Proton helium ion treatment device and proton CT imaging method thereof
Through the proton helium ion therapy device combined with the proton CT imaging system, the problem of range error in traditional particle therapy is solved, and a higher-precision treatment plan formulation and implementation is achieved.
Patent Information
- Application Number
- CN202510710892.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-29
- Publication Date
- 2025-08-22
AI Technical Summary
There is a range error problem in the treatment plan based on CT images in traditional particle therapy, resulting in insufficient treatment accuracy.
Design a proton helium ion therapy device, combined with a proton CT imaging system, through multi-angle proton CT imaging and reconstruction, the three-dimensional relative barrier ability distribution of the imaging object is obtained for accurate dose calculation.
It realizes that without adding additional devices, the accuracy of the treatment plan is improved, the range error is reduced, and the particle therapy needs of higher accuracy are met.
Smart Images
Figure CN120515019A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of proton imaging in the field of particle radiotherapy imaging, and specifically relates to a proton helium ion therapy device and a proton CT imaging method thereof, which are applicable to CT imaging and ion therapy technology. Background Art
[0002] Ion radiotherapy is one of the most advanced cancer treatment technologies. Because ions release energy at depth, resulting in a Bragg peak effect, ion radiotherapy can better concentrate energy loss within the tumor target, minimizing damage to normal tissue. Compared to traditional photon or electron radiotherapy, ion radiotherapy offers advantages such as shorter treatment cycles, more precise targeting, higher cure rates, and fewer side effects.
[0003] Ion radiotherapy systems consist of an accelerator system, a rotating gantry, a treatment head, an image-guided positioning system, and a treatment couch. Accelerator systems primarily fall into two categories: cyclotrons and synchrotrons. Cyclotrons output a fixed-energy beam, which is then de-energized to a specified energy level within a delivery line by a de-energizer before being delivered to the treatment room for treatment. Synchrotrons accelerate the beam to the required energy level before delivering it to the treatment room for treatment. The rotating gantry is a key system in the rotational treatment room, capable of rotating the Gantry delivery line portion of the beam around the isocenter to any angle within the designed angle range to achieve intensity-modulated therapy. The treatment head, comprised of a scanning magnet, primary and secondary dose ionization chambers, a position ionization chamber, a range adjuster, and an optional range modulator, delivers the beam to the tumor area for treatment. Ion radiation techniques typically fall into two categories: scattered radiation and scanning radiation.
[0004] Currently, more mature ion therapy systems typically use protons and carbon ions. Helium ions, as a light ion between protons and carbon ions, combine the advantages of both proton and carbon ion therapies. From 1975 to 1993, the Lawrence Berkeley National Laboratory in the United States conducted research on cancer treatment using broad-beam helium ions, treating a total of 2,054 patients. In August 2020, the Heidelberg Ion Beam Therapy Center in Germany treated its first patient using helium ion therapy and subsequently initiated clinical trials to determine the effectiveness and safety of helium ion therapy.
[0005] Before ion therapy is performed, the traditional method is to calculate and optimize the dose based on the planned CT images, thereby formulating the treatment plan required by the clinic. In the dose calculation process, the CT value is converted into a stopping power model for the dose based on empirical data. The stopping power model for the dose is performed by performing a CT scan on the Gammex467 phantom (CT calibration phantom) containing multiple plug-ins with known electron density, mass density and material composition, thereby establishing a correspondence between the CT value (i.e., HU value) of different plug-ins and their electron density and relative stopping power (RSP), such as Figure 1 This correspondence only considers the effect of electron density and is affected by factors such as cavity, component differences, imaging artifacts, and RSP conversion, resulting in a range error of 3-5%.
[0006] Therefore, a new proton CT imaging system for a proton helium ion therapy device is needed to resolve the range error caused by this conversion. Summary of the Invention
[0007] The purpose of the present invention is to provide a proton helium ion therapy device and a proton CT imaging method thereof, so as to solve the range error problem caused by the formulation of treatment plans based on CT images in traditional particle therapy.
[0008] To achieve the above-mentioned objectives, the present invention provides a proton helium ion therapy device, comprising an injector, an accelerator system, a high-energy transport line, a rotating gantry, a treatment head equipped with a beam delivery system, and a proton CT detection and imaging system, all arranged in sequence along a beam transport direction. The injector comprises a switchable hydrogen ion source and a helium ion source. The beam delivery system comprises a scanning system and an irradiation control system. The proton CT detection and imaging system comprises a front position detector, a rear position detector, and a proton residual energy detector, all arranged in sequence along the beam transport direction, and a data acquisition and imaging system connected to the front position detector, the rear position detector, and the proton residual energy detector. The data acquisition and imaging system is configured to process detection results of the front position detector, the rear position detector, and the proton residual energy detector at different imaging angles to obtain a three-dimensional distribution of the relative stopping power of the imaging object in three-dimensional space.
[0009] The accelerator system is a shared synchrotron accelerator.
[0010] The scanning system includes a scanning magnet and a scanning power supply electrically connected to the scanning magnet, and is used to change the direction of the proton beam by changing the magnetic field of the scanning magnet through the scanning power supply, thereby realizing scanning of the imaging object.
[0011] The rotating gantry can switch between multiple imaging angles, each imaging angle corresponding to one of the beam distribution angles, so that the rotating gantry can acquire a proton projection image at each imaging angle.
[0012] The front position detector is fixed at the bottom of the treatment head, and the treatment head bracket is fixed on the rotating frame; the rear position detector and the proton residual energy detector are installed on the rotating frame and are retractable relative to the rotating frame, extending to the downstream position of the imaging object during proton CT imaging.
[0013] The front position detector and the rear position detector adopt two strip ionization chambers or multi-filament ionization chambers spaced at a fixed distance; the proton residual energy detector is a multi-layer flat plate ionization chamber.
[0014] The image reconstruction algorithm is a filtered back projection algorithm, an iterative reconstruction algorithm, or a compressed sensing algorithm.
[0015] In another aspect, the present invention provides a proton CT imaging method for a proton helium ion therapy device, comprising:
[0016] S1: Provide the proton helium ion therapy device described above and set the flux and proton energy for proton CT imaging;
[0017] S2: rotating the rotating gantry to a first imaging angle to perform scanning irradiation at an imaging angle of the rotating gantry;
[0018] S3: Using a data acquisition and imaging system, the detection results collected by the front position detector, the rear position detector, and the proton residual energy detector are obtained as the position of the proton beam before and after the incident imaging object; based on the position and beam direction of the proton beam at each irradiation point before and after the incident imaging object, the most likely path of the proton beam passing through the imaging object is obtained by a most likely path estimation method; based on the energy of the proton beam before and after the incident imaging object, the proton energy attenuation value corresponding to the most likely path of the proton beam passing through the imaging object at each irradiation point is calculated to obtain the water equivalent length attenuation value; based on the scanning results of all irradiation points at the same imaging angle, a distribution map of the water equivalent length attenuation values of all irradiation points is obtained as the proton CT projection image at the current imaging angle;
[0019] S4: rotating the rotating gantry to the next imaging angle, repeating steps S2 and S3 to generate a proton projection image at the next imaging angle, until proton projection images at all imaging angles are obtained;
[0020] S5: Based on the proton projection images from multiple imaging angles and the most likely paths of all irradiation points, an image reconstruction algorithm is used to reconstruct the distribution of the relative stopping power of the imaging object in three-dimensional space.
[0021] The image reconstruction algorithm is a filtered back projection algorithm, an iterative reconstruction algorithm, or a compressed sensing reconstruction algorithm.
[0022] The proton-helium ion therapy device of the present invention simultaneously implements proton CT imaging and ion therapy through a therapeutic device. This device enables proton CT imaging and ion therapy planning without requiring additional booster devices or extending the device's operating range. Furthermore, through multi-angle proton CT imaging and reconstruction, the relative stopping power distribution of all voxels in the imaged object can be determined, making RSP-based dose calculation more accurate and resolving the range error associated with traditional CT image-based planning. This device can meet the needs of various cancer treatment centers and patients for higher-performance particle therapy. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a corresponding relationship diagram between the relative stopping power RSP and the CT value obtained by the prior art.
[0024] Figure 2 This is an overall structural diagram of the proton helium ion therapy device of the present invention.
[0025] Figure 3 This is a schematic diagram of the working principle of the scanning system.
[0026] Figure 4 The figure is a schematic diagram showing the positional relationship among the rotating frame, the treatment head and the proton CT detection imaging system of the proton helium ion treatment device of the present invention.
[0027] Figure 5 This is a diagram showing the detector structure of the proton CT detection imaging system of the proton helium ion therapy device of the present invention.
[0028] Figure 6 1 is a schematic diagram of the principle of the reconstruction algorithm adopted by the proton helium ion therapy device of the present invention, which shows the maximum likelihood path and the reconstructed image pixel grid.
[0029] Figure 7 It is a flow chart of the proton CT imaging method of the proton helium ion therapy device of the present invention. DETAILED DESCRIPTION
[0030] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.
[0031] The main feature of the proton helium ion therapy device of the present invention is the integrated design of proton CT and proton helium ion therapy on the accelerator and rotating gantry, wherein proton CT imaging and proton therapy and helium ion therapy are achieved through the same device and range errors in treatment planning can be avoided.
[0032] First embodiment: a proton helium ion therapy device
[0033] like Figure 2 As shown, the proton helium ion therapy device of the present invention includes an injector 10, an accelerator system 20, a high-energy transport line 30, a rotating gantry 40, a treatment head 50 equipped with a beam delivery system, and a proton CT detection imaging system 60, which are arranged in sequence along the beam transport direction.
[0034] In this embodiment, the injector 10 includes a switchable hydrogen ion source and a helium ion source, which can be switched using a computer. Thus, proton or helium ion therapy can be selected based on the patient's indications, or mixed ion therapy (irradiation in sequence is determined by the treatment plan). The accelerator system 20 is shared, preferably a synchrotron. This achieves the use of integrated synchrotron technology, which supports both proton and helium ion therapy and proton CT imaging. To support the acceleration of helium ions to 230 MeV, protons can be accelerated to 700 MeV under the same conditions. Compared to existing accelerators, this accelerator does not require any additional components. It can accelerate helium ions to 230 MeV and protons to over 700 MeV, while meeting the energy requirements for proton CT scanning (350 MeV), proton therapy, and helium ion therapy.
[0035] The rotating gantry 40 is capable of switching between multiple imaging angles. Each imaging angle (i.e., a projection angle of the imaging object) corresponds to one of the beam distribution angles, so that the rotating gantry 40 can acquire a proton projection image at each imaging angle. Furthermore, the rotating gantry 40 can acquire proton projection images at multiple imaging angles at fixed intervals, and reconstruct a three-dimensional relative stopping power (RSP) image by combining the projection images at the multiple imaging angles.
[0036] like Figure 4 As shown, the treatment head 50 is used to mechanically support the various components of the beam delivery system and the front position detector. The treatment head 50 is fixed to the rotating gantry 40, so that the beam delivery system is mounted on the treatment head 50 within the rotating gantry 40 for secure positioning. The beam delivery system includes a scanning magnet, a scanning power supply electrically connected to the scanning magnet, an irradiation control system, and a range modulator. The irradiation control system is used to control the irradiation time, synchronizing it with the rotation of the rotating gantry and image acquisition. The range modulator is used to adjust the focus of the beam.
[0037] The scanning magnet and the scanning power supply electrically connected to the scanning magnet constitute a scanning system, which is used to change the direction of the proton beam by changing the magnetic field of the scanning magnet through the scanning power supply, thereby realizing scanning irradiation of the treatment object or imaging object, so that different proton beams are emitted uniformly and orderly to different lateral positions of the treatment object over time. The scanning path is as follows: Figure 3 In this embodiment, the scanning magnet includes two groups of mutually orthogonal scanning magnets to achieve deflection of the proton beam in two mutually orthogonal directions.
[0038] The structures of the treatment head 50 and the scanning system are basically the same as those of the prior art, with the only difference being that the same set of devices can be used to implement the distribution adjustment of the proton beam and the distribution adjustment of the helium ions respectively by switching modes.
[0039] like Figure 2 、 Figure 4 and Figure 5 As shown, the proton CT detection imaging system 60 includes a pre-position detector 61, a post-position detector 63, and a proton residual energy detector 64, which are sequentially arranged along the beam transport direction, and a data acquisition and imaging system 65 connected to the pre-position detector 61, the post-position detector 63, and the proton residual energy detector 64. The imaging object 62 is placed between the post-position detector 63 and the proton residual energy detector 64. The pre-position detector 61 is also connected to the beam delivery system to provide an online position monitoring signal for proton imaging as a feedback signal. Thus, the pre-position detector 61 of the present invention can be used for CT proton imaging to detect the position of protons before entering the imaging object, and can also serve as an ion therapy device.
[0040] The front position detector is fixed to the extreme end of the treatment head 50, which is fixed to the rotating gantry 40. The rear position detector 63 and the proton residual energy detector 64 are mounted on the rotating gantry 40 and are retractable relative to the rotating gantry 40. During proton CT imaging, they extend downstream of the imaging subject 62. This positions the rear position detector 63, the proton residual energy detector 64, and the front position detector 61 on opposite sides of the imaging subject 62. Thus, the treatment head 50, the front position detector 61, the rear position detector 63, and the proton residual energy detector 64 can rotate with the rotating gantry around the isocenter with high precision, achieving an isocenter position accuracy of less than ±0.3 mm.
[0041] In this embodiment, the front position detector 61 and the rear position detector 63 preferably employ two high-speed strip or multi-filament ionization chambers spaced a fixed distance apart, replacing conventional silicon microstrip detectors or fiber optic scintillation detectors. This achieves high-precision and fast response position detection, and can respectively measure the position of the proton beam before and after impacting the imaging object, thereby obtaining the trajectory of the proton beam as it passes through the imaging object. Silicon microstrip detectors have a short lifespan due to radiation damage and a small detection area, requiring large-area detection to be achieved only by splicing multiple pieces. Fiber optic scintillation detectors, on the other hand, have poor stability and repeatability. The proton residual energy detector 64 is a multi-layer flat-panel ionization chamber used to measure the range or energy of protons after exiting the imaging target. The multi-layer flat-panel ionization chamber has a layer thickness of 1 mm, a layer spacing of 1 mm, and a total of 280 layers. The intermediate layers are omitted with dashed layers. The maximum measurable residual energy is 350 MeV, meeting the requirements of proton imaging. Therefore, the multi-layer flat-plate ionization chamber can collect the current signal of protons incident through each layer, thereby obtaining the current distribution in the depth direction. This distribution presents a Bragg peak curve, and the residual energy of the emitted protons can be determined by the peak position and calibration relationship.
[0042] The data acquisition and imaging system 65 is configured to obtain a two-dimensional proton CT image based on the detection results of the front position detector 61, the rear position detector 63, and the proton residual energy detector 64 at different imaging angles, and then perform three-dimensional reconstruction using the two-dimensional images at all angles to obtain a three-dimensional distribution image of the relative stopping power of the imaging object in three-dimensional space.
[0043] Second embodiment: a proton CT imaging method for a proton helium ion therapy device
[0044] like Figure 7 As shown, the proton CT imaging method of the proton helium ion therapy device of the present invention specifically includes the following steps:
[0045] Step S1: providing the proton helium ion therapy device described above, and setting the flux intensity and proton energy for proton CT imaging;
[0046] The proton energy is set to 350 MeV.
[0047] Step S2: rotating the rotating gantry to a first imaging angle to perform scanning irradiation at an imaging angle of the rotating gantry 40;
[0048] Step S3: At each irradiation point, the detection results collected by the front position detector 61, the rear position detector 63, and the proton residual energy detector 64 are obtained by using the data acquisition and imaging system 65 as the position and beam direction of the proton beam before and after the incident imaging object; based on the position of the proton beam before and after the incident imaging object at each irradiation point, the most likely path (MLP) of the proton beam passing through the imaging object is obtained by the most likely path estimation method (e.g. Figure 6 As shown); Based on the residual energy of the proton beam after exiting the imaging object, combined with the initial energy before incidence, the proton energy attenuation value △E corresponding to the most likely path of the proton beam passing through the imaging object at each irradiation point is calculated, thereby obtaining the path-integrated water equivalent length attenuation value △WEL; Based on the scanning results of all irradiation points at the same imaging angle, a distribution map of the water equivalent length attenuation values corresponding to all irradiation points is obtained as the proton CT projection image at the current imaging angle;
[0049] The most likely path method uses the energy, position, and direction before incident and the energy, position, and direction at exit to calculate the most likely path using an empirical formula. For more information on the most likely path method, please refer to [Phys. Med. Biol. 49, 2899–2911 (2004)] and [Med. Phys. 35, 4849–4856 (2008)].
[0050] Step S4: rotating the gantry to the next imaging angle, and repeating steps S2 and S3 to generate a proton projection image at the next imaging angle, until proton projection images at all imaging angles are obtained;
[0051] Step S5: Based on the proton projection images at multiple imaging angles and the most likely paths of all irradiation points, an image reconstruction algorithm is used to reconstruct the distribution of the relative stopping power RSP(i, j, k) of the imaging object in three-dimensional space.
[0052] Specifically, the imaging object is divided into cubic voxels in three-dimensional space. The chord length △s(i,j,k) within the voxel is calculated for each incident proton based on the intersection of its most likely path and the voxel (i,j,k) it passes through. The formula for the water equivalent length attenuation value △WEL is converted into a differential expression. The sum of the relative resistance power RSP of the voxels passed by the most likely path of each irradiation point is obtained based on the proton projection image, thereby executing the image reconstruction algorithm.
[0053] The formula for water equivalent length attenuation value △WEL is:
[0054] (1)
[0055] in, is the relative stopping power at voxel (i, j, k), (i, j, k) is the voxel coordinate, is the chord length within the voxel, and L is the set of all voxels.
[0056] Therefore, the spatial resolution of the proton CT image reconstructed by the estimation method based on the most likely path is higher than that by the straight-line path method.
[0057] In this embodiment, the image reconstruction algorithm used is the FDK algorithm in the filtered back projection algorithm. In other embodiments, the image reconstruction algorithm is a filtered back projection algorithm, an iterative reconstruction algorithm, or a compressed sensing reconstruction algorithm.
[0058] The proton-helium ion therapy device of the present invention simultaneously implements proton CT imaging and ion therapy through a treatment device. The resulting proton-helium ion therapy device can achieve proton CT imaging and be used for ion therapy planning and implementation without adding an additional booster device or increasing the device's operating range. Furthermore, through multi-angle proton CT imaging and reconstruction, the relative stopping power distribution of all voxels in the imaged object can be determined. Dose calculation based on RSP images is more accurate, eliminating the range error associated with traditional CT image-based planning. This invention can meet the needs of various cancer treatment centers and patients for higher-performance particle therapy.
[0059] The proton helium ion therapy system of the present invention is the first system designed and developed in China. When the maximum energy of the helium ion beam is 235MeV / u, the accelerator system can accelerate protons to an energy of more than 350MeV / u without an additional energy boosting device, which provides low-cost and high-yield convenient conditions for achieving proton CT imaging.
[0060] The 360-degree rotating gantry included in the treatment system provides high-precision isocenter rotation conditions for multi-angle imaging of proton CT.
[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. In other words, any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention constitutes conventional technology.
Claims
1. A proton helium ion therapy device, characterized in that: It includes an injector, an accelerator system, a high-energy transport line, a rotating gantry, a treatment head equipped with a beam delivery system, and a proton CT detection imaging system, which are arranged in sequence along the beam transport direction; The injector includes a switchable hydrogen ion source and a helium ion source; The beam distribution system includes a scanning system and an irradiation control system; The proton CT detection imaging system includes a front position detector, a rear position detector, and a proton residual energy detector arranged in sequence along the transport direction of the beam, and a data acquisition and imaging system connected to the front position detector, the rear position detector, and the proton residual energy detector; The data acquisition and imaging system is configured to obtain the three-dimensional distribution of the relative stopping power of the imaging object in three-dimensional space based on the detection results of the front position detector, the rear position detector, and the proton residual energy detector at different imaging angles.
2. The proton helium ion therapy device according to claim 1, characterized in that: The accelerator system is a shared synchrotron accelerator.
3. The proton helium ion therapy device according to claim 1, characterized in that: The scanning system includes a scanning magnet and a scanning power supply electrically connected to the scanning magnet, and is used to change the direction of the proton beam by changing the magnetic field of the scanning magnet through the scanning power supply, thereby realizing scanning of the imaging object.
4. The proton helium ion therapy device according to claim 1, characterized in that: The rotating gantry can switch between multiple imaging angles, each imaging angle corresponding to one of the beam distribution angles, so that the rotating gantry can acquire a proton projection image at each imaging angle.
5. The proton helium ion therapy device according to claim 1, characterized in that: The front position detector is fixed at the bottom of the treatment head, and the treatment head bracket is fixed on the rotating frame; the rear position detector and the proton residual energy detector are installed on the rotating frame and are retractable relative to the rotating frame, extending to the downstream position of the imaging object during proton CT imaging.
6. The proton helium ion therapy device according to claim 1, characterized in that: The front position detector and the rear position detector respectively adopt two strip ionization chambers or multi-filament ionization chambers spaced at a fixed distance; the proton residual energy detector is a multi-layer flat plate ionization chamber.
7. The proton helium ion therapy device according to claim 1, characterized in that: The three-dimensional distribution of the relative stopping power of the imaging object in the three-dimensional space is reconstructed by an image reconstruction algorithm, which is a filtered back projection algorithm, an iterative reconstruction algorithm, or a compressed sensing algorithm.
8. A proton CT imaging method for a proton helium ion therapy device, characterized in that: include: Step S1: providing the proton helium ion therapy device according to any one of claims 1 to 7, and setting the flux intensity and proton energy for proton CT imaging; Step S2: rotating the rotating gantry to a first imaging angle to perform scanning irradiation at an imaging angle of the rotating gantry; Step S3: Detection results collected by the front position detector, the rear position detector, and the proton residual energy detector are acquired using a data acquisition and imaging system as the position of the proton beam before and after the incident imaging object; based on the position and beam direction of the proton beam at each irradiation point before and after the incident imaging object, the most likely path of the proton beam passing through the imaging object is obtained using a most likely path estimation method; based on the energy of the proton beam before and after the incident imaging object, the proton energy attenuation value corresponding to the most likely path of the proton beam passing through the imaging object at each irradiation point is calculated to obtain a water equivalent length attenuation value; based on the scanning results of all irradiation points at the same imaging angle, a distribution map of the water equivalent length attenuation values of all irradiation points is obtained as a proton CT projection image at the current imaging angle; Step S4: rotating the gantry to the next imaging angle, and repeating steps S2 and S3 to generate a proton projection image at the next imaging angle, until proton projection images at all imaging angles are obtained; Step S5: Based on the proton projection images at multiple imaging angles and the most likely paths of all irradiation points, an image reconstruction algorithm is used to reconstruct the distribution of the relative stopping power of the imaging object in three-dimensional space.
9. The proton CT imaging method of the proton helium ion therapy device according to claim 8, characterized in that: The image reconstruction algorithm is a filtered back projection algorithm, an iterative reconstruction algorithm, or a compressed sensing reconstruction algorithm.