Method and apparatus for magnetic reluctance linear localization detection in radiotherapy systems

Abstract

A multi-leaf collimator includes a plurality of movable leaves (351) for shaping a radiotherapy beam, wherein each leaf is capable of moving independently in the same linear direction of travel. Each leaf includes a linear array (720) of magnets (721) disposed on a measuring surface of the leaf, and an array of magnetoresistive sensors (651) disposed near the measuring surface of the leaf.

Description

[0001] Cross-reference to related applications

[0002] The subject matter of this application relates to U.S. Patent Application No. 17 / 072,046, which is incorporated herein by reference. Background Technology

[0003] Unless otherwise stated herein, the methods described in this section are not prior art to the claims of this application and are not acknowledged as prior art by virtue of their inclusion in this section.

[0004] Radiation therapy using ionizing radiation is a localized treatment of a specific target tissue, such as a cancerous tumor. Ideally, radiation therapy is performed on the target tissue (also known as the planned target volume) in such a way that the surrounding normal tissue is spared from receiving a dose exceeding a specified tolerance, thereby minimizing the risk of damage to normal tissue. Conformal radiation therapy and intensity-modulated radiation therapy have been developed to ensure that a prescribed dose is correctly delivered to the planned target volume during radiation therapy.

[0005] In conformal radiotherapy, the radiation beam can be shaped around the target tissue, for example, using a beam-limiting device, to deliver a high dose of radiation to the cancerous tumor while minimizing the dose to surrounding healthy tissue. In intensity-modulated radiotherapy (IMRT), the intensity of the radiation beam is modulated so that the prescribed radiation dose more precisely conforms to the three-dimensional shape of the tumor. Both conformal and IMRT can significantly reduce the risk of side effects and / or enable increased doses to the target tissue.

[0006] The beam-limiting device commonly used in conformal and intensity-modulated radiotherapy (IMRT) is the multi-leaf collimator (MLC). Typically, an MLC in a radiotherapy system comprises multiple movable “leaves” of radiation-blocking material independently positioned within the path of the radiotherapy beam. In this way, the MLC enables targeted beamforming and / or variations in the intensity of the radiotherapy beam.

[0007] To ensure the correct delivery of the prescribed dose to the planned target volume during radiotherapy, the MLC and the individual leaves contained within it must be precisely positioned relative to the linear accelerator providing the radiotherapy. However, current radiation-resistant positioning sensors used to measure the positioning of the MLC and its leaves have several drawbacks. For example, electromechanical positioning sensors suffer from repeatability and reliability issues due to wear over time. Furthermore, some electromechanical positioning sensors may experience gravity-related inaccuracies when positioned at specific angles, further increasing the uncertainty of their output. Summary of the Invention

[0008] In one aspect, the invention provides a multi-leaf collimator as defined in claim 1. In another aspect, the invention provides a method for measuring the position of a movable leaf among a plurality of leaves in a multi-leaf collimator as defined in claim 16. Optional features are specified in the dependent claims.

[0009] According to at least some embodiments of the present disclosure, a radiotherapy system is configured to use a magnetoresistive sensor to measure the positioning of a multi-leaf collimator turntable and / or the positioning of individual leaves within the multi-leaf collimator turntable. In some embodiments, the positioning of the multi-leaf collimator turntable is measured along an axis of linear motion via an array of linear magnets coupled to the surface of the turntable and a magnetoresistive sensor. In some embodiments, the positioning of individual leaves within the multi-leaf collimator turntable is measured along an axis of linear motion via a linear array of magnets coupled to the surface of the leaves and a magnetoresistive sensor.

[0010] The foregoing description of the invention is merely illustrative and is not intended to be limiting in any way. Other aspects, embodiments, and features will become apparent from the accompanying drawings and the following detailed description, in addition to the illustrative aspects, embodiments, and features described above. Attached Figure Description

[0011] The foregoing and other features of this disclosure will become more fully apparent from the accompanying drawings, the following description, and the appended claims. These drawings depict only a few embodiments according to this disclosure and are therefore not intended to limit its scope. This disclosure will be described with additional specificity and detail using the accompanying drawings.

[0012] Figure 1 It is a perspective view of a radiotherapy system according to one or more embodiments.

[0013] Figure 2 Schematic illustrations of various embodiments Figure 1 The drive frame and stand for the radiotherapy system.

[0014] Figure 3 Schematic illustrations of various embodiments Figure 1 The collimator assembly of a radiotherapy system.

[0015] Figure 4 A linear motion detection device according to various embodiments is schematically illustrated.

[0016] Figure 5 Schematic illustrations of various embodiments Figure 3 A side view of a single leaf of the collimator assembly.

[0017] Figure 6 According to the embodiments Figure 1 A perspective view of the multi-leaf collimator turntable of a radiotherapy system.

[0018] Figure 7 According to the embodiment, when inserted into Figure 6 A perspective view of the printed circuit board in the multi-leaf collimator turntable.

[0019] Figure 8 According to the embodiments Figure 6 End view of the multi-leaf collimator turntable.

[0020] Figure 9 This is a partial end view of the multi-leaf collimator layer and the printed circuit board according to an embodiment.

[0021] Figure 10 A linear rotational motion detection device according to various embodiments is schematically illustrated.

[0022] Figure 11 This is a graph illustrating the output values ​​of the ideal sine output signal, the actual sine output signal, and the cosine output signal from the magnetoresistive sensor.

[0023] Figure 12 A flowchart illustrating a calibration process for rotational positioning detection via a magnetoresistive sensor, according to one or more embodiments, is provided.

[0024] Figure 13 A flowchart illustrating a process for rotational positioning detection via a magnetoresistive sensor according to one or more embodiments is provided.

[0025] Figure 14 This is an illustration of a computing device configured to perform various embodiments of the present disclosure.

[0026] Figure 15 This is a block diagram illustrating various embodiments of a computer program product for implementing the present disclosure. Detailed Implementation

[0027] In the following detailed description, reference is made to the accompanying drawings, which form a part of this document. In the drawings, similar symbols generally identify similar parts unless the context otherwise requires. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that aspects of this disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, and designed in a variety of different configurations, all of which are clearly contemplated and constitute a part of this disclosure.

[0028] As mentioned above, beamforming plays a crucial role in improving the accuracy, efficiency, and quality of certain radiotherapies. For this purpose, multi-leaf collimators (MLCs) have been used in radiotherapy as beamformers for conformal radiotherapy, and as modulators for intensity-modulated radiotherapy (IMRT) and volume-modulated arc therapy (VMAT). In such treatments, accurate beamforming depends on the precise positioning of the MLC and its individual leaves relative to the treatment beam. According to various embodiments, improved and more reliable leaf positioning and MLC turntable positioning in radiotherapy systems are facilitated by measuring linear and / or rotational positioning using magnetoresistive sensors, as described below.

[0029] Figure 1 This is a perspective view of a radiotherapy system 100 according to one or more embodiments. The radiotherapy (RT) system 100 is configured to provide stereotactic radiosurgery and precise radiotherapy to lesions, tumors, and conditions in the body that indicate radiotherapy. Thus, the RT system 100 may include one or more of the following: a linear accelerator (LINAC) generating a megavolt (MV) treatment beam of high-energy X-rays, a kilovolt (kV) X-ray source, an X-ray imager, and, in some embodiments, an MV electron entry imaging device (EPID) (not shown for clarity). Alternatively or additionally, the RT system 100 may be configured to generate high-energy or very high-energy electrons, protons, heavy ions, and / or the like. As an example, the radiotherapy system 100 described herein is configured with a circular gantry. In other embodiments, the RT system 100 may be configured with a C-shaped gantry capable of infinite rotation via slip ring connections or configured with a robotic arm.

[0030] Typically, the RT system 100 is capable of kV imaging of the target volume during the application of an MV treatment beam, enabling the execution of IMRT, VMAT, image-guided radiotherapy (IGRT), and / or conformal radiotherapy procedures. The RT system 100 may include one or more touchscreens 101, a bed motion controller 102, a chamber 103, a base positioning assembly 105, a bed 107 mounted on the base positioning assembly 105, and an image acquisition and treatment control computer 106, all located within the treatment room. The RT system 100 also includes a remote console 110 located outside the treatment room, enabling treatment delivery and patient monitoring from a remote location. The base positioning assembly 105 is configured to precisely position the bed 107 relative to the chamber 103, and the motion control 102 includes input devices, such as buttons and / or switches, allowing a user to operate the base positioning assembly 105 to automatically and precisely position the bed 107 at a predetermined position relative to the chamber 103. Motion control 102 also allows the user to manually position the couch 107 to a predetermined location. In some embodiments, the RT system 100 also includes one or more cameras (not shown) for patient monitoring in the treatment room.

[0031] Figure 2 The drive rack 200 and the bench 210 of the RT system 100 according to various embodiments are schematically illustrated. For clarity, in Figure 2 The cover, base positioning assembly 105, bed 107, and other components of the RT system 100 are omitted. The drive frame 200 is a fixed support structure for the components of the RT system 100, including a platform 210 and a drive system 201 for rotatably moving the platform 210. The drive frame 200 rests on and / or is fixed to a support surface (such as the floor of an RT treatment facility) outside the RT system 100. The platform 210 is rotatably coupled to the drive frame 200 and is the support structure on which various components of the RT system 100 are mounted, including a linear accelerator (LINAC) 204, an electronic entry imaging device (EPID) 205, an imaging X-ray source 206, and an X-ray imager 207. During operation of the RT system 100, the platform 210 rotates about the chamber 103 when actuated by the drive system 201.

[0032] A drive system 201 rotatably actuates a stage 210. In some embodiments, the drive system 201 includes a linear motor that can be fixed to a drive frame 200 and interact with magnetic rails (not shown) mounted on the stage 210. In other embodiments, the drive system 201 includes another suitable drive mechanism for precisely rotating the stage 210 about a bore 103. A LINAC 204 generates a high-energy X-ray (or in some embodiments, electrons, protons, heavy ions, etc.) MV treatment beam 230, and an EPD 205 is configured to acquire X-ray images via the treatment beam 230. An imaging X-ray source 206 is configured to guide a cone beam of X-rays (hereinafter referred to as imaging X-ray 231) through an isocenter 203 of the RT system 100 to an X-ray imager 207. The isocenter 203 typically corresponds to the location of the target volume to be treated. The X-ray imager 207 receives the imaging X-ray 231 and generates an appropriate projected image based on it. Such projected images can then be used to construct or update portions of imaging data corresponding to a digital volume encompassing a 3D region including the target volume. In some embodiments, cone-beam computed tomography (CBCT) and digital tomography synthesis (DTS) can be used to process the projected images generated by the X-ray imager 207.

[0033] exist Figure 2 In the embodiment shown, the X-ray imager 207 is depicted as a planar device. In other embodiments, the X-ray imager 207 may have a curved configuration. Furthermore, in... Figure 2 In the embodiment shown, the RT system 100 includes a single X-ray imager and a single corresponding imaging X-ray source. In other embodiments, the RT system 100 may include two or more X-ray imagers, each having a corresponding imaging X-ray source.

[0034] The LINAC 204 includes a collimator assembly 250 and / or operates in conjunction with the collimator assembly 250. The collimator assembly 250 includes one or more collimators for shaping and / or modifying the intensity of the MV treatment bundle 230. The following is a further explanation. Figure 3 An embodiment of the collimator assembly 250 is described.

[0035] Figure 3 A collimator assembly 250 according to an embodiment is schematically illustrated. Figure 3In the embodiment shown, the collimator assembly 250 includes a main collimator 310 and an MLC turntable 300 including at least one MLC layer. The collimator assembly 250 is positioned close to the radiation source (not shown) of the LINAC 204 and between the radiation source and the isocenter 203 of the RT system 100. Furthermore, in some embodiments, the main collimator 310 is fixed relative to the radiation source, while the MLC turntable 300 is configured to move relative to the radiation source. In some embodiments, the MLC turntable 300 is configured to translate along one or more linear axes, such as a first linear motion axis 301, a second linear motion axis 302, and / or a third linear motion axis 303 (outside the page). In some embodiments, the MLC turntable 300 is configured to rotate about at least one rotation axis (such as rotation axis 304). In some embodiments, rotation axis 304 is substantially parallel to the centerline 305 of the X-ray field 306. Figure 3 In the example illustrated, the rotation axis 304 coincides with the center line 305 of the X-ray field 306, but in many instances, the rotation axis 304 deviates from the center line 305 along the first linear motion axis 301 and / or the third motion axis 303.

[0036] In some embodiments, the MLC turntable 300 is configured with primary and secondary positioning detection for linear movement along a first linear motion axis 301, a second linear motion axis 302, a third linear motion axis 303, and / or a rotation axis 304. In some embodiments, primary motion detection relative to one or more of the aforementioned axes is provided by a servo system associated with the motion. For example, in one embodiment, the servo system associated with the linear movement of the MLC turntable 300 along the first linear motion axis 301 includes specific positioning feedback indicating the current positioning of the MLC turntable 300 along the first linear motion axis 301. In such an embodiment, such positioning feedback is considered primary linear positioning detection along the linear motion axis 301. In another example, in one embodiment, the servo system associated with the rotational movement of the MLC turntable 300 about the rotation axis 304 includes specific positioning feedback indicating the current rotational positioning of the MLC turntable 300 about the rotation axis 304. In such an embodiment, such rotational positioning feedback is considered primary rotational positioning detection.

[0037] In some embodiments, motion detection (e.g., secondary motion detection) relative to one or more of the aforementioned axes is provided by a corresponding magnetoresistive sensor. Therefore, in such an embodiment, the MLC turntable 300 includes one or more of the following: a magnetoresistive sensor 321 for motion detection of the MLC turntable 300 relative to a first linear motion axis 301; a magnetoresistive sensor 322 for motion detection of the MLC turntable 300 relative to a second linear motion axis 302; a magnetoresistive sensor 323 for motion detection of the MLC turntable 300 relative to a third linear motion axis 303; or a magnetoresistive sensor 324 for motion detection of the MLC turntable 300 relative to a rotation axis 304. In such an embodiment, magnetoresistive sensor 321 performs motion detection via a linear array 331 of magnets disposed on the surface 341 of the MLC turntable 300, magnetoresistive sensor 322 performs motion detection via a linear array 332 of magnets disposed on the surface 342 of the MLC turntable 300, magnetoresistive sensor 323 performs motion detection via a linear array 333 of magnets disposed on the surface 342 of the MLC turntable 300, and / or magnetoresistive sensor 324 performs motion detection via a toothed ring 334 disposed on the peripheral region 344 of the MLC turntable 300. In such an embodiment, the International Electrotechnical Commission (IEC) requires that the linear and rotational axes of all LINAC turntables be satisfied by corresponding magnetoresistive sensors.

[0038] The following is combined with Figure 4 An embodiment of a magnetoresistive sensor for linear motion detection in an MLC turntable 300 is described below. Figure 10 An embodiment of a magnetoresistive sensor for detecting the rotational motion of an MLC turntable 300 is described.

[0039] Figure 4 A linear motion detection device 400 according to various embodiments of the present invention is schematically illustrated. Figure 4 In the embodiment shown, the linear motion detection device 400 includes a magnetoresistive sensor 410 and a linear array 420 of magnets 421. In some embodiments, the linear array 420 is implemented as a magnetic scale of magnets 421 with alternating magnetic poles (i.e., NSNS, etc.), wherein each magnet 421 is separated from the other by a uniform magnetic pole spacing 422.

[0040] The magnetoresistive sensor 410 is positioned close to the linear array 420 and separated from it by an air gap 401. Therefore, the magnetoresistive sensor 410 does not have physical contact with the linear array 420. As a result, neither the magnetoresistive sensor 410 nor the linear array 420 experiences mechanical wear during use.

[0041] As shown, the linear array 420 is configured as a linear array of magnets 421 longitudinally oriented in a specific linear travel direction 403. The magnetoresistive sensor 410 is configured to detect movement of the linear array 420 relative to the magnetoresistive sensor 410 in the linear travel direction 403 and / or generate positioning information that enables the detection of movement of the linear array 420 relative to the magnetoresistive sensor 410 in the travel direction 403. In some embodiments, the magnetoresistive sensor 410 includes a magnetoresistive device 412, a bias magnet 414, and a resistor bridge (not shown). In some embodiments, the resistor bridge is included in the magnetoresistive device 412. In some embodiments, the magnetoresistive device 412 includes at least one of anisotropic magnetoresistive (AMR) sensor, giant magnetoresistive (GMR) sensor, tunneling magnetoresistive (TMR) sensor, or other magnetic positioning sensors that measure changes in the magnetic field that occur when the magnets 421 of the linear array 420 move relative to the magnetoresistive sensor 410.

[0042] The magnetoresistive sensor 410 generates positioning information based on the magnetoresistive effect, where an external magnetic field affects the resistance of the magnetoresistive material in the magnetoresistive sensor 410. For example, in some embodiments, the magnetoresistive sensor 410 is configured to operate as a sinusoidal encoder that generates positioning information of the magnet 421 in the form of a sine output signal and a cosine output signal based on the current angle of the magnetic field. Based on the sine and cosine output signals, the positioning of the magnetoresistive sensor 410 between two adjacent magnets 421 can be determined. In such embodiments, the sine and cosine output signals enable accurate determination of the positioning of the magnetoresistive sensor 410 between two adjacent magnets 421. For example, in an embodiment where the magnetoresistive sensor 410 is configured to generate a signal for resolving the positioning of the magnetoresistive sensor 410 to within 1° (where the pole spacing 422 is equal to 360°), the positioning of the magnetoresistive sensor 410 can be determined to be within 1% of the pole spacing 422. Furthermore, as the magnetoresistive sensor 410 moves from one end of the linear array 420 of magnets 421 to the other end, the repetition periods of the sinusoidal and / or cosine output signals can be counted. This allows for the identification of two adjacent magnets 421, with the magnetoresistive sensor 410 positioned between them. Therefore, the magnetoresistive sensor 410 can provide precise positioning information about the linear array 420 relative to the magnetoresistive sensor 410.

[0043] Note that the magnetoresistive sensor 410 does not actively generate positioning signals, but rather acts as a passive device. As a result, the output of the magnetoresistive sensor 410 is typically unaffected by the X-ray field present in the radiotherapy system (such as...). Figure 3 The high radiation environment of the X-ray field (306) in the field has an impact.

[0044] Back Figure 3The primary collimator 310 is configured to define the external environment of the X-ray field 306. The primary collimator 310 can be a fixed collimator or a collimator configured with one or more movable claws. Typically, the primary collimator 310 is positioned close to the radiation source of the LINAC 204. Figure 3 In the embodiment illustrated, the main collimator 310 is described as a single collimating device, but in other embodiments, the main collimator 310 includes multiple collimating devices positioned in series within the X-ray field 306.

[0045] In some embodiments, the MLC turntable 300 includes a proximal MLC layer 350 and a distal MLC layer 360. In other embodiments, the MLC turntable 300 includes a single MLC layer. The proximal MLC layer 350 includes a plurality of leaves 351, each leaf capable of independently moving in the direction of travel into the X-ray field 306. Similarly, the distal MLC layer 360 includes a plurality of leaves 361, each leaf capable of independently moving in the direction of travel into the X-ray field 306. Figure 3 In the embodiment illustrated, each leaf 351 of the proximal MLC layer 350 is capable of moving in a specific direction of travel perpendicular to the centerline 305 of the X-ray field 306. Furthermore, in Figure 3 In the embodiment illustrated, the direction of travel of leaf 351 is depicted as along a third linear motion axis 303 extending outward from the page. Similarly, each leaf 361 of the distal MLC layer 360 is capable of moving in a specific direction of travel perpendicular to the centerline 305 of the X-ray field 306. Figure 3 In the embodiment illustrated, the direction of travel of leaf 361 is the same as that of leaf 351, and the direction of travel of leaf 351 is along the linear motion axis 303. Figure 3 In the middle, leaves 351 and 361 are viewed from the ends, that is, along the direction of travel parallel to the third linear motion axis 303.

[0046] In some embodiments, the proximal MLC layer 350 includes multiple rows of leaflets 351 and the distal MLC layer 360 includes multiple rows of leaflets 361. In such an embodiment, the MLC layer 350 includes two opposing multiple rows of leaflets 351 positioned on opposite sides of the central plane of the X-ray field 306, and the distal MLC layer 360 includes two opposing multiple rows of leaflets 361 located on opposite sides of the central plane of the X-ray field 306.

[0047] Leaflets 351 and 361 are typically formed of a high atomic number material, such as tungsten or its alloys. Furthermore, in some embodiments, leaflets 351 and 361 have a generally trapezoidal cross-section that matches the beam divergence occurring in the direction perpendicular to leaf travel. In practice, the cross-sections of leaflets 351 and 361 may not be precisely trapezoidal. In some embodiments, leaflets 351 and 361 may be configured to project to the same projection size at isocenter point 203. In such embodiments, leaflet 351 has a smaller cross-section than leaflet 361 in the direction perpendicular to leaf travel.

[0048] In some embodiments, motion detection of each leaf in leaf 351 and leaf 361 along the linear travel direction is achieved by a corresponding magnetoresistive sensor. In such embodiments, each leaf 351 and each leaf 361 includes a magnetoresistive sensor for linear motion detection of the corresponding leaf. The following is in conjunction with... Figure 5 Describe one such embodiment.

[0049] Figure 5 A side view of a single blade 500 of an MLC turntable 300 according to various embodiments is schematically illustrated. As shown, the blade 500 is positioned at the beginning edge 501 of a travel range in a particular travel direction 502, and is therefore positioned close to but outside the X-ray field 306. The blade 500 (dashed line) is also shown after partially traveling along the travel range in the travel direction 502.

[0050] Leaf 500 includes a magnetoresistive sensor 521 and a linear array 531 of magnets disposed on the edge surface 541 of leaf 500. In some embodiments, the magnetoresistive sensor 521 may be coupled with... Figure 4 The configuration of one or more embodiments of the magnetoresistive sensor 410 is consistent, and the linear array 531 can be with Figure 4 The configuration of one or more embodiments of the linear array 420 is consistent.

[0051] In operation, as leaf 500 moves along travel direction 502, magnetoresistive sensor 521 generates positioning information for accurately determining the current position of magnetoresistive sensor 521 between the two closest magnets included in linear array 531. In some embodiments, magnetoresistive sensor 521 generates this positioning information in the form of a sine output signal and a cosine output signal. In some embodiments, this positioning information is used for secondary motion detection of leaf 500 along travel direction 502. In such embodiments, a servo system associated with moving leaf 500 along travel direction 502 provides primary linear motion detection. Therefore, in such embodiments, the IEC requirement that all moving leaves in a radiotherapy system have both primary and secondary positioning sensors is met.

[0052] Figure 6 This is a perspective view of the MLC turntable 300 according to an embodiment. Figure 6 In the diagram, an array 650 of magnetoresistive sensors 651 for the proximal MLC layer 350 is shown disassembled from the MLC turntable 300. Figure 6 In the embodiment illustrated, a magnetoresistive sensor 651 is disposed on a printed circuit board (PCB) 652. In some embodiments, an array 650 of magnetoresistive sensors 651 is configured as a linear array extending longitudinally in a direction 602 perpendicular to the linear travel direction 603 of the leaf 351. Figure 6 In the embodiment illustrated, array 650 includes multiple rows 653 of magnetoresistive sensors 651. In some embodiments, the magnetoresistive sensors 651 in the multiple rows 653 are staggered, allowing the magnetoresistive sensors 651 to be spaced closer together along direction 602. A PCB 652 is inserted into the MLC turntable 300 such that each magnetoresistive sensor 651 is positioned close to the measurement surface of a corresponding leaf 351 of the MLC layer 350.

[0053] Figure 7 This is a perspective view of PCB 652 when inserted into MLC turntable 300 according to an embodiment. Figure 7 For clarity, parts of the MLC turntable 300, such as the housing of the enclosed leaf 351, are omitted. As shown, magnetoresistive sensors 651 are mounted on the PCB 652, such that each magnetoresistive sensor 651 is positioned near the measuring surface 701 of the corresponding leaf 351 of the proximal MLC layer 350. Figure 7 In the embodiment shown, each measuring surface 701 is an edge surface of leaf 351, and each measuring surface is an edge surface of leaf 361. Figure 7 In the embodiment shown, PCB 652 is configured to position magnetoresistive sensor 651 near magnet 721 on measuring surface 701 of blade 351. In other embodiments, magnetoresistive sensor 651 is disposed on any other suitable surface of MLC turntable 300 that positions magnetoresistive sensor 651 near measuring surface 701 of blade 351.

[0054] Figure 8 This is an end view of the MLC turntable 300 when the PCB 652 is inserted into the MLC turntable 300 according to an embodiment. Figure 8 For clarity, parts of the MLC turntable 300, such as the housing of the enclosed leaf 351, are omitted. As shown, each linear array 720 of the magnet 721 (in...) Figure 8 (Viewed from the end) It is separated from the corresponding magnetoresistive sensor 651 through the air gap 801. The following is in conjunction with... Figure 9An embodiment describing the configuration of magnet 721, air gap 801, blade 351 and magnetoresistive sensor 651.

[0055] Figure 9 This is a partial end view of the proximal MLC layer 350 and PCB 652 according to an embodiment. As shown, the blades 351 of the MLC layer 350 are spaced apart by a blade pitch 901 in direction 602, which is the center-to-center distance between two adjacent blades 351 (also referred to as the center-to-center distance). Figure 9 In the embodiment shown, direction 602 is perpendicular to the linear travel direction 603 of leaf 351, and the linear travel direction 603 is oriented towards entering and exiting the page. Leaf spacing 901 is typically selected based on the desired functionality of the radiotherapy system including the MLC turntable 300. In some embodiments, each magnetoresistive sensor 651 on the PCB 652 is also spaced apart from an adjacent magnetoresistive sensor 651 by leaf spacing 901. An air gap 801 is shown separating each linear array 720 of magnets 721 from its corresponding magnetoresistive sensor 651.

[0056] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the proximal MLC layer 350, the width 921 of a particular magnet 721 in a direction perpendicular to the linear travel direction 603 is selected to be equal to or less than a threshold. In some instances, the direction perpendicular to the linear travel direction 603 is direction 602, and in other embodiments, the direction perpendicular to the linear travel direction 603 is another direction, such as direction 902 which is also perpendicular to the length of the blade 351 coupled to the particular magnet 721. In some embodiments, the threshold may be based on the blade spacing 901, the air gap 801, the field strength of the particular magnet 721, and / or one or more other factors associated with the configuration of the proximal MLC layer 350, such as the size, relative positioning, and / or orientation of the particular magnet 721, magnetoresistive sensors 651, etc. For example, in one such embodiment, the threshold for the width 921 of the particular magnet 721 is half the blade spacing 901. In another such embodiment, a threshold for the width 921 of a particular magnet 721 is determined based on the dimensions of the leaf spacing 901 and the air gap 801. In yet another such embodiment, a threshold for the width 921 of a particular magnet 721 is determined based on the minimum distance between the particular magnet 721 and an adjacent magnetoresistive sensor 651.

[0057] Note that when the width 921 of magnet 721 is equal to or less than such a threshold, crosstalk between adjacent magnetoresistive sensors 651 is reduced due to the greater distance between the magnet 721 coupled to one of the leaves 351 and the magnetoresistive sensor 651 associated with the adjacent leaf 351. For example, when the width 921 of magnet 721 is reduced, magnet 721A of leaf 351A moves away from the magnetoresistive sensor 651B associated with the adjacent leaf 351B. As a result, magnetoresistive sensor 651B is less likely to falsely detect the movement of leaf 351A. Similarly, the reduction in the width 921 of magnet 721B makes magnetoresistive sensor 651A less likely to falsely detect the movement of leaf 351B.

[0058] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the near-side MLC layer 350, each magnet 721 in a particular linear array 720 is selected with a pole spacing equal to or less than a threshold (in Figure 9 (Invisible in the middle) Separated. An example of the pole spacing in a linear array of magnets is shown in Figure 4 The image is illustrated as a magnetic pole spacing 422. In some embodiments, the threshold may be based on the leaf spacing 901, the air gap 801, the field strength of the magnets 721 included in the particular linear array 720, and / or one or more other factors associated with the configuration of the proximal MLC layer 350, such as the size, width, relative positioning, and / or orientation of the magnets 721 included in the particular linear array 720, the magnetoresistive sensor 651, etc. For example, in some embodiments, the threshold for the magnetic pole spacing separating the magnets 721 in the particular linear array 720 is based on the leaf spacing 901. In one such embodiment, the threshold for the magnetic pole spacing separating the magnets 721 in the particular linear array 720 is equal to or less than the leaf spacing 901. In another such embodiment, the threshold for the magnetic pole spacing separating the magnets 721 in the particular linear array 720 is equal to or less than a specified fraction of the leaf spacing 901.

[0059] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the proximal MLC layer 350, each magnet 721 in a particular linear array 720 is configured to have a field strength selected to be equal to or less than a threshold. In some embodiments, the threshold may be based on the leaf spacing 901, the air gap 801, and / or one or more other factors associated with the configuration of the proximal MLC layer 350, such as the size, width, relative positioning, and / or orientation of the magnets 721, magnetoresistive sensors 651, etc., included in the particular linear array 720. Thus, in some embodiments, the threshold for the field strength of the magnets 721 in the particular linear array 720 is selected to have a field strength that, when measured by the magnetoresistive sensor 651 associated with an adjacent leaf 351, is not greater than a specific fraction (e.g., 20%) of the field strength measured by the magnetoresistive sensor 651 associated with the adjacent leaf 351 for the magnet coupled to the adjacent leaf 351. For example, in one such embodiment, the field strength of the magnet 721A of leaf 351A, as measured by magnetoresistive sensor 651B, is selected to be no greater than a specific fraction of the field strength of magnet 721B when measured by magnetoresistive sensor 651B. In such an embodiment, the possibility that magnetoresistive sensor 651 erroneously measures the movement of magnet 721 coupled to adjacent leaf 351 is greatly reduced or eliminated.

[0060] Figure 10 A linear rotational motion detection device 1000 according to various embodiments is schematically illustrated. Figure 10 In the embodiment shown, the rotational motion detection device 1000 includes a magnetoresistive sensor 324 and a toothed ring 334, which are disposed on the peripheral region 344 of the MLC turntable 300, as shown. Figure 3 As shown. The gear ring 334 includes an array of ferromagnetic gear teeth 1020. In some embodiments, the magnetoresistive sensor 324 performs secondary (or primary) rotational motion detection by detecting the positioning of the magnetoresistive sensor 324 relative to the ferromagnetic gear teeth 1020 included in the gear ring 334.

[0061] exist Figure 10 In the embodiment illustrated, the magnetoresistive sensor 324 includes a bias magnet 1005 coupled to the magnetoresistive device 1010. The magnetoresistive device 1010 is configured to generate positioning information about one or both ferromagnetic gear teeth 1020 currently proximate to the magnetoresistive sensor 324. The magnetoresistive device 1010 is positioned proximate to the ferromagnetic gear teeth 1020 and separated from them by an air gap 1001. Therefore, the magnetoresistive device 1010 does not physically contact the ferromagnetic gear teeth 1020. As a result, neither the magnetoresistive device 1010 nor the ferromagnetic gear teeth 1020 experience mechanical wear during use.

[0062] During operation, as the gear ring 334 rotates together with the MLC turntable 300 (not shown), the magnetoresistive sensor 324 generates rotational positioning information to precisely determine the current rotational position of the magnetoresistive sensor 324 between the two closest ferromagnetic gear teeth 1020 included in the gear ring 334. In some embodiments, the magnetoresistive sensor 324 generates this positioning information in the form of a sine output signal and a cosine output signal. In some embodiments, such positioning information is used for secondary motion detection of the gear ring 334 (and therefore the MLC turntable 300) about the rotation axis 1002. In such embodiments, a servo system associated with the rotation of the MLC turntable 300 about the rotation axis 1002 provides primary linear motion detection. Thus, in such embodiments, the IEC requirement of having both primary and secondary positioning sensors for all rotation axes of the MLC turntable in a radiotherapy system is met.

[0063] Ideally, when positioning information is generated by the magnetoresistive sensor 324 in the form of sinusoidal and cosine output signals, both signals should be centered at the same value. For example, if the magnetoresistive sensor 324 is powered by a 5V supply, both signals should ideally be centered at 2.5V, with amplitudes varying from 0V to 5V within a single cycle. However, in reality, various factors typically produce signals that deviate from the ideal output value, which can lead to inaccurate rotational positioning measurements of the toothed ring 334. The following section combines... Figure 11 Describe an instance of this.

[0064] Figure 11 This is a graph 1100 showing the output values ​​of the ideal sinusoidal output signal 1120, the actual sinusoidal output signal 1130, and the cosine output signal 1140 from the magnetoresistive sensor 324. As shown, both the ideal sinusoidal output signal 1120 and the cosine output signal 1140 change from 0V to 5V, and the ideal sinusoidal output signal 1120 and the cosine output signal 1140 are out of phase by 90°. In this graph, the toothed ring 334 (… Figure 10In the embodiment shown, where the rotation from one ferromagnetic gear tooth 1020 to an adjacent ferromagnetic gear tooth 1020 corresponds to a single 360° cycle of the magnetoresistive sensor 324, a 90° phase shift between the ideal sinusoidal output signal 1120 and the cosine output signal 1140 corresponds to 1 / 4 of the rotational displacement between the two adjacent ferromagnetic gear teeth 1020. Based on the 90° phase shift between the sinusoidal and cosine output signals generated by the magnetoresistive sensor 324, the precise positioning of the magnetoresistive sensor between the two adjacent ferromagnetic gear teeth 1020 of the gear ring 334 is determined. The control system can track which particular tooth 1020 of the gear ring 334 is currently passing the magnetoresistive sensor at any given time, making it possible to determine the two adjacent ferromagnetic gear teeth 1020 of the gear ring 334 between which the magnetoresistive sensor 324 is located at any given time.

[0065] In reality, the sine and cosine output signals generated by the magnetoresistive sensor 324 are not ideal. For example, the sine and cosine output signals generated by the magnetoresistive sensor 324 typically include signal offsets. For instance, in the case of a sine output signal, there is a signal offset 1121 between the ideal sine output signal 1120 and the actual sine output signal 1130. As shown, the signal offset 1121 causes the output value of the actual sine output signal 1130 to intersect with the output value of the cosine output signal 1140 at the actual intersection point 1102. Figure 11 In the example depicted, signal offset 1121 is portrayed as approximately +0.5V, but in reality it is typically much smaller. The actual crossover point 1102 occurs at a different rotational position R1 than the ideal crossover point 1103, which occurs at rotational position R2. The difference between rotational positions R1 and R2 corresponds to an inaccuracy in the phase shift between the sinusoidal and cosine output signals generated by the magnetoresistive sensor 324. As a result, when determining the rotational position of the magnetoresistive sensor 324 between two adjacent ferromagnetic teeth 1020 based on the actual sinusoidal output signal 1130 and the cosine output signal 1140, the determined rotational position may be inaccurate. Factors that can contribute to and / or cause signal offset 1121 include variations in the resistance of the resistors included in the resistive bridge of the magnetoresistive sensor 324, other artifacts of the electronics included in the magnetoresistive sensor 324, and / or variations in the physical tooth-to-tooth pair of the ferromagnetic teeth 1020.

[0066] According to various embodiments, a calibration process is performed to determine a first signal offset value for the sinusoidal output signal generated by the magnetoresistive sensor 324 and a second signal offset value for the cosine output signal generated by the magnetoresistive sensor 324. In one embodiment, one or more pseudo-cycles are executed to quantize the first and second signal offset values. The first and second signal offset values ​​can then be used to compensate for rotational positioning inaccuracies arising from non-ideal sinusoidal and non-ideal cosine output signals generated by the magnetoresistive sensor 324.

[0067] In some embodiments, during a pseudo-cycle, an excitation is applied to an actuator for rotating the toothed ring 334, causing the toothed ring 334 to rotate by a specified rotational displacement, such as the rotational displacement between two adjacent ferromagnetic teeth 1020. In some embodiments, the specified rotational displacement corresponds to a rotational displacement of the toothed ring 334, wherein a first ferromagnetic tooth 1020 near the magnetoresistive sensor 324 rotates from a first rotational position to a second rotational position, and a second ferromagnetic tooth 1020 adjacent to the first ferromagnetic tooth 1020 rotates from the second rotational position to a third rotational position. Thus, at the specified rotational displacement, the first ferromagnetic tooth 1020 moves to the position occupied by the second ferromagnetic tooth 1020 at the beginning of the cycle. Therefore, during the pseudo-cycle, the values ​​of the sine and cosine output signals generated by the magnetoresistive sensor 324 are collected as the toothed ring 334 rotates through a rotational displacement corresponding to one tooth pitch of the toothed ring 334. The following is in conjunction with... Figure 12 Describe one such embodiment.

[0068] Figure 12 A flowchart illustrating a calibration process for rotational positioning detection via a magnetoresistive sensor, according to one or more embodiments, is provided. The method may include one or more operations, functions, or actions as shown in blocks 1201-1232. Although these blocks are illustrated in sequence, they may be performed in parallel and / or in a different order than described herein. Furthermore, based on desired implementation, the various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated. Despite the combination Figures 1 to 11 The method is described in this system, but those skilled in the art will understand that any properly configured radiotherapy system is within the scope of this disclosure. In some embodiments, the control algorithm for the method steps may reside in the image acquisition and treatment control computer 106, the remote control console 110, or a combination of both. The control algorithm may be implemented wholly or partially as software or firmware logic and / or as hardware logic circuitry.

[0069] Method 1200 begins at step 1201, at which point the RT system 100 begins the calibration process. In some embodiments, method 1200 is performed once for a specific radiotherapy system, such as during commissioning, acceptance testing, and / or installation of the radiotherapy system. In alternative embodiments, method 1200 is performed periodically for a specific radiotherapy system, such as when the radiotherapy system is powered on, when the radiotherapy system completes a specified duration of operation, and / or when the radiotherapy system completes a specified number of processes.

[0070] In step 1202, the RT system 100 begins to apply excitation to a rotary actuator configured to rotate the MLC turntable 300 about a rotation axis 304. In some embodiments, the excitation may correspond to a rotational displacement of the toothed ring 334, wherein a first ferromagnetic tooth 1020 adjacent to the magnetoresistive sensor 324 rotates from a first rotational position to a second rotational position, and a second ferromagnetic tooth 1020 adjacent to the first ferromagnetic tooth 1020 rotates from the second rotational position to a third rotational position. Such a particular rotational displacement is also referred to herein as an excitation cycle.

[0071] In step 1203, the RT system 100 determines whether a measurement position has been reached. In some embodiments, multiple measurement positions are set across a specified rotational displacement or excitation cycle. In one embodiment, a measurement position of 10s or 100s is passed over a rotational displacement corresponding to the excitation cycle. In such an embodiment, a highly accurate curve of the output value of the magnetoresistive sensor 324 can be generated across a single excitation cycle. As a result, an accurate signal offset value can be determined based on such a curve.

[0072] When the RT system 100 determines that the measurement position has been reached, the method 1200 proceeds to step 1221; when the RT system 100 determines that the measurement position has not been reached, the method 1200 proceeds to step 1211.

[0073] In step 1211, the RT system 100 continues to apply excitation to the rotary actuator, and the rotary actuator continues to cause the MLC turntable 300 (and gear ring 334) to rotate.

[0074] In step 1221, the RT system 100 measures one or more output signals from the magnetoresistive sensor 324. In some embodiments, the RT system 100 measures a sine output signal and a cosine output signal at the current rotational position. In some embodiments, the RT system 100 measures multiple sine output signals (e.g., 4, 8, 10, etc.) and multiple cosine output signals (e.g., 4, 8, 10, etc.) at the current rotational position. In such embodiments, the multiple sine output signals are averaged to produce a single average sine output signal for the current rotational position, and the multiple cosine output signals are averaged to generate a single average cosine output signal for the current rotational position. It should be noted that the rotation of the toothed ring 334 typically occurs at a relatively low rotational frequency (e.g., approximately 2 to 20 Hz). As a result, multiple sine output signals and multiple cosine output signals can be sequentially acquired at a sufficiently high acquisition rate during step 1221 such that the toothed ring 334 does not rotate significantly during step 1221. Therefore, multiple sine output signals and multiple cosine output signals are effectively measured at the same rotational position.

[0075] In step 1222, the RT system 100 determines whether the current rotational positioning of the gear ring 334 is at the final measured position of the excitation cycle. If yes, method 1200 proceeds to step 1231; if no, method 1200 proceeds to step 1211.

[0076] In step 1231, the RT system 100 determines whether an additional excitation cycle should be performed during the calibration process. In some embodiments, steps 1202-1222 are performed for a single excitation cycle. In other embodiments, steps 1202-1222 are performed for multiple excitation cycles (e.g., 2-5), such that signal offset values ​​(e.g., for sine and cosine output signals) can be averaged over multiple excitation cycles. In still other embodiments, steps 1202-1222 are performed for each ferromagnetic tooth 1020 of the toothed ring 334. In such embodiments, different signal offset values ​​can be determined for rotational motion measured between each ferromagnetic tooth 1020 of the toothed ring 334. In such embodiments, each signal offset value can provide compensation for different rotational positioning inaccuracies associated with physical changes between the ferromagnetic teeth 1020.

[0077] Figure 13A flowchart illustrating a process for rotational positioning detection via a magnetoresistive sensor according to one or more embodiments is shown. The method may include one or more operations, functions, or actions as shown in one or more of blocks 1301-1305. Although these blocks are illustrated in sequence, they may be performed in parallel and / or in a different order than described herein. Furthermore, based on desired implementation, the individual blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated. Despite the combination Figures 1 to 12 The method is described in this system, but those skilled in the art will understand that any properly configured radiotherapy system is within the scope of this disclosure. In some embodiments, the control algorithm for the method steps may reside in an image acquisition and treatment control computer 106, a remote console 110, or a combination of both. The control algorithm may be implemented wholly or partially as software or firmware logic and / or as hardware logic circuitry.

[0078] Method 1300 begins at step 1301, at which point the RT system 100 begins operation. For example, in one instance, the MLC turntable 300 rotates about the rotation axis 304 during a radiotherapy session.

[0079] In step 1302, the RT system 100 begins to apply excitation to the rotary actuator configured to rotate the MLC turntable 300 about the rotation axis 304.

[0080] In step 1303, the RT system 100 measures one or more output signals from the magnetoresistive sensor 324. In some embodiments, the RT system 100 measures a sine output signal and a cosine output signal at the current rotational position.

[0081] In step 1304, the RT system 100 generates one or more calibrated output signals by modifying each of the one or more output signals measured in step 1303 with a corresponding signal offset value determined during a calibration process (such as method 1200). Therefore, in some embodiments, a first signal offset value is used to modify the sine output signal measured in step 1303, and a second signal offset value is used to modify the cosine output signal measured in step 1303.

[0082] In step 1305, the RT system 100 determines the current rotational positioning of the gear ring 334 based on one or more corrected output signals generated in step 1304.

[0083] After step 1305, method 1300 typically continues as the RT system 100 rotates the MLC turntable 300 during operation.

[0084] Figure 14This is an illustration of a computing device 1400 configured to perform various embodiments of the present disclosure. The computing device 1400 may be a desktop computer, laptop computer, smartphone, or any other type of computing device suitable for practicing one or more embodiments of the present disclosure. For example, in some embodiments, the computing device 1400 may be used as an image acquisition and processing control computer 106 and / or a remote control console 110. Note that the computing device described herein is illustrative, and any other technically feasible configuration falls within the scope of this disclosure.

[0085] As shown in the figure, computing device 1400 includes, but is not limited to, interconnects (buses) 1440 connecting processing unit 1450, input / output (I / O) device interfaces 1460 coupled to input / output (I / O) devices 1480, memory 1410, storage devices 1430, and network interfaces 1470. Processing unit 1450 can be any suitable processor implemented as a central processing unit (CPU), graphics processing unit (GPU), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), any other type of processing unit, or a combination of different processing units (such as a CPU configured to operate in conjunction with a GPU or digital signal processor (DSP)). Typically, processing unit 1450 can be any technically feasible hardware unit capable of processing data and / or executing software applications, including a calibration process 1401 consistent with method 1200 and / or a rotational positioning detection process 1402 consistent with method 1300.

[0086] I / O device 1480 may include devices capable of providing input, such as a keyboard, mouse, touchscreen, etc., and devices capable of providing output, such as a display device, etc. Additionally, I / O device 1480 may include devices capable of receiving input and providing output, such as a touchscreen, Universal Serial Bus (USB) port, etc. I / O device 1480 may be configured to receive various types of input from end users of computing device 1400 and also to provide various types of output to end users of computing device 1400, such as displayed digital images or digital video. In some embodiments, one or more I / O devices 1480 are configured to couple computing device 1400 to a network.

[0087] Memory 1410 may include random access memory (RAM) modules, flash memory cells, or any other type of memory cell or a combination thereof. Processing unit 1450, I / O device interface 1460, and network interface 1470 are configured to read data from memory 1410 and write data to memory 1410. Memory 1410 includes various software programs executable by processor 1450 and application data associated with said software programs, including calibration process 1401 and / or rotational positioning detection process 1402.

[0088] Figure 15 This is a block diagram of an illustrative embodiment of a computer program product 1500 for implementing various embodiments of the present disclosure. The computer program product 1500 may include a signal carrying medium 1504. The signal carrying medium 1504 may include one or more sets of executable instructions 1502, which, when executed by a processor of, for example, a computing device, can at least provide the above-mentioned... Figures 1 to 14 The described function.

[0089] In some implementations, the signal-bearing medium 1504 may include a non-transient computer-readable medium 1508, such as, but not limited to, a hard disk drive, an optical disc (CD), a digital video disc (DVD), a digital magnetic tape, a memory, etc. In some implementations, the signal-bearing medium 1504 may include a recordable medium 1510, such as, but not limited to, a memory, a read / write (R / W) CD, a R / W DVD, etc. In some implementations, the signal-bearing medium 1504 may include a communication medium 1506, such as, but not limited to, digital and / or analog communication media (e.g., fiber optic cables, waveguides, wired communication links, wireless communication links, etc.). The computer program product 1500 may be recorded on the non-transient computer-readable medium 1508 or another similar recordable medium 1510.

[0090] In summary, the embodiments described herein enable accurate and repeatable positioning measurements of MLCs and individual leaflets in high-radiation environments. Furthermore, the positioning measurements described herein are non-contact, thereby reducing wear-based inaccuracies and hysteresis.

[0091] The description of various embodiments has been presented for illustrative purposes and is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0092] Various aspects of this embodiment may be embodied as a system, method, or computer program product. Therefore, various aspects of this disclosure may take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be collectively referred to herein as a “circuit,” “module,” or “system.” Furthermore, various aspects of this disclosure may take the form of a computer program product embodied in one or more computer-readable media on which computer-readable program code is embodied.

[0093] Any combination of one or more computer-readable media may be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination thereof. More specific examples (not an exhaustive list) of computer-readable storage media will include the following: electrical connections having one or more wires; portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In the context of this document, a computer-readable storage medium can be any tangible medium capable of containing or storing a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0094] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, wherein the true scope and spirit are indicated by the appended claims.

Claims

1. A multileaf collimator comprising: a plurality of movable leaves for shaping a radiotherapy beam, wherein: each leaf is independently movable in a same linear direction of travel, and each leaf comprises a linear array of magnets disposed on a measurement surface of the leaf; and an array of magnetoresistive sensors disposed proximate the measurement surface of the leaf; wherein each magnet of the linear array of magnets is separated by a pole pitch that is less than a leaf pitch between a first movable leaf of the plurality of movable leaves and a second movable leaf of the plurality of movable leaves, the second movable leaf being adjacent to the first movable leaf.

2. The multileaf collimator of claim 1, further comprising one or more processors configured to determine a current positioning of the leaf of the plurality of movable leaves based on output from a magnetoresistive sensor of the array of magnetoresistive sensors disposed proximate the measurement surface of the leaf.

3. The multileaf collimator of claim 2, wherein the output from the magnetoresistive sensor of the array of magnetoresistive sensors disposed proximate the measurement surface of the leaf comprises a sine signal output and a cosine signal output.

4. The multileaf collimator of claim 2 or 3, wherein the one or more processors are configured to determine the current positioning of the leaf in the same linear direction of travel.

5. The multileaf collimator of any one of claims 1 to 3, wherein the array of magnetoresistive sensors is a linear array extending in a direction perpendicular to the same direction of travel.

6. The multileaf collimator of any one of claims 1 to 3, wherein each magnetoresistive sensor is disposed proximate a different corresponding leaf of the plurality of movable leaves.

7. The multileaf collimator of claim 6, wherein each magnetoresistive sensor is separated from the corresponding leaf by an air gap.

8. The multileaf collimator of any one of claims 1 to 3, wherein each magnet of the linear array of magnets has a width in a direction perpendicular to the same linear direction of travel, the width being determined based on a leaf pitch between the first movable leaf of the plurality of movable leaves and the second movable leaf of the plurality of movable leaves, the second movable leaf being adjacent to the first movable leaf.

9. The multileaf collimator of claim 8, wherein the width in the direction perpendicular to the same linear direction of travel is equal to or less than half of the leaf pitch between the first movable leaf and the second movable leaf.

10. The multileaf collimator of any one of claims 1 to 3, wherein each magnet of the linear array of magnets disposed on a measurement surface of a first leaf of the plurality of movable leaves has a first field strength measured by a first magnetoresistive sensor associated with the first leaf and a second field strength measured by a second magnetoresistive sensor associated with a second leaf of the plurality of movable leaves, the second field strength being less than the first field strength.

11. The multileaf collimator of claim 10, wherein the second field strength is no more than 20% of the first field strength.

12. The multileaf collimator of claim 10, wherein the first leaf of the plurality of moveable leaves is adjacent to the second leaf of the plurality of leaves.

13. The multileaf collimator of any one of claims 1-3, wherein the measurement surface comprises an edge surface of the moveable leaf.

14. The multileaf collimator of any one of claims 1-3, wherein the linear array of magnets is oriented longitudinally in the same linear direction of travel.

15. A method for measuring a position of a moveable leaf in a plurality of leaves in a multileaf collimator, the method comprising: receiving a first output from a first magnetoresistive sensor included in a first array of magnetoresistive sensors, wherein: the first magnetoresistive sensor is disposed proximate to a linear array of magnets disposed on a measurement surface of a first moveable leaf, and the first output is caused by a particular magnet of the linear array of magnets moving proximate to the first magnetoresistive sensor; each magnet of the linear array of magnets is separated by a pole pitch that is less than a leaf pitch between a first moveable leaf of the plurality of moveable leaves and a second moveable leaf of the plurality of moveable leaves, the second moveable leaf being adjacent to the first moveable leaf; and based on the first output, determining a position of the first moveable leaf in a direction of travel of the first moveable leaf.

16. The method of claim 15, wherein determining the position of the first moveable leaf based on the first output comprises determining a positioning of the particular magnet relative to the first magnetoresistive sensor.

17. The method of claim 15 or 16, wherein the output comprises a sine signal output and a cosine signal output.

18. The method of claim 15 or 16, further comprising: receiving a second output from a second magnetoresistive sensor included in the array of magnetoresistive sensors, wherein: the second magnetoresistive sensor is disposed proximate to a second linear array of magnets disposed on a measurement surface of a second moveable leaf, and the second output is caused by a particular magnet of the second linear array of magnets moving proximate to the second magnetoresistive sensor; and based on the second output, determining a position of the second moveable leaf in a direction of travel of the second moveable leaf.

19. The method of claim 18, wherein receiving the second output occurs simultaneously with receiving the first output.

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