Radiation therapy system and method

Abstract

The present application relates to a radiotherapy system and method, wherein the radiotherapy system includes an accelerator and a beam transport system that generates a particle beam. The accelerator and the beam transport system direct the beam onto a path and into a nozzle that is operable to direct the beam toward an object. The nozzle includes a scanning magnet operable to direct the beam toward different locations within the object, and also includes a beam energy modifier that is configured to modulate the beam by, for example, placing materials of different thicknesses in the path of the beam to affect the energy of the particles in the beam.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a divisional application of the invention patent application with international application number PCT / US2017 / 025732, international application date April 3, 2017, priority date April 1, 2016, date of entry into the Chinese national phase November 30, 2018, Chinese national application number 201780034145.5, and invention name “Radiation therapy system and method”. Technical Field

[0003] Embodiments described in the present disclosure generally relate to radiation therapy systems and methods. Background Art

[0004] The use of radiation therapy to treat cancer is well known. Radiation therapy (radiotherapy) involves directing a beam of high-energy particles, such as electrons, protons, or heavy ions, into a target volume (eg, a tumor or lesion) within a patient's body.

[0005] Before a patient is treated with radiation, a treatment plan specific to that patient is developed. The plan defines various aspects of the radiation therapy using simulations and optimizations based on past experience. For example, for intensity modulated particle therapy (IMPT), the plan may specify the appropriate beam type and the appropriate beam energy. Other parts of the plan may specify, for example, the angle of the beam relative to the patient / target volume, the beam shape, etc. In general, the goal of a treatment plan is to deliver sufficient radiation to the target volume while minimizing exposure of surrounding healthy tissue to the radiation.

[0006] Existing IMPT dose delivery techniques utilize raster scanning, which exploits the well-known Bragg peak characteristic of a single energy particle (e.g., proton) beam. By scanning the beam in the X and Y directions, "layers" of dose can be "painted" within the target volume. Subsequent layers are painted in an overlapping raster scan pattern using particles with different energies, which will therefore stop at different ranges (distances). This scan pattern typically starts at the farthest edge of the planned target volume, and delivers each subsequent layer after pausing to change the beam energy to a smaller range, thereby producing a spread-out Bragg peak (SOBP), until the last layer is delivered to the proximal edge of the planned target volume.

[0007] A fundamental concern during radiation therapy is that the target volume may move during dose delivery (e.g., due to patient movement, breathing, etc.). Movement during dose delivery may inadvertently place healthy tissue in the path of radiation intended for the target volume. While in theory a raster scan pattern can track the in-plane motion of the target volume by vector superimposing the raster scan pattern with the instantaneous two-dimensional (XY) corresponding to the motion, any out-of-plane motion (especially those of normal healthy structures close to the target) may introduce motion-related uncertainties, which in turn may produce dose overlap ("hot spots") or even more severe gaps ("cold spots") within the target volume.

[0008] Recent radiobiological studies have demonstrated the beneficial effects of protecting normal healthy tissue from damage by delivering the entire relatively high therapeutic radiation dose in a single short period of time (e.g., less than one second). However, in conventional raster scanning IMPT, because the dose delivery along each ray passing through the patient occurs continuously at different time points in the scan pattern and is therefore spread out in time, the inevitable dose delivered to normal healthy structures is also spread out in time. Therefore, the radiobiological tissue protection effects reported in the above studies have not been achieved using existing IMPT technology.

[0009] In addition, modern radiotherapy delivery systems include dipole electromagnets and scanning magnets. The dipole magnets (commonly referred to as "bending magnets") guide (e.g., bend) the particle beam in the direction toward the nozzle, and the scanning magnets guide (deflect or scan) the beam in the X and Y directions. Dipole magnets typically utilize a large amount of ferromagnetic return paths and therefore have much slower hysteresis relative to scanning magnets. That is, it takes much longer to change (increase or decrease) the magnetic level in the dipole bending magnet than to use scanning magnets to guide the beam during IMPT delivery. Moreover, the relative slowness of changing the magnetic field of the dipole bending magnet is the main reason why existing IMPT systems utilize a method of scanning the dose one layer at a time. The time spent changing the magnetic strength of the dipole magnet to change the incident beam energy constitutes an important part of the time required to deliver the IMPT treatment dose. Considering the comfort of the patient, for example, shorter radiotherapy is highly preferred. Therefore, reliance on magnets, and in particular the use of dipole bending magnets, for conditioning the particle beam is a barrier to realizing the benefits of using relatively high therapeutic radiation doses in very short times for dose delivery in radiotherapy. Summary of the invention

[0010] In an embodiment according to the present disclosure, a radiotherapy system includes an accelerator and a beam delivery system and a nozzle that can be aimed toward an object. The nozzle includes at least one scanning magnet that guides (e.g., directs, deflects, or scans) the beam toward various locations within a target volume within the object. The nozzle also includes a beam energy modulator that is configured to adjust the beam by, for example, placing materials of different thicknesses in the path of the beam to affect the energy of particles in the beam. The beam energy modulator may include one or both of a range shifter and a range modulator. In one embodiment, the range shifter is configured to place materials of different thicknesses in the path of the beam to affect the distance that the particles penetrate into the object. In one embodiment, the range modulator is configured to place materials of different thicknesses in the path of the beam to reduce the energy of at least a portion of the particles by changing the energy of the outgoing beam particles over time to expand the Bragg peak.

[0011] Importantly, the range shifter and / or range modulator placed in a nozzle as described in the present disclosure is "dynamically variable" (e.g., functions faster than a dipole magnet in a beam delivery system). Thus, a nozzle according to the present disclosure is able to rapidly adjust the particles in the beam to produce a scanned beam (as opposed to a scattered beam) that delivers an overall relatively high therapeutic radiation dose in a target volume. For example, a dose of four Grays can be delivered along a specified beam direction (e.g., a given ray) in less than one second.

[0012] Each ray is part of a scan pattern and irradiates tissue along a different line segment ("target line segment") through the target volume. A high dose that can be delivered in a short period of time along a target line segment may be referred to herein as a "shot". In one embodiment, the shot may be adjusted in energy (intensity) or range and delivered to the target volume below the extended Bragg peak (SOBP) that provides a uniform and otherwise appropriately modified dose to the entire target line segment.

[0013] The intensity of the dose delivered in a shot can be adjusted to match the dose prescribed for a particular target segment. Shots can be delivered using, for example, a predefined scan pattern to irradiate different target segments: a first adjusted beam is generated that can deliver a first dose with SOBP along a first target segment in the target volume, and a second adjusted beam is generated that can deliver a second dose with a second SOBP along a second target segment in the target volume, wherein the second target segment is displaced from the first target segment. Each shot can be triggered and / or aimed in time to coincide with the position of a moving target within the patient, based on, for example, a motion tracking system. Subsequent shots can be independently adjusted in intensity, range, and with appropriate SOBP, and can also be triggered or aimed to coincide with the 4D (three dimensions plus time) position of each target segment in the scan pattern until the entire target volume has been irradiated to the prescribed dose.

[0014] In one embodiment, the range shifter is located in the nozzle and downstream of the scanning magnet(s). In another embodiment, the range shifter is located in the nozzle and upstream of the scanning magnet(s). The range shifter provides a fast way to quickly change the range of the Bragg peak to match the distal edge of the planned target volume.

[0015] In one embodiment, the nozzle includes a range modulator and a range shifter. The range modulator is located downstream of the scanning magnet(s); the range shifter can be located downstream or upstream of the scanning magnet(s). In one embodiment, the range modulator includes a plurality of arms extending from a hub. In one embodiment, each arm has a non-uniform thickness and a non-uniform width (and therefore a non-uniform amount of space between adjacent arms). The range modulator can be rotated about the hub so that the beam will pass through at least one arm and may also pass through the space between adjacent arms.

[0016] In one embodiment, the range modulator can be moved in a first direction (e.g., laterally, transverse to the path of the beam) so that it is completely out of the path of the beam or in the path of the beam. In one embodiment, the range modulator can also be moved in a second direction different from (e.g., perpendicular to) the first direction and transverse to the path of the beam.

[0017] The range modulator provides a means of rapidly varying the energy in the scanning beam in order to produce a desired SOBP breadth in a dynamically variable manner. By adjusting the position of the range modulator and rotating the range modulator, the beam can pass through different portions of at least one of its arms, and therefore through materials of different thicknesses, and also through different amounts of space between adjacent arms, and thus the spread breadth of the SOBP can be rapidly varied over a useful range.

[0018] The range modulator and / or range shifter matches the SOBP (distal and proximal) to the target volume (planned target volume). Because the range modulator and range shifter can achieve these effects quickly, the transmission can be advantageously used for dose delivery. Therefore, by using transmission, the entire target volume can be irradiated to the dose specified by the treatment plan, while exposing healthy tissue to only one very short radiation burst. Moreover, by delivering the entire dose in a short time, the movement of the target volume becomes less problematic. Similarly, the rapid delivery of emission patterns with different intensities from a single beam direction results in intensity modulated radiotherapy delivery. In addition, by delivering emission patterns from multiple beam directions, finer intensity modulation can be achieved with lower doses delivered to healthy tissue. Importantly, because no dose is delivered distal to the Bragg peak, the dose delivered to any healthy tissue outside the target volume in this way can therefore be limited to a single, very short, low-dose radiation burst.

[0019] In summary, embodiments according to the present disclosure provide spatially and temporally precise regulated irradiation of moving targets in patients, and take advantage of the tissue protection effects studied above. Compared with the use of the conventional raster scanning technique described above, embodiments according to the present disclosure provide a more direct target volume scanning method. By using (multiple) scanning magnets, each shot is directly aimed to coincide with the in-plane motion of the target, rather than having to distort the raster scan pattern. Therefore, aiming subsequent shots avoids the generation of motion artifacts, such as those caused by the interaction between the target motion of consecutive raster scan patterns. Similarly, target motion in the distal to proximal direction can be compensated by changing the range shifter accordingly between shots. Quality assurance also becomes easier because the tracking and scanning processes are more independent of each other. Importantly, since the SOBP covering the entire length of each target segment (from the distal edge to the proximal edge of the planned target volume) is delivered in short bursts, motion-induced uncertainties do not produce gaps or overlaps (cold spots or hot spots) within the target volume.

[0020] Those of ordinary skill in the art will recognize these and other objects and advantages of the various embodiments of the present disclosure after reading the following "Detailed Description" of the embodiments illustrated in the various drawing figures.

[0021] This Summary is provided to introduce some concepts in a simplified form that are further described in the Detailed Description below. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings illustrate embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the present disclosure. The accompanying drawings are incorporated in and form a part of this specification. Like reference numerals in the drawings depict like elements.

[0023] Figure 1 is a block diagram illustrating selected components of a radiation therapy system upon which embodiments according to the present disclosure may be implemented.

[0024] Figure 2A , Figure 2B , Figure 2C and Figure 2D is a block diagram illustrating selected components of a nozzle in an embodiment according to the present disclosure.

[0025] Figure 3 An example of dose delivery along a target line segment in a planned target volume in an embodiment according to the present disclosure is shown.

[0026] Figure 4A Shown is a front view of a range modulator in an embodiment according to the present disclosure.

[0027] Figure 4B and Figure 4C Shown is a cross-sectional view of an arm of a range modulator in an embodiment according to the present disclosure.

[0028] Figure 4D The positioning of the range modulator in an embodiment according to the present disclosure is shown.

[0029] Figure 5 A range shifter in an embodiment according to the present disclosure is shown.

[0030] Figure 6 A plurality of spots representing the intersection of an incident particle beam with a planned target volume layer in an embodiment according to the present disclosure are shown.

[0031] Figure 7 is a flow chart of a radiation therapy method in an embodiment according to the present disclosure. DETAILED DESCRIPTION

[0032] Reference will now be made in detail to various embodiments of the present disclosure, examples of which are shown in the accompanying drawings. Although described in conjunction with these embodiments, it should be understood that they are not intended to limit the present disclosure to these embodiments. On the contrary, the present disclosure is intended to cover: alternatives, modifications and equivalents that may be included in the spirit and scope of the present disclosure as defined by the appended claims. In addition, in the following detailed description of the present disclosure, many specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it should be understood that the present disclosure can be practiced without these specific details. In other cases, well-known methods, processes, components and circuits are not described in detail to avoid unnecessarily obscuring various aspects of the present disclosure.

[0033] A "ray" is part of a scan pattern and irradiates tissue along different line segments ("target segments") through the target volume. A high dose that can be delivered in a short time along a target segment may be referred to herein as a "shot."

[0034] Figure 1 is a block diagram illustrating selected components of a radiation therapy system 100 upon which embodiments according to the present disclosure may be implemented. Figure 1 In the example of FIG. 1 , system 100 includes an accelerator and beam delivery system 104 and a nozzle 106 .

[0035] The accelerator and beam transport system 104 generates and accelerates a charged particle beam, such as electrons, protons, and heavy ions, and contains the particles in a well-defined beam. In one embodiment, the accelerator is an isochronous cyclotron capable of continuous wave output. The accelerator (e.g., a cyclotron) extracts particles at a specified energy. This provides a high continuous wave beam current for a high dose rate per emission. Other types of accelerators can be used, such as a pulsed proton accelerator, such as a synchrocyclotron or a synchrotron. The accelerator (e.g., a cyclotron) can be a lower power output cyclotron, such as a cyclotron that accelerates particles to a range of 70MeV-300MeV.

[0036] The accelerator and beam transport system 104 includes components (e.g., dipole magnets, also called bending magnets) that direct (e.g., bend, steer, or guide) the beam through the accelerator and beam transport system in a direction toward and into the nozzle 106. The accelerator and beam transport system 104 may also include components for adjusting the energy of the beam entering the nozzle 106 so that it is different from the energy of the beam extracted from the accelerator. In one embodiment, a set of quadrupole magnets is positioned along the beam path in the accelerator and beam transport system 104.

[0037] The nozzle 106 is used to aim the beam toward various locations within a subject (e.g., a patient) that is supported on a support device 108 (e.g., a chair or table) in the treatment room. The nozzle 106 can be mounted on or part of a gantry (not shown) so that it can move relative to the support device 108; the support device can also be movable. In one embodiment, the accelerator and beam delivery system 104 are also mounted on or part of the gantry; in another embodiment, the accelerator and beam delivery system are separate from (but in communication with) the gantry.

[0038] The control system 110 receives and implements the prescribed treatment plan. In one embodiment, the control system 110 includes a computer system having a processor, a memory, an input device (e.g., a keyboard), and possibly a display in a known manner. The control system 110 can receive data regarding the operation of the system 100. The control system 110 can control parameters of the accelerator and beam delivery system 104, the nozzle 106, and the support device 108 based on the data it receives and in accordance with the prescribed treatment plan, including parameters such as the energy, intensity, direction, size, and / or shape of the beam.

[0039] As described above, the particles entering the nozzle 106 have a specific energy. Therefore, in an embodiment according to the present disclosure, the nozzle 106 includes one or more components that affect (e.g., reduce, adjust) the energy of the particles in the beam. In one embodiment, the nozzle 106 also includes a component (e.g., an XY scanning magnet) that guides (e.g., directs, deflects, or scans) the beam particles in the X and Y directions to scan a target volume in a patient on the support device 108.

[0040] The term "beam energy modulator" is used herein as a general term for a component or components that affect the energy of particles in the beam. In various embodiments, the beam energy modulator 107 includes a range modulator, a range shifter, or both a range modulator and a range shifter. That is, when the term "beam energy modulator" is used, the element in question may be a range modulator, a range shifter, or both a range modulator and a range shifter. Note that in embodiments where the beam energy modulator includes both a range modulator and a range shifter, the range modulator and the range shifter may be separated from each other by other nozzle components. This is particularly useful in Figure 2A , Figure 2B , Figure 2C and Figure 2D Further details are given in .

[0041] Figure 2A 1 is a block diagram showing selected components of the nozzle 106A in an embodiment according to the present disclosure. The nozzle 106A is connected to the accelerator and beam delivery system 104 ( Figure 1) receives the charged particle beam 101. Figure 2A In the example of the nozzle 106A, the nozzle 106A includes one or more scanning magnets that direct the beam 101. In one embodiment, the XY scanning magnet includes a first (Y) magnet 204 and a second (X) magnet 206 for vertical and horizontal beam deflection to scan the beam across a planned target volume in an object (e.g., a patient). In the nozzle 106A, the Y magnet 204 can be placed before or after the X magnet 206.

[0042] In one embodiment, the nozzle 106A includes a vacuum chamber 208 and a monitoring chamber 210. The monitoring chamber 210 monitors radiation exhausted from the vacuum chamber 208.

[0043] exist Figure 2A In an embodiment of the present invention, the nozzle 106A includes a range modulator 212 downstream of the XY scanning magnets 204 and 206. Thus, the range modulator 212 acts to scan the particle beam (as opposed to scattering the particle beam). In one embodiment, the range modulator 212 is located at the end of the vacuum chamber (outside thereof) and before the monitoring chamber 210; the vacuum ends at the range modulator 212.

[0044] As described above, the initial energy of the particles in beam 101 is determined by the accelerator and beam transport system 104 ( Figure 1 ) is determined by the acceleration provided to the particles. The range modulator 212 changes (adjusts) the energy of a portion of the particles in the scanning beam. More specifically, the range modulator 212 reduces the energy of a portion of the individual particles (e.g., by changing the energy of the emitted beam particles over time), thereby increasing the energy distribution of the scanning particle beam, and expanding the dose distribution along the traveling direction of the scanning particle beam to deliver a dose with an expanded Bragg peak (SOBP) to a target line segment ( Figure 3 ).

[0045] Continue to refer Figure 2A As described above, the range modulator 212 is located downstream of the XY scanning magnets 204 and 206. This avoids producing rapidly changing beam energies within the fixed or slowly changing magnetic fields of the XY scanning magnets. This also avoids causing the beam to expand because lower energy particles bend more tightly than higher energy particles.

[0046] The range modulator 212 rapidly changes the outgoing beam particle energy in order to produce the desired SOPB width in a dynamic manner. Furthermore, the range modulator 212 is movable so that it can be moved in and out of the beam path and change the thickness of the material exposed to the beam, thereby also changing the SOBP width. This will be discussed below in conjunction with Figure 4A-4DFurther Discussion. From this discussion it can be seen that the range modulator 212 is configured so that the spread of the SOBP can be varied rapidly over the useful range of the beam, which is scanned separately in both the X and Y directions.

[0047] exist Figure 2A In the embodiment of the invention, the nozzle 106A also includes a range shifter 214. This is in contrast to conventional radiation therapy (e.g., proton) systems in which the de-stager (range shifter) is located after the accelerator and before the gantry entry point. Figure 2A In the embodiment of FIG. 1 , the range shifter 214 is located in the nozzle 106A and is located downstream of the XY scanning magnets 204 and 206 and upstream of the range modulator 212. That is, the range shifter 214 is located in the nozzle 106A and is located between the range modulator 212 and the XY scanning magnets 204 and 206.

[0048] The range shifter 214 is configured to: change (e.g., reduce) the energy of particles in the particle beam to affect the distance that the particles penetrate into the target volume; the range shifter affects the range of the beam. More specifically, the range shifter 214 provides a quick way to change the range of the Bragg peak so that for each shot, the Bragg peak appears at the far edge of the planned target volume. Figure 5 Embodiments of the range shifter 214 are further described.

[0049] exist Figure 2A In the embodiment of the present invention, the range modulator 212 and the range shifter 214 constitute the beam energy adjuster 107 ( Figure 1 ). Effectively, the range modulator 212 and the range shifter 214 each affect or condition the beam, but in different ways: the range shifter is used to change (eg, reduce) the beam energy to control the range (penetration) of the beam, while the range modulator is used to extend the Bragg peak.

[0050] Figure 2B is a block diagram showing selected components of a nozzle 106B in another embodiment according to the present disclosure. Figure 2A Compared to nozzle 106A, the range shifter 214 in nozzle 106B is located upstream of the XY scanning magnets 204 and 206 and between the XY scanning magnets and the accelerator and beam transport system 104 ( Figure 1 ). Positioning the range shifter 214 upstream of the XY scanning magnets 204 and 206 means that the particle beam does not have to be compensated for the effects of the scanning magnets on the beam. Figure 2B In the embodiment of the present invention, the range modulator 212 and the range shifter 214 constitute the beam energy adjuster 107 ( Figure 1 ).

[0051] Figure 2C is a block diagram showing selected components of a nozzle 106C in another embodiment according to the present disclosure. Figure 2A and 2B In contrast to the nozzles 106A and 106B of the embodiment, the nozzle 106C includes: a nozzle 106C upstream of the XY scanning magnets 204 and 206 and located between the XY scanning magnets and the accelerator and beam transport system 104 ( Figure 1 ) between the range shifter 214, but does not include the range modulator. Figure 2C In the embodiment of the present invention, the range shifter 214 constitutes the beam energy adjuster 107 ( Figure 1 ).

[0052] Figure 2D is a block diagram showing selected components of a nozzle 106D in another embodiment according to the present disclosure. Figure 2C The nozzle 106C and the nozzle 106D include the range shifter 214 but do not include the range modulator. Figure 2C In contrast to the embodiment of FIG. 1 , the range shifter 214 is located downstream of the XY scanning magnets 204 and 206. Figure 2D In the embodiment of the present invention, the range shifter 214 constitutes the beam energy adjuster 107 ( Figure 1 ).

[0053] Figure 3 An example of a target line segment 302 in a planning target volume 304 is shown. The planning target volume refers to the size of the volume to be irradiated and includes a clinical target volume 306, which refers to the size of the actual tumor to be treated. Figure 3 In the example of FIG. 3 , the particle beam (emission) 308 travels in a direction from left to right. Figure 3 In the orientation of the target volume 304, the edge on the right hand side (the edge farthest from the direction of the incident particle beam 308) is called the distal edge, and the edge on the left hand side (the edge closest to the direction of the incident particle beam) is called the proximal edge. In an embodiment according to the present disclosure, the SOBP delivers a uniform dose from the proximal edge to the distal edge in the direction along the target line segment 302.

[0054] Figure 4AA front view (from the perspective of an incident particle beam) of a range modulator 212 in an embodiment according to the present disclosure is shown. In this embodiment, the range modulator 212 is configured to place different thicknesses of material (including zero thickness; i.e., no material) in the path of the scanning beam to change the energy of the particles, as described above. More specifically, in one embodiment, the range modulator 212 includes a plurality of arms 404 or blades extending from a hub 402. However, the range modulator 212 can be implemented using a single arm. In one embodiment, the arms 404 of the range modulator 212 are all made of the same material (e.g., graphite). In another embodiment, the arms 404 are made of different materials; that is, one arm can be made of one material or a combination of materials, while the other arm can be made of a different material.

[0055] Each arm 404 has a non-uniform thickness. In one embodiment, the thickness of the arm 404 decreases as the distance from the hub increases.

[0056] In one embodiment, the length of the chord of the arms 404 decreases as the distance from the hub 402 increases; that is, the width of the arms decreases as the distance from the hub increases (where the width W is the dimension facing the incident particle beam). Thus, in one embodiment, the amount of space S between the arms 404 increases as the distance from the hub 402 increases. Although the arms 404 are shown as semi-elliptical, the present disclosure is not limited thereto; for example, the arms can be a more rectangular shape with rounded corners. In general, the shape of the arms 404 can be optimized to achieve design goals regarding, for example, selecting and controlling the breadth of the SOBP.

[0057] The range modulator 212 can be rotated clockwise and / or counterclockwise about an axis 420 passing through the center of the hub 402 to place the arms 404 (one arm at a time) into the path of the scanning beam (into the beamline). The range modulator 212 can also be rotated to a position that allows the beam to pass through the space between two adjacent arms. The range modulator 212 can be continuously rotated to allow the beam to pass through a varying thickness / width of a combination of at least one arm and at least one amount of space; the varying material thickness due to the rotation produces the desired SOBP. As will be further described below, the range modulator 212 can be moved in a horizontal direction so that as the range modulator rotates, the incident particle beam will pass through different portions of the arm, and therefore through materials of different thicknesses and widths, and also through different amounts of space. The range modulator 212 can also be moved to a position that places it completely outside the beam. In one embodiment, the range modulator 212 can also be moved in a vertical direction to allow the range modulator to be placed at almost any position within or outside the beam.

[0058] Figure 4B In the embodiment according to the present disclosure, Figure 4A A cross-sectional view of arm 404 taken along cutting line AA. Figure 4B In the embodiment of the present invention, the thickness of the arm 404 decreases as the distance from the hub 402 increases. That is, the arm 404 is thickest where it meets the hub 402 and thinnest at its tip.

[0059] Figure 4C In the embodiment according to the present disclosure, Figure 4A A cross-sectional view of arm 404 taken along cutting line BB. Figure 4C In the embodiment of the present invention, the thickness of the arm 404 varies along its chord. That is, the arm 404 is thickest at one edge and thinnest at the other edge.

[0060] The shape (profile and cross-section) of arm 404 is not limited to Figure 4B and Figure 4C .

[0061] refer to Figure 4D In one embodiment, the range modulator 212 can be moved in a first direction (e.g., transverse to the path of the beam) so that it is completely outside the path of the beam or in the path of the beam. In one embodiment, the range modulator 212 can also be moved in a second direction that is different from (e.g., perpendicular to) the first direction and transverse to the path of the beam. In other words, in one embodiment, the range modulator 212 can be moved in only one direction (e.g., horizontally); and in another embodiment, the range modulator can be moved both horizontally and vertically (and therefore diagonally). In embodiments where the range modulator 212 can be moved in only one direction, the diameter of the hub 402 can be sized so that it is equal to or nearly equal to the maximum transverse beam scan field width at the height of the hub.

[0062] Any of a number of different mechanisms may be used to move the range modulator 212 horizontally and / or vertically. For example, the range modulator 212 may be mounted on a sliding stage or assembly that allows it to be moved in either or both directions, depending on the embodiment.

[0063] exist Figure 4D, the maximum beam scan field size is represented by box 406, and the path of the particle beam (beam shot) is represented by the black circle 408 within the box. The range modulator 212 can be positioned corresponding to the scanning position of the particle beam within the maximum beam scan field size 406, as deflected by the scanning magnets 204 and 205. For example, if the range modulator 212 is in the position indicated by the dashed circle 410, the beam will pass through a specific thickness of one of the arms 404; if the range modulator is then moved to the right, the beam will pass through a thicker portion of one of the arms; if the range modulator is instead moved to the left, the beam will pass through a thinner portion of one of the arms. For example, if the range modulator 212 is in the position indicated by the dashed circle 412, it is not affected by any beam path. As described above, the range modulator 212 can be continuously rotated while it is in place to produce the desired SOBP; the SOBP breadth is selected and controlled by moving the range modulator laterally (horizontally and / or vertically) to different positions.

[0064] When the range modulator 212 rotates in the beam path, the beam passes through at least one space between at least one arm 404 and an adjacent arm. The rotation speed of the range modulator 212 can be changed so that the beam is emitted through more than one space between more than one arm 404 and an adjacent arm. The rotation speed of the range modulator 212 can also be adjusted so that it is synchronized with the operation of the accelerator. Any of a number of different mechanisms can be used to rotate the range modulator 212. For example, the range modulator 212 can be driven directly or indirectly by a motor connected to the hub 402.

[0065] In one embodiment, as the range modulator 212 rotates in the beam path, the position of the range modulator in the beam path is selected (and the range modulator is moved to that position) so that the varying material thickness due to the different thicknesses / widths of the arms 404 and the amount of space between the arms produces a desired SOBP. At any point in time, the Bragg peak is a function of the radial distance of the beam from the hub 402. The range of the SOBP can vary continuously, from no particle beam impact and therefore no SOBP (raw Bragg peak) when the beam exceeds the tip of one of the arms 404 (such as the position indicated by the dashed circle 412), to a maximum SOBP when the beam passes through the thickest portion of one of the arms (e.g., near the hub 402). The desired SOBP breadth can be achieved by moving the range modulator 212 so that the beam passes through the range modulator at a radial distance from the hub 402 corresponding to the desired SOBP. By moving the range modulator 212 rotationally and / or radially (in the horizontal and / or vertical directions), any desired SOBP can be achieved.

[0066] The range modulator 212 can be positioned rapidly (rotationally and radially) and can therefore be used to rapidly change the SOBP, much faster than can be achieved using magnets. Thus, a dose of four Gy can be delivered along the target segment in less than one second. Furthermore, a dose of at least 20 Gy can be delivered along the target segment in less than 500 milliseconds.

[0067] Figure 5 The range shifter 214 in an embodiment according to the present disclosure is shown. In this embodiment, the range shifter 214 includes a pair of wedges 502 and 504. In one embodiment, the wedges 502 and 504 are made of graphite. The wedges 502 and 504 can be moved in opposite directions to provide a uniform but variable cross-sectional thickness to the particle beam passing through the wedges.

[0068] In one embodiment, wedges 502 and 504 can be quickly adjusted to move along a programmed motion profile. When placed between XY scanning magnets 204 and 206 ( Figure 6 ) downstream, wedges 502 and 504 can be used as range modulators to produce the desired SOBP width in a dynamically variable manner.

[0069] The range shifter 214 is not limited to Figure 5 The range shifter 214 may be implemented in many different ways to achieve its function of generating desired and dynamic SOBP.

[0070] For example, wedges 502 and 504 can be made of the same material or combination of materials, or the wedges can be made of different materials or combinations of materials; that is, one wedge can be made of one material or combination of materials, while the other wedge can be made of a different material. The materials can have different densities. Thus, range shifter 214 can be made of components other than wedges. For example, the components can be blocks. The density of each block can be non-uniform, so that the incident beam will pass through materials of different densities, depending on where and how the blocks are placed in the beam path, and where and how the blocks are placed relative to each other. In addition, materials of different densities and thicknesses can be used; for example, a wedge component can be used that also has non-uniform density. Range shifter 214 can be implemented using more than two components (e.g., more than two wedges or blocks).

[0071] As described above, in one embodiment, an isochronous cyclotron capable of continuous wave output can be used to generate a particle beam. In one embodiment, the movement (e.g., rotation, radial, lateral) of the range modulator 212 can be synchronized with the beam source or generator (e.g., synchronized with the isochronous cyclotron). For example, a sensor can be used to monitor the speed, position, and phase of the range modulator 212, and this information can be used (e.g., by the control system 110) to synchronize the movement of the range modulator to compensate for changes in the intensity of the beam output by the isochronous cyclotron or to compensate for the effects of the XY scanning magnets 204 and 206. The range shifter 214 is then used to "trim" the distal edge of the planned target volume to reduce scattering.

[0072] Figure 6 6 shows a plurality of spots 602 representing the intersection of an incident particle beam with a layer 604 of a target volume in an embodiment according to the present disclosure. In one embodiment, by changing the focusing magnets (such as along the accelerator and beam transport system 104 ( Figure 1 ) to incorporate a variable spot size feature. By varying the spot size, the volume of the cylinder of target tissue exposed to radiation along the target segment can be varied, with a corresponding inverse variation in dose rate for a given beam current. This capability is useful for improving the coverage and speed of dose delivery to a variety of target volume sizes and shapes. For example, larger spot sizes are useful for spreading dose over larger areas, particularly where the desired dose is not too high, while smaller spot sizes are useful for outlining complex shapes. The scan pattern can utilize staggered points arranged similarly to a hexagonal grid, such as Figure 6 As shown. Particle scattering commonly encountered in SOBP naturally provides a penumbra region around a cylinder around each target segment. This unavoidable penumbra is useful for maintaining uniformity of dose to target tissue between shots. The planned breadth of overlap between adjacent shots can be used to ensure adequate target coverage in the "gaps" between adjacent spots of the hexagonal grid. Alternatively, larger spot patterns can be staggered with smaller spots to fill any gaps. The breadth of particle scattering, and therefore the cross-sectional diameter covered by significant radiation dose, is greatly increased in the region of the SOBP (e.g., within the target volume) compared to the region along the proximal beam (through healthy normal tissue). Therefore, a significant degree of overlap of doses from adjacent shots within the target volume can be accommodated without generating dose overlap in the normal tissue through which the beam passes. Therefore, due to the use of shots as described herein, positive radiobiological effects can be maintained.

[0073] Figure 7700 is a flow chart of a radiation therapy method in accordance with an embodiment of the present disclosure. Figure 7 The steps and order describing the operation of the method are disclosed in , but such steps and order are examples. Embodiments are well suited to perform various other steps or variations of the steps described in flowchart 700, and in an order different from that depicted and described herein.

[0074] In block 702, a particle beam is received into a nozzle.

[0075] In block 704, the beam is scanned (raster scanned) using a plurality of XY scanning magnets.

[0076] In block 706, in one embodiment, the distance that the particles penetrate into the target volume is adjusted using a range shifter configured to place different thicknesses of material in the path of the beam. In one embodiment, the range shifter is located in the nozzle and downstream of the scanning magnet and can be used as a range modulator; in another embodiment, the range shifter is located in the nozzle and upstream of the scanning magnet.

[0077] In block 708, in one embodiment, the energy of at least a portion of the particles in the beam is also adjusted using a range modulator located in the nozzle and downstream of the scanning magnet (so the range modulator is exposed to the scanning beam).

[0078] Thus, the nozzle can be used to generate a conditioned beam that delivers a dose (shot) having a SOBP along a target line segment in a target volume aligned with the nozzle. The intensity of the dose delivered in the shot can be adjusted to match a dose prescribed for a particular target line segment. The shots can be delivered using, for example, a predefined scan pattern to irradiate different target line segments; a first conditioned beam can be generated that delivers a first dose having a SOBP along a first target line segment in the target volume, and a second conditioned beam can be generated that delivers a second dose having a second SOBP along a second target line segment in the target volume, wherein the second target line segment is displaced from the first target line segment.

[0079] The range shifter and / or range modulator placed in the nozzle as described in the present disclosure is dynamically variable (e.g., functions faster than a dipole bending magnet in a beam delivery system). In one embodiment, the dose delivered along the target line segment is at least four grays and is delivered in less than one second. In another embodiment, the dose delivered along the target line segment is at least 20 grays and is delivered in less than 500 milliseconds.

[0080] In one embodiment, treatment planning and dose delivery are performed using multiple beams from different directions and nozzles, rather than using a single nozzle as described above. Each beam can be delivered at a separate time, with an obtuse angle or a large acute angle between each direction. Due to the basic characteristics of the particle beam in which no dose is delivered to the distal end of the Bragg peak, normal healthy tissue along the ray beyond this point will not receive unwanted doses. Moreover, for directions with an obtuse angle relative to each other, the proximal portions of any light rays aimed from different beam directions do not overlap with each other. Even for beam directions at large acute angles, the extent of overlap is small. Any such overlap outside the target will reduce the positive effects attributable to the use of emission as described herein, so it is desirable to minimize any overlap.

[0081] Multiple beam directions are beneficial for at least two reasons. First, scanning the dose through the target from multiple directions will greatly reduce the extent and magnitude of any dose inhomogeneities (caused by range uncertainty caused by the scanning pattern or motion from any one direction) since any of these effects, if present, will overlap within the target volume from different directions. Second, scanning from multiple directions provides far greater independent degrees of freedom that can be used for treatment plan optimization while also significantly reducing the dose level to any normal healthy tissue; the entrance dose is spread over a larger volume of normal tissue.

[0082] Two nozzles as described above can be placed coaxially and opposite each other, both aiming at the isocenter. A fast "kicker" magnet in the fixed beam will guide the beam back and forth between the separate gantry-mounted paths feeding each nozzle. Scanning within each nozzle will cause the beams from both nozzles to hit the same tissue in actual time sequence or close to each other in time (e.g., within one second of each other or within 500 milliseconds), thereby taking advantage of the positive radiobiological effects attributable to the use of emission as described herein. Because the planning target volume is usually not in the exact center of the patient, a range shifter such as the above-mentioned range shifter 214 can be employed in each nozzle to make the SOBP from the two nozzles spatially consistent. Because very similar SOBPs are delivered to the same target line segment from two directions, the size of the dose delivered to any normal healthy tissue along the same line (approaching the target from each direction) is reduced by half. Another advantage is that this nozzle arrangement allows the treatment planner to independently optimize the shape and intensity of the scan pattern delivered from each direction to advantageously balance different dose targets or constraints during planning. For example, paired nozzles can be used to limit dose to specific organs at risk that partially overlap with the planned target volume. No dose is delivered to the distal end of the target outside the Bragg peak, and this feature can be exploited during treatment planning, particularly when proton beams are to be used.

[0083] As described above, fixed beams may also be employed rather than gantry-mounted beams, either individually or as described above, as opposed pairs. The inability to preferably aim the beam in an ideal direction may be offset by a significant reduction in capital expenditures. Some disease sites may not require a rotating gantry in order to be effectively treated with IMPT. For example, a pair of fixed nozzles placed in a vertical plane may be arranged as an AP / PA (anteroposterior / posteroanterior) pair that simultaneously delivers opposing beams to treat lung tumors. Similarly, a bilateral beam arrangement with opposing nozzles in a horizontal plane may be useful for other disease sites, such as sites in the head and neck.

[0084] Other relative beam orientations in a multi-nozzle system may be used (such as orthogonal), or additional nozzle beamlines and nozzles may be added (eg, to achieve three or four beam directions simultaneously).

[0085] In summary, embodiments according to the present disclosure provide spatially and temporally precise regulated irradiation of moving targets in patients and take advantage of the tissue protection effects studied above. Compared to using the conventional raster scanning techniques described above, embodiments according to the present disclosure provide a more direct target volume scanning method. By using an XY scanning magnet, each shot is directly aimed to coincide with the in-plane motion of the target, rather than having to distort the raster scan pattern. Quality assurance also becomes easier because the tracking and scanning processes are more independent of each other. Importantly, because the SOBP covering the entire length of each target segment (from the distal edge to the proximal edge of the planned target volume) is delivered in short bursts, motion-induced uncertainties do not create gaps or overlaps (cold spots or hot spots) within the target volume.

[0086] Embodiments according to the present invention may be used for types of external beam radiation therapy other than IMPT, such as, for example, intensity modulated radiation therapy (IMRT), image guided radiation therapy (IGRT), RapidArc TMRadiation therapy, stereotactic body radiation therapy (SBRT) and stereotactic ablative radiation therapy (SABR). Embodiments according to the present disclosure may be incorporated into methods and systems for planning radiation therapy treatments based on IMPT and other types of radiation therapy. Emissions - high doses that can be delivered along a target segment in a short period of time - can be adjusted in terms of energy (intensity) or range, and delivered to the target volume under the following extended Bragg peak (SOBP), which provides a uniform and otherwise appropriately modified dose to the entire target segment. The intensity of the dose delivered in the emission can be adjusted to match the dose prescribed for a specific target segment. Subsequent emissions can be independently adjusted in terms of intensity, range, and under appropriate SOBP conditions, and can also be triggered or aimed to coincide with the 4D (three-dimensional plus time) position of each target segment in the scan pattern until the entire target volume has been irradiated to the prescribed dose. Radiation therapy can be improved by using this ability to quickly and accurately change energy and range on the fly (dynamically). Treatment planning can also be improved because planners have the ability to precisely control dose delivery.

[0087] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A radiotherapy system, comprising: an accelerator and beam transport system that generates a beam of particles, wherein the accelerator and beam transport system includes focusing magnets along a path of the beam; a nozzle operable to direct the beam toward an object, wherein the nozzle comprises: a scanning magnet operable to direct the beam toward different locations within the object; as well as A beam energy modulator configured to modulate the beam by affecting the energy of the particles in the beam, wherein the beam energy modulator includes a range modulator, the range modulator including a plurality of arms extending from a hub, the plurality of arms having non-uniform thicknesses, the width of the arms decreasing with increasing distance from the hub, wherein the width is a dimension facing the incident particle beam, wherein the range modulator is operable to rotate about the hub to allow the beam to pass through at least one of the plurality of arms to place material of different thicknesses in the path of the beam to change the energy of at least a portion of the particles and achieve an extended Bragg peak.

2. The radiation therapy system of claim 1 , wherein the beam energy modifier further comprises a range shifter configured to place materials of varying thicknesses in the path of the beam to affect the distance that the particles penetrate into the object and to position the extended Bragg peak within the object.

3. The radiation therapy system of claim 1 , wherein the range modulator is configured to move in a first direction between: a position completely outside the path of the beam, and a position in the path of the beam, wherein the first direction is transverse to the path of the beam, and wherein the range modulator is further configured to move in a second direction that is different from the first direction and is transverse to the path of the beam.

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