone 22, and FIG. 3 (b) shows a case of osteoporosis. As shown in FIG. 3 (b), the main symptom of osteoporosis is the back and back pain, and then the vertebrae are repeatedly broken, collapsed, the spine is gradually bent, and the height is lowered. In people with osteoporosis, the spinal cancellous bone concentration distribution becomes asymmetrical, and the vertebrae are being destroyed. Therefore, as a simple method, the degree of asymmetry of the concentration distribution can be measured, and the degree of progression of osteoporosis can be measured to quantify the trabecular structure.

First, as shown in FIGS. 2 (a) and 2 (b), the cancellous bone 30 is divided by a center line 31 that is divided into right and left objects. For each of the right region 33 and the left region 32 after the division, the area S1 of the region where the CT value of the right region−the CT value of the left region> the threshold value is obtained according to the following equation. Similarly, the area S2 of the region where the CT value of the left region−the CT value of the right region> the threshold value is obtained in accordance with the following equation. Here, the CT value indicates a specific example of the density value of the image, and when an image other than the X-ray CT image is used, it means the density value of the image.

The variable δ is obtained by substituting the obtained areas S1 and S2 into the following equation.
・ Δ = abs (standard CT value of bone-average CT value of region excluding S1 and S2)
Here, abs means an absolute value. Based on the variable δ thus determined, the following determination is made and defined as the degree of progression of osteoporosis.
・ If (δ <constant value) {Osteoporosis progression = constant × (S1 + S2) / S} else {not measurable}
Here, S is the entire area of the cancellous bone 30.

  Accordingly, the progress of osteoporosis of the spine can be calculated using a general low-dose CT image. In other words, the trabecular structure can be quantified.

  FIG. 2 defines the degree of progression of osteoporosis based on the case where the spinal cancellous bone concentration distribution is asymmetrical.

  When the accuracy of the progression of osteoporosis is further increased, as shown in FIG. 3, the area and volume of the bone cavity portion destroyed by osteoporosis are reflected in the index of the progression of osteoporosis. These bones have a hollow portion, but the shape and size of the hollow portion are not constant, so the values calculated using information on areas with lower density than the average density value of a given bone area in a tomogram The size of the hollow portion is used as a factor of the degree of progression of osteoporosis as the feature amount.

  Thereby, more detailed diagnosis support can be performed by using the size of the hollow portion as an index for predicting a disorder such as a fracture of the subject.

  In the following description, threshold processing and region expansion are used to extract the area and volume of the broken bone cavity.

  FIG. 4 is a flowchart showing an example of a process for extracting the area and volume of a broken bone cavity.

  FIG. 5 is an example of a 3D image shaded by cancellous bone. As shown by arrows in FIG. 5 (b), it is said that when the space 51 between the beams increases, the bone becomes brittle. In addition, the three-dimensional image is configured by stacking binarized cancellous bone regions 62 among a plurality of tomographic images 61 as shown in FIG. Below, it demonstrates according to the procedure of FIG.

(step 1)
The CPU 10 extracts a cancellous bone region from an image including, for example, the spine bone (vertebra) using a density histogram and a threshold value. The threshold value may be set by an operator such as a doctor while referring to the image using the mouse 15 or the like, or when the CT value (concentration value) is known, the main memory 11 or magnetic disk that the CPU 10 can read in advance The data stored in the memory 12 may be read out. The cancellous bone region is extracted from the region including the cortical bone. Further, since the vertebra is composed of cortical bone and cancellous bone, the vertebra is extracted as a region having a high CT value, a threshold value is determined from the histogram of the vertebra region, and the sea surface bone region is obtained by threshold processing.

(Step 2)
The CPU 10 calculates the volume (V) of the cancellous bone region. Since the threshold value is a value for distinguishing the beam in the cancellous bone region from the other region (gap between the beams), a histogram is taken and the CT value near the boundary of the distribution is used as the threshold value. However, when the slice thickness is large, the CT value (concentration value) average value that is not a beam in the cancellous bone region may be approximated as a threshold value.

(Step 3)
The CPU 10 thresholds the cancellous bone region into a beam region and a region that is not a beam region (gap between the beams) to obtain a binary image.

(Step 4)
The CPU 10 calculates the average value (RLx, run length 52 of the gaps in three directions orthogonal to the region (binary image representing the gap 51 between the beams in FIG. 5) lower than the threshold value obtained in the previous step. RLy, RLz) are obtained respectively. The three directions for determining the run length 52 need not be parallel to the main axes X, Y, and Z axes.

(Step 5)
The CPU 10 obtains an average CT value in an area lower than the cancellous bone threshold (= the average value obtained in step 2).

スライス厚が厚い場合などでは、

のように、近似してもよい。
ここで定数は、例えば、90とする。一般には、部位に依存する。 (Step 6)
The CPU 10 obtains the degree of progression or faintness (sparse value) of osteoporosis using the following equation.

When the slice thickness is thick,

It may be approximated as follows.
Here, the constant is, for example, 90. In general, it depends on the site.

FIG. 7 shows an example in which the faint degree is displayed as a graph.
A three-dimensional image of the target bone is arranged on the horizontal axis of the graph, and “slight degree” is taken on the vertical axis.

In the threshold processing from step S52 to step 55, the following feature quantity 1 to feature quantity 4 may be used.
-Feature value 1: Average run length of CT value lower than the statistical value of the portion excluding the cancellous bone portion in the sea surface bone region-Feature amount 2: In the feature amount 1, the cancellous bone portion in the sea surface bone region is excluded Values / features calculated by three-dimensional directions perpendicular to each other in areas with CT values lower than the statistical values of the parts 3: Average values / features of CT values of parts excluding the cancellous cancellous bones in the sea surface bone area4 : The value of the volume of the cancellous bone excluding the cancellous bone in the sea surface bone region
Accordingly, it is possible to provide an image diagnosis support system and an image diagnosis support program that can quantify the characteristics of the three-dimensional structure of the beam in the cancellous bone.

  The preferred embodiments of the image diagnosis support system according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1 is a block diagram showing a hardware configuration of an entire diagnostic imaging support system to which the present invention is applied. The figure which shows an example in the case of measuring the progress degree of osteoporosis using the left-right asymmetry of the spinal cancellous bone. The figure which shows an example of a CT image in the case of normal and osteoporosis. The flowchart figure which shows an example of the process which extracts the area and volume of the cavity part of the destroyed bone. The figure which shows the example of a display of the cancellous bone three-dimensional image. FIG. 6 is a principle diagram of the three-dimensional image configuration of FIG. The figure which shows the example of a display of the graph of the relationship between the position of a spine, and the progression degree of osteoporosis.

Explanation of symbols

  10 Central processing unit (CPU), 11 Main memory, 12 Magnetic disk, 13 Display memory, 14 CRT display, 15 Mouse, 16 Controller, 17 Keyboard, 18 Speaker, 19 Common bus, 1a Communication network, 1b Other computer or CT apparatus.

Claims (3)

Means for extracting cancellous bone regions from a plurality of images of a subject;
Means for separating the cancellous bone region into a beam region and a gap region between the beams;
Means for calculating the progression of osteoporosis based on the ratio of the gap region to the cancellous bone region and the pixel value of the cancellous bone region;
Means for displaying the degree of progress;
Equipped with a,
The average values of the run lengths of the three orthogonal gaps obtained with respect to the gap area are RLx, RLy, and RLz, respectively, the volume of the cancellous bone area is V, and the pixel value of the cancellous bone area is When the average value is Av1, the average value of the pixel values in the gap region is Av2, and the constant depending on the part is C, the progress S is

An image diagnosis support system characterized by being calculated as follows. The diagnostic imaging support system according to claim 1 ,
3. The diagnostic imaging support system according to claim 1, wherein the three orthogonal directions are parallel to the principal axes X, Y, and Z axes of the image. The diagnostic imaging support system according to claim 1,
The means for displaying the degree of progress arranges a three-dimensional image of the cancellous bone region on the horizontal axis, and displays a graph showing the degree of progress on the vertical axis.

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