JPH119708A - Radiotherapy device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily, accurately and quickly position the part of the body of a patient to be treated with radiation at the isocenter of a radiotherapy device and to prevent the patient from being exposed to radiation as the result of positioning. SOLUTION: The gantry 1 of a radiotherapy device and the gantry 3 of an MRI device are opposed to each other with a bed 2 between them. Positioning of a patient 100 prior to treatment starts with the photographing of the diseased part of the patient 100. After an MR image is taken, a characteristic organ part whose position does not change is searched near the diseased part within the image, and a plurality of points called control points are set there. Next, the center point of the diseased part is designated. The coordinates of the control points within the image and of the center point of the diseased part are calculated as values on an actual space with respect to the coordinates of the reference position of the bed 22. Movement of the bed 22 is controlled according to the calculated values to automatically move the center position of the diseased part to the isocenter of the gantry 1 to the radiotherapy device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for positioning a treatment site of a patient at an isocenter of a gantry of a radiotherapy apparatus in a radiotherapy system.

[0002]

2. Description of the Related Art Radiation therapy is one of the methods for treating cancer and malignant tumors formed in the human body. In radiotherapy, high-energy X-rays or electron beams are intensively applied to cancers or malignant tumors in the human body to destroy and treat tissue cells of the cancers or malignant tumors. There are a radiotherapy apparatus that irradiates the tumor with X-rays generated by accelerating electrons and colliding with an X-ray target, and a radiotherapy apparatus that uses γ-rays emitted from a radioisotope. There are also those using accelerated electrons, those using a linear accelerator (linear accelerator), and those using an electron beam accelerator having a circular orbit (cyclotron, microtron, etc.).

[0003] Such a radiation therapy apparatus is not used alone in any apparatus, but is used as a system composed of a combination of a positioning apparatus and a treatment planning apparatus. In radiotherapy, since the radiation is intensively applied only to the affected part of the cancer or malignant tumor, it is important to accurately align the affected part with the isocenter of the radiation treatment apparatus.

As the positioning device, an X-ray positioning device (X-ray simulator) or a cross-sectional X-ray tomography device has been conventionally used. In recent years, these devices have been replaced with two-dimensional images and three-dimensional images. It has been devised to use an X-ray CT apparatus which can easily obtain the above as a simulator. X
A technique using a line CT apparatus as a simulator is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-309091.

[0005] As described above, it is important for radiation treatment to accurately irradiate the affected part of a cancer or malignant tumor. However, radiation treatment does not end with one irradiation treatment, but is necessary. The total irradiation dose is divided into a plurality of times and performed at predetermined intervals. The fact that this radiation therapy is performed a plurality of times at predetermined intervals means that after one irradiation treatment, the patient gets off the bed of the treatment apparatus and returns to the hospital room or home, and the next irradiation When performing treatment, it is necessary to again align the treatment site of the patient with the isocenter of the radiotherapy apparatus.

[0006] Positioning of a treatment site will be described by taking a case where a CT simulator is used as an example.
The affected part of the patient diagnosed as having cancer or malignant tumor by the image diagnosis and the pathological examination is identified by the CT simulator. As the CT simulator, one capable of imaging an affected part including at least a tissue in the vicinity thereof using at least a plurality of continuous tomographic images without gaps is used. After imaging the affected part, the center point of the affected part is specified on the image. After identifying the center point of the affected area,
The affected part is moved to the position of a light projector provided so as to be able to irradiate a patient with a laser beam from a plurality of directions outside the gantry of the CT apparatus, and the laser beam is emitted from the light projector toward the patient. Then, when the laser beams from a plurality of directions coincide with the center of the affected part, the laser beam is marked on the body surface of the patient, and is used as an affected part center indicating mark. The affected area center indicating marker is provided in three orthogonal axes directions.

[0007] The radiation therapy apparatus is also provided with a plurality of projectors having the same function as the above-mentioned projector, and each of these projectors is provided with a projector in which laser beams intersect at the isocenter of the radiation therapy apparatus. By aligning the center mark of the affected part with the laser beam, positioning of the treatment site to the isocenter is performed.

[0008]

As described above, in the radiation therapy, a treatment plan including a total irradiation dose is created by a treatment planning device based on a treatment site and the size of a cancer or a tumor, and the total irradiation dose is prepared. Is divided into a plurality of parts and irradiated several times. In the course of treatment, it is essential to confirm the effect of treatment. In order to confirm the therapeutic effect, the current status of X-ray equipment and X-ray C
Although a T apparatus is used, there are not a few cases where X-ray imaging or X-ray CT imaging is not performed in each treatment in consideration of the adverse effect of radiation exposure on a patient.

Further, in the positioning method in which the marking as described above is applied to the surface of the patient's body and the marking is aligned with the laser beam position indicating the isocenter of the radiation treatment apparatus, accurate treatment positioning can be performed at the first treatment. Even so, it involves the problem of lack of accuracy during the second and subsequent treatments. The reasons are that the marking position changes due to the patient's weight loss or the like due to the illness, and that errors caused by manual operation of the operator are included.

SUMMARY OF THE INVENTION In view of the above problems, it is a first object of the present invention to provide a radiotherapy system capable of accurately and quickly positioning a radiotherapy and allowing an operator to focus on a therapy. . A second object of the present invention is to provide a radiotherapy system in which the patient is less exposed to radiation during image acquisition for positioning during treatment performed multiple times in the treatment process and for confirming the treatment effect.

A third object of the present invention is to provide a radiotherapy system capable of accurately and easily performing positioning during the second and subsequent treatments. Still another object of the present invention is to provide a radiation treatment system that can easily re-do a treatment plan.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a radiotherapy apparatus for irradiating a radiotherapy site of a patient, and a medical image diagnosis for specifying the center of the radiotherapy site of the patient. Device, the isocenter of the radiotherapy device and the center of the image acquisition position of the critical image diagnostic device are installed with a predetermined positional relationship, the patient is placed thereon, and the treatment site is positioned at the center of the image acquisition position of the medical image diagnostic device. And a bed having a bed that moves between the radiotherapy device and the isocenter, and a couch for automatically aligning the center of the treatment site specified by the image of the diagnostic imaging device with the isocenter of the radiotherapy device. The radiation therapy system was configured to include the movement control means. (Claim 1)

[0013] As the medical image diagnostic apparatus, a magnetic resonance imaging apparatus capable of imaging a tissue structure in a living body by using a magnetic resonance phenomenon is used. (Claim 2)

In the magnetic resonance imaging apparatus, since the MR image acquired due to the non-uniformity of the static magnetic field or the non-linearity of the gradient magnetic field has a positional distortion, the distortion of the generated MR image is measured in advance, and the measured value is used. A means for generating an MR image in which distortion has been corrected is provided. (Claim 3)

Further, the present invention has been made in order to solve the above problems.
A radiotherapy device that irradiates radiation to a radiotherapy site of a patient, an X-ray CT device that acquires the radiotherapy site of the patient and the vicinity thereof as a two-dimensional image or a three-dimensional image, and a radiotherapy site of the patient and the vicinity thereof Is a two-dimensional image or 3
A magnetic resonance imaging apparatus for imaging as a two-dimensional image; and an isocenter of the radiotherapy apparatus and an image acquisition center position of the magnetic resonance imaging apparatus, which are installed in a predetermined positional relationship with each other, and carry the patient on the magnetic resonance imaging apparatus. A bed having a bed that moves between an image acquisition center position of an imaging apparatus and an isocenter of the radiotherapy apparatus; and a characteristic portion near an affected part from an image of the X-ray CT apparatus and an image of the magnetic resonance imaging apparatus. Means for specifying and storing, means for specifying the relationship between the characteristic site and the center position of the affected part, and a couch movement control means for automatically aligning the center position of the affected part with the isocenter of the radiation therapy apparatus. The radiation therapy system was configured with the above. (Claim 4)

Then, an image area smaller than the original image is set so that the radiotherapy site of the patient and the image near the radiotherapy site acquired by the X-ray CT apparatus or the magnetic resonance imaging apparatus include the characteristic area. A means for storing the set small image in a readable manner is provided. (Claim 5)

The extraction of the characteristic region near the affected part on the image of the magnetic resonance imaging is performed by pattern matching with the image taken during the previous treatment in which the characteristic region is designated. (Claim 6) Further, the characteristic part near the affected part and the center position of the affected part are stored as coordinates in association with each other. (Claim 7)

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external view showing a configuration of a radiotherapy system according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a gantry of a radiation therapy apparatus. The gantry 1 has a base unit 11 on which the apparatus is fixedly installed on a floor surface and rotatably supports a rotating arm by a rotation support mechanism (not shown). The rotating arm 12 includes a guide section for accelerating electrons, and an irradiation head 13 attached to a tip of the rotating arm 12. Inside the irradiation head 13, a target (not shown) for emitting radiation, for example, X-rays by collision of electrons accelerated to high energy by an accelerator is incorporated, and the emitted radiation is used for a treatment site of a patient. A collimator (not shown) that irradiates only the irradiation area only is provided.

Reference numeral 2 denotes a bed provided with a base 21 and a bed 22 on which the patient 100 is placed. The bed 22 has a longitudinal direction (hereinafter referred to as X direction) and a direction perpendicular to the longitudinal direction (hereinafter referred to as Y direction). ) And a vertical direction (hereinafter, referred to as a Z direction). An operating device for moving the bed 22 in each direction is provided near the bed 22. A reference position is determined for each movement of the bed 22 in the X, Y, and Z directions. The reference position of the movement in each of these directions is, for example, a specific position of the bed 22 when the bed 22 is a movement position of ± 0 mm in the longitudinal direction and a direction orthogonal to the longitudinal direction, for example, the position shown in FIG. X
o, Yo, Zo) can be selected.

Reference numeral 3 denotes a magnetic resonance imaging apparatus (hereinafter referred to as M
Gantry). In the present invention, the MRI apparatus converts the bed 22 of the bed 2 into an MRI.
In order to be able to move also in the Y direction within the gantry opening of the device, a cylindrical magnet was not used as a static magnetic field generation source.
A gantry opening with a horizontally long type or a type with a measurement space exposed is used. It is assumed that the MRI apparatus incorporates a pulse sequence for acquiring a three-dimensional image in addition to a pulse sequence for acquiring a two-dimensional image as a pulse sequence for imaging.

Although a general MRI apparatus is not shown in FIG. 1, a static magnetic field generating apparatus for generating a uniform static magnetic field with a predetermined intensity in a measurement space inside the gantry 3 and a high-frequency high frequency A transmitting coil for irradiating a magnetic field, a gradient coil for giving a gradient to the uniform static magnetic field, and a magnetic resonance signal (hereinafter, referred to as a signal) generated from within the subject by a magnetic resonance phenomenon.
A receiving coil for detecting an NMR signal) is housed in the gantry 3, and a control device 31 drives and controls them according to a predetermined program; a gradient power supply 32 for supplying power to the gradient coil; The image processing apparatus further includes an image processing device 33 for imaging the NMR signal detected by the receiving coil, and a display device for displaying an image. Since these are already known in various documents, a detailed description will be omitted here.

The gantry 1 of the above radiotherapy apparatus,
The bed 2 and the gantry 3 of the MRI apparatus are arranged at a predetermined accurate distance with the bed 2 interposed therebetween. More specifically, the isocenter 15 of the gantry 1 of the radiotherapy device
The distance between the distance and the center 35 of the measurement space of the gantry 3 of the MRI apparatus is set to a predetermined accurate distance. In other words, the distance between the specific reference position on the moving bed 22 of the couch 2 located therebetween and the isocenter 15 of the gantry 1 of the radiation therapy apparatus, the specific reference position on the bed 21 and the MRI apparatus Center 35 of measurement space of gantry 3
The value obtained by adding the distance between the two is set to a constant value.

Next, the procedure of radiotherapy by the radiotherapy system having the above configuration will be described. First, MRI
The treatment site of the patient is photographed by the device, and the center position of the treatment site is determined. For this purpose, the patient is laid on the bed 22 and the bed 22 is adjusted to the reference position. As an example, the reference position of the bed 21 is such that the movement of the bed 22 in each of the X direction and the Y direction is ± 0 mm and the bed 22 is in the Z direction at the position of the imaging reference height of the MRI apparatus. A specific point above is set as a reference point. It is assumed that the coordinates of this reference point are (Xo, Yo, Zo) of the X, Y, Z coordinates in the real space. In the above description, the patient is laid on the bed 22 and then the reference position is adjusted. However, this is not necessary if the bed is a bed where movement of the bed 22 is always detected.

Then, the part diagnosed as the diseased part by the image diagnosis is moved in the opening direction of the gantry 3 of the MRI apparatus, and the position estimated to be the center of the diseased part is determined by the laser beam of the projector provided at the entrance of the opening. Perform positioning for combined shooting. Thereafter, the affected part is moved toward the center of the measurement space inside the opening of the gantry 3.

The affected part of the patient is located at the center 3 of the measurement space of the MRI apparatus.
5 When the real space coordinates are set to (Xm, Ym, Zm), the MRI apparatus performs imaging. For imaging, a pulse sequence for three-dimensional imaging is used, and the field of view (FOV: Fie
(ld of View) is set to a size that sufficiently covers the affected part of the patient, and imaging is performed. The center of the affected part to be treated and the size of the peripheral area are extracted from the captured image. For that purpose, the captured image is displayed on the display device 34.

An imaging region is obtained as a plurality of slice images from measurement data measured by a pulse sequence for three-dimensional imaging. As a method for displaying the captured images, there are a method of displaying the slice images as a three-dimensional image obtained by stacking projection, and a method of sequentially displaying a plurality of slice images. With reference to the image displayed on the display device 35, the doctor specifies the size of the center of the affected part to be treated and the size of the surrounding area. The center position of the affected part is obtained as three-dimensional coordinates of x, y, and z on the image. Then, the center position (xi, yi, zi) of the affected part obtained on the image is represented by (Xr, Yr,
Zr) Convert to coordinates. In this conversion, since the center of the measurement space is determined in the captured image and the size of the FOV is set in the real space, the center of the affected part is measured in the X, Y, and Z directions on the obtained image. This can be easily performed by counting how many pixels are shifted from the center of the space by software incorporated in the apparatus. For example, when a 10 cm FOV is imaged with 256 pixels, one pixel corresponds to a distance of 0.39 mm in the real space, and thus conversion can be performed by multiplying the number of pixels by this 0.39 mm. In addition, the size of the treatment area can be similarly converted to a size in the real space.

Next, a method of moving the center position of the affected part in the real space specified by the MRI apparatus to the isocenter of the radiotherapy apparatus will be described. The coordinates in the real space of the isocenter 15 of the gantry 1 of the radiation therapy apparatus are (Xt, Yt,
Zt). This movement corresponds to (X
r, Yr, Zr) by (Xt, Yt,
Zt) is to move to the isocenter of the gantry 1 represented by Zt). An operating device for this is provided near the bed 22, and the coordinates of the center of the affected area on the image are input,
It is converted to coordinates in the real space and the bed 22
A control unit including an arithmetic circuit for calculating an amount by which the upper (Xr, Yr, Zr) point is moved to the isocenter (Xt, Yt, Zt) of the gantry 1 is provided.

The control unit 36 controls the coordinates (Xo, Yo, Zo) of the reference point of the bed 22 and the center position (X
r, Yr, Zr) and coordinates (Xo, Yo, Zo)
And gantry 1 isocenters (Xt, Yt, Zt)
A path for moving the bed 22 to move the affected center to the isocenter is set between the X-direction driving mechanism 23, the Y-direction driving mechanism 24, and the Z-direction driving mechanism 2 of the bed 22.
5 is driven and controlled. The calculation in the control unit 36 may be executed when the operation device is operated, or may be executed immediately when the center of the affected part is designated on the image. In any case, when the operating device is operated, the bed 2
2 is controlled to move so that the center of the affected part coincides with the isocenter 15 of the gantry 1. In FIG. 1 showing the present embodiment, a radiation therapy apparatus 1, a bed 2, and an MRI apparatus 3 are shown.
Although the example in which the and are arranged on a straight line has been described, the length of the arm 12 having the radiation irradiation port of the gantry 1 of the radiation treatment apparatus may be insufficient depending on the treatment site of the patient. Assuming such a case, the bed 22 is set to 90
A rotation mechanism may be provided on the bed 2 so that the bed 2 can be rotated by 180 ° or 180 °, or the entire bed 2 may be placed on a turntable for installation. In a case where a rotation mechanism of the bed 22 is provided and operated, it goes without saying that the calculation in the control unit 36 takes this into consideration.

The bed 22 is moved and controlled so that the center of the treatment site of the patient is the isocenter 1 of the gantry 1 of the radiotherapy apparatus.
After matching to 5, radiation treatment is performed. And
At the time of the second treatment, the above procedure is repeated. According to the above-described first embodiment of the present invention, since the positioning of the affected part can be performed below the image of the MRI apparatus, a conventional X-ray simulator, an X-ray rotational transverse tomography apparatus, and an X-ray CT apparatus are used. In comparison with the above, the patient is not exposed to X-rays during positioning.

Next, a second embodiment of the present invention will be described. Also in this embodiment, the radiation therapy apparatus, the bed and the MR
The I device is arranged in the same manner as in the first embodiment shown in FIG.

The difference between this embodiment and the first embodiment is that the first embodiment uses an MR image to specify a treatment site and find the center of the treatment site.
I have added distortion correction for images. It is known that an image of an MRI apparatus is distorted when there is non-uniformity or non-linearity in a static magnetic field and a gradient magnetic field superimposed thereon. It is also known that when a patient is inserted into the measurement space, the captured image is distorted due to the uneven distribution of the magnetic permeability of the body tissue of the patient. Therefore, in the first embodiment, the MR
If there is non-uniformity of the static magnetic field or non-linearity of the gradient magnetic field in the I apparatus, the treatment site designated on the image and the center of the treatment region may be different from the position in the patient's body.

Therefore, in this embodiment, the distortion correction of the MR image used for specifying the treatment site and the center of the treatment site is performed. An MR image distortion correction method will be described below.

Since the positional deviation of each point of the coordinates in the limited three-dimensional real space, which is the measurement space of the MRI apparatus, on the captured image is a distortion of the image, nuclear magnetic resonance is transferred to the measurement space. The distortion of MR images can be grasped by regularly arranging and imaging the substances presenting the image, and correctly grasping the positional relationship between the pixels of the imaging data and the substance in the real space. This can be done by moving to a position corresponding to that.

In this embodiment, a three-dimensional lattice phantom is used to obtain distortion correction data of an MR image. This phantom is a medium in which a cubic space having a thickness of about 1 mm and a side of about 10 mm is accurately and regularly arranged in a cubic space, and a magnetic resonance phenomenon is caused in the space, for example, an aqueous solution of nickel chloride or copper sulfate. May be sealed.

The phantom is mounted on the bed 22 so as not to change its position, moved to the center of the measurement space of the MRI apparatus, and the FOV is set so that the entire phantom is included in the FOV of the MRI apparatus. The phantom is photographed by activating a pulse sequence for three-dimensional imaging. The photographed three-dimensional image of the phantom is compared with the actual dimensions of the phantom, and the position of each pixel on the three-dimensional image as it should be on the image is obtained. The obtained data is data for distortion correction. The obtained distortion correction data is MR
It is stored in the image processing unit 33 of the I device, the control unit of the radiotherapy system, or the treatment planning device.

In the present embodiment, the MR image of the affected part taken in the first embodiment is corrected using the distortion correction data and displayed on a display device. Then, the shape of the affected part and the center of the affected part are specified on the image in which the distortion has been corrected, and the specified position is converted into coordinates in the real space to be used as bed movement data in the first embodiment. Used. According to the present embodiment, even an MRI apparatus in which the uniformity of the static magnetic field and / or the linearity of the gradient magnetic field is slightly poor, can perform a sufficient function as a simulator of the radiation therapy apparatus. In the second embodiment, the description of the correction of the image distortion due to the non-uniformity of the magnetic permeability distribution of the body tissue of the patient has been omitted, but this is achieved by providing the static magnetic field generator with a shimming mechanism. Response is possible. Further, the shape of the affected part and the center position of the affected part are specified in the distortion-corrected MR image. However, the specified shape and position are specified on the distorted MR image, and the specified shape and position are stored. Even if the correction is performed using the distortion correction data, it is considered that the accuracy is not greatly deteriorated in practical use.

Next, a third embodiment of the present invention will be described with reference to FIG. A radiation therapy system requires a device to know the radiation sensitivity of a patient. In the first and second embodiments, only the MRI apparatus is used as a simulator. Therefore, the radiation dose applied to a patient required for treatment is calculated based on past data accumulated in a hospital or data on a doctor's experience. It is set by estimation based on this. This is unreliable as to whether the affected area is irradiated with a radiation dose that is truly necessary for proper and sufficient treatment. The embodiments described below are used to determine the X-ray C
This is a combination of the T device with the first or second embodiment.

FIG. 2 shows an example of an arrangement of the radiotherapy system according to the third embodiment. The gantry 1 and the bed 2 of the radiotherapy apparatus and the gantry 3 of the MRI apparatus are shown in FIG.
The gantry 1 of the radiotherapy device is arranged in the same manner as
It is preferable that the isocenter 15 and the reference position of the bed 2 and the center 35 of the static magnetic field of the gantry 3 of the MRI apparatus are measured and arranged with an accuracy of 1 mm or less. The gantry 4 of the X-ray CT apparatus is installed so that the center line of the opening intersects the opposing line of the gantry 1 of the radiotherapy apparatus and the gantry 3 of the MRI apparatus. This is to stop providing a separate bed for the X-ray CT apparatus 4 and to use only one bed 2 in the entire system. However,
If the gantry 3 of the MRI apparatus and the gantry 4 of the X-ray CT apparatus are too close to each other, the magnetic field of the MRI apparatus will be affected. In such a case, the gantry 4 of the X-ray CT apparatus and the bed for it will be used. It is a good idea to consider placing it in a separate room.

Next, the positioning method in the present embodiment will be described with reference to the flowchart of FIG. First, the phantom is arranged so that the center of the phantom coincides with the center of the static magnetic field of the MRI apparatus in order to acquire data for correcting image distortion of the MRI apparatus, and the entire phantom is photographed using a pulse sequence for three-dimensional imaging. . (Step 101)

Next, the distortion of the MR image is analyzed by comparing the obtained three-dimensional phantom image with the phantom itself. In this analysis, while obtaining the distortion correction data,
The size ratio between the MR image and the real phantom is determined. Then, when the distortion correction data is obtained, it is preferable to correct the phantom image using the data and confirm that the correction data is correct. The size ratio between the MR image and the actual phantom is determined from the ratio between the lattice size of the real phantom and the lattice size on the image.
This is for setting the value of the image enlargement / reduction ratio when comparing the MR image and the X-ray CT image described later. (Step 102)

Next, landmarks are set near the treatment site of the patient. This landmark can be imprinted on both the image photographed by the MRI apparatus and the image photographed by the X-ray CT apparatus, and is a target when comparing the MR image and the X-ray CT image. . It is desirable to select a landmark that is a characteristic organ near the affected part in the patient's body and does not move even by the beating or respiratory movement of the patient (internal body landmark method). When the characteristic organ does not exist, the X-ray CT apparatus and the M
A method of attaching a mark formed of a material that can be photographed by both the RI device (external body landmark method) may be adopted. In the case where the extracorporeal landmark method is adopted, a plurality of marks are pasted on a place where the amount of movement of the body surface near the affected part is small based on the image diagnostic information, and then the procedure proceeds to the following positioning procedure. (Step 103)

First, X-ray CT imaging is performed. This shoot is 3
The imaging is performed using a dimensional imaging method, for example, an imaging method called spiral scanning in the field of X-ray CT, and the landmark is included in the imaging region. The reason why the X-ray CT imaging is performed prior to the MR imaging is that the positional relationship between the X-ray CT apparatus and the radiation therapy apparatus does not directly affect each other. The measurement data obtained by the X-ray CT apparatus is image-reconstructed, and can be displayed as a two-dimensional image or a three-dimensional image as necessary. Then, the CT image is displayed on the display device, a plurality of characteristic points of the characteristic organ are found near the affected part of the patient, and these characteristic points are marked in the image, and the characteristic points including these characteristic points are limited. The image of the area is extracted and stored so that it can be read.
(See FIG. 4) The image size extracted here is 32 pixels ×
A voxel image of about 32 pixels × 32 pixels is enough,
These voxel image data are referred to as CT chip files. Note that the feature points near the affected part in the extracted image are named CT control points here. These CT chip files and C
The T control point also needs to be stored so as to be used as positioning data for the second and subsequent radiation treatments. The number of CT control points is desirably three or more. (Step 104)

Next, MR imaging is performed. This MR shooting is also 3
The imaging is performed using a two-dimensional imaging method so that the landmark at the time of the CT imaging is included in the imaging region. And this M
In the R imaging, the movement control of the bed 22 of the bed 2 is controlled with an accuracy of 1 mm or more with respect to the reference position of the bed. That is, when the affected part is moved to the center of the static magnetic field in order to image the affected part of the patient, it is possible to accurately grasp how much the bed 22 has moved from the reference position.

Using the data measured by the MRI apparatus, the MR is reduced using a two-dimensional image reconstruction technique or a three-dimensional image reconstruction technique.
Get an image. Since the obtained MR image has a distortion as described above, the distortion correction of the MR image is performed using the distortion correction data previously measured and acquired using the phantom.
Thereby, the positional distortion of the landmark in the MR image is corrected together with the distortion of the organ image. (Step 10
5)

Next, the CT image and the MR after distortion correction have been performed.
The images are superimposed at the same magnification. At this time, the reference position of the superposition of both images is a landmark imprinted on both images. Then, the CT control points marked in the CT image are copied in the MR image,
This is marked as an MR control point. Then, the coordinates of these MR control points on the image and in the real space are obtained by calculation, and their values are stored. Next, an image of a limited area including the plurality of MR control points is extracted. (See FIG. 4) The image size to be extracted is sufficient if it is about 32 × 32 × 32 pixel voxel image like the CT chip file, and the voxel image data can be read as MR chip file. store. Here, this chip image is referred to as a CP chip image. This CP chip image is used for positioning during the second and subsequent treatments, which will be described later. (Step 106)

Next, the treatment site is determined on the MR image, and the center coordinates (xi,
yi, zi) are determined as shown in FIG. Then, the center coordinates (xi, yi, zi) of the treatment site obtained on the image are converted into coordinates (Xr, Yr, Zr) in the real space. Since this conversion can be performed in the same manner as in the first embodiment described above, detailed description is omitted here. These coordinates are stored in a readable manner in a radiation treatment planning system or the like together with ID data such as the patient's name, age, treatment site, and treatment date, and the center coordinates of the treatment site with respect to the MR control point are imaged. Above and in real space. (Step 107)

When the center coordinates of the treatment site in the real space are determined, the bed 2 is drive-controlled to control the isocenter (Xt, Yt, Z) of the gantry 1 of the radiotherapy apparatus.
t) Automatically move its center coordinates. (Step 1
08)

The radiotherapy is performed on the treatment site moved to the isocenter of the gantry 1 of the radiotherapy apparatus. In this example, the setting of a radiation irradiation area, the amount of radiation irradiation, the number of irradiations, and the like are determined based on an X-ray CT image having no image distortion by a radiation treatment planning system that has already been developed. (Step 109) The radiation treatment is performed a plurality of times. Therefore, it is required that not only the first alignment be performed accurately, but also the second and subsequent alignments be performed accurately and quickly. Embodiments of the second and subsequent alignments of the present invention that meet this requirement will be described below.

First, the patient is laid down on the couch 2 and the couch top of the couch 2 is moved, and the position assumed to be the center of the treatment site is determined by MRI.
Align to the projector's floodlight. Thereafter, the bed 22 of the couch 2 is moved in the direction of the measurement center of the gantry of the MRI apparatus, the position assumed to be the center of the treatment site is positioned at the center 35 of the static magnetic field of the MRI apparatus, and the MRI apparatus is operated. An imaging field of view that includes the entire region is set, and MR imaging is executed. The imaging here is for the purpose of extracting the control points used during the first treatment.
(Step 201)

In extracting control points, control points for the current positioning are automatically extracted by performing matching processing with the stored CP chip image taken during the first treatment. Therefore, if the CP chip image at the time of the first treatment is a three-dimensional image, the second MR imaging is also executed according to the same imaging sequence as the first.

When the MR imaging is completed, the CP chip image acquired at the time of the first treatment is read out and the M
A pattern matching process is performed with the R image, and control points in the current MR image are extracted. As an extraction method, for example, the MR image captured this time is fixedly displayed on the display device, and the read-out first CP chip image is moved left / right and up / down on the screen of the display device and orthogonally intersects. Controlling the current positioning by comparing the images by superimposing them by applying rotation in the axial direction, and searching for points in the MR image that correspond to the marking positions in the first CP chip image Points can be extracted. Needless to say, it is desirable to perform the above-described procedure for extracting control points for positioning at this time by automatic calculation using a computer, but it is also possible for an operator to manually confirm the procedure. (Step 202)

The coordinates of the extracted current control point are obtained by calculation (step 203), and are compared with the coordinates of the first control point to calculate the coordinates on the bed 22 of the couch 2 during the current treatment. A positional deviation (possibly including a change in body position) from the reference position of the patient is determined. The calculation of the coordinate comparison is performed in the X, Y, and Z axes. When the positional deviation is obtained in the X, Y, and Z axis directions, the positional deviation is corrected by addition / subtraction to the center coordinates of the affected part at the time of the first treatment, and is corrected with respect to the reference position of the bed. The radiation treatment target site, that is, the center position of the affected part is obtained. (Step 204)

Then, movement of the determined center position of the affected part to the isocenter 15 of the radiotherapy apparatus is controlled. (Step 205) When the center position of the affected part matches the isocenter 15 of the radiotherapy apparatus, the second treatment is executed. (Step 206)

The comparison between the MR image and the CP chip image includes the comparison of the affected part, and the shape and size of the affected part are determined by the affected part before the previous treatment and the affected part in the current MR image. If the change is greater than the value, that is, if the affected part has changed due to the treatment effect, the treatment plan should be reworked. (Step 301)

When the treatment plan is determined again, the various image data, CT control points, MR control points, CT chip file, CP chip file, and coordinate data of each point can be stored.
The re-planning can be completed by changing the center coordinate data of the affected part in addition to extracting the shape of the affected part. (Step 302)

Although the present invention has been described with reference to the drawings, the present invention is not limited to the above-described embodiment, and can be modified without departing from the scope of the invention. For example, instead of the embodiment in which the shape of the affected part, the center of the affected part, and the control points are extracted using the three-dimensional images of the X-ray CT apparatus and the MRI apparatus, the extraction is troublesome, but the two-dimensional image (slice) is used. Image).

The extraction of the control points in the MR images from the second time onward is the first in the description of the embodiment.
Although the example of performing the pattern matching with the image of the first X-ray CT has been described, it is also possible to extract the pattern by pattern matching with the first MR image.

[0058]

As described above, according to the present invention, an affected part can be extracted and designated by an image, and the affected part can be automatically positioned at the isocenter of the radiotherapy apparatus based on the data, so that positioning can be performed quickly. And accurately.
Thus, the operator can concentrate on the treatment. For this reason, the effect that the operation rate of an apparatus improves is also acquired.

Further, according to the present invention, in the second and subsequent positioning of the radiation treatment performed a plurality of times, an MR image can be taken and the positioning can be performed using only the MR image. X-ray exposure during positioning is eliminated. Furthermore, according to the present invention, since the positioning of the affected part can be mechanically performed from the image data acquired at the time of the first treatment and the image data acquired at the time of the subsequent treatment, the positioning can be performed easily and quickly.

In addition, by storing the control points in addition to the image data, it is possible to use the control points as a reference for positioning when the treatment progresses and it becomes necessary to redo the treatment plan. Because it is possible, treatment planning becomes easy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a portion related to positioning of a radiotherapy system according to a first embodiment of the present invention.

FIG. 2 is a flowchart of positioning according to the present invention.

FIG. 3 is a configuration diagram of a portion related to positioning of a radiotherapy system according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between an affected part, a chip image, and a control point according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gantry of radiotherapy apparatus 2 Bed 22 Bed 3 Gantry of MRI apparatus 36 Control unit 4 Gantry of X-ray CT apparatus 100 Patient

Claims (7)

[Claims] 1. A radiation treatment apparatus for irradiating a radiation treatment part of a patient with radiation, a medical image diagnostic apparatus for specifying the center of the radiation treatment part of the patient, an isocenter of the radiation treatment apparatus, and the medical image diagnostic apparatus A bed which is installed with a predetermined positional relationship with the image acquisition center position of the patient, places the patient thereon, and moves the treatment site between the image acquisition center position of the medical image diagnostic apparatus and the isocenter of the radiotherapy apparatus. And a couch movement control means for automatically aligning the center of the treatment site specified by the image of the diagnostic imaging apparatus with the isocenter of the radiotherapy apparatus. 2. The radiotherapy system according to claim 1, wherein the medical image diagnostic apparatus is a magnetic resonance imaging apparatus. 3. The magnetic resonance imaging apparatus measures an MR image distortion caused by an inhomogeneity of a static magnetic field or a nonlinearity of a gradient magnetic field, and uses the measured value to correct the M distortion.
3. The radiotherapy system according to claim 2, further comprising means for generating an R image. 4. A radiation treatment apparatus for irradiating a radiation treatment part of a patient with radiation, an X-ray CT apparatus for acquiring the radiation treatment part of the patient and its vicinity as a two-dimensional image or a three-dimensional image, and a radiation treatment for the patient A magnetic resonance imaging apparatus for imaging a treatment site and its vicinity as a two-dimensional image or a three-dimensional image, and an isocenter of the radiotherapy apparatus and an image acquisition center position of the magnetic resonance imaging apparatus are installed with a predetermined positional relationship. A bed having a bed on which the patient is placed and whose treatment site is moved between an image acquisition center position of the magnetic resonance imaging apparatus and an isocenter of the radiotherapy apparatus; and an image of the X-ray CT apparatus and the magnetic resonance imaging Means for identifying and storing a characteristic part near the affected part from an image of the apparatus, and a relationship between the characteristic part and the center position of the affected part And a couch movement control means for automatically aligning the center position of the affected part with the isocenter of the radiation treatment apparatus. 5. An image area smaller than an original image is set so as to include the characteristic part in a radiotherapy part of a patient acquired by the X-ray CT apparatus or the magnetic resonance imaging apparatus and an image in the vicinity thereof. The radiotherapy system according to claim 4, further comprising a unit configured to store the set small image in a readable manner. 6. The method according to claim 1, wherein the extraction of the characteristic region near the affected part on the image of the magnetic resonance imaging is performed by pattern matching with an image photographed at the time of the previous treatment in which the characteristic region is designated. 5. The radiotherapy system according to 4. 7. The radiotherapy system according to claim 4, wherein the characteristic part near the affected part and the center position of the affected part are stored as coordinates in association with each other.