JPH10113400A - Radiotherapy system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operability by adjusting a rotational coordinate system drawn by an X-ray CT device and a rotational coordinate system drawn by a radiotherapy device, and setting therapeutic radioactive ray irradiation area data of the radiotherapy device on the basis of data by measuring a subject by the X-ray CT device. SOLUTION: A patient 1 is put on a bed 2, and projection data for a therapeutic plan is gathered by a scanner 3 and an image reconstituting device 4, and a scanner image or a slice image is obatined from the gathered projection data, and is displayed on a display means. A radioactive ray irradiation area is set by a radiotherapy device 8 by operating a console while referring to the displayed image. In this case, a sinogram (reprojection data) of an irradiation expected area is prepared by a reprojection converter 6, but in this case, when a radius RA of gyration of an X-ray source of an X-ray CT device and a radius RB of gyration in the radiotherapy device 8 are different from each other, the sinogram is converted into a sinogram to set a radioactive ray irradiation area from the ratio of RA to RB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiotherapy system using an X-ray CT apparatus, and more particularly, to converting projection data obtained by an X-ray CT apparatus into irradiation direction data and irradiation width data of radiation in the radiotherapy apparatus. The present invention relates to a radiation therapy system that converts the radiation direction data and irradiation width data of the radiation and controls the radiation therapy device based on the data.

[0002]

2. Description of the Related Art In a conventional radiotherapy apparatus, a radiation irradiation head can rotate around a patient about a patient's body axis as a center axis, so that the radiation can be irradiated obliquely depending on the rotational position. In addition, a multi-leaf collimator capable of forming various irradiation fields has been put into practical use, and it has become possible to irradiate only the affected part with radiation.

[0003] Incidentally, medical image diagnostic apparatuses for planning treatment of a radiation therapy apparatus include an X-ray fluoroscope, an ultrasonic apparatus, and an M-ray diagnostic apparatus.
An RI device and an X-ray CT device are used. It is difficult for the X-ray fluoroscopy apparatus and the ultrasound apparatus to obtain three-dimensional information of the subject, and for the MRI apparatus, although various high-speed sequences have been developed, it is difficult to obtain high-definition images in real time. X-ray CT equipment has recently been launched in Tokiko 7-67445.
It is possible to continuously obtain a tomographic image of a subject by a spiral scan as shown in Japanese Patent Application Laid-Open Publication No. H10-209, and obtain the three-dimensional information in real time.

[0004]

However, the above-mentioned prior art is based on a rotating coordinate system which describes a rotation for measuring data of an X-ray tube with respect to a subject in an X-ray CT apparatus, and a radiation irradiation head for a patient in a radiation therapy apparatus. In many cases, the rotation coordinate system drawn by the rotation is different. In order to use data measured by such an X-ray CT apparatus in a radiation therapy apparatus, there has been a problem that each rotating coordinate system must be matched.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to match a rotational coordinate system drawn by an X-ray CT apparatus with a rotational coordinate system drawn by a radiotherapy apparatus, and An object of the present invention is to provide a radiotherapy system using an X-ray CT apparatus capable of setting therapeutic radiation irradiation area data of a radiotherapy apparatus based on data obtained by measuring a subject by the apparatus.

[0006]

An object of the present invention is to rotate an X-ray source that emits X-rays toward a patient and an X-ray detector that detects X-rays transmitted through the patient as projection data, around the patient. A radiation treatment system that uses an X-ray CT device that measures projection data in multiple directions to irradiate high-energy radiation from around the patient to plan an irradiation pattern of the radiation treatment device. Means for inputting and setting an affected part requiring radiation treatment in an image obtained by the method, and first position data of the affected part viewed from a plurality of rotation positions of an X-ray source of an X-ray CT apparatus rotating around the set affected part Means for calculating a group, and the first diseased part position data group is obtained from a plurality of radiation sources of the radiation therapy apparatus from the ratio of the rotation radius of the X-ray source of the X-ray CT apparatus to the rotation radius of the radiation source of the radiation therapy apparatus. Of the affected part viewed from the rotation position Means for converting the second position data group, is achieved by the second position data group and means for converting the control data of the collimator of the radiation therapy device.

In addition, an X-ray source that emits X-rays toward a patient and an X-ray detector that detects X-rays transmitted through the patient as projection data are rotated around the patient to measure projection data in multiple directions. A radiation therapy system for irradiating high-energy radiation from around the patient and treating the radiation pattern using an X-ray CT device,
Means for inputting and setting an affected area requiring radiotherapy in an image obtained by the X-ray CT apparatus, and the position of the affected area viewed from a plurality of rotation positions of an X-ray source of the X-ray CT apparatus rotating around the set affected area This is achieved by providing means for calculating a data group and means for converting the position data group into control data of a collimator of the radiation therapy apparatus.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the radiation therapy system of the present invention will be described with reference to the drawings.

The X-ray CT apparatus employed in the radiation therapy system has a configuration as shown in FIG. This X-ray CT
The apparatus includes a bed 2, a scanner 3, an image reconstruction device 4, a condition input device 5, a reprojection data conversion device 6, and a control data conversion device 7.

The bed 2 places the patient 1 thereon. The scanner 3 has an opening through which the patient 1 is inserted.
The X-ray source and the X-ray detector are opposed to each other and attached to a rotating plate, and the X-ray source and the X-ray detector are rotated while irradiating the X-ray from the X-ray source. The image reconstruction device 4 performs X-ray imaging along the body axis direction of the patient 1 based on the projection data obtained from the X-ray detector.
Obtain a scanogram such as a fluoroscopic image, and use an X-ray source and X-ray
A slice image is obtained from multidirectional projection data obtained by rotating the line detector around the patient 1. The condition input device 5 is an imaging condition such as an X-ray irradiation condition by an operator, a measurement time determined by the rotation time of the scanner 3, and a moving amount of the bed 2 in the body axis direction of the patient 2 when performing a spiral scan. While inputting an input condition such as an area for irradiating radiation while viewing the scano image or the slice image. The projection data conversion device 6 converts the projection data into reprojection data (hereinafter, referred to as “sinogram”) based on the irradiation scheduled area. The control data conversion device 7 converts the sinogram into control data of a radiation irradiation area of the radiation therapy device.

Also, an irradiation system including a high-energy radiation source and a collimator for controlling an irradiation area of the high-energy radiation source is provided in parallel with the X-ray CT apparatus. A shield provided to prevent radiation from leaking beyond the reference value, and a radiation therapy apparatus 8 having a mechanism for rotating these irradiation systems and the shield are installed.

Next, the operation of the X-ray CT apparatus will be described. The patient 1 is placed on the bed 2 and the scanner 3 and the image reconstruction device 4 collect projection data for treatment planning. A scan image or a multi-directional projection data obtained from the acquired projection data along the body axis direction of the patient is reconstructed to obtain a slice image, and the slice image is displayed. The operator sets a radiation irradiation area to be irradiated with radiation by the radiation therapy apparatus 8 using the track ball or the like of the console while referring to the displayed image. The reprojection conversion device 6 creates a sinogram of the irradiation scheduled area as shown in FIG.

FIG. 2 is a diagram showing the principle of obtaining a sinogram from projection data. The orbit A in FIG. 2A is an X-ray CT
The trajectory of the rotation of the X-ray source and the X-ray detector of the apparatus is shown, and the trajectory B is the trajectory of the rotation of the high energy radiation source of the radiation therapy apparatus. It is assumed that these trajectories A and B are concentric circles of radii RA and RB (RA> RB) centered on the point O, respectively.

A method of converting projection data into a sinogram is to reconstruct the image of the projection data into a slice image, assuming the rotation of the X-ray source with respect to the reconstructed slice image to a geometric enemy, and determining the rotation angle of the X-ray source. Are set, and the position of the affected part requiring radiation treatment with respect to each rotation angle θ of the X-ray source is obtained as angles φ1 and φ2 shown in the figure. The sinogram obtained in this way is shown in FIG.

However, when the rotation radius of the X-ray source in the X-ray CT apparatus is different from the rotation radius of the radiation source in the radiation treatment apparatus, the data of the sinogram is used as the setting data of the radiation irradiation area of the radiation treatment apparatus. Can not.

Then, the first sinogram is converted to obtain a second sinogram 設定 for setting a radiation irradiation area of the radiation therapy apparatus. The conversion from the first sinogram to the second sinogram is simply a geometric conversion, where the radius of gyration of the X-ray source in the X-ray CT apparatus is RA and the radius of gyration of the radiation source in the radiation therapy apparatus is RB. Perform by doing.

Next, the principle of creating control data will be described with reference to FIG. In the second sinogram, X
From the position data of the affected part obtained by the X-ray CT apparatus, the irradiation area in the radiation therapy apparatus is obtained as angles φ1 ′ and φ2 ′, so this is the collimator control data for setting the radiation irradiation area in the radiation therapy apparatus Cannot be used directly. Therefore, it is necessary to convert the angle information φ1 and φ2 into data of the amount of movement of the collimator or the size of the aperture.
Hereinafter, the conversion method will be described.

FIG. 3 shows a principle diagram for converting a sinogram into control data. There are several mathematically conceivable methods for converting the angle information φ1 ′ and φ2 ′ into the movement amount or aperture size of the collimator. In the present embodiment, the angle information φ1 ′ and φ2 ′ are A method of converting the distance to the distance and obtaining the distance will be described.

FIG. 3A is a diagram in which the sinogram is arranged in the direction of the rotation angle of the radiation source or the like with the irradiation width direction of the radiation source of the radiation therapy apparatus as the horizontal axis, and FIG. 3B is the irradiation through the rotation angle p. FIG. 3C is a diagram illustrating a collimator opening width when a radiation source passes through a point O ′ at a point O ′ crossing the center axis in the width direction when viewed from a side surface in the irradiation width direction.

The control data is obtained from the parameters of the rotation angle of the radiation source, the extraction direction, the aperture width of the collimator, and the position of the sinogram. The extraction direction is the direction when a radiation source is covered with a shielded container and a window for extracting radiation in only one direction is provided.

In FIG. 3, the distance from the point O through which the radiation source passes through the rotation angle p to the point O 'on the projection plane on which the sinogram is arranged is h, the distance between the point O' and the center Op 'of the sinogram is dp, and the point is dp. Assuming that an angle formed by connecting the points O ′, O, and Op ′ is θ, the angle θ is θ = dp / h (1). The take-out direction is defined by this angle θ, as shown in FIG.

Assuming that the width of the sinogram is d, the distance from the point O to the collimator is h ', and the opening width of the collimator is w, the opening width w is, as shown in FIG. '× tan (d / 2 × h) (2)

Such a rotation irradiation plan is continuously performed for each rotation angle at which a normal slice image is obtained.

When the collimator of the radiation therapy apparatus is called a multi-leaf type formed by a plurality of blades, the aperture width of the collimator is calculated and set for each blade pair.

Next, the area which should not be irradiated with radiation,
An example for avoiding the spine, for example, will be described with reference to FIG.

FIG. 4A shows an example of an irradiation prohibited section (a section on the trajectory B where radiation irradiation must be stopped) while displaying a radiation irradiation area and a irradiation prohibition area together in a slice image. FIG. 4B is a diagram showing an example in which the sinogram of the irradiation prohibited area is subtracted from the sinogram of the irradiation area to obtain the sinogram of the corrected irradiation area.

The procedure for not irradiating the irradiation-prohibited area is as follows. After specifying the irradiation area, specifying and inputting the irradiation-prohibited area in the same manner as the irradiation area, obtaining a sinogram corresponding to each area, and prohibiting the irradiation from the sinogram of the irradiation area. The sinogram of the corrected irradiation area is obtained by subtracting the sinogram of the area, and the control data conversion device 7 creates control data based on the sinogram of the corrected irradiation area.

As described above, according to the present embodiment, the condition input device 5 for setting and inputting a sinogram by rotating the irradiation area formed by the radiation source, and the multi-directional sinogram based on the input sinogram. Since a projection data is obtained and the projection data is provided with a reprojection data conversion device 6 for performing coordinate conversion from the rotation coordinate system drawn by the X-ray CT device to the rotation coordinate system drawn by the radiotherapy device, the X-ray CT The rotation coordinate system drawn by the apparatus and the rotation coordinate system drawn by the radiation therapy apparatus can be matched.

In the above embodiment, the irradiation direction and the collimator opening angle have been described as examples for specifying the irradiation field of the radiation therapy apparatus. However, in order to obtain three-dimensional information, the irradiation direction and the collimator opening angle are applied in the slice thickness direction. Is also good. Further, although the image obtained by the X-ray CT apparatus to obtain the sinogram is a slice image, a scanogram (X-ray fluoroscopic image) may be used instead.

Further, the opening width of the collimator that determines the X-ray irradiation area of the X-ray CT apparatus may be directly converted and controlled as the irradiation width of the radiotherapy apparatus.

[0031]

Since the present invention has the above-described configuration and operation, the X-ray C in which the rotational coordinate system drawn by the X-ray CT apparatus and the rotational coordinate system drawn by the radiotherapy apparatus are matched.
There is an effect of providing a radiation therapy system using the T device.

[Brief description of the drawings]

FIG. 1 shows an X-ray C used in a radiotherapy system according to the present invention.
The figure which shows the structural example of a T apparatus.

FIG. 2 is a view showing the principle of obtaining a sinogram from projection data.

FIG. 3 is a principle diagram for converting a sinogram into control data.

FIG. 4 is a diagram showing an example of avoiding an irradiation prohibited area.

[Explanation of symbols]

 5 Condition input device 6 Reprojection data conversion device 7 Control data conversion device

Claims (2)

[Claims] 1. An X-ray source that emits X-rays toward a patient and an X-ray detector that detects X-rays transmitted through the patient as projection data are rotated around the patient to measure projection data in multiple directions. In a radiation therapy system for irradiating high-energy radiation from around a patient and treating the radiation pattern using an X-ray CT device, the X-ray C
Means for inputting and setting an affected part requiring radiotherapy in an image obtained by the T apparatus, and a first part of the affected part viewed from a plurality of rotational positions of an X-ray source of an X-ray CT apparatus rotating around the set affected part. Means for calculating the position data group of the X-ray CT apparatus and the ratio of the rotation radius of the X-ray source of the X-ray CT apparatus to the rotation radius of the radiation source of the radiation treatment apparatus. Means for converting to a second position data group of the affected part viewed from a plurality of rotational positions, and means for converting the second position data group to control data of the collimator of the radiation therapy apparatus, Radiation therapy system. 2. An X-ray source for exposing X-rays to a patient and an X-ray detector for detecting X-rays transmitted through the patient as projection data are rotated around the patient to measure projection data in multiple directions. In a radiation therapy system for irradiating high-energy radiation from around a patient and treating the radiation pattern using an X-ray CT device, the X-ray C
Means for inputting and setting an affected area requiring radiotherapy in an image obtained by the T apparatus, and position data of the affected area viewed from a plurality of rotation positions of an X-ray source of an X-ray CT apparatus rotating around the set affected area A radiotherapy system comprising: means for calculating a group; and means for converting the position data group into control data of a collimator of the radiotherapy apparatus.