CN108671418A - Guide of magnetic resonant image device for ion beam radiation therapy - Google Patents

Abstract

A magnetic resonance image guiding device for ion beam radiotherapy, comprising: a magnetic field generating device that generates a uniform magnetic field; a C-arm that is used to fix the magnetic field generating device; a transmission mechanism that includes a rotating track, the The C-shaped arm can rotate 180 degrees around the center point in the rotating track, so as to change the magnetic field direction of the magnetic field generating device; the translation track is arranged at the bottom of the transmission mechanism for the transmission mechanism to move along the The pan track described above switches between the treatment position and the idle position. The magnetic resonance image guidance device of the present invention has high soft tissue resolution capability, does not generate bone artifacts in imaging, and does not generate ionizing radiation to the human body, and can be applied to ion beam radiotherapy equipment with fixed racks and rotating racks, and can Always keep the direction of the magnetic field consistent with the direction of the beam, so the quality of the beam will not be affected.

Description

Magnetic resonance image guidance for ion beam radiotherapy

technical field

The invention particularly relates to a magnetic resonance image guiding device for ion beam radiotherapy.

Background technique

The main advantage of ion beam radiotherapy compared with traditional photon radiotherapy lies in the inverted depth dose distribution characteristics, that is, when the ion beam penetrates the target material, the energy loss in the front part of the incident channel is very small, forming a relatively low dose plateau, while in the near range The energy of the terminal ion beam decreases rapidly to form a dose deposition peak, namely the Bragg peak. This property enables the ion beam to precisely deposit doses on tumor targets while minimizing radiation damage to organs at risk. However, the premise of fully utilizing the advantages of ion beam dose distribution is to know the precise location of the target area, and a misalignment of a few millimeters may cause >80% dose deviation in the target area, while the surrounding normal tissues are irradiated with high doses. On the one hand, in the stage of treatment plan design, errors in the dose calculation model, CT image resolution, and the conversion relationship between CT value and tissue water equivalent coefficient will lead to uncertainty in the range of the ion beam, and the target area needs to be placed outside. On the other hand, during the treatment process, the position and movement of the target area and normal tissues should be monitored and corrected, and the scanning parameters should be corrected in time. Therefore, accurate imaging of target volumes and organs at risk before and during ion beam radiation therapy is of paramount importance.

Image-guided radiation therapy adds the concept of time series on the basis of three-dimensional radiation therapy, and uses various imaging equipment to monitor the position and movement of the target area and normal tissues before and during treatment, providing a powerful tool for precise imaging of target areas and organs at risk. means. Currently widely used image guidance systems include: electronic portal imaging system, kV-level cone-beam CT, kV-level X-ray radiography and fluoroscopy, MV-level cone-beam CT, and magnetic resonance image-guidance systems. Among them, the electronic portal imaging system has the advantages of small size, high sensitivity, and simple operation. It can be used to correct the portal shape, patient positioning, and directly measure the dose distribution in the portal. The disadvantage is that soft tissue imaging is not clear; kV Class cone beam CT has the advantages of small size, light weight, and can be directly integrated into the linear accelerator. The disadvantage is that the density resolution is low, and there is still a big gap compared with clinical diagnostic CT; kV-class X-ray photography and fluoroscopy have The advantages of high contrast between bone and air and clear soft tissue imaging are usually combined with treatment equipment; the biggest advantage of MV-level cone beam CT is that the treatment and image guidance are from the same source, and the outgoing dose can be measured when detecting images. The disadvantage is that the image Low spatial resolution and even lower resolution at low contrast. The above image guidance systems all use X-rays to irradiate the human body, so they cannot be used for real-time image guidance, so the positions and movements of the target area and normal tissues cannot be reflected in real time during the treatment process.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a magnetic resonance image guidance device for ion beam radiation therapy, so as to solve at least one of the above-mentioned problems.

The present invention is achieved through the following technical solutions:

A magnetic resonance image guiding device for ion beam radiotherapy, comprising: a magnetic field generating device that generates a uniform magnetic field; a C-arm that is used to fix the magnetic field generating device; a transmission mechanism that includes a rotating track, and The C-shaped arm can rotate 180 degrees around the center point in the rotating track, so as to change the direction of the magnetic field of the magnetic field generating device; the translation track is arranged at the bottom of the transmission mechanism for the transmission mechanism to move along the The pan track described above switches between the treatment position and the idle position.

Preferably, the magnetic field generating device is two parallel permanent magnets.

Preferably, the permanent magnet is in the shape of a round cake with a hole in the middle, with a diameter of 800-1500 mm, a thickness of 80-150 mm, and a hole diameter of 80-100 mm.

Preferably, the distance between the inner surfaces of the two permanent magnets is 400-650mm, and the generated magnetic field strength is 0.25-1.0T.

Preferably, a treatment head is arranged in the middle hole of a permanent magnet in the magnetic field generating device, the magnetic resonance image guidance device rotates synchronously with the treatment head, and the direction of the magnetic field generated by the magnetic field generating device is always in line with the The direction of the ion beam generated by the treatment head is parallel.

Preferably, in ion beam radiation therapy, a part of the treatment bed is located between the two permanent magnets and inside the C-shaped arm, and the transmission mechanism moves along the translation track to guide the magnetic resonance image The device switches between a treatment position and an idle position.

Preferably, the magnetic resonance image guidance device includes a control device, which stores a program for performing the following steps: S1: verify the patient's position in the treatment room before the treatment starts; S2: monitor the target area in real time during the treatment and the position and movement of normal tissues; S3: During the treatment process, the target area moves to the set range to irradiate it.

Preferably, step S1 includes the following sub-steps: S11: perform initial positioning of the patient, aligning the laser light with the marker points on the patient's body surface; S12: move the magnetic resonance image guidance device to the treatment position, and place the treatment The bed is restored to the initial position; S13: Perform magnetic resonance imaging on the patient, compare the magnetic resonance images acquired during planning design with the currently acquired magnetic resonance images, and calculate the six-dimensional offset; S14: According to the six-dimensional offset Move the treatment bed as much as possible, and collect the patient's magnetic resonance images again, and compare the differences until the deviation is within the acceptable range, and the setup verification is completed.

Preferably, step S2 includes the following steps: for a fixed frame, the magnetic resonance image guidance device always adjusts the magnetic field generated by the permanent magnet to be consistent with the ion beam direction generated by the treatment head before the treatment starts, There is no need to adjust the direction of the magnetic field again during the process; for the rotating gantry, it is necessary to irradiate the target area at different angles during intensity-modulated radiation therapy, so the magnetic resonance image guidance device rotates synchronously with the treatment head. During the process, when a large movement of the patient's body position is detected, the irradiation should be stopped immediately and the patient should be repositioned; on the other hand, the movement of the target area and normal tissues should be monitored, and the beam scanning parameters should be adjusted in time according to the movement position.

Preferably, step S3 includes one of the following steps: according to the real-time monitoring of the moving position of the target area by the magnetic resonance image guidance device, a threshold is set, and when the target area moves within the threshold, the beam irradiation is turned on; otherwise, the beam is turned off. According to the movement position of the target area, the beam scanning parameters are adjusted in real time, so that the beam irradiation position and the movement position of the target area are always consistent; a patient-specific breathing guide curve is generated according to the monitored target area movement curve, and the guide curve Synchronized with the magnetic excitation cycle of the accelerator, the patient adjusts his breathing movement to make it consistent with the breathing guidance curve, ensuring that the target area moves within the set range to irradiate it.

It can be seen from the above technical scheme that the magnetic resonance image guidance device for ion beam radiation therapy of the present invention has the following beneficial effects:

(1) Magnetic resonance imaging has a high soft tissue resolution capability, and the imaging will not produce bony artifacts like those in CT scans, and will not produce ionizing radiation to the human body;

(2) The magnetic resonance imaging equipment of the present invention can be applied to ion beam radiotherapy equipment with a fixed frame and a rotating frame, and can always keep the direction of the magnetic field consistent with the direction of the beam, thus not affecting the quality of the beam;

(3) Magnetic resonance imaging is non-invasive imaging. During the treatment process, the position and shape of the target area and normal tissue can be monitored in real time. If the patient's body position changes too much, the beam irradiation can be stopped, and the beam scanning can be adjusted in time according to the movement position of the target area. parameters, to achieve the purpose of synchronous irradiation, to eliminate the impact of the interaction of the target area movement and the dynamic beam delivery process on the dose distribution, and to achieve precise radiation therapy;

(4) The high tissue resolution of magnetic resonance imaging makes it more accurate in the process of patient positioning verification.

Description of drawings

Fig. 1 is a structural diagram of a magnetic resonance image guidance device in ion beam radiotherapy in an embodiment of the present invention;

Fig. 2 is the trajectory figure of carbon ion beam under the action of magnetic field in the embodiment of the present invention;

Figure 3 is a graph showing the lateral distribution of beam spots at the Bragg peak position of carbon ion beams with different energies under different magnetic field strengths;

[Description of attached components]

1-Permanent magnet pole plate; 2-Pole plate opening;

3-Permanent magnet pole plate; 4-Pole plate opening;

5-C-arm; 6-transmission mechanism;

7-rotation orbit; 8-translation orbit;

9-translation track; 10-treatment bed;

11-Treatment head.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The present invention provides a magnetic resonance image guiding device for ion beam radiotherapy, comprising: a magnetic field generating device that generates a uniform magnetic field; a C-shaped arm that is used to fixedly install the magnetic field generating device; a transmission mechanism that includes a rotating Track, the C-arm can rotate 180 degrees around the center point in the rotating track, so as to change the magnetic field direction of the magnetic field generating device; the translation track is arranged at the bottom of the transmission mechanism for the transmission The mechanism switches between the treatment position and the idle position along the translation track. The magnetic resonance image guiding device of the present invention has high soft tissue resolution capability, does not generate bone artifacts in imaging, and does not generate ionizing radiation to the human body, and can be applied to ion beam radiotherapy equipment with fixed racks and rotating racks, and can Always keep the direction of the magnetic field consistent with the direction of the beam, so the quality of the beam will not be affected.

Specifically, the present invention provides a magnetic resonance image guiding device for ion beam radiotherapy, and FIG. 1 is a structural diagram of the magnetic resonance image guiding device in ion beam radiotherapy in an embodiment of the present invention. As shown in Figure 1, comprise: magnetic field generating device, produce uniform magnetic field; C-shaped arm 5, be used for fixedly installing described magnetic field generating device; Transmission mechanism 6, it comprises a rotating track 7, and described C-shaped arm is in place The rotation track 7 rotates 180 degrees around the center point; the translation track 8 is connected to the bottom of the transmission mechanism, so that the transmission mechanism can switch between the treatment position and the idle position along the translation track 8.

The magnetic field generating device is two parallel permanent magnets 1 .

The permanent magnet 1 is in the shape of a round cake with a hole in the middle, with a diameter of 800-1500 mm, a thickness of 80-150 mm, and a hole diameter of 80-100 mm.

The distance between the inner surfaces of the two permanent magnets is 400-650mm, and the generated magnetic field strength is 0.25-1.0T.

A treatment head 9 is arranged in the middle hole of a permanent magnet in the magnetic field generating device, and the magnetic resonance image guidance device rotates synchronously with the treatment head, and the direction of the magnetic field produced by the magnetic field generating device is always in line with the treatment head The direction of the generated ion beam is parallel.

In ion beam radiation therapy, a part of the treatment couch 10 is located between the two permanent magnets and inside the C-arm, and the transmission mechanism moves along the translation track so that the magnetic resonance image guidance device Toggle between treatment position and idle position.

The magnetic resonance image guidance device includes a control device, which stores a program, and runs the following steps: S1: verify the patient's position in the treatment room before the treatment starts; S2: monitor the position of the target area and normal tissue in real time during the treatment process and movement; S3: During the treatment process, the target area moves to the set range to irradiate it.

Step S1 includes the following sub-steps: S11: perform initial positioning of the patient, and align the laser light with the marker points on the patient's body surface; S12: move the magnetic resonance image guidance device to the treatment position, and restore the treatment bed to Initial setup position; S13: Perform magnetic resonance imaging on the patient, compare the magnetic resonance image acquired during planning design with the currently acquired magnetic resonance image, and calculate the six-dimensional offset; S14: move the treatment according to the six-dimensional offset Bed, and MRI images of the patient were collected again, and the difference was compared until the deviation was within the acceptable range, and the set-up verification was completed.

Step S2 includes the following steps: for a fixed frame, the magnetic resonance image guidance device always adjusts the magnetic field generated by the permanent magnet to be consistent with the direction of the ion beam current generated by the treatment head before the treatment starts, and does not change the direction of the ion beam during the treatment. It is necessary to adjust the direction of the magnetic field again; for the rotating gantry, it is necessary to irradiate the target area at different angles during intensity-modulated radiation therapy, so the magnetic resonance image guidance device rotates synchronously with the treatment head. When a large movement of the patient's body position is detected, the irradiation should be stopped immediately and the patient should be repositioned; on the other hand, the movement of the target area and normal tissues should be monitored, and the beam scanning parameters should be adjusted in time according to the movement position.

Step S3 includes one of the following steps: according to the real-time monitoring of the moving position of the target area by the magnetic resonance image guidance device, a threshold is set, and when the target area moves within the threshold, the beam irradiation is turned on, otherwise the beam is turned off; The moving position of the target area, adjust the beam scanning parameters in real time, so that the beam irradiation position and the moving position of the target area are always consistent; generate a patient-specific breathing guide curve according to the monitored target area movement curve, and the guide curve and the accelerator magnetic The excitation cycle is synchronized, and the patient adjusts his breathing movement to make it consistent with the breathing guidance curve, so as to ensure that the target area moves within the set range to irradiate it.

The magnetic resonance image guiding device for ion beam radiation therapy of the present invention will be further described in detail below in conjunction with specific embodiments and accompanying drawings.

Example

Magnetic resonance image guidance will generate a magnetic field, and the trajectory of the ion beam will be shifted under the action of the magnetic field. In the present invention, the direction of the magnetic field and the direction of the beam are always consistent. In order to verify the effect of the magnetic field on the beam, we treat cancer according to heavy ions The beam distribution system and the energy of the ion beam on the special device (HIMM), using the Monte Carlo method to simulate the range of the ion beam and the change of the beam spot size under the action of the magnetic field. The carbon ion beam energy was 120MeV/u, 260MeV/u and 400MeV/u, and the magnetic field strength was 0T, 0.35T, 0.5T and 1.5T. The results are shown in Figure 2. From the analysis results, without the action of a magnetic field, the ranges of 120MeV/u, 260MeV/u and 400MeV/u energy carbon ion beams are 35.6mm, 135mm and 267.6mm respectively; There is no change in the range, which means that the magnetic field parallel to the beam direction will not affect the range of the ion beam. Figure 3 shows the lateral distribution of beam spots at the Bragg peak of carbon ion beams with different energies under the action of different magnetic field intensities. The beam spot size (σ) and position can be obtained by Gaussian fitting. According to the analysis of the results, in the absence of a magnetic field, the beams of 120MeV/u, 260MeV/u and 400MeV/u energy carbon ion beams at the Bragg peak The spot sizes are 2.84mm, 3.04mm, and 3.47mm, and the center of the beam spot is at the zero point; under the action of different strength magnetic fields, the beam spot sizes of ion beams of different energies do not change, and the center positions remain unchanged, indicating that the ion beams parallel to the beam direction The magnetic field has no effect on the beam spot size and position of the ion beam. The above embodiments illustrate that the method of the present invention is feasible, and the position and movement of the target area and normal tissues can be monitored in real time through magnetic resonance images during ion beam radiotherapy without affecting the quality of the beam current.

In summary, the magnetic resonance image guidance device of the present invention has high soft tissue resolution capability, does not produce bony artifacts in imaging, and does not generate ionizing radiation to the human body, and can be applied to ion beam radiation in fixed racks and rotating racks. On the treatment equipment, the direction of the magnetic field and the direction of the beam can be kept consistent at all times, so the quality of the beam will not be affected.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. A magnetic resonance image guidance device for ion beam radiotherapy, characterized in that it comprises: A magnetic field generating device for generating a uniform magnetic field; A C-shaped arm, used for fixedly installing the magnetic field generating device; The transmission mechanism includes a rotating track, and the C-shaped arm can rotate 180 degrees around the center point in the rotating track, so as to change the direction of the magnetic field of the magnetic field generating device; The translation track is arranged at the bottom of the transmission mechanism for the transmission mechanism to switch between the treatment position and the idle position along the translation track. 2. The magnetic resonance image guidance device according to claim 1, characterized in that, The magnetic field generating device is two parallel permanent magnets. 3. The magnetic resonance image guidance device according to claim 2, characterized in that, The permanent magnet is in the shape of a round cake with a hole in the middle, with a diameter of 800-1500 mm, a thickness of 80-150 mm, and a hole diameter of 80-100 mm. 4. The magnetic resonance image guidance device according to claim 2, characterized in that, The distance between the inner surfaces of the two permanent magnets is 400-650mm, and the generated magnetic field strength is 0.25-1.0T. 5. The magnetic resonance image guidance device according to claim 2, characterized in that, A treatment head is arranged in the middle hole of a permanent magnet in the magnetic field generating device, the magnetic resonance image guiding device rotates synchronously with the treatment head, and the direction of the magnetic field generated by the magnetic field generating device is always in line with the treatment head The direction of the ion beam flow is parallel. 6. The magnetic resonance image guidance device according to claim 2, characterized in that, In ion beam radiation therapy, a part of the treatment bed is located between the two permanent magnets and inside the C-arm, and the transmission mechanism moves along the translation track so that the magnetic resonance image guidance device Toggles between a bit and a free bit. 7. The magnetic resonance image guidance device according to claim 1, characterized in that, The magnetic resonance image guiding device includes a control device in which a program is stored for performing the following steps: S1: Verify the positioning of the patient in the treatment room before the treatment starts; S2: Real-time monitoring of the position and movement of the target area and normal tissues during the treatment process; S3: During the treatment process, the target area moves to the set range to irradiate it. 8. The magnetic resonance image guidance device according to claim 7, wherein step S1 comprises the following sub-steps: S11: Perform initial positioning of the patient to align the laser light with the marking points on the patient's body surface; S12: moving the magnetic resonance image guidance device to a treatment position, and restoring the treatment couch to an initial setup position; S13: Perform magnetic resonance imaging on the patient, compare the magnetic resonance images acquired during planning design with the currently acquired magnetic resonance images, and calculate the six-dimensional offset; S14: Move the treatment bed according to the six-dimensional offset, and collect the patient's magnetic resonance image again, and compare the difference until the deviation is within an acceptable range, and complete the setup verification. 9. The magnetic resonance image guidance device according to claim 7, wherein step S2 comprises the following steps: For a fixed frame, the magnetic resonance image guiding device always adjusts the magnetic field generated by the permanent magnet to be consistent with the direction of the ion beam current generated by the treatment head before the treatment starts, and there is no need to adjust the direction of the magnetic field again during the treatment; For the rotating gantry, it is necessary to irradiate the target area at different angles during intensity-modulated radiation therapy, so the magnetic resonance image guidance device rotates synchronously with the treatment head. When there is a large movement, the irradiation should be stopped immediately and the patient should be repositioned; on the other hand, the movement of the target area and normal tissues should be monitored, and the beam scanning parameters should be adjusted in time according to the movement position. 10. The magnetic resonance image guidance device according to claim 7, characterized in that step S3 comprises one of the following steps: According to the real-time monitoring of the moving position of the target area by the magnetic resonance image guidance device, a threshold is set, and when the target area moves within the threshold, the beam irradiation is turned on, otherwise, the beam is turned off; or According to the moving position of the target area, adjust the beam scanning parameters in real time, so that the beam irradiation position and the moving position of the target area are always consistent; or According to the monitored movement curve of the target area, a patient-specific breathing guide curve is generated. The guide curve is synchronized with the magnetic excitation cycle of the accelerator. The patient adjusts his breathing movement to make it consistent with the breathing guide curve to ensure that the target area moves to the set irradiate it within the range.