Rotary radiation collimator

Abstract

The present invention relates to rotational radiotherapy collimators. Provided herein are devices, systems, and methods that allow for the delivery of different sized or shaped treatment radiation beams during radiotherapy. Such devices can include a rotatable collimator body having a plurality of collimator channels of different sizes or shapes defined therein, the channels extending through the collimator body substantially perpendicular to the axis of rotation. The collimator body can include markings thereon to facilitate detection of alignment positions by sensors of a control system, allowing for rapid and accurate movement of the collimator body between alignment positions to facilitate delivery of different treatment beams during treatment.

Description

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 62 / 502,472, filed May 5, 2017, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of radiotherapy, and more specifically to collimator systems and related methods for controlling the size and shape of a radiotherapy beam during radiotherapy. Background Technology

[0003] The overall goal of a collimator system is to deliver a beam of radiation generated by a source (e.g., LINAC) to a target (e.g., a tumor in a patient's brain). Since it is desirable to irradiate the tumor but generally not the surrounding healthy tissue, the size and shape of each beam are crucial. Collimators are used to control the shape of the radiation beam (e.g., diameter or 2D cross-sectional area). Collimators are generally sheets of dense, radiopaque metal that essentially block the radiation beam except where formed or machined apertures allow the radiation to pass through. A large radiation coverage area can be produced by a radiation source (e.g., LINAC or cobalt), but only those particles aligned and passing through the collimator are allowed to pass through to reach the target; the extras are absorbed or scattered internally. Besides the tubular channels of machined or formed collimators, another existing type is called a multi-leaf collimator. These conventional designs are very complex, bulky, and expensive. One example is a "multi-leaf collimator" using multiple thin tungsten plates that move in and out of the beam path to produce the desired beam exposure shape during treatment. This complex mechanism is prone to mechanical failure.

[0004] Different sizes and shapes of radiotherapy targets require different sizes and shapes of radiation beams. There is a need for systems and methods that allow for rapid and predictable changes in radiation beams. There is also a need to keep such systems small, reliable, and low-cost. Summary of the Invention

[0005] This invention relates to the field of radiotherapy, and more specifically to collimator systems and related methods for controlling the size and shape of a radiotherapy beam during radiotherapy.

[0006] In a first aspect, the invention relates to a radiation collimator assembly comprising a rotatable collimator body or collimator wheel having a plurality of collimator channels defined therein. In some embodiments, the collimator channels extend longitudinally perpendicular to the axis of rotation of the collimator wheel, extending from the periphery of the wheel, through the center of the wheel, and to the opposite periphery of the wheel. The collimator wheel is at least partially surrounded by a collimator shroud, except for the portion having selected collimator channels aligned with a radiation source and a patient target to allow the radiation beam to pass through. In some embodiments, the rear portion of the collimator wheel facing LINAC is sheathed within the shroud to prevent stray radiation from passing through unselected collimator channels. The collimator shroud is made of a suitable radiation-absorbing material (typically tungsten or a tungsten alloy) to block and absorb any scattered radiation emitted from the apertures of unaligned channels.

[0007] In another embodiment, the collimator body is electromechanical and precisely indexed for rapid and accurate computer-controlled positioning of the selected collimator channel geometry with the radiation source, thereby delivering the desired beam shape to the precise dimensions required at the target location. By using a rotating collimator wheel, multiple beam sizes can be used during a single treatment, with rapid and automatic switching between two or more selected collimators.

[0008] These collimator assemblies offer the advantages of rapid, computer-controlled changes while remaining small, reliable, and low-cost. Furthermore, such assemblies can utilize a single motor to switch between selecting one or more collimator channels. The aspects of the invention described herein allow for more reliable radiation collimators capable of rapidly and precisely changing X-ray exposure with isocentric diameters from 1 mm to 30 mm, and operating more reliably than many prior art collimators. These collimator assemblies enable rapid, automated (electromechanical and computer-controlled) changes in the beam aperture during therapeutic radiation delivery services, such as for treating brain tumors.

[0009] The collimator system described in this article allows for beam collimation without the need for conventional blocking collimators and / or multi-leaf collimator systems, such as those commonly used in conventional radiotherapy systems, which are bulky and prone to mechanical failure over time.

[0010] In one aspect, an exemplary radiation collimator assembly includes a radiation source and a collimator wheel rotatable about its axis of rotation. The collimator wheel has a plurality of collimator channels, including first and second collimator channels defined within the collimator wheel, the first and second collimator channels being arranged substantially perpendicular to the axis of rotation of the collimator wheel. The collimator may include additional channels, such as three or more channels. The collimator may include any desired number of channels (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 channels or more). In some embodiments, each of the first and second collimator channels passes through the center of the collimator wheel, through which the axis of rotation extends. Preferably, at least some of the collimator channels have different sizes and / or shapes. In some embodiments, the plurality of collimator channels are distributed along the collimator wheel at regular intervals.

[0011] In another embodiment, the first and second collimator channels can be selected by rotatably moving the collimator wheel, thereby aligning one of the first and second collimator channels with the radiation source. Selective rotation of the collimator wheel can be facilitated by a motor and a control unit operatively coupled to the wheel. In some embodiments, the collimator assembly includes: a motor operatively coupled to the collimator wheel to rotate the collimator wheel about the axis of rotation; and a control unit operatively coupled to the motor to control rotation of the collimator wheel to a collimator position corresponding to the alignment of the selected collimator channel and the radiation source. In some embodiments, the control unit is communicatively coupled to one or more sensors configured to detect the collimator position. The one or more sensors may include one or more encoder readers, and the collimator wheel includes a plurality of markers positioned on the collimator wheel such that detection of the markers corresponds to the alignment of the respective collimator channel.

[0012] In another aspect, this document provides a radiotherapy system utilizing such a collimator assembly. An exemplary treatment system may include: a radiocollimator assembly, such as those described above, configured to deliver a radiation beam from a radiation source through one or more selected collimator channels of the collimator wheel to a target within a patient. Such a system may include: a motor operatively coupled to the collimator wheel to rotate the collimator wheel about the rotation axis; and a control unit operatively coupled to the motor to control the rotation of the collimator wheel to a position corresponding to the alignment of one or more selected collimator channels with the radiation source. The control unit is configured to rotate the collimator wheel to align one or more selected collimator channels with the radiation source, the one or more selected collimator channels corresponding to one or more desired treatment beams.

[0013] In another aspect, the treatment system includes a collimator shroud. The collimator shroud may be configured to surround at least a portion of the collimator body during treatment delivery to block radiation from an misaligned collimator channel while allowing a treatment beam from a selected, aligned collimator channel to pass through. In some embodiments, the collimator shroud substantially surrounds the portion of the collimator wheel facing the radiation source, except for an inlet aperture of the selected, aligned collimator channel. In some embodiments, the collimator shroud substantially surrounds the collimator body, except for an outlet aperture at the top of the shroud through which the selected, aligned collimator channel is exposed, and a channel at the inlet aperture of the aligned channel to allow the radiation beam to enter through the selected channel. While the embodiments presented herein depict a conical shroud, it is understood that the collimator shroud may be formed in various shapes, as long as the shroud allows radiation through the selected, aligned channel while blocking radiation emitted from an unselected channel.

[0014] In another aspect, the treatment system may include an alignment verification mechanism. Such verification features may include optical alignment features, such as an optical laser mechanism that guides the laser beam through a selected collimator channel and detects the laser beam emanating from an exit aperture. In some embodiments, the treatment system further includes one or more imaging devices for monitoring the patient during treatment.

[0015] In some embodiments, the collimator includes: a collimator body having a pivoting feature, the collimator body being rotatable about a pivot axis about the pivoting feature; and a plurality of collimator channels extending through the collimator body, each of the plurality of collimator channels being substantially perpendicular to the pivot axis, the collimator body being rotatable about the pivot axis. In some embodiments, each of the plurality of collimator channels intersects the pivot axis.

[0016] In another aspect, this document provides a method for delivering therapeutic beams of different sizes and / or shapes to a target within a patient during treatment. An exemplary method includes: selecting a first collimator channel from a plurality of collimator channels in a collimator body, the selected first collimator channel corresponding to a desired first therapeutic beam. The collimator body is rotatable within the treatment system along a rotation axis of the collimator body, and the plurality of collimator channels differ in size and / or shape and extend substantially perpendicular to the rotation axis. The collimator body is then rotated along the rotation axis until the selected first collimator channel is aligned with the radiation source; then, a first particle beam is emitted from the radiation source through the selected first collimator channel to guide the desired first therapeutic beam to the target within the patient. Such a method may further include: selecting a second collimator channel in the collimator body, the selected second collimator channel corresponding to a desired second therapeutic beam, the second therapeutic beam differing in size and / or shape from the first therapeutic beam. Next, the collimator body is rotated along the rotation axis until the selected second collimator channel is aligned with the radiation source. Then, a second particle beam is emitted from the radiation source through the selected second collimator channel to guide the desired second therapeutic beam to the target within the patient. In some embodiments, rotating the collimator body until the selected first collimator channel is aligned includes rotating the collimator body until a sensor of the system's control unit detects a mark disposed on the collimator body indicating a collimator position corresponding to the alignment of the first collimator channel. Such a method may further include verifying the alignment of the first collimator channel with the radiation source by emitting a laser beam through the collimator channel and detecting the laser beam emitted from the exit aperture of the first collimator channel.

[0017] Various aspects and details of the invention can be further understood by referring to the exemplary embodiments depicted in the accompanying drawings and the description provided below. Attached Figure Description

[0018] Figure 1 A cross-section of an example rotary collimator wheel is shown, the rotary collimator wheel having a collimator channel passing through it.

[0019] Figure 2 An example rotary collimator wheel mounted on a conical shroud is shown, the collimator wheel having a magnetic encoder tracker that senses when the wheel has reached the desired collimator position.

[0020] Figure 3The top of an example cone-shaped shield is shown, including the collimator wheel, the collimator channel outlet, and a camera for monitoring the patient.

[0021] Figure 4 An example collimator wheel and associated motors configured to drive between positions are shown, as well as a linear accelerator that causes radiation to pass through the collimator wheel and associated features.

[0022] Figure 5 Another example of a conical shield is shown, which surrounds the periphery of the collimator wheel to cover the opening of the misaligned channel. Detailed Implementation

[0023] This invention generally relates to radiotherapy systems and methods of use, particularly collimator systems that provide selective control and delivery of collimated radiation beams.

[0024] Figure 1 A cross-sectional view of a rotary collimator wheel 100 is shown, the rotary collimator wheel 100 having a collimator channel 140 passing through it. The collimator wheel 100 has longitudinally extending channels or collimator channels 105, 115, and 125 defined therein (e.g., machined through the body of the collimator wheel 100). Several other channels are shown in the figure, which are not labeled for clarity. Collimator channels can have various sizes, diameters, or shapes. In some embodiments, each collimator channel has a different diameter. For example, as... Figure 1 As shown, collimator channel 105 has a larger bore than collimator channel 115, and collimator channel 115 has a larger bore than collimator channel 125. Each collimator channel extends from a radiation inlet port 106 to an outlet port 107. In some embodiments, the inlet port 106 is smaller than the outlet port 107 to facilitate delivery of the maximum radiation dose at the edge of the target where the radiation ultimately strikes. Collimator wheel 100 is rotated such that a selected collimator channel is aligned with the radiation source 110 to allow a particle radiation beam 111 to pass through the selected channel, thereby providing the desired therapeutic beam to the target 112 within the patient's body. Figure 1In the side sectional view of the collimator wheel 100 shown at the bottom, the inlet and outlet holes 150 are visible around the perimeter, and the collimator wheel 100 rotates on the shaft 101. In this example, the collimator wheel 100 is coupled to a 50:1 reduction gearbox and a motor. In some embodiments, the channel 105 and the outlet hole 107 are circular. It should be understood that in alternative embodiments, the channel can have any size or shape, such as a square. The collimator wheel 100 can be formed from any suitable material, such as a titanium alloy. Although the collimator wheel 100 is shown as vertically oriented relative to the surface where the patient is located, it should be understood that the collimator wheel 100 can be configured in any orientation as long as the treatment beam through the collimator channel is guided to the target. Furthermore, although the collimator wheel is shown as having eight collimator channels, it should be understood that such a collimator wheel may include more or fewer collimator channels.

[0025] Figure 2 A cross-section of a rotating collimator wheel 200 is shown. The rotating collimator wheel 200 is mounted on a collimator housing 210 and rotates between various collimator positions on a shaft 205. In this embodiment, the collimator housing 210 substantially sheaths the portion of the collimator wheel facing the radiation source to prevent radiation from entering an misaligned collimator channel. The rotational position of the collimator wheel can be precisely controlled by a control system using one or more sensors or encoders that monitor the position of the collimator wheel 200, for example by detecting a mark set on the periphery of the collimator wheel. In this embodiment, the position of the collimator wheel is precisely monitored by encoder reader heads 215 and 216, which track a thin strip encoder bar fixed to the inner edge 214 of the collimator wheel 100 adjacent to the paths of the reader heads 215 and 216. The control system detects signals generated by changes in the precise placement of the encoder and the encoder bar in terms of electromagnetic interaction. Using this combination of an encoder reader head and an encoder bar fixed to the inner edge 214, the control system senses when the wheel has reached the desired collimator position. Also shown in the cross-section of the collimator housing 210 is a LINAC head 230, which is the source of radiation delivered to the inlet orifice of the selected collimator. In some embodiments, an ion chamber is included within the collimator housing, between the LINAC head 230 and the collimator wheel 200. Alternative position encoder schemes may include mechanical stops, such as gear teeth and racks, and / or optically sensed position markers.

[0026] In one aspect, the aforementioned collimator assembly and control system are incorporated into a treatment system. The control system includes a processor configured to facilitate controlled rotation of a collimator wheel to select a position corresponding to the alignment of a selected collimator channel and a radiation source, the selected collimator channel corresponding to a desired treatment beam. In some embodiments, the treatment system includes a user interface that allows a therapist to select one or more treatment beams associated with one or more collimator channels. In other embodiments, the control system automatically determines one or more collimator channels corresponding to a selected treatment process.

[0027] Figure 3 The top of the conical shroud is shown, including the exit of the collimator channel and a camera for monitoring the patient. The collimator wheel 300 is laterally visible and includes a selected channel exit hole 305 and other holes that are not identified and therefore not aligned with the LINAC (below and not visible). A motor 315 rotates the collimator wheel 305 to a selected position where the desired holes are aligned with the LINAC. In some embodiments, the system includes one or more cameras, such as camera 310, positioned to allow monitoring of the patient while undergoing radiation therapy. An encoder interpretation computer subsystem 320 reads data from the encoder reader head (see [link to documentation]). Figure 2 The system receives signals to calculate the precise rotational position of the collimator wheel 300, and thereby calculates the position of any one of the selectable collimator channels. For example, in the feedback loop, the motor control computer subsystem 330 acts to activate the motor 315 until the encoder indicates that the selected collimator is aligned with the LINAC. In one aspect, the system is configured to change the collimator wheel position among multiple positions associated with the selected collimator channel during treatment so that the size of the treatment beam reaching the target varies.

[0028] Figure 4 A cross-sectional view of the collimator wheel is shown, which includes a motor that drives the vehicle between positions, a linear accelerator that aligns the radiation through the collimator channel, and related features.

[0029] As shown, the collimator wheel 449 has a selected channel 451 aligned with the outlet port 452 and the inlet port 450. A collimator shroud 410 surrounds the collimator wheel 449 along the portion facing the radiation source to allow the particle beam to pass through the inlet and outlet ports of the channel 451, while preventing radiation from entering an misaligned channel. In this embodiment, the collimator wheel 449 is selectively rotated to a desired position via a shaft 453 with a bushing 434, which is connected to a gearbox 444 via a coupling bracket and a base 420. The gearbox 444 is coupled to and driven by a motor 445, providing a reduction in rotation at a predefined ratio, thereby allowing very fine control over the degree to which the collimator wheel rotates and aligns with the radiation source, the LINAC head 460, and the distal edge of the LINAC body 461. The predefined ratio can be 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, or any ratio suitable for a given geometry of the collimator wheel and the desired adjustment of resolution in the treatment system. In this embodiment, the energy exiting the LINAC head 460 enters a sealed ion chamber 403. By virtue of the fact that the radiation entering the ion chamber will generate a measurable ionizing current proportional to the X-ray beam intensity, the ion chamber 403 allows for monitoring of dose, dose rate, and field symmetry.

[0030] In this embodiment, beam technology is used to optimize mechanical alignment. This has the advantage of maximizing the delivery of radiation from the ion chamber 403 to the inlet aperture 450. To this end, the system includes a laser shroud holding a laser 416, from which a beam is bent at a right angle by a mirror 415 and guided into an aperture iris lens 419. Afterward, the laser passes through a shroud bore 421 defined in a shroud 410 to reach a beam path right-angle optical mirror 422. Because the beam path right-angle optical mirror 422 is reflective but transmissive to radiation, a properly aligned collimator can be detected by the laser beam emitted from the exit aperture 452 of the collimator 451, while maintaining the functionality of the primary radiation delivery alignment (a useful feature in the initial verification and calibration of each machine).

[0031] Figure 5 Another example system is shown, which has the following characteristics: Figure 1The collimator wheel and related components shown are identical or similar, as is the conical collimator shroud 510, which substantially surrounds the periphery of the collimator wheel to block and absorb radiation emitted from the orifice of an misaligned collimator channel, while allowing the particle beam 111 to travel from the radiation source 110 through a selected, aligned collimator channel to deliver the desired therapeutic beam to the target 112. In this embodiment, the collimator shroud 510 covers any orifice of the misaligned channel. In some embodiments, the shroud may cover less than all of the orifice of the misaligned channel. It should be understood that in any embodiment herein, the shroud may include multiple shroud components to cover the orifice of the misaligned channel and is not required to be a single component. Various configurations of the shroud can be implemented according to the concepts described herein.

[0032] Although these components are shown in a specific arrangement in this example, it should be understood that, as those skilled in the art will appreciate, various other means of rotating the collimator wheel can be used to achieve alternative configurations. Furthermore, it should be understood that certain elements (such as the camera, ion chamber, and beam alignment features) can be omitted while still retaining some of the aforementioned advantages of the invention.

[0033] In the foregoing description, the invention has been described with reference to specific embodiments thereof, but those skilled in the art will recognize that the invention is not limited thereto. The various features and aspects of the invention described above can be used individually or in combination. Furthermore, the invention can be used in any number of settings and applications beyond those described herein without departing from the broader spirit and scope of this specification. Therefore, this specification and the accompanying drawings are to be regarded as illustrative rather than restrictive. It will be appreciated that the terms “comprising,” “including,” and “having” as used herein are specifically intended to be interpreted as open-ended terms in the art.

Claims

1. A radiation collimator assembly, comprising: A radiation source, the radiation source including a linear accelerator for generating a therapeutic beam for therapeutic radiotherapy; and A collimator wheel, rotatable about its axis of rotation, having a plurality of collimator channels, the plurality of collimator channels including at least: The first collimator channel, and confined within the collimator wheel, The second collimator channel is confined within the collimator wheel. Each collimator channel in the collimator wheel extends longitudinally in a direction perpendicular to the rotation axis of the collimator wheel; Each collimator channel extends through the entire diameter of the collimator wheel; The collimator wheel is configured to guide the treatment beam through only a single collimator channel of the plurality of collimator channels at a time; and The first and second collimator channels have different sizes and / or shapes.

2. The radiation collimator assembly of claim 1, wherein the collimator wheel is configured to be positioned between the radiation source and the target.

3. The radiation collimator assembly of claim 1, wherein each of the first and second collimator channels passes through the center of the collimator wheel, and the rotation axis extends through the center of the collimator wheel.

4. The radiation collimator assembly as claimed in claim 1 or 2, wherein the plurality of collimator channels are distributed at regular intervals along the collimator wheel.

5. The radiation collimator assembly of claim 1 or 2, wherein the plurality of collimator channels comprises three or more collimator channels.

6. The radiation collimator assembly of claim 1 or 2, wherein the first and second collimator channels can be selected by rotatably moving the collimator wheel, thereby aligning one of the first and second collimator channels with the radiation source.

7. The radiation collimator assembly as claimed in claim 1 or 2, further comprising: An electric motor, operatively coupled to the collimator wheel to rotate the collimator wheel about the rotation axis; and A control unit, operatively coupled to the motor, controls the rotation of the collimator to a collimator position corresponding to the alignment of a selected collimator channel and the radiation source.

8. The radiation collimator assembly of claim 7, wherein the control unit is communicatively coupled to one or more sensors configured to detect the position of the collimator.

9. The radiation collimator assembly of claim 8, wherein the one or more sensors include one or more encoder readers, and the collimator wheel includes a plurality of markers positioned to correspond to the alignment of the plurality of collimator channels.

10. A radiotherapy system, comprising: The radiation collimator assembly of claim 1, wherein the radiation collimator assembly is configured to deliver a radiation beam from the linear accelerator through a selected collimator channel of the collimator wheel to a target within the patient body; An electric motor, operatively coupled to the collimator wheel to rotate the collimator wheel about the rotation axis; and A control unit, operatively coupled to the motor, controls the rotation of the collimator to a position corresponding to the alignment of the selected collimator channel and the radiation source.

11. The radiotherapy system of claim 10, wherein the control unit is configured to rotate the collimator wheel to align a selected collimator channel of the plurality of collimator channels with the radiation source, the selected collimator channel corresponding to a desired treatment beam.

12. The radiotherapy system of claim 10 or 11, further comprising: A collimator cover, substantially surrounding at least the portion of the collimator wheel facing the radiation source that includes an misaligned collimator channel, thereby suppressing radiation through the misaligned collimator channel while allowing the particle beam to pass through a selected, aligned collimator channel.

13. The radiotherapy system of claim 10 or 11, further comprising one or more imaging devices for monitoring the patient during treatment.

14. The radiotherapy system of claim 10 or 11, further comprising: A beam alignment feature configured to monitor or verify the alignment of the selected collimator channel with the radiation source.

15. A collimator that collimates a treatment beam generated by a linear accelerator for therapeutic radiotherapy, and comprises: The collimator body has a pivoting feature, and the collimator body is rotatable about a pivot axis around the pivoting feature; as well as Multiple collimator channels, the multiple collimator channels extending through the collimator body; Each collimator channel in the collimator extends longitudinally in a direction perpendicular to the pivot axis, and the collimator body rotates about the pivot axis; Each collimator channel extends through the entire diameter of the collimator body; The collimator is configured to guide the treatment beam through only a single collimator channel of the plurality of collimator channels at a time; and The first and second collimator channels of the plurality of collimator channels have different sizes and / or shapes.

16. The collimator of claim 15, wherein the collimator is configured to be positioned between the linear accelerator and the target.

17. The collimator of claim 15, wherein each of the plurality of collimator channels intersects the pivot axis.

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