Magnetic reluctance rotary position detection in radiation treatment systems

Abstract

A method of measuring a rotational position of an assembly having circumferential ferromagnetic teeth includes applying (1302) a periodic excitation signal to an actuator, the periodicity causing a first rotational displacement of a first ferromagnetic tooth from a first rotational position to a second rotational position and a second rotational displacement of a second ferromagnetic tooth from the second rotational position to a third rotational position. The method also includes measuring (1303) a plurality of first signal outputs from a magnetoresistive sensor during the periodicity; determining one or more signal offset values based on the plurality of first signal outputs; applying the excitation signal to the actuator for a portion of a second periodicity; measuring a second signal output from the magnetoresistive sensor; generating (1304) a corrected signal by modifying the second signal output with the signal offset values; and determining (1305) the rotational position of the assembly based on the corrected signal.

Description

[0001] Cross-reference to related applications

[0002] The subject matter of this application relates to U.S. Patent Application No. 17 / 072,042, 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 treatment of the target tissue (also known as the planning target area) is performed in such a way that the surrounding normal tissue is protected from receiving a dose exceeding the specified tolerance level, thereby minimizing the risk of damage to normal tissue. Conformal radiation therapy and intensity-modulated radiation therapy have been developed to ensure that the prescribed dose is correctly delivered to the planning target area during radiation treatment.

[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 radiation dose to the cancerous tumor while minimizing the dose to surrounding healthy tissue. In intensity-modulated radiotherapy, 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 intensity-modulated radiotherapy can significantly reduce the risk of side effects and / or increase the dose to the target tissue.

[0006] A commonly used beam-limiting device in conformal and intensity-modulated radioprocessing is the multi-leaf collimator (MLC). Typically, an MLC in a radioprocessing system comprises multiple movable radiation-blocking material "leaves" independently positioned within the path of the radioprocessing beam. In this way, the MLC enables targeted beam shaping and / or variation of the radioprocessing beam intensity.

[0007] To ensure the prescribed dose is correctly delivered to the planned target area during radiation treatment, the MLC and the individual blades contained within it must be precisely positioned relative to the linear accelerator providing the radiation treatment. However, current radiation-tolerant position sensors used to measure the position of the MLC and its blades suffer from several drawbacks. For example, electromechanical position sensors exhibit repeatability and reliability issues due to wear over time. Furthermore, some electromechanical position sensors are subject to gravity-related inaccuracies when positioned at certain angles, further increasing the uncertainty in their output. Summary of the Invention

[0008] According to at least some embodiments of the present disclosure, the radiation processing system is configured to use a magnetoresistive sensor to measure the position of a multi-leaf collimator disk. In some embodiments, the rotational position of the multi-leaf collimator disk is measured via a magnetoresistive sensor configured to detect ferromagnetic teeth of a gear ring coupled to the disk surface.

[0009] 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

[0010] The foregoing and other features of this disclosure will become more 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 features and details using the accompanying drawings.

[0011] Figure 1 It is a perspective view of a radiation processing system according to one or more embodiments.

[0012] Figure 2 The illustrations schematically depict various embodiments. Figure 1 The drive support and gantry of the radiation processing system.

[0013] Figure 3 The illustrations schematically depict various embodiments. Figure 1 The collimator assembly of the radiation processing system.

[0014] Figure 4 A linear motion detection device according to various embodiments is schematically illustrated.

[0015] Figure 5 The illustrations schematically depict various embodiments. Figure 3 A side view of a single blade of the collimator assembly.

[0016] Figure 6 According to one embodiment Figure 1 A perspective view of the multi-leaf collimator turntable of the radiation processing system.

[0017] Figure 7 According to one embodiment, when inserted into Figure 6 A perspective view of the printed circuit board in the multi-leaf collimator turntable.

[0018] Figure 8 According to one embodiment Figure 6 End view of the multi-leaf collimator turntable.

[0019] Figure 9This is a partial end view of a multi-leaf collimator layer and a printed circuit board according to one embodiment.

[0020] Figure 10 A linear rotational motion detection device according to various embodiments is schematically illustrated.

[0021] Figure 11 It 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.

[0022] Figure 12 A flowchart is provided for a calibration process for rotational position detection via a magnetoresistive sensor, according to one or more embodiments.

[0023] Figure 13 A flowchart is provided for a process for rotational position detection via a magnetoresistive sensor according to one or more embodiments.

[0024] Figure 14 This is a diagram of a computing device configured to execute various embodiments of the present disclosure.

[0025] Figure 15 This is a block diagram illustrating an embodiment of a computer program product for implementing various embodiments of the present disclosure. Detailed Implementation

[0026] In the following detailed description, reference is made to the accompanying drawings, which form part of the specification. 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 used, 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 expressly contemplated and form part of this disclosure.

[0027] As mentioned above, beam shaping plays a crucial role in improving the accuracy, efficiency, and quality of certain radiographic processes. For this purpose, multi-leaf collimators (MLCs) have been used in radiographic processes as beam shapers for conformal radiographic processes, and as intensity modulators for intensity modulated radiographic processes (IMRT) and volume modulated arc processes (VMAT). In such processes, accurate beam shaping depends on the precise positioning of the MLC and its individual blades relative to the processed beam. According to various embodiments, improved and more reliable blade positioning and MLC turntable positioning in radiographic systems are facilitated by measuring linear and / or rotational positions using magnetoresistive sensors, as described below.

[0028] Figure 1 This is a perspective view of a radiation processing system 100 according to one or more embodiments. The radiation processing (RT) system 100 is configured to provide stereotactic radiosurgery and precise radiation treatment to any lesion, tumor, or condition in the body that indicates radiation treatment. Thus, the RT system 100 may include one or more of the following: a linear accelerator (LINAC) generating a megavolt (MV) processing beam of high-energy X-rays, a kilovolt (kV) X-ray source, an X-ray imager, and, in some embodiments, an MV electron field 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 radiation processing 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 rings or with a robotic arm.

[0029] Typically, the RT system 100 is capable of kV imaging of the target area during the application of an MV processing beam, thereby 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 table motion controller 102, an aperture 103, a pedestal positioning assembly 105, a table 107 mounted on the pedestal positioning assembly 105, and an image acquisition and processing control computer 106, all located within the treatment room. The RT system 100 also includes a remote console 110 located outside the treatment room, capable of remote treatment delivery and patient monitoring. The pedestal positioning assembly 105 is configured to precisely position the table 107 relative to the aperture 103, and the motion controller 102 includes input devices, such as buttons and / or switches, enabling a user to operate the pedestal positioning assembly 105 to automatically and precisely position the table 107 relative to the aperture 103 at a predetermined location. Motion control 102 also allows the user to manually position the examination table 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.

[0030] Figure 2 The drive bracket 200 and gantry 210 of the RT system 100 according to various embodiments are schematically illustrated. For clarity, in Figure 2The cover, base positioning assembly 105, examination table 107, and other components of the RT system 100 are omitted. The drive bracket 200 is a fixed support structure for the components of the RT processing system 110, including a gantry 210 and a drive system 201 for rotatably moving the gantry 210. The drive bracket 200 rests on and / or is fixed to a support surface outside the RT processing system 110, such as the floor of the RT processing facility. The gantry 210 is rotatably coupled to the drive bracket 200 and is the support structure on which various components of the RT system 100 are mounted, including the linear accelerator (LINAC) 204, the MV electron field imaging device (EPID) 205, the imaging X-ray source 206, and the X-ray imager 207. During operation of the RT processing system 110, the gantry 210 rotates about the aperture 103 when actuated by the drive system 201.

[0031] Drive system 201 rotatably actuates gantry 210. In some embodiments, drive system 201 includes a linear motor that can be fixed to drive bracket 200 and interact with a magnetic track (not shown) mounted on gantry 210. In other embodiments, drive system 201 includes another suitable drive mechanism for precisely rotating gantry 210 about aperture 201. LINAC 204 generates a high-energy X-ray (or electron, proton, heavy ion, etc. in some embodiments) MV processing beam 230, and EPD 205 is configured to acquire X-ray images via processing beam 230. Imaging X-ray source 206 is configured to guide a cone beam of X-rays (referred to herein as imaging X-ray 231) through isocenter 203 of RT system 100 to X-ray imager 207. Isocenter 203 typically corresponds to the location of the target area to be processed. X-ray imager 207 receives imaging X-ray 231 and generates an appropriate projected image therefrom. Such projected images can then be used to construct or update portions of imaging data corresponding to a digital volume of a 3D region including the target area. 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.

[0032] exist Figure 2 In the illustrated embodiment, 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 illustrated embodiment, 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.

[0033] The LINAC 204 includes and / or operates in conjunction with a collimator assembly 250. The collimator assembly 250 includes one or more collimators for shaping and / or modifying the intensity of the MV processing beam 230. The following is a related description... Figure 3 An embodiment of the collimator assembly 250 is described.

[0034] Figure 3 A collimator assembly 250 according to one embodiment is schematically illustrated. Figure 3 In the illustrated embodiment, the collimator assembly 250 includes a primary collimator 310 and an MLC turntable 300 including at least one MLC layer. The collimator assembly 250 is positioned near 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 primary collimator 310 is fixed in place 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 (off-page). In some embodiments, the MLC turntable 300 is configured to rotate about at least one rotation axis, such as a rotation axis 304. In some embodiments, the rotation axis 304 is substantially parallel to the centerline 305 of the X-ray field 306. Figure 3 In the example shown, the rotation axis 304 coincides with the center line 305 of the X-ray field 306, but in many examples, the rotation axis 304 is displaced from the center line 305 along the first linear motion axis 301 and / or the third motion axis 303.

[0035] In some embodiments, the MLC turntable 300 is configured with primary and secondary position detection for linear motion 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 with respect 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 motion of the MLC turntable 300 along the first linear motion axis 301 includes specific position feedback indicating the current position of the MLC turntable 300 along the first linear motion axis 301. In such an embodiment, such position feedback is considered primary linear position detection along the linear motion axis 301. In another example, in one embodiment, the servo system associated with the rotational motion of the MLC turntable 300 about the rotation axis 304 includes specific position feedback indicating the current rotational position of the MLC turntable 300 about the rotation axis 304. In such an embodiment, such rotational position feedback is considered primary rotational position detection.

[0036] 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) requirement for secondary position sensors is that the linear and rotational axes of all LINAC turntables can be satisfied by corresponding magnetoresistive sensors.

[0037] The following is combined 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.

[0038] Figure 4 A linear motion detection device 400 according to various embodiments of the present invention is schematically illustrated. Figure 4 In the illustrated embodiment, 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 (e.g., NSNS, etc.), wherein each magnet 421 is separated from the other by a uniform magnetic pole spacing 422.

[0039] The magnetoresistive sensor 410 is disposed near the linear array 420 and separated from the linear array 420 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 is subjected to mechanical wear during use.

[0040] As shown, the linear array 420 is configured as a linear array of magnets 421 oriented longitudinally along a specific linear travel direction 403. A 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 position information enabling 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 the following: anisotropic magnetoresistive (AMR) sensor, giant magnetoresistive (GMR) sensor, tunneling magnetoresistive (TMR) sensor, or other magnetic position sensor that measures changes in the magnetic field that occur when the magnets 421 of the linear array 420 move relative to the magnetoresistive sensor 410.

[0041] The magnetoresistive sensor 410 generates position 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 position 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 position of the magnetoresistive sensor 410 between two adjacent magnets 421 can be determined. In such embodiments, the sine and cosine output signals enable precise determination of the position 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 position of the magnetoresistive sensor 410 to within 1° (where the pole spacing 422 is equal to 360°), the position of the magnetoresistive sensor 410 can be determined to be within 1% of the pole spacing 422. Additionally, 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 positional information about the linear array 420 relative to the magnetoresistive sensor 410.

[0042] Note that the magnetoresistive sensor 410 does not actively generate position signals; it is a passive device. As a result, the output of the magnetoresistive sensor 410 is typically unaffected by the X-ray field (such as...) present in the radiation processing system. Figure 3 The influence of the high-radiation environment of the X-ray field (306) in the field.

[0043] Back Figure 3The primary collimator 310 is configured to define the outer boundary of the X-ray field 306. The primary collimator 310 can be a fixed collimator or a collimator configured with one or more movable grippers. Typically, the primary collimator 310 is positioned near the radiation source of the LINAC 204. Figure 3 In the illustrated embodiment, the primary collimator 310 is described as a single collimating device, but in other embodiments, the primary collimator 310 includes multiple collimating devices positioned in series within the X-ray field 306.

[0044] 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 blades 351, each blade being independently movable into the X-ray field 306 in the direction of travel. Similarly, the distal MLC layer 360 includes a plurality of blades 361, each blade being independently movable into the X-ray field 306 in the direction of travel. Figure 3 In the illustrated embodiment, each blade 351 of the proximal MLC layer 350 can move in a specific direction of travel perpendicular to the centerline 305 of the X-ray field 306. Furthermore, in Figure 3 In the illustrated embodiment, the direction of travel of blade 351 is depicted as along a third linear axis of motion 303 outside the page. Similarly, each blade 361 of the distal MLC layer 360 can move in a specific direction of travel perpendicular to the centerline 305 of the X-ray field 306. Figure 3 In the illustrated embodiment, the travel direction of blade 361 is the same as that of blade 351, and blade 351 travels along the linear motion axis 303. Figure 3 In the image, blades 351 and 361 are observed at opposite ends, i.e., along the direction of travel parallel to the third linear motion axis 303.

[0045] In some embodiments, the proximal MLC layer 350 includes multiple sets of blades 351 and the distal MLC layer 360 includes multiple sets of blades 361. In such an embodiment, the MLC layer 350 includes two opposing sets of blades 351 positioned on opposite sides of the central plane of the X-ray field 306, and the distal MLC layer 360 includes two opposing sets of blades 361 positioned on opposite sides of the central plane of the X-ray field 306.

[0046] Blades 351 and 361 are typically formed of a high atomic number material, such as tungsten or its alloys. Furthermore, in some embodiments, blades 351 and 361 have a generally trapezoidal cross-section that matches the beam divergence occurring in the direction perpendicular to the blade's travel. In practice, the cross-sections of blades 351 and 361 may not be precisely trapezoidal. In some embodiments, blades 351 and 361 may be configured to project to the same projection size at the isocenter point 203. In such embodiments, blade 351 has a smaller cross-section than blade 361 in the direction perpendicular to the blade's travel.

[0047] In some embodiments, motion detection of each of blades 351 and 361 along the linear travel direction is achieved by a corresponding magnetoresistive sensor. In such embodiments, each blade 351 and each blade 361 includes a magnetoresistive sensor for linear motion detection of the corresponding blade. The following describes... Figure 5 Describe one such embodiment.

[0048] 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 along a particular travel direction 502, and is thus positioned close to but outside the X-ray field 306. The blade 500 is also shown (dashed line) after it has traveled partially along the travel range in the travel direction 502.

[0049] The blade 500 includes a magnetoresistive sensor 521 and a linear array 531 of magnets disposed on the edge surface 541 of the blade 500. In some embodiments, the magnetoresistive sensor 521 can 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.

[0050] During operation, as the blade 500 moves along the travel direction 502, the magnetoresistive sensor 521 generates position information to accurately determine the current position of the magnetoresistive sensor 521 between the two closest magnets included in the linear array 531. In some embodiments, the magnetoresistive sensor 521 generates this position information in the form of a sine and a cosine output signal. In some embodiments, this position information is used for secondary motion detection of the blade 500 along the travel direction 502. In such an embodiment, a servo system associated with the movement of the blade 500 along the travel direction 502 provides primary linear motion detection. Therefore, in such an embodiment, the IEC requirement that all moving blades in the radiation processing system have both primary and secondary position sensors is met.

[0051] Figure 6 This is a perspective view of an MLC turntable 300 according to one embodiment. Figure 6 In the diagram, an array 650 of magnetoresistive sensors 651 for the near-end MLC layer 350 is shown disassembled from the MLC turntable 300. Figure 6 In the illustrated embodiment, the magnetoresistive sensor 651 is disposed on a printed circuit board (PCB) 652. In some embodiments, the array 650 of the magnetoresistive sensors 651 is configured as a linear array extending longitudinally in a direction 602 perpendicular to the linear travel direction 603 of the blade 351. Figure 6 In the illustrated embodiment, 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 more closely spaced along direction 602.

[0052] Inserting the PCB 652 into the MLC turntable 300 results in each magnetoresistive sensor 651 being positioned near the measurement surface of the corresponding blade 351 adjacent to the MLC layer 350.

[0053] Figure 7 This is a perspective view of PCB 652 when inserted into MLC turntable 300 according to one embodiment. Figure 7 For clarity, some parts of the MLC turntable 300, such as the housing of the enclosed blade 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 blade 351 adjacent to the MLC layer 350. Figure 7 In the illustrated embodiment, each measuring surface 701 is the edge surface of blade 351, and each measuring surface 702 is the edge surface of blade 361.

[0054] exist Figure 7 In the illustrated embodiment, PCB 652 is configured to position magnetoresistive sensor 651 near magnet 721 on the 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.

[0055] 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 one embodiment. Figure 8 For clarity, some parts of the MLC turntable 300, such as the housing of the enclosed blades 351, are omitted. As shown, each linear array 720 of the magnets 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 9 An embodiment describing the configuration of magnet 721, air gap 801, blade 351 and magnetoresistive sensor 651.

[0056] Figure 9 This is a partial end view of the near-end MLC layer 350 and PCB 652 according to one embodiment. As shown, the blades 351 of the MLC layer 350 are spaced apart in direction 602 by a blade pitch 901, where the blade pitch 901 is the center-to-center distance between two adjacent blades 351 (also referred to as the center-to-center distance). Figure 9 In the illustrated embodiment, direction 602 is perpendicular to the linear travel direction 603 of blade 351, and the linear travel direction 603 is oriented towards the in-and-out page. Blade spacing 901 is typically selected based on the desired functionality of the radiation processing 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 blade spacing 901. An air gap 801 is shown separating each linear array 720 of magnet 721 from its corresponding magnetoresistive sensor 651.

[0057] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the near-end 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 cases, the direction perpendicular to the linear travel direction 603 is direction 602, while 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 near-end MLC layer 350, such as the size, relative position, 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 of 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 blade spacing 901 and the air gap 801. In yet another such embodiment, the threshold for the width 921 of a particular magnet 721 is determined based on the minimum distance between the particular magnet 721 and the adjacent magnetoresistive sensor 651.

[0058] 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 blades 351 and the magnetoresistive sensor 651 associated with the adjacent blade 351. For example, when the width 921 of magnet 721 decreases, magnet 721A of blade 351A moves away from the magnetoresistive sensor 651B associated with the adjacent blade 351B. As a result, magnetoresistive sensor 651B is less likely to falsely detect the movement of blade 351A. Similarly, the reduction in the width 921 of magnet 721B makes it less likely that magnetoresistive sensor 651A will falsely detect the movement of blade 351B.

[0059] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the near-end MLC layer 350, each magnet 721 in a particular linear array 720 is selected by 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 in Figure 4 The threshold is shown as the pole spacing 422. In some embodiments, the threshold may be based on the blade 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 near-end MLC layer 350 (such as the size, width, relative position, 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 pole spacing of the isolated magnets 721 in the particular linear array 720 is based on the blade spacing 901. In one such embodiment, the threshold for the pole spacing of the isolated magnets 721 in the particular linear array 720 is equal to or less than the blade spacing 901. In another such embodiment, the threshold for the pole spacing of the isolated magnets 721 in the particular linear array 720 is equal to or less than a specified portion of the blade spacing 901.

[0060] In some embodiments, to reduce crosstalk between magnetoresistive sensors 651 in the near-end 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 blade spacing 901, the air gap 801, and / or one or more other factors associated with the configuration of the near-end MLC layer 350 (such as the size, width, relative position, and / or orientation of the magnets 721 included in the particular linear array 720), the magnetoresistive sensors 651, etc. 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 blade 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 blade 351 for magnets coupled to the adjacent blade 351. For example, in one such embodiment, the field strength of the magnet 721A of the blade 351A, as measured by the magnetoresistive sensor 651B, is selected to be no greater than a specific portion of the field strength of the magnet 721B as measured by the magnetoresistive sensor 651B. In such an embodiment, the possibility that the magnetoresistive sensor 651 erroneously measures the movement of the magnet 721 coupled to an adjacent blade 351 is greatly reduced or eliminated.

[0061] Figure 10 A linear rotational motion detection device 1000 according to various embodiments is schematically illustrated. Figure 10 In the illustrated embodiment, the rotational motion detection device 1000 includes a magnetoresistive sensor 324 and a gear ring 334. The gear ring 334 is disposed on the peripheral region 344 of the MLC turntable 300, such as... 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 position of the magnetoresistive sensor 324 relative to the ferromagnetic gear teeth 1020 included in the gear ring 334.

[0062] exist Figure 10 In the illustrated embodiment, the magnetoresistive sensor 324 includes a bias magnet 1005 coupled to the magnetoresistive device 1010. The magnetoresistive device 1010 is configured to generate position information about one or both ferromagnetic gear teeth 1020 currently approaching the magnetoresistive sensor 324. The magnetoresistive device 1010 is disposed near the ferromagnetic gear teeth 1020 and separated from them by an air gap 1001. Therefore, the magnetoresistive device 1010 does not have physical contact with the ferromagnetic gear teeth 1020. As a result, neither the magnetoresistive device 1010 nor the ferromagnetic gear teeth 1020 undergoes mechanical wear during use.

[0063] During operation, as the gear ring 334 rotates together with the MLC turntable 300 (not shown), the magnetoresistive sensor 324 generates rotational position 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 position information in the form of a sine output signal and a cosine output signal. In some embodiments, such position information is used for secondary motion detection of the gear ring 334 (and therefore the MLC turntable 300) around the rotation axis 1002. In such embodiments, a servo system associated with the rotation of the MLC turntable 300 around the rotation axis 1002 provides primary linear motion detection. Thus, in such embodiments, the IEC requirement of having primary and secondary position sensors for all rotation axes of the MLC turntable in the radiographic processing system is met.

[0064] Ideally, when position 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 the sinusoidal and cosine output 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 values, which can lead to inaccurate rotational position measurements of the gear ring 334. The following section combines... Figure 11 Describe an instance of this.

[0065] 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 in the figure, the ideal sinusoidal output signal 1120 and the cosine output signal 1130 each 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 the gear ring 334 ( Figure 10 In 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, the 90° phase difference between the ideal sinusoidal output signal 1120 and the cosine output signal 1140 corresponds to 1 / 4 of the rotational displacement between 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 position of the magnetoresistive sensor between 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 which two adjacent ferromagnetic gear teeth 1020 of the gear ring 334 the magnetoresistive sensor 324 is located between at any given time.

[0066] 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 depicted example, signal offset 1121 is portrayed as approximately +0.5V, but in reality it is typically much smaller. The actual crossover 1102 occurs at a different rotational position R1 than the ideal crossover 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: resistance variations in 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 ratio of the ferromagnetic teeth 1020.

[0067] 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 performed to quantize the first and second signal offset values. The first and second signal offset values ​​can then be used to compensate for inaccuracies in the rotational position that would otherwise be caused by non-ideal sinusoidal and cosine output signals generated by the magnetoresistive sensor 324.

[0068] In some embodiments, during a pseudo-cycle, an excitation is applied to an actuator for rotating the gear ring 334, causing the gear 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 gear ring 334 in which 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. 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 gear ring 334 rotates through a rotational displacement corresponding to one tooth pitch of the gear ring 334. The following is in conjunction with... Figure 12 Describe one such embodiment.

[0069] Figure 12 A flowchart is provided for a calibration process for rotational position detection via a magnetoresistive sensor, according to one or more embodiments. The method may include one or more operations, functions, or actions as shown in one or more of blocks 1201-1232. Although these blocks are shown sequentially, they may be performed in parallel and / or in a different order than described herein. Furthermore, depending on the desired implementation, the various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated. Despite the combination Figure 1-11 The method is described in this system, but those skilled in the art will understand that any properly configured radiation processing 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 processing control computer 106, a remote console 110, or a combination of both. The control algorithm may be implemented in whole or in part as software or firmware logic, and / or hardware logic circuitry.

[0070] 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 particular radioprocessing system, such as during commissioning, acceptance testing, and / or installation of the radioprocessing system. In alternative embodiments, method 1200 is performed periodically for a particular radioprocessing system, such as when the radioprocessing system is powered on, when the radioprocessing system completes a specified operating duration, and / or when the radioprocessing system completes a specified number of processes.

[0071] In step 1202, the RT system 100 begins to apply excitation to the rotary actuator that rotates the MLC turntable 300 about the rotation axis 304. In some embodiments, the excitation may correspond to the rotational displacement of the gear 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.

[0072] In step 1203, the RT system 100 determines whether a measurement position has been reached. In some embodiments, multiple measurement positions are set over specified rotational displacements or excitation cycles. In one embodiment, a 10s or 100s measurement position traverses a rotational displacement corresponding to the excitation cycle. In such embodiments, a high-precision curve of the output value of the magnetoresistive sensor 324 can be generated over a single excitation cycle. As a result, a precise signal offset value can be determined based on such a curve.

[0073] 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.

[0074] In step 1211, the RT system 100 continues to apply excitation to the rotary actuator, and the rotary actuator continues to rotate the MLC turntable 300 (and gear ring 334).

[0075] 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 (e.g., 4, 8, 10, etc.) sine output signals and multiple (e.g., 4, 8, 10, etc.) cosine output signals at the current rotational position. In such embodiments, the multiple sine output signals are averaged to generate 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 gear ring 334 typically occurs at a relatively low rotational frequency (e.g., on the order of 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 gear 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.

[0076] In step 1222, the RT system 100 determines whether the current rotational position 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.

[0077] In step 1231, the RT system 100 determines whether additional excitation cycles 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 (e.g., 2-5) excitation cycles, such that signal offset values ​​(e.g., for sine and cosine output signals) can be averaged over multiple excitation cycles. In other embodiments, steps 1202-1222 are performed for each ferromagnetic tooth 1020 of the gear ring 334. In such embodiments, different signal offset values ​​can be determined for the rotational motion measured between each ferromagnetic tooth 1020 of the gear ring 334. In such embodiments, each signal offset value can provide compensation for inaccuracies in the different rotational positions associated with physical changes between the ferromagnetic teeth 1020.

[0078] Figure 13 A flowchart is provided for a process of rotational position detection via a magnetoresistive sensor according to one or more embodiments. The method may include one or more operations, functions, or actions as shown in one or more boxes 1301-1305. Although these boxes are shown sequentially, they may be performed in parallel and / or in a different order than described herein. Furthermore, depending on the desired implementation, various blocks may be combined into fewer blocks, divided into additional blocks, and / or eliminated. Despite the combination Figure 1-12 The method is described in this system, but those skilled in the art will understand that any properly configured radiation processing 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 processing control computer 106, a remote console 110, or a combination of both. The control algorithm may be implemented in whole or in part as software or firmware logic, and / or as hardware logic circuitry.

[0079] When the RT system 100 begins operation, method 1300 begins at step 1301. For example, in one instance, the MLC turntable 300 rotates about the rotation axis 304 during a radiation treatment session.

[0080] 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.

[0081] 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.

[0082] 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). Thus, 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.

[0083] In step 1305, the RT system 100 determines the current rotational position of the gear ring 334 based on one or more correction output signals generated in step 1304.

[0084] After step 1305, method 1300 typically continues as the RT system 100 rotates the MLC turntable 300 during operation.

[0085] Figure 14 This is a diagram 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.

[0086] As shown in the figure, computing device 1400 includes, but is not limited to, interconnect (bus) 1440 connecting processing unit 1450, input / output (I / O) device interface 1460 coupled to input / output (I / O) device 1480, memory 1410, storage device 1430, and network interface 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 calibration process 1401 consistent with method 1200 and / or rotational position detection process 1402 consistent with method 1300.

[0087] 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.

[0088] Memory 1410 may include random access memory (RAM) modules, flash memory cells, or any other type of memory cell or 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 position detection process 1402.

[0089] 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... Figure 1-14 The described function.

[0090] In some implementations, the signal-bearing medium 1504 may include a non-transitory 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 embodiments, 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 embodiments, 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-transitory computer-readable medium 1508 or another similar recordable medium 1510.

[0091] In summary, the embodiments described herein enable accurate and repeatable measurement of the position of the MLC and its individual blades in high-radiation environments. Furthermore, the position measurements described herein are non-contact, reducing wear-based inaccuracies and hysteresis.

[0092] Various embodiments have been described for illustrative purposes, but are 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.

[0093] Various aspects of this embodiment can be implemented as a system, method, or computer program product. Accordingly, various aspects of this disclosure can 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 are collectively referred to herein as "circuit," "module," or "system." Furthermore, various aspects of this disclosure can take the form of a computer program product implemented on one or more computer-readable media having computer-readable program code implemented thereon.

[0094] 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 of the foregoing. More specific examples (not an exhaustive list) of computer-readable storage media will include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium capable of containing or storing a program used by or connected to an instruction execution system, apparatus, or device.

[0095] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The 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 method for measuring the rotational position of a component, the method comprising: An excitation signal is applied to an actuator coupled to the component, the component including an array of ferromagnetic teeth arranged circumferentially around the component, wherein the excitation signal causes a first rotational displacement of a first ferromagnetic tooth included in the array from a first rotational position to a second rotational position; When the first ferromagnetic tooth is set in the second rotational position, one or more signal outputs from the magnetoresistive sensor are measured; One or more corrected signals are generated by modifying each of the one or more signal outputs with a corresponding signal offset value, wherein factors causing the signal offset include resistance variations in the resistors included in the resistive bridge of the magnetoresistive sensor, artifacts of the electronic components included in the magnetoresistive sensor, and / or physical tooth-to-tooth variations of the ferromagnetic teeth; and The rotational position of the component is determined based on the corrected signal.

2. The method according to claim 1, wherein the one or more signal outputs include a sine signal output and a cosine signal output.

3. The method according to claim 1 or 2, wherein measuring the one or more signal outputs includes measuring a sine signal output and a cosine signal output.

4. The method of claim 3, wherein modifying each of the one or more signal outputs with the corresponding signal offset value comprises: The sine signal output is modified using a sine signal offset value, and the cosine signal output is modified using a cosine signal offset value.

5. The method of claim 4, wherein the sine signal offset value and the cosine signal offset value are calibration factors associated with the component.

6. The method according to claim 4 or 5, wherein the sine signal offset value and the cosine signal offset value are associated with the first ferromagnetic tooth in the ferromagnetic tooth array, but not with the second ferromagnetic tooth.

7. The method of claim 4 or 5, wherein the sine signal offset value and the cosine signal offset value are associated with each ferromagnetic tooth in the ferromagnetic tooth array.

8. The method according to claim 1 or 2, wherein: The magnetoresistive sensor is disposed near the edge of the array; and The rotation of the component causes each ferromagnetic tooth in the ferromagnetic tooth array to move sequentially past the magnetoresistive sensor.

9. A method for measuring the rotational position of a component, the method comprising: An excitation signal is applied to an actuator coupled to the component for a first cycle, the component including an array of ferromagnetic teeth arranged circumferentially around the component, wherein: The first period of the excitation signal causes a first rotational displacement, including a first ferromagnetic tooth in the array, from a first rotational position to a second rotational position, and a second rotational displacement, including a second ferromagnetic tooth in the array, from the second rotational position to a third rotational position; and The first ferromagnetic tooth is adjacent to the second ferromagnetic tooth; During the first cycle, multiple first signal outputs from the magnetoresistive sensor are measured; One or more signal offset values ​​are determined based on the plurality of first signal outputs; After determining the one or more signal offset values, the excitation signal is applied to the actuator for at least a portion of the second cycle; In response to the completion of the portion of the second cycle, one or more second signal outputs from the magnetoresistive sensor are measured; One or more corrected signals are generated by modifying one or more second signal outputs with the one or more signal offset values; and The rotational position of the component is determined based on the corrected signal.

10. The method of claim 9, wherein the plurality of first signal outputs includes a plurality of sine signal outputs and a plurality of cosine signal outputs.

11. The method of claim 10, wherein determining the one or more signal offset values ​​includes determining a sine signal offset value and a cosine signal offset value.

12. The method according to claim 9, 10 or 11, wherein measuring the one or more second signal outputs includes measuring a sine signal output and a cosine signal output.

13. The method of claim 12, wherein modifying the one or more second signal outputs with the one or more signal offset values ​​comprises: The sine signal output is modified using a sine signal offset value included in the one or more signal offset values, and the cosine signal output is modified using a cosine signal offset value included in the one or more signal offset values.

14. The method of claim 12, wherein: Measuring the sinusoidal signal output includes: measuring multiple sinusoidal signal outputs and averaging the multiple sinusoidal signal outputs; and Measuring the cosine signal output includes: measuring multiple cosine signal outputs and averaging the multiple cosine signal outputs.

15. The method according to claim 9, 10 or 11, further comprising: An excitation signal is applied to the actuator for a second cycle, wherein the second cycle of the excitation signal causes a third rotational displacement of the first ferromagnetic tooth from the second rotational position to the third rotational position; During the second cycle, multiple third signal outputs from the magnetoresistive sensor are measured; as well as One or more signal offset values ​​are determined based on the multiple third signal outputs.

16. The method of claim 15, wherein determining the one or more signal offset values based on the plurality of first signal outputs comprises: Determining one or more signal offset values ​​associated with the first ferromagnetic tooth, and determining the one or more signal offset values ​​based on the plurality of third signal outputs, includes: determining one or more signal offset values ​​associated with the second ferromagnetic tooth.

17. The method of claim 15, wherein determining the one or more signal offset values ​​based on the plurality of third signal outputs comprises: The one or more signal offset values ​​based on the output of the plurality of third signals are averaged with the one or more signal offset values ​​based on the output of the plurality of first signals.

18. The method according to claim 9, 10 or 11, wherein: The magnetoresistive sensor is disposed near the edge of the array; and The rotation of the component causes each ferromagnetic tooth in the ferromagnetic tooth array to move sequentially past the magnetoresistive sensor.

19. A radiation processing system, comprising: Rotatable multi-leaf collimator turntable; A ferromagnetic tooth array is arranged circumferentially around the turntable; A magnetoresistive sensor is located near the edge of the turntable; as well as The processor is configured as follows: An excitation signal is applied to an actuator coupled to the turntable, wherein the excitation signal causes a first rotational displacement of the first ferromagnetic teeth included in the array from a first rotational position to a second rotational position; When the first ferromagnetic tooth is positioned in the second rotational position, one or more signal outputs from the magnetoresistive sensor are measured; One or more corrected signals are generated by modifying each of the one or more signal outputs with a corresponding signal offset value, wherein factors causing the signal offset include resistance variations in the resistors included in the resistive bridge of the magnetoresistive sensor, artifacts of the electronic components included in the magnetoresistive sensor, and / or physical tooth-to-tooth variations of the ferromagnetic teeth; and The rotational position of the turntable is determined based on the corrected signal.

20. The radiation processing system of claim 19, wherein the one or more signal outputs include a sine signal output and a cosine signal output.

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