Devices and methods for adjusting the position of a charged particle beam

Abstract

To solve problems of the prior art devices and methods for tuning the position of a charged particle beam in a particle therapy apparatus.SOLUTION: A particle therapy apparatus is configured to scan a charged particle beam over a target according to a pre-defined treatment field which covers a treatment surface in an isocenter plane of the apparatus. The apparatus is capable of scanning the beam over a reachable surface, which covers the treatment surface and is larger than the treatment surface. A beam stopper is arranged downstream of the scanning magnets of the apparatus, at a position to prevent the beam from reaching at least a portion of the reachable surface and to allow the beam to reach any portion of the treatment surface. A control system is configured to control the apparatus to direct the beam to the beam stopper and to meanwhile measure a position of the beam, to calculate a difference between a desired position of the beam and the measured position of the beam when it is directed to the beam stopper, and to scan the beam over the target according to the predefined treatment field by taking into account the calculated difference.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a device and a method for adjusting the position of a charged particle beam, and more specifically, to adjusting the position of a charged particle beam in a charged particle beam therapy apparatus. Background Art

[0002] Charged particle therapy apparatuses that treat a target such as a patient's tumor with such a charged particle beam have been known for many years. It is also known that the position of the charged particle beam needs to be adjusted to correspond to a desired position when irradiating the target with the beam. This adjustment is even more relevant when the particle beam is scanned across the target.

[0003] Pencil beam scanning (hereinafter referred to as PBS herein) uses tuning spots, for example, to ensure proper alignment of the pencil beam for each layer within the target to be irradiated. To accomplish this, a "tuning" loop is used. This tuning loop checks the position of the non-scanned beam in an ionization chamber (IC) and calculates the deviation for application to the scanning magnets in order to achieve correct absolute spot positioning at the isocenter.

[0004] The method described in EP2552545B1 employs a PBS scanning algorithm. This PBS scanning algorithm selects a tune-up spot in each layer of the target by finding the highest dose spot within the layer, irradiates this spot with the lowest possible dose, and checks the beam position in the ionization chamber during this time. From the position measured in the ionization chamber, the landing location of the spot within the target volume can be geometrically determined / calculated. A correction is then applied to the scanning magnet, the spot is irradiated again, and the beam position is re-checked in the ionization chamber. This process is known as the tune-up loop. During the tune-up loop, the total dose emitted to this tune-up spot is measured and subtracted from the spot dose to ensure that the desired dose measurement is maintained for this spot. As shown in paragraph 57 of EP2552545B1, "By using the irradiation device and method of the invention, the need to insert a beam stop between the irradiation unit and the target during the tune-up phase is eliminated." This is indeed advantageous because it allows time for controlling the beam position and the treatment equipment remains simple. However, this method is not suitable when high dose rates should be delivered to a target in a single scan, for example, using flash irradiation technology.

[0005] In FLASH treatment procedures, a single beam scan is performed across the ridge filter at a very high dose rate to irradiate the target volume in one go. If the conventional PBS adjustment loop described herein is used, this proportionally results in a higher dose rate, which in turn results in a proportionally higher dose at the adjustment spot, as a higher dose rate will emit a proportionally larger dose within a given time. This higher dose adjustment spot risks further lowering the dose rate for the PBS field and negating the FLASH effect. Reducing the dose rate during spot adjustment is suboptimal because the adjustment is performed under a beamline condition different from that used during treatment beam emission, and the results of the adjustment may not be transferable from one beamline condition to another.

[0006] In conventional technology, alternative methods for beam position control have been proposed.

[0007] EP2833970B1 describes, for example, a method in which beam position correction data can be introduced into the beam steering dataset, or automatically introduced after the execution of a treatment-independent test irradiation dataset. This method proposes a beam position correction model that is created by testing the treatment equipment before patient treatment, and therefore requires time that is unavailable for patient treatment.

[0008] U.S. Patent No. 10195465(B2) covers a system that provides real-time correction of the position of a charged particle beam. This system can be used when a patient is in their treatment position in an isocenter, for example, during a therapeutic procedure. In this case, a movable beam stop is placed between the detector and the scanning magnet. The beam stop can block the beam from reaching the patient without requiring the patient to be moved during readjustment / calibration / setup, and once readjustment / calibration / setup is complete, it can allow the beam to pass through and reach the patient, for example, to provide treatment. The beam stop may be a three-dimensional object that moves orthogonally to the beam in the X or Y direction, such as a rocker or guillotine. Beam position measurement and deflector correction are performed in front of the scanning magnet. However, this solution is not adapted to account for position errors that may be introduced by the scanning magnet. It is also complex and expensive because it requires a movable beam stop whose movement is more prone to failure, in which case an incorrect dose may be delivered to the patient. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] EP2552545B1 [Patent Document 2] EP2833970B1 [Patent Document 3] US Patent No. 10195465(B2) [Patent Document 4] EP2532385B1 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The objective of the present invention is to solve the problems of conventional devices and methods for adjusting the position of a charged particle beam within a particle beam therapy apparatus. [Means for solving the problem]

[0011] The present invention is defined by the independent claims. The dependent claims define advantageous embodiments.

[0012] According to the present invention, a particle beam therapy device is provided, - A particle accelerator for emitting charged particle beams, - A beam transport system for emitting a charged particle beam along the main beam axis (Z) to a target in an isocenter plane perpendicular to the main beam axis (Z), - A scanning magnet for scanning a charged particle beam across a target, - A beam position detector positioned downstream of the scanning magnet and adapted to detect the X and Y positions of the charged particle beam when the charged particle beam intersects the detector, - A beam stopper positioned downstream of a beam position detector, which is adapted to stop a charged particle beam when it strikes the beam stopper, - A control system configured to drive a scanning magnet to scan a charged particle beam across a target according to a predetermined treatment field covering a treatment surface in the isocenter plane, and further capable of driving the scanning magnet to scan a charged particle beam according to a reachable field covering a reachable surface in the isocenter plane, wherein the reachable surface covers the treatment surface and is larger than the treatment surface, and A particle beam therapy device equipped with the following features is provided.

[0013] The beam stopper is positioned such that it prevents the charged particle beam from reaching at least a portion of the reachable surface, while allowing the charged particle beam to reach any portion of the treatment surface.

[0014] The control system is - A charged particle beam is directed towards a beam stopper, and during this time, the X and Y positions of the charged particle beam are measured using a beam position detector. - Calculate the difference between the desired X and Y positions of the charged particle beam and the respective measured X and Y positions of the charged particle beam when directed towards the beam stopper. - Scan the charged particle beam across the target according to the predetermined treatment area, taking the calculated difference into account. It is configured to control the particle beam therapy device.

[0015] Furthermore, since the beam stopper is positioned downstream of the scanning magnet, the apparatus according to the present invention is adapted to take into account beam position errors that may be caused by the scanning magnet.

[0016] Furthermore, the beam stopper is positioned to prevent the charged particle beam from reaching at least a portion of the reachable surface, while allowing the charged particle beam to reach any portion of the treatment surface. This eliminates the need to remove the beam stopper along with the treatment area to irradiate the target, thus saving treatment time.

[0017] Furthermore, the device according to the present invention is well adapted for FLASH therapy because the dose delivered to the target during treatment is not or hardly affected by the beam position adjustment step.

[0018] In some examples, the control system is configured to control the particle beam therapy device to scan the charged particle beam across the target according to a predetermined treatment field by correcting the beam position according to a difference between a desired X and Y position of the charged particle beam and a measured X and Y position of the charged particle beam when directed toward the beam stopper.

[0019] In some examples, the beam stopper is held in a fixed position while the charged particle beam is scanned across the target according to the predetermined treatment field. As a result, time is saved for patient treatment, and the device is also more reliable because the beam stopper does not move. The fact that the beam stopper does not move also makes the device safer because the risk of incorrect positioning of the beam stopper after moving the beam stopper in other methods is eliminated or reduced.

[0020] In some examples, the beam stopper is arranged as close as possible to the main beam axis (Z), thereby enabling more accurate adjustment of the beam position.

[0021] In some examples, the particle accelerator is a cyclotron or a synchrotron. In some examples, the charged particle beam is a beam of protons or carbon ions.

[0022] Regarding particle beam therapy devices, it should be noted that, conventionally, the X and Y axes form an orthogonal referential with the Z axis.

[0023] The present invention also relates to a method for adjusting the position of a charged particle beam in a particle beam therapy device.

[0024] These and further aspects of the present invention will be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram of an exemplary apparatus according to the present invention. [Figure 2] This is a schematic cross-sectional view of an exemplary beam shaping device equipped with a beam stopper according to the present invention. [Modes for carrying out the invention]

[0026] The line drawings in the diagrams are not drawn to isometric scale and are not harmonious. Overall, similar or identical components in the diagrams are indicated by the same reference numerals.

[0027] Figure 1 schematically shows an exemplary particle beam therapy apparatus according to the present invention. The apparatus comprises a particle accelerator, such as a cyclotron or synchrotron, which emits a charged particle beam, such as a beam of protons or carbon ions.

[0028] The apparatus also includes a beam transport system that directs a charged particle beam along the main beam axis (Z) to a target in an isocenter plane perpendicular to the main beam axis (Z). The target is, for example, a tumor to be treated in a patient.

[0029] The apparatus further comprises a scanning magnet for scanning a charged particle beam across a target; a beam position detector located downstream of the scanning magnet, adapted to detect the X and Y positions of the charged particle beam as it passes the detector; a beam stopper located downstream of the beam position detector, adapted to stop the charged particle beam when it strikes the beam stopper; and a control system configured to drive the scanning magnet to scan the charged particle beam across the target according to a predetermined treatment field covering a treatment surface in the isocenter plane. The control system is further capable of driving the scanning magnet to scan the charged particle beam according to a reachable field covering an reachable surface in the isocenter plane, the reachable field covering and larger than the treatment surface.

[0030] The reachable surface is one surface in the isocenter plane to which the device can direct the particle beam by driving its scanning magnets in the X and Y directions. The reachable surface is, for example, the largest surface in the isocenter plane to which the device can direct the particle beam by driving its scanning magnets in the X and Y directions.

[0031] For example, considering a conventional proton therapy device using a pencil beam scanning (PBS) irradiation method, when projected onto an isocenter in the treatment room, the scanning magnet in the nozzle of such a device has the ability to emit a pencil beam spot somewhere within a reachable surface of up to 400 mm x 300 mm. However, the maximum treatment surface for flash treatment using such a device may be smaller, for example, 80 mm x 80 mm.

[0032] Such devices themselves are well known in the industry and will not be described further. The unique features of the present invention are, in particular, the position of the beam stopper and the method for adjusting the beam position, as will be detailed below in this specification.

[0033] As shown in Figure 1, the beam stopper is positioned such that it prevents the charged particle beam from reaching at least a portion of the reachable surface, while allowing the charged particle beam to reach any portion of the treatment surface. As can be understood from this representation, Figure 1 shows projections of the reachable surface and the treatment surface, both of which lie on a plane perpendicular to the main beam axis (Z) and where the beam stopper is located (hereinafter referred to as the stop plane). The projections follow various beam directions as the beam is scanned across the X and Y directions.

[0034] Furthermore, as shown in Figure 1, the beam stopper is positioned within the stop plane, not within the projection image of the treatment surface, but within the projection image of the reachable surface. Therefore, when the particle beam is directed towards the beam stopper, the beam stopper stops the beam, and the beam does not reach the target. On the other hand, when the particle beam is directed towards any point on the treatment surface, it is not stopped by the beam stopper, and the beam reaches the target and the treatment is performed.

[0035] The beam stopper can be a piece of metal, such as brass.

[0036] The control system is configured to direct the charged particle beam towards the beam stopper, measure the X and Y positions of the charged particle beam using a beam position detector, calculate the difference (or deviation) between the desired (or planned) X and Y positions of the charged particle beam and the respective measured X and Y positions of the charged particle beam when directed towards the beam stopper, and control the particle beam therapy apparatus to scan the charged particle beam across the target according to a predetermined treatment field, taking the calculated difference (or deviation) into consideration.

[0037] In some examples, the control system is configured to control the particle beam therapy apparatus to scan the charged particle beam across a target according to a predetermined treatment field by correcting the beam position according to the difference between the desired X and Y positions of the charged particle beam and the respective measured X and Y positions of the charged particle beam when directed towards a beam stopper.

[0038] If the desired or planned X-position of the beam is, for example, 125 (a hypothetical value), and the measured X-position of the beam when it is directed towards the beam stopper is, for example, 130 (a hypothetical value), the control system can compensate for the difference, in particular by correcting the magnetic setting of the X-scanning magnet to cancel out or reduce the difference between the two values. The same applies, by analogy, to the Y-position of the beam and the Y-scanning magnet.

[0039] Once the difference or deviation between the desired X and Y positions of the charged particle beam and the measured X and Y positions of the charged particle beam at the reference point (here, the beam stopper position) is known, the corrections to be applied to the magnet settings of the X and Y scanning magnets are commonly known in the art, for example, from EP2552545B1 incorporated herein by reference.

[0040] In some examples, while the device is operating, the beam stopper is held in place while the charged particle beam is scanned across the target according to a predetermined treatment field.

[0041] In some examples, the beam stopper is positioned as close as possible to the main beam axis (Z) without overlapping with the projection of the treatment surface (21') on the stop plane. Generally, as in conventional methods, the main beam axis (Z) is the axis of the non-scanning particle beam, i.e., the axis at which the beam intersects the isocenter, as shown in Figure 1, for example.

[0042] The beam stopper can be positioned anywhere longitudinally (along the beam path) between the detector and the target. Preferably, the beam stopper is part of the device or mounted on the device.

[0043] In some examples, the treatment apparatus includes a beam shaping device located downstream of the beam position detector. The beam shaping device may be, for example, a ridge filter and / or range shifter and / or compensator and / or collimator, which are commonly known in the art and serve to shape and / or modulate the particle beam before it reaches the target.

[0044] In some examples, the beam stopper is an integral component of the beam shaping device or one of the beam shaping devices, or is attached to the beam shaping device or one of the beam shaping devices, preferably detachably attached to the beam shaping device or one of the beam shaping devices.

[0045] In some examples, the beam stopper is fixed to a part of the particle beam therapy apparatus, preferably located in an accessory holder fixed to the nozzle of the particle beam therapy apparatus.

[0046] In some examples, the beam shaping device comprises a ridge filter and a collimator, which is preferably located downstream of the ridge filter. In such cases, the beam stopper is, for example, an integral part of the collimator or is attached to the collimator, preferably detachably attached to the collimator.

[0047] In some examples, the collimator has an annular shape, such as disclosed in EP2532385B1. In such cases, the beam stopper may be, for example, a part of the collimator or located next to the outer side surface of the collimator. Figure 2 schematically shows a cross-section of an exemplary collimator with a beam stopper according to the present invention. The collimator has an annular shape that includes a central aperture whose shape is determined according to the shape of the target and defines a path for a particle beam toward the target during treatment. In this example, the beam stopper has a "bulge" shape relative to the collimator ring. This bulge is positioned such that when a particle beam strikes the center of the bulge, it is blocked by the bulge, at least 10 * It is preferable that the beam stopper has a sigma diameter. Generally speaking, in order to identify any possible errors in the beam position before adjusting the position, the size of the beam stopper should preferably be larger than the size of the beam spot at the beam stopper's location. Therefore, the size of the beam stopper is preferably selected according to the size of the beam spot foreseen by the treatment plan.

[0048] In some examples, the control system is configured to control the particle beam therapy apparatus to emit a predetermined treatment field onto a target by scanning a charged particle beam across the target in a single scan.

[0049] The present invention also relates to a method for adjusting the position of a charged particle beam within a particle beam therapy apparatus, wherein the particle beam therapy apparatus is - A particle accelerator (2) for emitting a charged particle beam, - A beam transport system (4) for emitting a charged particle beam along the main beam axis (Z) to a target (50) in an isocenter plane (11) perpendicular to the main beam axis (Z), - Scanning magnet (5) for scanning a charged particle beam across a target, - A beam position detector (6) positioned downstream of the scanning magnet and adapted to detect the X and Y positions of the charged particle beam when the charged particle beam intersects the detector, - A beam stopper (10) located downstream of the beam position detector, which is adapted to stop the charged particle beam when it hits the beam stopper, - A control system (20) configured to drive a scanning magnet to scan a charged particle beam across a target according to a predetermined treatment field covering a treatment surface (21) in an isocenter plane (11), and further capable of driving the scanning magnet to scan a charged particle beam according to a reachable field covering a reachable surface (22) in an isocenter plane (11), wherein the reachable surface (22) covers and is larger than the treatment surface (21), and the control system (20), Equipped with, The method involves the following steps: - The steps include positioning a beam stopper (10) in such a location that it prevents the charged particle beam from reaching at least a portion of the reachable surface (22) and allows the charged particle beam to reach any portion of the treatment surface (21), - A step of directing a charged particle beam towards a beam stopper, and during that time, measuring the X and Y positions of the charged particle beam using a beam position detector, - A step of calculating the difference between the desired X and Y positions of the charged particle beam and the measured X and Y positions of the charged particle beam when directed towards the beam stopper, - A step of applying a correction to the magnet settings of the X and Y scanning magnets, taking into account the calculated difference between the desired X and Y positions of the charged particle beam and the measured X and Y positions of the charged particle beam when directed towards the beam stopper. Includes.

[0050] The present invention has been described with respect to specific embodiments that should not be considered as illustrative or limiting. More specifically, it will be apparent to those skilled in the art that the present invention is not limited by what is specifically illustrated and / or described herein.

[0051] Reference numbers in the claims do not limit the scope of their protection.

[0052] The use of the verbs “to prepare,” “to include,” “to consist of,” or any other variations thereof, as well as their respective conjugations, does not exclude the existence of elements other than those listed.

[0053] The use of the articles "a," "an," or "the" preceding an element does not exclude the existence of multiple such elements.

[0054] The present invention may also describe a particle beam therapy apparatus configured to scan a charged particle beam across a target according to a predetermined treatment field covering a treatment surface in the isocenter plane of the apparatus, as follows: The apparatus can scan the beam over a reachable surface that covers the treatment surface and is larger than that. A beam stopper is positioned downstream of the scanning magnet of the apparatus such that it prevents the beam from reaching at least a portion of the reachable surface and allows the beam to reach any portion of the treatment surface. A control system is configured to direct the beam towards the beam stopper, measure the position of the beam in the meantime, calculate the difference between a desired position of the beam and the measured position of the beam when directed towards the beam stopper, and control the apparatus to scan the beam across the target according to a predetermined treatment field, taking the calculated difference into consideration. [Explanation of Symbols]

[0055] 2 Particle accelerator 4 Beam Transport System 5 Scanning Magnet 6. Beam position detector 10 Beam Stopper 11 Isocenter Plane 20 Control Systems 21 Treatment surface 21' Treatment surface 22 Reachable plane 50 targets Z Main beam axis

Claims

1. It is a particle beam therapy device, A particle accelerator (2) for emitting a charged particle beam, A beam transport system (4) for emitting the charged particle beam, which follows the main beam axis (Z), to a target (50) in an isocenter plane (11) perpendicular to the main beam axis (Z), A scanning magnet (5) for scanning the charged particle beam across the target, A beam position detector (6) positioned downstream of the scanning magnet, the beam position detector (6) being adapted to detect the X and Y positions of the charged particle beam when the charged particle beam intersects with the beam position detector (6), A beam stopper (10) positioned downstream of the beam position detector, wherein the beam stopper (10) is configured to stop the charged particle beam when the charged particle beam strikes the beam stopper, A control system (20) configured to drive a scanning magnet to scan the charged particle beam across the target according to a predetermined treatment field covering a treatment surface (21) in the isocenter plane (11), and further capable of driving the scanning magnet to scan the charged particle beam according to a reachable field covering a reachable surface (22) in the isocenter plane (11), wherein the reachable surface (22) covers the treatment surface (21) and is larger than the treatment surface (21), Equipped with, The beam stopper (10) is positioned such as to prevent the charged particle beam from reaching at least a portion of the reachable surface (22) and to allow the charged particle beam to reach any portion of the treatment surface (21), and the control system is configured to The charged particle beam is directed towards the beam stopper, and during this time, the X and Y positions of the charged particle beam are measured using the beam position detector. The difference between the desired X and Y positions of the charged particle beam and the measured X and Y positions of the charged particle beam when directed towards the beam stopper is calculated. Taking the calculated difference into consideration, the charged particle beam is scanned across the target according to the predetermined treatment area. A particle beam therapy apparatus characterized by being configured to control the particle beam therapy apparatus as described above.

2. The particle beam therapy apparatus according to claim 1, wherein the control system is configured to control the particle beam therapy apparatus to scan the charged particle beam across the target according to the predetermined treatment area by correcting the beam position according to the difference between the desired X and Y positions of the charged particle beam and the measured X and Y positions of the charged particle beam when directed toward the beam stopper.

3. The particle beam therapy apparatus according to claim 1, wherein, during operation, the beam stopper is held in a fixed position while the charged particle beam is scanned across the target according to the predetermined treatment area.

4. The particle beam therapy apparatus according to claim 1, wherein the beam stopper is positioned as close as possible to the main beam axis (Z).

5. The particle beam therapy apparatus according to claim 1, further comprising a beam shaping device disposed downstream of the beam position detector.

6. The particle beam therapy apparatus according to claim 5, wherein the beam shaping device comprises a ridge filter and / or a range shifter and / or a compensator and / or a collimator.

7. The particle beam therapy apparatus according to claim 5, wherein the beam stopper is an integral component of the beam shaping device or one of the beam shaping devices, or is attached to the beam shaping device or one of the beam shaping devices.

8. The particle beam therapy apparatus according to claim 1, wherein the beam stopper is disposed within an accessory holder fixed to a part of the particle beam therapy apparatus.

9. The particle beam therapy apparatus according to claim 5, wherein the beam shaping device comprises a ridge filter and a collimator.

10. The particle beam therapy apparatus according to claim 9, wherein the beam stopper is an integral member of the collimator or is attached to the collimator.

11. The particle beam therapy apparatus according to claim 10, wherein the collimator has an annular shape.

12. The particle beam therapy apparatus according to claim 1, wherein the control system is configured to control the particle beam therapy apparatus so as to emit the predetermined treatment field onto the target by scanning the charged particle beam across the target in a single scan.

13. The particle beam therapy apparatus according to claim 1, wherein the particle accelerator is a cyclotron or a synchrotron.

14. The particle beam therapy apparatus according to claim 1, wherein the charged particle beam is a beam of protons or carbon ions.

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