JP2005253755A - Tumor region setting method and tumor region setting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tumor region setting method and a tumor region setting system capable of setting a tumor region easily and accurately. <P>SOLUTION: An arithmetic unit 6 extracts profile data of a tumor region from a PET image read out from a medical image server 2 and converts the extracted profile data into vector line drawing data. The tumor region 20 composed of the vector line drawing data is superimposed on an X-ray CT image 10 read out from the medical image server 2 and is displayed on a monitor 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tumor region setting method and a tumor region setting system for setting a tumor region using nuclear medicine image information acquired from a nuclear medicine diagnostic apparatus in radiology.

  In general, radiotherapy is performed by (1) taking an X-ray CT image of a patient, (2) making a treatment plan using the X-ray CT image, and (3) a treatment procedure using a radiation irradiation apparatus based on the treatment plan. . The purpose of the treatment plan is mainly to set the tumor area on the X-ray CT image and to set the irradiation dose for the set tumor area. Tumor area setting is performed directly on an X-ray CT image, or by using an MRI image (an image taken with an MRI apparatus (nuclear magnetic resonance apparatus)) that makes it easier to observe soft tissue than an X-ray CT image It may be done.

  In recent years, a positron CT (PET) apparatus has been spotlighted at home and abroad as a radiation diagnostic instrument useful for early detection of malignant tumors. This PET device administers a radionuclide released by positron decay into the body as a drug, and captures and images a pair of γ-rays (511 KeV) emitted when the positron and electron disappear in the body. Device. As the drug, for example, FDG (2-deoxy-2-fluoro-D-glucose) which is an analog of glucose is used. Since this FDG has a property of accumulating in a tumor that undergoes active energy metabolism, it is possible to photograph a tumor using this property.

  The image captured by the PET apparatus in this way is an image showing the activity of cell functions and is different from a morphological image showing the shape of a body or organ such as an X-ray CT image or an MRI image. It is reflected (this is called a functional image). Therefore, by using this PET image in combination with the setting of the tumor region, it is possible to set the tumor region up to a portion that is difficult to find in the X-ray CT image or the MRI image.

  As a conventional technique using such a PET image in combination, there is a technique in which an X-ray CT image and a PET image are aligned and displayed in a superimposed manner to set a tumor region (for example, Patent Document 1 and Patent Document 2). reference.).

Japanese Patent Laid-Open No. 9-133771 JP 2000-105279 A

  Although not explicitly described in Patent Document 1 and Patent Document 2, generally, medical images such as an X-ray CT image and a PET image are composed of raster data (a two-dimensional array that is a set of pixels). The state in which the PET image is displayed superimposed on the X-ray CT image is also composed of raster data. On the other hand, the data format of the tumor area used by the treatment plan is usually composed of vector line drawing data (lines and points having a size and a direction) such as a polygon line drawing. Therefore, in the above prior art, even if the PET image is superimposed and displayed on the X-ray CT image, the operator can directly use the tumor region that can be identified by the PET image data as the tumor region for the treatment plan. For example, an outline of a tumor region that can be discriminated by PET image data using an input means such as a mouse is traced and converted to vector line drawing data manually. In this case, it takes time to set the tumor region, and a difference occurs in the tumor region depending on the skill level of the operator.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a tumor region setting method and a tumor region setting system capable of setting a tumor region simply and accurately.

  (1) A feature of the first invention that achieves the above-described object is that, in a tumor region setting method in radiotherapy, the contour information of a tumor region is extracted from nuclear medicine image information, and the extracted contour information is converted into vector line drawing information. A method for setting a tumor region is characterized by converting.

  In the present invention, for example, by setting a threshold value using a count value or an SUV value, a contour of a tumor region is automatically extracted from a PET image using an arithmetic unit, and the contour data is converted into a vector line drawing. It is possible. This eliminates the need for the operator to trace the outline of the tumor region as in the prior art, so that the region setting operation can be greatly simplified. Furthermore, since the contour is automatically extracted using the threshold value, it is possible to set a reproducible tumor region regardless of the skill level of the operator. Therefore, according to the present invention, a tumor region can be set easily and accurately.

  (2) The feature of the second invention for achieving the above object is that the tumor region contour information is extracted from the nuclear medicine image information by using a threshold value. It is in.

  (3) The feature of the third invention for achieving the above object is the method of setting a tumor region according to claim 2, wherein a radioactivity count value included in the nuclear medicine image information is used as the threshold value. .

  (4) A feature of the fourth invention for achieving the above object is the tumor region setting method according to claim 2, wherein an SUV value is used as the threshold value.

  (5) A feature of a fifth invention for achieving the above object is the tumor region setting method according to claim 2, wherein the vector line drawing information and the X-ray CT image information are displayed in an overlapping manner.

  (6) A feature of the sixth invention for achieving the above object is the tumor region setting method according to claim 5, wherein the vector line drawing information is Bezier curve information.

  (7) The feature of the seventh invention for achieving the above object is the tumor region setting method according to claim 5, wherein the vector line drawing information is polygon line drawing information.

  (8) The feature of the eighth invention for achieving the above object is the tumor region setting method according to claim 5, wherein the nuclear medicine image information is PET image information.

  (9) A feature of the ninth invention for achieving the above object is an image storing X-ray CT image information and nuclear medicine image information including a tumor region in a tumor region setting system for setting a tumor region during radiotherapy. A server, a computing device for extracting contour information of a tumor region from the nuclear medicine image information, converting the extracted contour information into vector line drawing information, and the vector line drawing information converted by the computing device as the X-ray CT image A tumor region setting system comprising: a display device that displays information in a superimposed manner.

  (10) A feature of the tenth invention for achieving the above object is an image storing X-ray CT image information and nuclear medicine image information including a tumor region in a tumor region setting system for setting a tumor region during radiotherapy. A server, a computing device for extracting contour information of the tumor region from the nuclear medicine image information, converting the extracted contour information into vector line drawing information, first image information as the X-ray CT image information, and the X A display device that displays line CT image information and second image information obtained by superimposing the nuclear medicine image information side by side, and displays the vector line drawing information converted by the arithmetic unit on the first image information. A tumor region setting system comprising:

  (11) A feature of the eleventh invention for achieving the above object is that in a tumor region setting system for setting a tumor region during radiotherapy, X-ray CT image information, nuclear medicine image information, and MRI image including the tumor region An image server for storing information; a computing device for extracting contour information of a tumor region from the nuclear medicine image information; and converting the extracted contour information into vector line drawing information; and a first image that is the X-ray CT image information Information and the second image information obtained by superimposing the MRI image information and the nuclear medicine image information are displayed side by side, and the vector line drawing information converted by the arithmetic unit is displayed superimposed on the first image information. A tumor region setting system comprising a display device.

  According to the present invention, it is possible to easily and accurately set a tumor region by extracting the contour information of a tumor region from nuclear medicine image information and converting the extracted contour information into vector line drawing information.

  Hereinafter, an embodiment of a tumor region setting method and a tumor region setting system according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an overall configuration of a tumor region setting system according to the present embodiment. In FIG. 1, there is a medical planning server 1 and a medical image server 2 for archiving X-ray CT images, PET images (nuclear medicine image information), etc., and these therapeutic planning device 1 and medical image server 2 are installed in a hospital, for example. A network cable 4 is connected to the in-hospital network 3 installed. The treatment planning device 1 includes a monitor (display device) 5 for displaying medical images and medical information, a computing device 6, a keyboard 7, and a mouse 8 serving as input means. Note that the mouse 8 as the input means may be other input means such as a pen tablet.

  FIG. 2 shows a processing flow performed by the tumor region setting system of the present embodiment. A tumor region setting method provided by the present invention will be described with reference to FIG.

  An operator who uses the treatment planning apparatus 1 first obtains an X-ray CT image and a PET image for a treatment plan of a patient who will make a treatment plan from the medical image server 2 (step 101).

  When the medical image acquisition from the medical image server 2 is completed, an X-ray CT image (first image information) and an image obtained by superimposing a PET image on the X-ray CT image on the monitor 5 of the treatment planning apparatus 1 (second image information) ) Are displayed side by side (step 102). The state of the monitor 5 at this time is as shown in FIG. 3A. For example, only the X-ray CT image 10 is displayed in the left image display area 11 and X in the right image display area 12 is displayed. An image in which a PET image display region 13 (hereinafter referred to as PET image 13) is superimposed on the line CT image 10 is displayed.

  When the display of the image is completed, the operator sets a threshold value for extracting the contour in the PET image display area 13 (step 103). This threshold may be specified for either the radioactivity count value or the SUV value. Here, the radioactivity count value is a radioactivity count value (hereinafter referred to as a count value) originally stored as raster data of a PET image. This is a value detected by a radiation detector attached to the PET apparatus. On the other hand, the SUV (Standardized Uptake Value) value is a value obtained by dividing the count value by the average count value when the drug is uniformly distributed in the patient's body, and SUV = 1 represents the average distribution of the drug. For example, if the SUV value is 2 to 3 or more, a tumor is suspected. Note that if the display of the PET image is a count value when the operator tries to specify the threshold value with the SUV value, the display of the PET image is converted when the threshold value is selected. On the contrary, when the display of the PET image is an SUV value when the operator tries to specify the threshold value by the count value, the display is similarly converted to the display by the count value. The threshold setting uses a threshold setting dialog 14 as shown in FIG. The operator selects the radio button 15 for selecting the type of threshold value, inputs a value in the text field 16 for inputting the threshold value, and then presses the OK button 17 to complete the setting of the threshold value. In this embodiment, it is assumed that the conversion region 18 in the PET image 13 in FIG. 3A is designated as a tumor region to be extracted by setting a threshold value.

  When the setting of the threshold is completed, the arithmetic device 6 automatically extracts a contour from the PET image 13 (step 104). Although PET images are raster images, contour extraction for raster images can be achieved using widely known algorithms (see, for example, “Practical Image Processing Learned in C Language” Ohmsha, 1999). Specifically, a pixel that is equal to or greater than the threshold is searched from the upper left pixel of the PET image, and an image that includes only pixels that are equal to or greater than the threshold is created. At this time, all pixels equal to or greater than the threshold value are converted to the same value (this image data is referred to as a binary image). By applying an edge extraction algorithm such as Pewitt's method to the binary image, the contour of the tumor region surrounded by the set threshold can be formed on the PET image 13. Further, a thinning algorithm such as the Hilditch method is used to convert the extracted contour into a one pixel wide contour.

  When the contour extraction on the PET image is completed, the arithmetic unit 6 converts the contour data thinned to the width of one pixel extracted automatically into vector line drawing data (step 105). A vector line drawing refers to a line drawing having a size and direction such as a Bezier curve or a polygon line, and is composed of lines connecting point sequences. A procedure and method for converting the contour data into vector line drawing (herein, Bezier curve) data will be described below.

（数式１）
曲率Ｒが一定値以下の場合は輪郭データから該当する点を間引いていき、図５（Ｃ）のようなデータを作成する。ここでは番号２の点が間引かれている。 First, as shown in FIG. 5A, the contour data is in a state in which lines having a width of one pixel are continuous. FIG. 5A shows an enlarged part of the contour data for the purpose of explanation. If this contour data is converted into vector data as it is, there are many useless parts, so it is necessary to sample and thin out points. This sampling is performed so that the shape of the original contour data is not impaired. In the present embodiment, sampling is performed based on the curvature between pixels. That is, pixels having a certain curvature or less are thinned out. Specifically, the pixels in FIG. 5A are numbered. The points with these numbers are schematically shown in FIG. The coordinates of the numbered points are (x0, y0), (x1, y1), and (x2, y2), respectively. When viewed from the point of number 1, the angle θ formed by the lines of numbers 0 and 1 and numbers 1 and 2 is expressed as the following Equation 1 when the cosine of θ is defined as the curvature R.

(Formula 1)
When the curvature R is below a certain value, the corresponding points are thinned out from the contour data, and data as shown in FIG. 5C is created. Here, the number 2 is thinned out.

  In this way, when the scanning of all the contour data is completed, two points that are just divided into three equal parts are inserted on the straight line between the points as shown in FIG. These two points are called temporary control points. A Bezier curve is generated using the temporary control points and the points on both sides of the temporary control points.

（数式２）

（数式３）
ベジエ曲線を利用した輪郭データのベクトル化は以下のように行う。サンプリングした輪郭データをベジエ曲線で近似する場合、図５（Ｄ）の４点を近似の対象とする。図７に考え方を示す。対象とする４点をＱ０〜Ｑ３とする。これらの点をベジエ曲線は通過しなければならない。また、ベジエ曲線は、制御点を持ち、それは一般的には図７に示すようにＰ０〜Ｐ３の点で表される。すなわち、Ｑ０〜Ｑ３の点をベジエ曲線が通過できるように制御点Ｐ０〜Ｐ３を決定すればよい。 Before describing vectorization of contour data using a Bezier curve, the Bezier curve will be briefly described. The Bezier curve can be expressed by the following (Equation 2) and (Equation 3). Here, R (t) represents a curve represented by a parameter t, and Pi represents a control point. The range of t is 0 or more and 1 or less, and Bi (t) is called a Bernstein function. A curve as shown in FIG. 6 can be generated by (Expression 2) and (Expression 3). Here, P3 is a control point, and a curve sandwiched between P0 to P3 is a Bezier curve.

(Formula 2)

(Formula 3)
Vectorization of contour data using a Bezier curve is performed as follows. When approximating the sampled contour data with a Bezier curve, the four points in FIG. The concept is shown in FIG. The four points of interest are Q0 to Q3. The Bezier curve must pass through these points. A Bezier curve has control points, which are generally represented by points P0 to P3 as shown in FIG. That is, the control points P0 to P3 may be determined so that the Bezier curve can pass through the points Q0 to Q3.

（数式４）

（数式５）
となる。（数式４）及び（数式５）をＰ１及びＰ２について解くことにより、制御点が全て求まり、図７の点Ｑ０〜Ｑ３をベジエ曲線で近似できる。以上の手順により輪郭データをベクトル線画データに変換する。 First, from FIG. 7, P0 = Q0 and P3 = Q3. Since it is known from (Equation 2) that the curve can be expressed by the parameter t, the parameter between Q0 and Q1 is t1, the parameter between Q1 and Q2 is t2, and the parameter between Q2 and Q3 is t3. P1 and P2 can be determined using (Formula 2). Considering Q1 and Q2 as temporary control points and formulating Q1 and Q2,

(Formula 4)

(Formula 5)
It becomes. By solving (Equation 4) and (Equation 5) for P1 and P2, all the control points are obtained, and the points Q0 to Q3 in FIG. 7 can be approximated by a Bezier curve. The contour data is converted into vector line drawing data by the above procedure.

  The arithmetic device 6 displays the result on the monitor 5 when the conversion of the contour data into the vector line drawing is completed. FIG. 3B shows the display of the result. In the image display area 12 on the right side, a tumor area 20 converted into vector line drawing data is displayed on the X-ray CT image 10 on which the PET image 13 is superimposed. At the same time, the tumor region 20 represented by the vector line drawing is copied and displayed on the X-ray CT image 10 displayed in the left image display region 11 (step 106). Since the tumor region 20 converted into the vector line drawing is composed of a curve connecting the points, the operator edits the tumor region converted into the vector line drawing to form a more accurate tumor region. You can also. The editing result is immediately reflected on the X-ray CT image.

  When the setting of the tumor region on the X-ray CT image is completed in this way, the setting of the irradiation dose for the set tumor region is performed thereafter.

According to the tumor region setting method and the tumor region setting system of the present embodiment configured as described above, the following operations can be obtained.
That is, as described above, generally, a medical image is composed of raster data (a two-dimensional array that is a set of pixels), and the data format of a tumor region used by a treatment plan is vector line drawing data (such as a polygon line drawing) ( It is composed of lines and dots having size and direction. For this reason, in the conventional techniques such as those described in Patent Document 1 and Patent Document 2 described above, although not clearly described, the operator usually displays the PET image superimposed on the X-ray CT image. The tumor area that can be discriminated by the PET image data cannot be directly used as the tumor area for the treatment plan. For example, the outline of the tumor area that can be discriminated by the PET image data by using an input means such as a mouse is traced. I had to manually convert it to a polygon line drawing. In this case, there is a problem that setting of the tumor region takes time and a difference occurs in the tumor region depending on the skill level of the operator and the like, and the accuracy of specifying the region is lacking.

  On the other hand, according to the present embodiment, the operator sets the threshold value using the count value or the SUV value, so that the computing device 6 automatically extracts the contour of the tumor region from the PET image 13, Further, the contour data can be converted into vector line drawing data and used for treatment planning. This eliminates the need for the operator to trace the outline of the tumor region as in the prior art, so that the region setting operation can be greatly simplified. Furthermore, since the contour is automatically extracted using the threshold value, it is possible to set a reproducible (in other words, highly reliable) tumor region regardless of the skill level of the operator. Therefore, according to the present embodiment, a tumor region can be set easily and accurately.

  In the embodiment described above, a Bezier curve is described as an example of the vector line drawing. However, it goes without saying that another vector line drawing such as a polygon line may be used instead of the Bezier curve.

  In the present embodiment, the X-ray CT image 10 and the PET image 13 are displayed so as to overlap each other on the image display area 12 on the right side of the monitor 5, but depending on the location of the part (soft tissue or the like) where a treatment plan is desired. In some cases, the MRI image may be better observed. In such a case, the MRI image and the PET image 13 may be displayed in an overlapping manner in the image display area 12.

  Furthermore, in the present embodiment, the display of the monitor 5 is divided into an image display region 11 and an image display region 12, and an X-ray CT image 10 and an image obtained by superimposing a PET image 13 on the X-ray CT image 10 are combined. The display is arranged side by side. However, the display is not limited to this. For example, the display of the monitor 5 is only one image display area, that is, the image display area 12 in which the X-ray CT image 10 and the PET image 13 are displayed in an overlapping manner. You may make it comprise.

It is a figure showing the whole structure of one Embodiment of the tumor area | region setting system of this invention. It is a figure which shows the processing flow which the tumor area | region setting system shown in FIG. 1 performs. It is a figure which shows an example of the image display by the monitor shown in FIG. 1, and displayed the X-ray CT image and the image which overlap | superposed the PET image on the X-ray CT image, and the outline of the tumor area on the X-ray CT image FIG. 6 is a diagram showing an image obtained by superimposing vector line drawing data indicating the image and an image obtained by superimposing a PET image on an X-ray CT image. It is a figure which shows a threshold value setting dialog. It is a figure for demonstrating the sampling process of the contour data of a tumor area | region. It is a figure for demonstrating a Bezier curve. It is a figure for demonstrating the process converted into a Bezier curve from outline data.

Explanation of symbols

2 Medical image server (image server)
5 Monitor (display device)
6 Arithmetic unit

Claims (11)

  A method for setting a tumor region in radiation therapy, comprising: extracting contour information of a tumor region from nuclear medicine image information; and converting the extracted contour information into vector line drawing information.   The tumor region setting method according to claim 1, wherein contour information of the tumor region is extracted from the nuclear medicine image information using a threshold value.   The method according to claim 2, wherein a radioactivity count value included in the nuclear medicine image information is used as the threshold value.   The tumor region setting method according to claim 2, wherein an SUV value is used as the threshold value.   The tumor region setting method according to claim 2, wherein the vector line drawing information and the X-ray CT image information are displayed in an overlapping manner.   6. The tumor region setting method according to claim 5, wherein the vector line drawing information is Bezier curve information.   6. The tumor region setting method according to claim 5, wherein the vector line drawing information is polygon line drawing information.   6. The tumor region setting method according to claim 5, wherein the nuclear medicine image information is PET image information. In the tumor area setting system for setting the tumor area during radiotherapy,
An image server for storing X-ray CT image information and nuclear medicine image information including a tumor region;
Extracting the outline information of the tumor region from the nuclear medicine image information, and converting the extracted outline information into vector line drawing information;
A tumor region setting system, comprising: a display device that displays the vector line drawing information converted by the arithmetic device on the X-ray CT image information. In the tumor area setting system for setting the tumor area during radiotherapy,
An image server for storing X-ray CT image information and nuclear medicine image information including a tumor region;
Extracting the outline information of the tumor region from the nuclear medicine image information, and converting the extracted outline information into vector line drawing information;
The first image information which is the X-ray CT image information and the second image information obtained by superimposing the X-ray CT image information and the nuclear medicine image information are displayed side by side, and the vector converted by the arithmetic device A tumor region setting system comprising: a display device that displays line drawing information superimposed on the first image information. In the tumor area setting system for setting the tumor area during radiotherapy,
An image server for storing X-ray CT image information including a tumor region, nuclear medicine image information, and MRI image information;
Extracting the outline information of the tumor region from the nuclear medicine image information, and converting the extracted outline information into vector line drawing information;
The first image information as the X-ray CT image information and the second image information obtained by superimposing the MRI image information and the nuclear medicine image information are displayed side by side, and the vector line drawing information converted by the arithmetic unit is displayed. And a display device that displays the image on the first image information.

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