KR20150065611A - Cone-Beam CT / Magnetic Resonance hybrid simulation system and method for generating reference images for radiotherapy - Google Patents

Abstract

The present invention relates to a cone-beam CT (CBCT)/magnetic resonance (MR) hybrid simulation system and a method for generating reference images for radiotherapy. The CBCT/MR hybrid simulation system of the present invention comprises: a table base; a cradle which is installed on the table base and is movable to the left and to the right on the table base; an MRI device which is installed in a top space of the table base and provides a magnetic resonance image; a CBCT device which is installed in a top space of the table base, has a collimator which limits the directions and diffusion of an X-ray to prevent the picture quality from decreasing due to a scattering of the X-ray, and provides a CT image by using the X-ray; and an image combining unit which uses position information of the MRI device and the CBCT device installed in a top space of the table base and combines an image created by the MRI device and an image created by the CBCT device. According to the present invention, the system provides a direct radiography image, automatically performs a fusion of a CT image and an MRI image, and can easily obtain a soft tissue contrast with a high picture quality. In addition, the present invention provides a reference image with a better picture quality than that of the existing ones, a higher soft tissue contrast, and a more useful image mixing information.

Description

[0001] The present invention relates to a CBCT / MR hybrid simulation system and a reference image generation method for radiotherapy,

The present invention relates to radiation therapy therapy, and more particularly, to a CBCT / MR hybrid simulation system (Cone (R)) which enables a radiotherapy treatment to be performed more accurately and efficiently by combining a CT apparatus using a cone beam with an MRI apparatus -Beam CT / Magnetic Resonance Simulation System) and a reference image generation method for radiation therapy used in a radiation treatment room.

In general, radiation therapy treatment consists of two stages: simulation and treatment. Conventional CT (computed tomography) is used in most simulations. Simulation CT is used for treatment planning. Once the plan is complete, the necessary information is sent to the treatment control system.

For treatment, the patient is placed in a position appropriate to the treatment plan with the help of typical localization imaging modality in most common modern treatment facilities. Specifically, local image modality generates a planar radiographic image and corrects an incorrect posture by comparing the reference radiographic image with a reference image obtained at the planning process stage.

Since currently used CT simulators do not provide a direct planar radiographic image in the same geometrical structure, unlike the local image modality, the image reconstructed digitally from the simulated CT image using computer software Digitally Reconstructed Radiography (DRR) is used as a reference image. As a result, compared with the localization image, the reference image has poor image quality. Also, in the case of a simulator using only MR, it is not possible to generate a DRR from an MR image, and it is common to input a virtual data to change it as if it is a CT image, and then obtain a DRR therefrom. Therefore, there is a high possibility that the image quality of the reference image deteriorates.

The advantage of high-quality local imaging is that the current clinical practice or MR simulator is not enough to know the true value. Conventional CT is also poor in image quality due to relatively poor soft tissue contrast.

A problem to be solved by the present invention is to provide a CBCT / MR hybrid simulation system that provides higher soft tissue contrast and more useful image mixing information for purposes of radiation therapy.

Another problem to be solved by the present invention is to provide a reference image of better quality than the conventional one for the purpose of radiotherapy.

According to an aspect of the present invention, there is provided a CBCT / MR hybrid simulation system including: a table base; A cradle installed on the table base and movable left and right on the table base; An MRI apparatus installed in the upper space of the table base for providing a magnetic resonance image; And a collimator provided in the upper space of the table base to limit the direction and the diffusion of the X-ray in order to prevent deterioration in image quality due to scattering of the X-ray, A Cone-Beam CT device providing computed tomography images; And an image combining unit for combining the image generated by the MRI apparatus and the image generated by the Cone-Beam CT apparatus using the MRI apparatus and the location information of the Cone-Beam CT apparatus installed in the upper space of the table base .

The collimator is a centric circular multi-slit collimator (CCMSC), and the X-ray passing through the circular multi-slit focusing unit is a multi-fanned cone beam (MFCB) .

 The Cone-Beam CT preferably includes two X-ray generators installed at right angles to each other and two circular multi-slit concentrators (CCMSC) installed at right angles to each other.

The CBCT / MR hybrid simulation system according to the present invention may further include a radiation dose calculation unit for calculating a dosage required for treatment using the image generated in the Cone-Beam CT.

According to another aspect of the present invention, there is provided a method of generating a reference image for radiotherapy, the method comprising: generating a magnetic resonance (MR) image for radiation therapy simulation using an MRI apparatus installed in an upper space of a table base; Determining a reference point for radiation therapy in the target if the target requiring radiation therapy is determined in the magnetic resonance imaging; Matching the center of the X-ray imaging system with the reference point of the magnetic resonance image; And obtaining two orthogonal plane images from the X-ray imaging system as reference images for radiation therapy.

According to the CBCT / MR hybrid simulation system according to the present invention, it is possible to provide a direct radiological image and to automatically perform fusion of a CBCT image and an MRI image.

Further, the simulation system according to the present invention includes MR, and high-quality soft tissue contrast can be easily obtained through MR imaging.

Also, with hybrid geometry, the image fusion between the CBCT and the MR is automatically made to obtain more information.

Further, it is possible to provide a reference image of higher image quality, higher soft tissue contrast, and more useful image blending information than in the conventional art, thereby making it possible to more effectively perform the radiation treatment.

1 shows the generation of a simulation image in a general CT simulator.
Figure 2 shows the generation of an image in Cone Beam CT.
FIG. 3 shows an example of comparing the image quality of the DRR image and the direct radiography of the head and neck and the chest of FIG. 1. FIG.
FIG. 4 shows an embodiment of a configuration of a CBCT / MR hybrid simulation system (Cone-Beam CT / Magnetic Resonance Simulation system) according to the present invention.
FIG. 5 shows an example of an MR image, a CT image, and a combined image of an MR image and a CT image.
6 shows Multi-Fanned Cone Beam CT (MFCBCT).
7 shows the operation of the MFCBCT.
Figure 8 shows dual energy CBCT.
Figure 9 shows an example of the advantages of a dual energy CBCT simulator with the advantages of a representative CBCT simulator.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention and therefore various equivalents And variations are possible.

1 shows the generation of a simulation image in a general CT simulator. A ring-shaped detector is provided, and simulation is performed under fan beam geometry. (DRR) images are generated as reference images instead of directly obtained planar images.

Figure 2 shows the generation of an image in a Cone Beam CT. The X-ray source 200 projects a X-ray while turning the object 210 in the center, and then, through a flat panel detector 230, And obtains a planar local image in the direction. Meanwhile, in the treatment room, a cone beam geometry having a flat panel detector 230 is used, and direct radiographic images are acquired for localization. Therefore, in the current simulation technique using the DRR as the reference image, the reference image has poor image quality than the local image.

FIG. 3 shows a comparison between the DRR images of the head and neck and the chest of FIG. 1 and the image quality of Direct Radiography. As shown in FIG. 3, it can be seen that the image quality of the Direct Radiography is much clearer than that of the DRR image.

FIG. 4 shows an embodiment of a configuration of a CBCT / MR hybrid simulation system (Cone-Beam CT / Magnetic Resonance Simulation system) according to the present invention. One embodiment of the CBCT / MR hybrid simulation system according to the present invention includes a table base 400, a cradle 410, an MRI apparatus 420, a Cone-Beam CT apparatus 430, And a combining unit 440, and further includes a DOSE calculating unit 450.

Referring to FIG. 4, a cradle 410 is installed on a table base 400 and is movable left and right on the table base.

The MRI apparatus 420 is installed in an upper space of the table base 400 and provides a magnetic resonance (MR) image. The MRI image is known to be superior to CT in soft tissue image acquisition, and the simulator according to the present invention can provide a high-quality soft tissue contrast over a conventional CT simulator image.

The Cone-Beam CT apparatus (MFCBCT) 430 is installed in the upper space of the table base 400 and is a collimator for limiting the X-ray direction and diffusion to prevent image deterioration due to X- And provides a computerized tomography image and a planar image using X-rays. When the scattered X-rays touch the detector, it causes the deterioration of the image quality. When the converters are used, the amount of the scattered X-rays can be known and the image can be corrected when the image is generated.

Preferably, the collimator is a centric circular multi-slit collimator (CCMSC), and the X-ray passing through the circular multi-slit focusing unit is a multi-fanned cone beam, MFCB).

The image combining unit 440 may convert the image generated by the MRI apparatus 420 and the image of the Cone-Beam CT apparatus 430 using the position information of the MRI apparatus 420 and the Cone-Beam CT apparatus 430 installed in the upper space of the table base 400, Combine the images generated by the Beam CT apparatus 430. [ That is, in the system according to the present invention, since the MR image and the CT image are consecutively formed on the same table, the MR image and the CT image can be automatically combined only with the position information of the table.

FIG. 5 shows an image obtained by combining an MR image, a CT image, and an MR image and a CT image, and shows image quality of the CT 520, the MR 500, and the image fusion between the CT and the MR. Referring to FIG. 5, in the image 520 of the CT, markers inserted in a patient's body are clearly displayed to assist localization. In the MR image 500, the prostate is clearly displayed. In the image 540 in which the CT image 520 and the MR image 500 are mixed, it can be seen that the prostate and the markers are clearly displayed. Image fusion allows DOES calculations to calculate the radiation dose required for treatment, and high soft tissue contrast can be obtained. In addition, as the MR image moves from the center of the entire body of the patient body to the outside, the deformation increases and the accuracy may be a problem. This disadvantage can be solved by the CT image. The CT image is more advantageous than the MR image in the body contouring problem, so correction of the deformity is possible.

The DOSE calculation unit 450 calculates the dose of radiation required for the treatment using the image generated by the Cone-Beam CT 430.

6 shows Multi-Fanned Cone Beam CT (MFCBCT). In order to minimize the image quality degradation due to X-ray scattering, the Multi-Fanned Cone Beam CT (MFCBCT) has been used for a cone-beam CT image with reduced scattering of X- And direct radiation reference images. To this end, a multi-fanned cone beam (MFCB) geometry is implemented by providing a centric circular multi-slit collimator (CCMSC) 602.

7 shows the operation of the MFCBCT. The circular multislit concentrator (CCMSC) 602 has open and closed septa, which are arranged in equi-angular intervals on a circular track in a central sagittal plane Is located. Thus, once a gantry rotates, you can only get half of the data set you need, and when you do two gantry rotations, you can get the entire data set you need. Referring to FIG. 7, during the first rotation of the gantry, the relative position of the CCMSC to the source is fixed. In the second rotation, the CCMSC rotates at an equi-angular interval. Thus, in the first turn, the open septa becomes the closed septa in the second turn and in the first turn the closed septa becomes the open septa in the second turn. In this way, all the necessary information is obtained by two rotations.

On the other hand, some signals are also obtained in the closed septa, which can be assumed to be caused entirely by scattered X-rays, and this information can be used to calculate the interpolation method in the open septa scatter contribution.

Now, the scattered ray signal is subtracted from the entire signal and the enhanced image is obtained using only the information.

Preferably, the Cone-Beam CT includes two X-ray generators installed at right angles to each other, two circular multi-slit concentrators (CCMSC) and two flat panel detectors installed at right angles to each other Do.

Figure 8 shows dual energy CBCT. Referring to FIG. 8, the dual energy CBCT includes a first X-ray source 800, a first CCMSC 810, a first flat panel detector 820, a second X-ray source 850 (CCMSC) 860, and a second flat panel detector 870. The second flat panel detector 870 includes a first flat panel detector 860,

The CBCT / MR hybrid simulation system according to the present invention can directly obtain a planar reference image (DRR) instead of the DRR (Cone-Beam CT / Magnetic Resonance Simulation System). That is, direct radiography. The process of obtaining the planar reference image may be described in connection with a method of using the system according to the present invention. First, after acquiring the MR image for simulation, the person in charge determines the position of the target to be treated and designates the reference point for the radiation treatment. The location information of the target and the reference point may be obtained through computer software.

 When the table is moved so that the reference point on the MR image coincides with the center of the X-ray image system, and the two orthogonal (i.e., intervals of 90 degrees) planar images are obtained, the obtained images become reference images. The two orthogonal plane images can be obtained by photographing in a 90 degree difference direction using an X-ray imaging system or by using an X-ray equipment capable of obtaining orthogonal images at one time, Can be obtained.

On the other hand, a reference image can be obtained regardless of the CBCT. MR imaging is performed by MRI scanning for radiation therapy simulation. When the MR image is generated, the person in charge designates the target to be treated in the MR image, and determines the isocenter accordingly. The isocenter may be determined automatically using software.

Then, when the patient is moved and fixed using the table so that the isocenter portion matches the center of the x-ray system, and then two orthogonal x-ray images are obtained, this is referred to as a reference image set ).

The system according to the present invention also automatically generates image fusion, the DOSE calculation is provided using CT images, and the soft tissue contrast is excellent.

Figure 9 shows the basic advantages of the CBCT simulator and further advantages obtained from the Dual Energy CBCT simulator. Referring to FIG. 9, when comparing the direct radiographic setup reference image (DRI) with the conventional reference image, the direct radiographic setup reference image (DRI) according to the present invention is much clearer than the conventional reference image. The metal artifacts are also significantly reduced. It also provides a virtual contrast-free image, which is a sensitive problem in charged particle therapy, which is removed through image processing. Since the contrast material is needed at the simulation stage but does not exist at the actual treatment, the accuracy is improved by removing the DOSE when calculating it.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. For example, a reference image generally consists of two images acquired from different angles as a set. In Dual Energy CBCT simulator, two images are obtained at the same time. Therefore, spatial information Can be eliminated. In addition, it is possible to independently generate general bone radiography as well as bone image and tissue image by image processing.

Meanwhile, the conventional simulator for radiation therapy is CT based. Recently, a study and an attempt have been made on a simulator using an MR having excellent soft tissue image. When using MR, there are two problems to be solved. One provides the information needed for DOSE computation, but the MR does not. Second, there is generally no MR in the treatment room, so you can not use images obtained directly from the MR as reference images for patient setup. This problem actually exists in existing CT simulators, and this is solved by DRR.

Returning to the MR simulator again, a general solution to the above-mentioned problems is to add the above-described virtual information to the MR image to make it like a CT image. In this case, it can be said that the uncertainty is basically growing.

The present invention provides a system in which these problems do not exist or can be easily solved. If necessary, CBCT can be performed to provide information necessary for calculation of DOES by combining X-rays of MR and cone beam geometry capable of rotation. As described above, Video can also be provided. For the sake of simplicity, the x-ray image is directly referenced to distinguish it from the DRR, which is the same as a normal x-ray image.

Image fusion usually refers to a process in which different types of images for the same patient, such as MR and CT, are positioned at the same position to maximize the advantages of both to obtain more information. Generally, images are acquired through two separate imaging devices at different times, so the coupling process is a little complicated and the patient's posture may be different, which may result in less accuracy in spatial combination. The present invention overcomes this problem because two images are consecutively made on the same table in the same posture.

400: table base
410: cradle (movable table)
420: MRI apparatus
430: Cone-Beam CT device
440:
450: DOSE calculation unit
800: first X-ray source
810: a first centric circular multi-slit collimator (CCMSC)
820: 1st Flat Panel Detector
850: second X-ray source
860: a second centric circular multi-slit collimator (CCMSC)
870: 2nd Flat Panel Detector

Claims (5)

Table base;
A cradle installed on the table base and movable left and right on the table base;
An MRI apparatus installed in an upper space of the table base for providing a magnetic resonance image;
And a collimator provided in the upper space of the table base for limiting the direction and the diffusion of the X-ray to prevent a deterioration in image quality due to scattering of the X-ray, And a Cone-Beam CT device providing computed tomography images; And
And an image combining unit that combines the image generated by the MRI apparatus and the image generated by the Cone-Beam CT apparatus using the position information on the table of the MRI apparatus and the Cone-Beam CT apparatus installed in the upper space of the table base, And a coupling unit for coupling the CBCT / MR hybrid simulation system to the CBCT / MR hybrid simulation system. The apparatus of claim 1, wherein the collimator comprises:
A centric circular multi-slit collimator (CCMSC)
Wherein the X-ray passing through the circular multi-slit focusing unit forms a multi-fan cone beam (MFCB). 3. The method of claim 2, wherein the Cone-Beam CT
And two circular multi-slit concentrators (CCMSCs) installed at right angles to each other, and two X-ray generators installed at right angles to each other. The method of claim 3,
Further comprising a DOSE calculation unit for calculating a dose of radiation necessary for the treatment using the image generated by the Cone-Beam CT. Generating a magnetic resonance (MR) image for radiation therapy simulation using an MRI apparatus installed in an upper space of a table base;
Determining a reference point for radiation therapy in the target if the target requiring radiation therapy is determined in the magnetic resonance imaging;
Matching the center of the X-ray imaging system with the reference point of the magnetic resonance image; And
And acquiring two orthogonal plane images from the X-ray imaging system as reference images for radiation therapy.

Images