WO2021158079A1

WO2021158079A1 - Computer tomography device comprising rotational beam-shielding structure, and method

Info

Publication number: WO2021158079A1
Application number: PCT/KR2021/001587
Authority: WO
Inventors: 이호; 이익재
Original assignee: 연세대학교 산학협력단
Priority date: 2020-02-05
Filing date: 2021-02-05
Publication date: 2021-08-12
Also published as: KR102344158B1; KR20210099907A

Abstract

Disclosed is a computer tomography device including a rotational beam-shielding unit, and in particular, a cone beam-type computer tomography device for improving distortions in a radiographic image caused by scattering. A computer tomography device of the present invention comprises: a gantry formed to be rotatable; a light source module which emits a radiographic imaging beam onto a subject; and a beam-blocking module which is located on the path from the light source module to the subject, selectively blocks a portion of the treatment beam or the imaging beam emitted from the light source module, and includes a shielding unit that is provided to be rotatable.

Description

Computed tomography apparatus and method including rotating beam shielding structure

The present invention relates to an apparatus and method for computed tomography, and more particularly, to a cone-beam type computed tomography apparatus and method for improving image quality deterioration due to a scattered beam. The research on the present invention was supported by the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning, and the high-speed, high-definition single-source dual-energy cone beam CT imaging technology development project for next-generation image-guided radiation therapy (2017M2A2A6A01070330, 2017-2020) and related It is also related to the core technology development project (2019R1I1A1A01062157, 2019-2022) for the generation of deep cone-beam-type computed tomography images, supported by the National Research Foundation, funded by the Ministry of Education.

Advances in radiation therapy technology have enabled advanced treatments such as stereotactic body radiation therapy (SBRT). SBRT can dramatically shorten the treatment period by dividing the number of treatments from 1 to 3 to 4 times and irradiating high-dose radiation. However, due to the large number of beam irradiation times per session, the treatment time of patients lying on the treatment table is increasing. Therefore, precisely monitoring and evaluating the patient's posture and changes during radiation therapy is a very important task that determines the success or failure of radiation therapy. am.

In advanced radiation therapy that requires higher accuracy in positioning the patient, the process of monitoring in real time whether the accurately planned dose is delivered to the patient during treatment is very important, but the current CBCT (Cone Beam CT) It is used to set the same position as when establishing a treatment plan for treatment or as a confirmation imaging device to quantify whether there is a change in patient posture between before and after treatment, but does not provide anatomical information during beam delivery.

With the addition of an option called Intrafraction Imaging, it is possible to acquire CBCT X-ray images simultaneously with Volumetric Modulated Arc Therapy (VMAT) through a flat-panel detector, so that the location of the tumor shown in the image is different from the actual beam. It is judged by the location of the tumor at the time of delivery, so it is possible to monitor the deformation and movement of the affected area. If CBCT X-ray images are acquired at the same time as VMAT, CBCT volume images can be generated during intrafraction, but MV X-rays and kV X-rays interact with particles inside the object, so As a result, the overall image quality deteriorates, and its clinical use is very limited. In particular, the CBCT with a detector with a large irradiation area has a problem in that it is difficult to obtain an accurate image because the effect of the scattered beam increases exponentially compared to the general CT.

In consideration of the limitations of the prior art, the present invention provides a computed tomography apparatus, which enables to more accurately determine the deformity and movement state of the affected area during treatment by improving the quality degradation of the computed tomography image due to the scattered beam. intended to provide

The present invention also provides a rotating beam blocking device for use in a computed tomography apparatus, in particular for prediction of scattered light incident on a detector in a cone beam type computed tomography apparatus. The beam blocking apparatus of the present invention is located between the imaging beam module of the radiation imaging apparatus and the detector, and is capable of more accurately predicting a scattered beam map through an operation of continuously blocking or non-blocking at least a portion of an image beam incident to the detector. make it possible

In addition, the present invention generates a model for the movement of a target during radiation treatment, recalculates the dose distribution for the target and adjacent risk organs using CBCT during segmentation treatment, and adaptive radiotherapy using CBCT images during segmentation treatment ( Adaptive Radiotherapy) aims to provide a technology that can be applied to clinical practice.

Other objects not specified in the present invention may be additionally considered within the scope that can be easily inferred from the following detailed description and effects thereof.

In order to solve the above technical problem, the computed tomography apparatus of the present invention includes a gantry formed to be rotatable; a light source module irradiating a radiation image beam to the subject; and a beam blocking module positioned in a path between the light source module and the subject to selectively block a portion of the treatment beam or image beam irradiated from the light source module, and including a rotatable shielding unit.

In the present invention, the shielding unit has a blocking region that selectively blocks the image beam and a non-blocking region that does not block the image beam. In addition, the blocking area of the shielding unit has a structure in which a strip portion that blocks the image beam irradiated from the image beam module and an open portion that does not block the image beam are alternately disposed. In addition, in a blocking section in which the image beam irradiated from the image beam module is blocked from the viewpoint of the time domain, a portion of the image beam may be continuously blocked.

The beam blocking module of the present invention may further include a driving wheel having an open inner shape and provided to be rotatable, and a motor for rotating the driving wheel. The shielding part may be located inside the driving wheel, and the shielding part may include arc-shaped strips arranged so that the strip part and the open part have a circular arc shape with respect to a rotation center of the driving wheel.

The computed tomography apparatus of the present invention provides a plurality of projection data for an object to be inspected, wherein the plurality of projection data is acquired irrespective of the influence of the scattered beam obtained by the selective blocking of the beam blocking module and the blocking effect. an image acquisition unit for acquiring - including an image according to the primary beam; and an image processor configured to generate a scattered beam map by estimating a scattered beam map from a plurality of projection data, and to generate a reconstructed image in which scattering is suppressed by using the scattered beam map.

The image acquisition unit may continuously acquire first projection data obtained when the image beam is partially blocked by rotation of the shielding unit and second projection data obtained when the image beam is not blocked in a time domain. there is.

In the present invention, the shielding portion may include arc-shaped strips arranged at regular intervals in at least a portion of the region. Estimating the scattered beam map from the projection data obtained through the shield having the structure of such an arc-shaped strip is,

An initial scattering beam map obtained under the influence of selective blocking according to the structure of the arc-shaped strip is interpolated, but a scattering beam map is obtained by interpolating the scattering beam in a direction orthogonal to an arc that can be defined according to the arc-shaped strip structure. It may further include the step of estimating.

In the present invention, the image processing unit performs distance-based weighted summing of first projection data at a first viewpoint and first projection data at a second viewpoint adjacent to the first viewpoint between the first viewpoint and the second viewpoint. Estimate a scattered beam map for the second projection data located in . In addition, the image processing unit of the present invention estimates a scattering beam map using the first projection data, and reconstructs a 3D scattering volume through backprojection on the estimated scattering beam map, A scattering beam map for the second projection data may be estimated by reprojecting the 3D scattering volume.

In addition, the image processing unit of the present invention generates scatter corrected data through a subtraction operation between the second projection data and the scatter beam map for the second projection data estimated by the method, and the scattering correction data can be used to generate a reconstructed image in which scattering is suppressed.

In the present invention, the computed tomography apparatus is a cone beam type computed tomography apparatus, and the light source module includes: a radiation module for irradiating a radiation treatment beam to the subject; and an imaging beam module configured to irradiate an imaging beam to the subject, wherein the radiation therapy beam and the imaging beam overlap at least in a partial intersection region.

In order to achieve another object of the present invention, a beam blocking device for removing noise caused by a scattered beam in a computed tomography image obtained by the computed tomography apparatus of the present invention includes: a driving wheel having an open inner side; a motor for generating rotational driving force; and a shielding unit positioned on a path between the light source module and the subject to selectively block a portion of the image beam irradiated from the light source module, but rotated according to the rotational driving force of the motor.

In the beam blocking device of the present invention, the shielding unit has a blocking region that selectively blocks the image beam and a non-blocking region that does not block the image beam, and the blocking region of the shielding unit includes the image beam irradiated from the image beam module. It has a structure in which a strip portion that blocks the image beam and an open portion that does not block the image beam are alternately arranged. The shielding unit has an arc-shaped structure so as to continuously block a portion of the image beam in a blocking section that blocks the image beam irradiated from the image beam module in the time domain.

In particular, the shielding portion preferably includes an arc-shaped strip in which the strip portion and the open portion are arranged to have an arc shape with respect to a rotation center of the driving wheel.

In order to achieve another object of the present invention, a computed tomography method by a computed tomography apparatus of the present invention includes: irradiating a radiation treatment beam to a subject; irradiating an image beam onto a path of a radiation treatment beam irradiated from the radiation module to an image beam module; continuously blocking or non-blocking at least a portion of the image beam irradiated from the imaging beam module with a beam blocking module located in a path between the imaging beam module and the subject; acquiring a plurality of projection data by detecting a radiation treatment beam that has passed through the subject and a scattered beam scattered by the image beam; and generating a reconstructed image by estimating a scattered beam map for the plurality of projection data.

The computed tomography apparatus for performing the computed tomography method of the present invention may further include a shielding unit formed of an arc-shaped strip arranged at regular intervals in at least a portion of the region. The estimating of the scattering beam map includes interpolating an initial scattering beam map obtained under the influence of selective blocking according to the structure of the arc-shaped strip, in a direction orthogonal to an arc that can be defined according to the structure of the arc-shaped strip. It is desirable to estimate the scattered beam map by interpolating the scattered beam.

In order to achieve another object of the present invention, the cone-beam-type computed tomography method by the cone-beam-type computed tomography apparatus of the present invention includes the steps of irradiating a radiation treatment beam to a subject with a radiation module, and using the image beam module as described above. irradiating an image beam on a path of a radiation therapy beam irradiated from a radiation module, and continuously applying at least a portion of the image beam irradiated from the imaging beam module to a beam blocking module located in a path between the imaging beam module and the subject blocking or non-blocking, detecting a radiation treatment beam that has passed through the subject and a scattered beam scattered by the image beam to obtain a plurality of projection data and scattering of the plurality of projection data and generating a reconstructed image by estimating the beam map.

Here, the beam blocking module includes a drive wheel rotatable in one direction and having an open inner side, a motor for rotating the drive wheel, and a shield provided to cover at least a portion of the inner side of the drive wheel, The shielding part has a structure in which a plurality of arc-shaped strips are disposed to coincide with the rotational direction of the driving wheel.

Here, the acquiring of the plurality of projection data may include, by rotation of the shielding part, first projection data when the image beam is blocked and second projection data when the image beam is not blocked. obtained successively.

Here, the step of generating a reconstructed image by estimating a scattered beam map for the plurality of projection data is orthogonal to the arc-shaped strip shape in the projection data when the image beam is blocked by the shielding unit. The scattered beam map is estimated by applying interpolation to the direction.

Here, the step of generating a reconstructed image by estimating a scattering beam map for the plurality of projection data includes estimating a scattering map for the entire first projection data and using a backprojection to perform a 3D scattering volume ( 3D Scatter Volume) and reprojecting the 3D scattering volume to estimate and generate a scattering map for the entire second projection data.

Here, the generating a reconstructed image by estimating a scattering beam map for the plurality of projection data includes subtracting a scattering map for the second projection data estimated from the second projection data to obtain scatter corrected data (Scatter Corrected Data). ) and generating the reconstructed image from the scattering correction data using a reconstruction algorithm.

In order to achieve another object of the present invention, a computed tomography imaging method of the present invention comprises: irradiating, by a light source module, an image beam on a path of a radiation treatment beam irradiated from the radiation module; rotating the shielding unit to selectively block the irradiated image beam during a first time period and not to block the irradiated image beam during the second time period; obtaining first projection data obtained when the image beam is partially blocked and second projection data obtained when the image beam is not blocked with rotation of the shielding unit; estimating a scattered beam map using the first projection data; estimating a scattered beam map for the second projection data using the estimated scattered beam map; and generating a reconstructed image by using the scattered beam map for the estimated second projection data.

The present invention further provides a computer application program for performing the above-described computed tomography method on a computer or a computer-readable recording medium in which the computer application program is recorded.

According to the present invention, a radiation module connected to a gantry and irradiating a radiation treatment beam to a subject, an image beam module irradiating an image beam on a path of a radiation treatment beam irradiated from the radiation module, and the image beam module and the subject By adopting a blocking structure including a beam blocking module that is located in the path between the cadavers and continuously blocks or does not block at least a portion of the image beam irradiated from the imaging beam module, the problem of image quality degradation due to scattering can be improved there is. In particular, obtaining a scattering beam passing through a rotational shielding structure configured in an arc-shaped strip shape is a major factor in improving the accuracy of estimation for a scattering beam map.

According to the present invention, by improving the quality of a medical image, it is possible to accurately grasp the deformation and movement state of the affected part during treatment. In addition, adaptive radiotherapy using CBCT images during segmentation treatment is possible by creating a model for the movement of the target during radiotherapy and recalculating the dose distribution for the target and adjacent risk organs using CBCT during segmentation treatment. It can be made clinically applicable.

Even if it is an effect not explicitly mentioned herein, the effects described in the following specification expected by the technical features of the present invention and their potential effects are treated as if they were described in the specification of the present invention.

FIG. 1 is a diagram for explaining the effect of scattered beams of MV X-rays and kV X-rays.

2 is a view showing a computed tomography apparatus according to an embodiment of the present invention.

3 is a view showing a cone beam type computed tomography apparatus according to another embodiment of the present invention.

4 and 5 are diagrams illustrating a beam blocking module of a cone beam type computed tomography apparatus according to another embodiment of the present invention.

6 is a diagram illustrating image acquisition using a cone-beam-type computed tomography apparatus according to an embodiment of the present invention.

7 is a view for explaining a method of calculating a scattered beam distribution map of the cone beam type computed tomography apparatus according to an embodiment of the present invention.

8 is a view for explaining a method of estimating a scattered beam distribution map from a blocked X-ray image of the cone beam type computed tomography apparatus according to an embodiment of the present invention.

9 is a view for explaining a method of estimating a scattered beam distribution map from a non-blocking X-ray image of the cone beam type computed tomography apparatus according to an embodiment of the present invention.

10 is a flowchart illustrating a computed tomography method according to an embodiment of the present invention.

Hereinafter, the rotational beam shielding apparatus of the present invention, and a computed tomography apparatus and method including the same will be described in more detail with reference to the drawings. The present invention may be embodied in several different forms, and is not limited to the described embodiments. In addition, in order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same elements.

The suffixes "module", "~ part", and "device" for the components used in the following description are given or mixed in consideration of only the ease of writing the specification, and have a meaning or role that is distinct from each other by itself. no.

The present invention relates to a computed tomography apparatus for generating a CT image and a method for acquiring a CT image. In particular, the present invention obtains a scattered beam through a rotating wheel blocking structure located between an image beam module and a detector (used in combination with an image acquisition unit in the present invention), and results through prediction of the obtained scattered beam. This is an invention for obtaining a CT image in which the effect of the scattered beam is suppressed. In this embodiment, an example has been described focusing on CBCT, but this is only an example and the scope of the present invention is not limited to CBCT.

As shown in FIG. 1 , when a CBCT X-ray image is acquired at the same time as VMAT, a CBCT volume image can be generated during intrafraction therapy. However, MV X-rays and kV X-rays interact with particles inside the object, resulting in overall image quality degradation due to the influence of the generated scattered beam, so its clinical use is very limited. In particular, the CBCT with a detector having a large irradiation area has a problem in that it is more difficult to obtain an accurate image because the effect of the scattered beam increases exponentially compared to the general CT.

A computed tomography apparatus according to an embodiment of the present invention has a novel circuit breaker structure for solving the above problems. In particular, the blocker according to an embodiment of the present invention is a rotatable wheel-based blocker that simultaneously acquires primary beam and scattered beam X-ray images. It is possible to implement a high-definition On-Treatment CBCT (Cone-Beam CT) imaging system in which the scattered beam is effectively removed using the primary beam and the scattered beam obtained through such a wheel-based blocker.

In particular, the CBCT device uses a light source of megavolts (MV)-kilovolts (kV) that is generated when a radiation therapy beam and a CBCT image beam are simultaneously transmitted. lowers the By using the blocker structure of the present invention, it is possible to improve image quality degradation due to the scattered beam, and to accurately grasp the deformation and movement state of the affected part during treatment, thereby helping to treat the patient.

2 is a block diagram illustrating a computed tomography apparatus according to an embodiment of the present invention. The computed tomography apparatus 10 of FIG. 2 includes a gantry 100 , a radiation module 200 , an image beam module 300 , a beam blocking module 400 , an image acquisition unit 500 , and an image processing unit 600 . include

In the present embodiment, the computed tomography apparatus 10 may be a cone-beam-type computerized (computerized) tomography apparatus that restores a plurality of tomography images at once from a two-dimensional fluoroscopic image obtained by irradiating cone-shaped X-rays. In the case of the CBCT device, it is possible to calculate a plurality of horizontal tomography images only by measuring the projection image in one rotation, so it has the advantage of rapidly reconstructing the three-dimensional structure of the subject. In addition, when the computed tomography apparatus of the present invention is applied to a CT imaging system using a plurality of detectors, the influence of scattering can be suppressed.

In FIG. 2 , the gantry 100 supports the radiation module 200 and is formed to be rotatable with respect to the subject.

The radiation module 200 is fixed to the gantry, and irradiates a radiation treatment beam to the subject.

The imaging beam module 300 irradiates the imaging beam on the path of the radiation treatment beam irradiated from the radiation module.

According to another embodiment of the present invention, the image beam module may further include an image beam module driver (not shown) for controlling the driving thereof. The image beam module driver may irradiate the image beam to the subject, and control the irradiation direction of the image beam so that the radiation therapy beam and the image beam overlap at least in a partial intersection area. The angle between the image beam and the treatment beam is preferably irradiated to be a right angle.

In the present embodiment, since both the radiation module 200 and the image beam module 300 irradiate a radiation beam to the subject, they are collectively referred to as a “light source module”. Although the present embodiment includes both the radiation module and the image beam module, it is of course possible to configure the light source only with the image beam module.

The beam blocking module 400 is positioned in a path between the imaging beam module and the object to continuously block or non-block at least a portion of the imaging beam irradiated from the imaging beam module. In particular, the beam blocking module selectively blocks a portion of the image beam and includes a rotatably shielding unit.

For example, the beam blocking module 400 uses an easy-to-machine lead or solid tungsten for shielding primary and scattered X-rays for kV and scattered X-rays for MV to match the direction of wheel rotation. It is preferable that the circuit breaker is a wheel type circuit breaker configured in the form of a strip.

Specifically, the beam blocking module is rotatable, and is formed in a partially shielded and partially open structure. When the scattered light incident to the image acquisition unit passing through the arc-shaped structures is used, the image processing unit can estimate a more accurate scattered beam map, and through this, it is possible to obtain

The size of the beam blocking module when the beam blocking module is located in front of the image beam module may be smaller than the size of the beam blocking module when the beam blocking module is located in front of the image acquisition unit (detector), so it is advantageous for miniaturization. When the beam blocking module is located between the image acquisition unit and the patient, it is possible to improve the performance of the image quality in that the distortion due to beam scattering that may be additionally generated by the patient can be further predicted through the wheel blocker structure.

The image acquisition unit 500 acquires a plurality of projection data by detecting the radiation treatment beam that has passed through the target object and the scattered beam scattered by the image beam. For reference, in this embodiment, the terms image acquisition unit and detector are used interchangeably.

The image acquisition unit 500 distinguishes and acquires the first projection data and the second projection data. The shielding unit has a blocking area that selectively blocks the image beam and a non-blocking area that does not block the image beam. The blocking area includes the strip portion where the strip is present. It is distinguished by an open part where there is no strip. The first projection data is information obtained by passing through the blocking area. The second projection data is information obtained through the non-blocking area.

The image processing unit 600 generates a reconstructed image by estimating a scattered beam map for the plurality of projection data.

Specifically, the image processing unit 600 estimates a scattered beam map by applying an interpolation method in a direction orthogonal to the arc strip shape in projection data when the image beam is blocked by the shielding unit.

3 shows a cone-beam-type computed tomography apparatus 10 according to an embodiment of the present invention. The CBCT device according to this embodiment is a gantry 100, a main body 110, a rotation shaft 120, a radiation irradiation module 200, an image beam module 300, a beam blocking module 400, an image acquisition unit 500 ), an image processing unit 600 , and a table 130 .

In FIG. 3 , the gantry 100 may be implemented in various forms according to required conditions and design specifications. The present invention is not limited or limited by the type and characteristics of the gantry 100 . As an example, the gantry 100 may be connected to the main body 110 by a rotation shaft 120 and configured to rotate. In some cases, a conventional ring gantry, a partial ring gantry, a C-shaped gantry, etc. may be used as the gantry, but instead of the gantry any other frame capable of positioning the radiation module in various rotational and/or axial positions relative to the patient. Work may also be used.

A radiation module 200 may be provided in a fixed form on one side of the gantry 100 . The radiation module 200 for emitting a treatment beam may include a radiation source operable to generate a radiation beam and a linear accelerator.

The CBCT device according to the present embodiment further includes a table 130 for positioning the patient. The table 130 is a place on which the patient to be treated lies, and may be provided to enable horizontal and vertical position adjustment.

As shown in FIG. 3 , in the cone beam type computed tomography apparatus 10 according to an embodiment of the present invention, when the radiation treatment beam L1 is irradiated to the subject from the radiation irradiation module 210 of the radiation module, the path The image beam module 300 irradiates the image beam L2 so that an overlap occurs on the image. It is preferable that the position of the overlapping section overlaps the area where the subject is located.

The beam blocking module 400 is positioned in a path between the imaging beam module and the object to block at least a portion of the image beam irradiated from the imaging beam module, and an arc-shaped strip to match the wheel rotation direction. As a circuit breaker in the shape of a wheel, the shield rotates during rotation, and a part rotates and a part opens continuously.

Accordingly, the detector 510 of the image acquisition unit 500 is positioned in parallel with the image beam irradiation direction to detect the radiation treatment beam passing through the subject and the scattered beam scattered by the image beam to perform a plurality of projections. data will be acquired.

The plurality of projection data acquired by the image acquisition unit includes a scattered beam acquired under the influence of the selective blocking of the beam blocking module and an image according to the primary beam acquired regardless of the influence of the blocking. Here, the selective blocking means acquiring a scattered beam obtained by the effect of selective blocking according to the pattern of the strip and the position of the strip.

4 and 5 are diagrams illustrating a beam blocking device (beam blocking module) used in a computed tomography apparatus according to various embodiments of the present disclosure.

4 and 5 , the beam blocking module 400 according to an embodiment of the present invention includes a driving wheel 410 , a shielding unit 420 , and a driving motor 440 .

The beam blocking module 400 is positioned in a path between the imaging beam module and the object to block at least a portion of the imaging beam irradiated from the imaging beam module. The position of the beam blocking module may be located between the patient and the imaging beam module as shown in FIG. 3 . In addition, the beam blocking module may be located between the patient and the image acquisition unit.

The beam blocking module 400 uses lead or solid tungsten, which is easy to process for shielding primary and scattered X-rays for kV and scattered X-rays for MV, in an arc-shaped strip shape to match the wheel rotation direction. It is preferably a circuit breaker of a constructed wheel model.

When the driving wheel 410 has an open inner side, the shield 420 is configured to be seated on the inner side. The shielding part 420 is provided to cover at least a part of the inner side of the driving wheel. The driving motor 440 generates rotational driving for rotation of the shield 420 and/or the driving wheel 410 . Depending on the specifications of the system to which the present system is applied, the driving wheel may be configured to rotate only the shield in a fixed state, and the driving wheel and the shield may be configured to rotate together.

The shielding part 420 has a structure in which a strip portion 421 in which arc-shaped strips are present and an open portion 423 in which a strip is not present are arranged to cross each other. In order to distinguish it from the unblocked region 430 in which the shielding part does not exist, the region in which the shielding part 420 is present is referred to as a blocked region in this embodiment.

In the blocking region, the incident image beam is selectively blocked. When the arc-shaped strip has a structure in which the arc-shaped strip is arranged, the incident image beam is a circular arc and a primary beam and a scattered beam according to a pattern specified according to the rotation direction of the shielding unit are transmitted to the image acquisition unit. In the region where the arc-shaped strip is present, the scattered beam affected by the block by the strip is transmitted to the image acquisition unit. In the open portion where the arc-shaped strip does not exist, the image beam (including the scattered scattered beam and the primary beam excluding the scattered) is transmitted to the image acquisition unit.

In the non-blocking area, an image beam that is not affected by the beam blocking module of the present embodiment (herein, a naturally occurring scattered beam is included) is transmitted to the image acquisition unit.

The shielding part is positioned in the direction in which the image beam is incident, and has a configuration for allowing the image beam to pass through the shielding section for a first time section and pass through the non-blocking area for a second time section. When the area of the shielding section is implemented at 90 degrees, the time for the image beam to pass through the non-blocking area is three times the time for passing through the blocking area. It is preferable that the shielding portion is provided to be perpendicular to an incident axis on which the image beam is incident.

The driving motor 440 may rotate only the shield or rotate the shield and the driving wheel together. For example, the drive motor is preferably a step motor.

As shown in FIG. 4 , the shielding part 420 has a structure in which a plurality of arc-shaped strips 421 are disposed to coincide with the rotational direction of the driving wheel. The arrangement structure of the strip portion and the open portion 423 is not limited thereto, and combinations of various widths and arrangements are possible. For example, a shape of a strip that draws an arc around a rotation axis is also possible, a shape in which a part of the strip is cut is possible, and a shape in which a part of the strip is cut off is deviated and arranged in the form of a checkerboard. In addition, the strip may be provided in a helical strip structure instead of in the form of an arc.

As the shape of the strip is designed to draw an arc around the axis of rotation, it is possible to estimate the scattered beam map from the projection data obtained by blocking or non-blocking of the image beam. Images can be acquired without performing.

That is, by rotation of the shielding unit 420 , the image acquisition unit may successively acquire first projection data when the image beam is blocked and second projection data when the image beam is not blocked.

In addition, the wheel breaker may further include an immobilization device so that it can be fixed well in front of the X-ray tube.

The shielding unit of the present embodiment is provided to continuously block a part of the image beam in a blocking section for blocking the image beam irradiated from the image beam module in the time domain. Here, the continuous in terms of the time domain means that the blocking is continuously made during a predetermined time period in which the arc-shaped strip is located.

5, the beam blocking module 400 according to an embodiment of the present invention may further include a shielding wall 450 to distinguish the boundary of the shielding part, and the shielding wall includes a lead material, , preferably located in the boundary region. In addition, it is preferable that the thickness T1 of the driving wheel is 1 to 4 mm, and when it is less than 1 mm, the blocking effect is reduced, and when it is more than 4 mm, it is difficult to rotate.

The area where the shielding part exists, that is, the blocking area, is preferably formed at an angle of 90 to 180 degrees with respect to the rotation center, but the specific gravity of the blocking area can be changed by those skilled in the art according to the purpose of correcting the image of the scattered beam. .

In addition, according to various embodiments of the present invention, another shield including copper for average energy modulation is placed on one side of the strip-shaped shield, so that the driving wheel is filled with the strip-shaped shield, copper. It may be provided in a structure capable of obtaining dual energy CBCT, including a shielding part and a space part.

The cone-beam-type computed tomography apparatus according to an embodiment of the present invention rotates a wheel breaker in one direction at a constant speed using a stepping motor at the same time as the gantry is rotated to provide a blocked X-ray image and a non-blocking X-ray image. - Acquire line images continuously. In the conventional method, it is important to synchronize the time for maintaining the blocked state when the radiation beam is on, and synchronize the time and delay time for changing the state when the radiation beam is off, whereas according to an embodiment of the present invention Since the wheel rotates in one direction without changing the direction, there is no backlash problem when changing the direction of rotation. That is, it is a device having a structure with a low burden on gantry rotation and synchronization. In the present invention, since the arc-shaped strip passes through the same position of the detector while the gantry rotates, it is an easy structure to automatically classify a non-blocking image and a blocked image after acquiring a projection image.

6 is a conceptual diagram illustrating a concept in which a cone beam type computed tomography apparatus having a rotating beam shield according to an embodiment of the present invention acquires a radiographic image.

Referring to FIG. 6 , the CBCT device may further include a driving unit (not shown) for rotationally moving the image beam module. The image beam module irradiates an image beam, that is, X-rays while rotating, and the beam blocking module blocks a portion of the X-rays in the path between the light source and the subject. The first projection data acquired by the image acquisition unit includes a shaded region and an unshaded region where a pattern of shadows is formed. The shaded area (blocking area) 420 corresponds to the area in which the arc-shaped strip pattern is formed. The second projection data acquired by the image acquisition unit includes a non-shaded area.

In the blocked state, a 'blocked X-ray image' is acquired, including the scattered beam (shaded area) due to the influence of the blocker and the image beam without the influence of the blocker (the primary beam and the scattered beam are accumulated). In the non-blocking state, there is no effect of the breaker, so a 'non-blocking X-ray image' containing only the image beam is acquired.

The image acquisition unit 500 acquires a plurality of projection data by detecting a radiation treatment beam that has passed through the target object and a scattered beam scattered by the image beam using a detector.

Specifically, by rotation of the shielding unit of the beam blocking module 400 , first projection data when the image beam is blocked and second projection data when the image beam is not blocked are successively acquired.

Referring to FIG. 7 , the image processing unit 600 uses information detected in a blocked region in the intercepted X-ray images configured in an arc-shaped strip shape in a direction orthogonal to the arc-shaped strip shape in a one-dimensional cubic shape. The scattered beam map is estimated by applying the 1D cubic B-Spline interpolation method.

In addition, the image processing unit 600 generates a reconstruction image through backprojection of the scattered beam map estimated through the above-described interpolation by receiving the plurality of projection data as inputs. Specifically, the image processing unit 600 estimates a scattered beam map by applying an interpolation method in a direction orthogonal to the arc strip shape in projection data when the image beam is blocked by the shielding unit.

FIG. 8 is a view for explaining a method of estimating a scattered beam distribution map from a blocked X-ray image by a cone beam type computed tomography apparatus according to an embodiment of the present invention.

The image processing unit 600 backprojects the image according to the first projection data obtained in the blocking region, that is, the scattered beam map estimated through interpolation on the blocked X-ray image, to obtain a three-dimensional scattered beam volume. can create In addition, the image processing unit includes an image obtained in the non-blocking area, that is, an image according to second projection data obtained from a non-blocking X-ray image (All unblocked projection), and a geometric shape specified according to the spatial structure of the rotating beam shielding unit. The relationship can be used to estimate the corresponding scattered beam distribution map. This will be described later.

The image processing unit 600 estimates a scattering map for the entire first projection data, reconstructs a 3D scattering volume using backprojection, and re-projects the 3D scattering volume. ) to estimate and generate a scattering map for the entire second projection data. For example, the back projection may be a method of continuously summing the values of the projection image obtained in each direction by turning them back upside down. After the summation is completed, the original pixel value can be reconstructed by subtracting the lowest basic value among all pixel values from each pixel value and dividing it by the least common multiple of the pixels.

Thereafter, the image processing unit generates scatter corrected data by subtracting a scatter map for the second projection data estimated from the second projection data, and uses a reconstruction algorithm to generate the reconstructed image from the scatter correction data. create

9 is a view for explaining a method of estimating a scattered beam distribution map from a non-blocking X-ray image of a cone beam type computed tomography apparatus according to an embodiment of the present invention.

The image processing unit may finally obtain a scattered beam-removed non-blocking X-ray image by subtracting the scattered beam map estimated from the non-blocking X-ray images from the image component. More specifically, the image processing unit 600 uses a weighted sum based on distances from two first projection data from scattering maps for two pieces of first projection data adjacent to the second projection data that are successively acquired. 2 Estimate and generate scatter maps for projection data. The image processing unit generates a CBCT image during scattering correction segmentation treatment by applying a compression sensing-based iterative reconstruction algorithm to the non-blocking X-ray image.

The image acquisition unit may continuously acquire the second projection data to acquire the first projection data and the second projection data in a ratio of 1 to N (where N is a natural number), and the image processing unit may acquire the N second projection data From the scattering maps for the two first projection data adjacent to , the scattering maps for the N pieces of second projection data may be estimated using a weighted sum based on distances from the two first projection data. The image processor may obtain scattering correction data in which scattering is suppressed by subtracting an image formed through the estimated scattering maps and the second projection data.

The embodiment of FIG. 9 shows an example of unblocked 2nd to 5th second projection data between the blocked 1st first projection data and 6th first projection data. The scattered beam map for the 2nd second projection data is more affected by the scattered beam map estimated for the 1st first projection data. Therefore, by increasing the weight of the scattered beam map estimated with respect to the 1st first projection data and lowering the weight of the scattered beam map estimated for the 6th first projection data and adding them, the scattered beam map for the 2nd second projection data is estimated can do.

10 is a flowchart illustrating a computed tomography method according to an embodiment of the present invention. Referring to FIG. 10 , the computed tomography method includes the following steps performed in the computed tomography apparatus 10 , in particular, the cone beam type computed tomography apparatus. Duplicate descriptions of the items already described will be omitted.

The radiation module 200 starts in the step (S100) of irradiating a radiation treatment beam to the subject.

The image beam module 300 irradiates an image beam on the path of the radiation treatment beam irradiated from the radiation module in step S200 . It is preferable that the image beam and the treatment beam be irradiated so that they overlap each other in the area where the patient is located. To this end, the CBCT apparatus according to the present embodiment may include a controller (not shown) for adjusting the irradiation direction and position of the image beam and/or the treatment beam.

The beam blocking module 400 blocks at least a portion of the image beam irradiated from the imaging beam module with a beam blocking module located in a path between the imaging beam module and the subject in step S300 . Here, the beam blocking module, a driving wheel rotatable in one direction, the inner side of which is open; a step motor for rotating the driving wheel and a shielding part provided to cover at least a part of the inside of the driving wheel, wherein the shielding part has a structure in which a plurality of arc-shaped strips are disposed to coincide with the rotational direction of the driving wheel am.

The image acquisition unit 500 acquires a plurality of projection data by detecting the radiation treatment beam that has passed through the target object and the scattered beam scattered by the image beam in step S400 .

In the step of acquiring a plurality of projection data (S400), the first projection data when the image beam is blocked and the second projection data when the image beam is not blocked by the rotation of the shielding part obtained successively.

The image processing unit 600 generates a reconstructed image by estimating a scattered beam map for the plurality of projection data in step S500 .

The step (S500) of generating a reconstructed image by estimating a scattered beam map for a plurality of projection data is orthogonal to the arc strip shape in the projection data when the image beam is blocked by the shielding unit. Estimate a scattering beam map by applying interpolation in the direction, estimating a scattering map for the entire first projection data, reconstructing a 3D scattering volume using backprojection, and the 3D The scattering volume is reprojected to estimate and generate a scattering map for the whole of the second projection data.

Thereafter, scattering corrected data is generated by subtracting a scattering map for the second projection data estimated from the second projection data, and the reconstructed image is generated from the scattering correction data using a reconstruction algorithm. .

The cone-beam computed tomography apparatus and method for correcting scattering using a wheel breaker according to an embodiment of the present invention can reduce the target adjacent margin during treatment planning by utilizing a CBCT image during high-definition segmentation treatment during VMAT treatment, Targeting accuracy is improved and the dose to at-risk organs adjacent to the tumor is reduced.

In addition, it is possible to create a model for the movement of the target during radiation therapy, and after each radiation therapy, CBCT during split therapy can be used to recalculate the dose distribution for the target and adjacent at-risk organs. Therefore, adaptive radiotherapy using CBCT images can be applied clinically during segmentation therapy and can be a new clinical guideline. As a result, the incidence of complications related to radiation therapy is lowered and the survival rate can be improved.

In the past, after only taking CBCT before and after treatment, the cone-beam-type computed tomography apparatus and method for correcting scattering using a wheel blocker according to an embodiment of the present invention, if the radiation was irradiated by estimating the location based on this during treatment. It is possible to perform CBCT for confirmation in real time while irradiating the radiation therapy beam during each treatment. It does not take more treatment time, but the accuracy of treatment can be further improved.

Since the manufactured wheel breaker does not need to stop in the middle of rotation, change direction, or change rotation speed while rotating, no backlash problem occurs, so it is easy to control. Compared to the linear type circuit breaker, it is possible to secure higher stability by reducing the problems caused by CBCT X-ray image acquisition synchronization during breaker movement and gantry rotation.

Even if all the components constituting the embodiment of the present invention described above are described as being combined or operated in combination, the present invention is not necessarily limited to this embodiment. That is, within the scope of the object of the present invention, all the components may operate by selectively combining one or more. In addition, although all the components may be implemented as one independent hardware, some or all of the components are selectively combined to perform some or all of the functions of the combined hardware in one or a plurality of hardware program modules It may be implemented as a computer program having In addition, such a computer program is stored in a computer readable media such as a USB memory, a CD disk, a flash memory, etc., read and executed by a computer, thereby implementing the embodiment of the present invention. The computer program recording medium may include a magnetic recording medium, an optical recording medium, and the like.

The above description is only one embodiment of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to implement it in a modified form without departing from the essential characteristics of the present invention. Therefore, the scope of the present invention is not limited to the above-described embodiments, and should be construed to include various embodiments within the scope equivalent to the content described in the claims.

[Explanation of code]

10: computed tomography apparatus

100: gantry

200: radiation module

300: image beam module

400: beam blocking module

500: image acquisition unit

600: image processing unit

The present invention is a technique applied to a computed tomography apparatus, particularly a cone beam type computed tomography apparatus. In addition, the present invention is a technique applied to a beam blocking module of a detector for improving distortion due to a scattered beam present in a radiation image obtained through a computed tomography apparatus. Also, the present invention may be applied to a stereotactic radiation therapy apparatus.

Claims

a gantry formed to be rotatable;

a light source module irradiating a radiation image beam to the subject; and

a beam blocking module located in a path between the light source module and the subject to selectively block a portion of the treatment beam or image beam irradiated from the light source module, and including a rotatable shielding unit;

A computed tomography apparatus comprising a.
The method of claim 1, wherein the shielding unit has a blocking area that selectively blocks the image beam and a non-blocking area that does not block the image beam,

The blocking area of the shielding unit has a structure in which a strip portion blocking the image beam irradiated from the image beam module and an open portion not blocking the image beam are alternately disposed,

A computerized tomography apparatus, characterized in that provided to continuously block a portion of the image beam in a blocking section for blocking the image beam irradiated from the image beam module in terms of time domain.
According to claim 1, wherein the beam blocking module,

a driving wheel provided to have an open inner side;

and a driving motor for generating a rotational driving force for rotation of the shield, wherein the shield is located inside the driving wheel, and the shield has a circular arc between the strip portion and the open portion with respect to the rotation center of the driving wheel. A computed tomography apparatus, characterized in that it comprises arc-shaped strips arranged to have a shape.
The method of claim 1,

A plurality of projection data for the subject - Here, the plurality of projection data includes an image according to a scattered beam obtained by the effect of selective blocking of the beam blocking module and a primary beam obtained regardless of the influence of the blocking Ham - an image acquisition unit to acquire; and

and an image processing unit for estimating a scattered beam map from the plurality of projection data and generating a reconstructed image in which scattering is suppressed by using the scattered beam map.
The method of claim 4, wherein the image acquisition unit,

first projection data obtained by partially blocking the image beam by rotation of the shielding unit;

Computational tomography apparatus, characterized in that the second projection data is continuously acquired in terms of time domain when the image beam is not blocked.
5. The method of claim 4, wherein the shield comprises arc-shaped strips arranged at regular intervals in at least a part of the area,

The image processing unit estimating the scattered beam map,

An initial scattering beam map obtained under the influence of selective blocking according to the structure of the arc-shaped strip is interpolated, but a scattering beam map is obtained by interpolating the scattering beam in a direction orthogonal to an arc that can be defined according to the arc-shaped strip structure. A computed tomography apparatus, characterized in that it is estimated.
According to claim 4, wherein the image processing unit,

first projection data at a first time point;

and estimating the scattered beam map for the second projection data located between the first and second viewpoints through distance-based weighted summing of first projection data at a second viewpoint adjacent to the first viewpoint. computerized tomography device.
The method of claim 7, wherein the image processing unit,

estimating a scattered beam map using the first projection data;

Reconstructing a 3D scattering volume through backprojection on the estimated scattering beam map,

Computed tomography apparatus, characterized in that by reprojecting the 3D scattering volume to estimate a scattering beam map for the second projection data.
The method of claim 7, wherein the image processing unit,

the second projection data and

A computer characterized in that generating scatter corrected data through a subtraction operation between scatter maps with respect to the estimated second projection data, and generating a reconstructed image in which scattering is suppressed by using the scattering correction data tomography device.
The method of claim 1,

The computed tomography apparatus is a cone beam type computed tomography apparatus,

The light source module includes: a radiation module for irradiating a radiation treatment beam to the subject; and

and an imaging beam module configured to irradiate an imaging beam to the subject, wherein the radiation therapy beam and the imaging beam overlap in at least a partial intersection area.
A beam blocking device for removing noise caused by a scattered beam from a computed tomography image obtained by a computed tomography apparatus, comprising:

a driving motor for generating rotational driving force;

a driving wheel having an open inner side; and

A beam blocking device comprising: a shielding unit positioned on a path between the light source module and the subject to selectively block a portion of the image beam irradiated from the light source module, but rotated by driving the motor.
The method of claim 11 , wherein the shielding unit has a blocking area that selectively blocks the image beam and a non-blocking area that does not block the image beam,

The blocking area of the shielding unit has a structure in which a strip portion blocking the image beam irradiated from the image beam module and an open portion not blocking the image beam are alternately disposed,

A beam blocking apparatus, characterized in that in a blocking section for blocking the image beam irradiated from the image beam module in the time domain, a part of the image beam is continuously blocked.
13. The beam blocking device according to claim 12, wherein the shield comprises arc-shaped strips arranged such that the strip portion and the open portion have the shape of an arc with respect to a center of rotation.
A computed tomography method using a computed tomography apparatus, comprising:

irradiating a radiation therapy beam to the subject;

irradiating an image beam onto a path of a radiation treatment beam irradiated from the radiation module to an image beam module;

continuously blocking or non-blocking at least a portion of the image beam irradiated from the imaging beam module with a beam blocking module located in a path between the imaging beam module and the subject;

acquiring a plurality of projection data by detecting a radiation treatment beam that has passed through the subject and a scattered beam scattered by the image beam; and

and generating a reconstructed image by estimating a scattered beam map with respect to the plurality of projection data.
15. The method of claim 14,

The computed tomography apparatus further includes a shielding unit made of an arc-shaped strip arranged at regular intervals in at least a part of the area,

The estimating of the scattering beam map includes interpolating an initial scattering beam map obtained under the influence of selective blocking according to the structure of the arc-shaped strip, in a direction orthogonal to an arc that can be defined according to the structure of the arc-shaped strip. A computed tomography method comprising estimating a scattered beam map by interpolating the scattered beam.