System and method for stage movement control

Abstract

The present invention is entitled "System and method for table movement control". The present invention discloses a magnetic resonance imaging (MRI) system (100) comprising a table (110) and at least one processor (120). The table (110) is configured to support a patient (102) and to travel along a length (112) in a movement direction (113) through an imaging region (114) to at least one imaging position (115). A spatial gradient field varies for at least a portion of the imaging region. At least one processor (120) is operably coupled to the table (110) and is configured to: obtain a spatial gradient field curve representing a magnitude of the spatial gradient field as a function of position along the movement direction (113); determine a table velocity curve using the spatial gradient field curve, wherein the table velocity varies along the movement direction; and control movement of the table (110) using the table velocity curve.

Description

Background Art

[0001] The subject matter disclosed herein generally relates to apparatus and methods for providing table motion control, eg, controlling movement of a patient table in a medical imaging system, such as a magnetic resonance imaging (MRI) system.

[0002] The table motion speed for MRI procedures is limited to avoid exposing the patient to excessive changes in magnetic field strength. However, some conventional methods for controlling table speed result in table speeds that are too slow, thereby increasing the amount of time spent transporting the patient and prolonging the imaging procedure. Summary of the Invention

[0003] In one exemplary embodiment, a magnetic resonance imaging (MRI) system is provided, comprising a table and at least one processor. The table is configured to support a patient and to travel along a length in a direction of motion through an imaging region to at least one imaging position. A spatial gradient field varies with respect to at least a portion of the imaging region. The at least one processor is operably coupled to the table and configured to: obtain a spatial gradient field curve representing a magnitude of the spatial gradient field as a function of position along the direction of motion; determine a table velocity curve using the spatial gradient field curve, wherein the table velocity varies along the direction of motion; and control movement of the table using the table velocity curve.

[0004] In another exemplary embodiment, a method is provided that includes obtaining a spatial gradient field curve representing a magnitude of a spatial gradient field as a function of position along a length through an imaging region to at least one imaging position of a table of a magnetic resonance imaging (MRI) system in a direction of motion. The spatial gradient field varies for at least a portion of the imaging region. The method also includes determining a table velocity curve using the spatial gradient field curve, wherein the table velocity varies along the direction of motion. Furthermore, the method includes controlling movement of the table using the table velocity curve.

[0005] In another exemplary embodiment, a tangible and non-transitory computer-readable medium is provided, the tangible and non-transitory computer-readable medium comprising one or more software modules configured to direct one or more processors to: obtain a spatial gradient field curve representing a magnitude of a spatial gradient field as a function of position along a length in a direction of movement through an imaging region to at least one imaging position of a table of a magnetic resonance imaging (MRI) system, wherein the spatial gradient field varies for at least a portion of the imaging region; determine a table velocity curve using the spatial gradient field curve, wherein the table velocity varies along the direction of movement; and control movement of the table using the table velocity curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A schematic block diagram of a magnetic resonance imaging (MRI) system according to various embodiments is provided.

[0007] Figure 2 Provided are diagrams of spatial gradient field curves according to various embodiments.

[0008] Figure 3 Provided are diagrams of stage velocity profiles according to various embodiments.

[0009] Figure 4 Flowcharts of methods according to various embodiments are provided.

[0010] Figure 5 Schematic diagrams of magnetic resonance imaging (MRI) systems are provided according to various embodiments. DETAILED DESCRIPTION

[0011] The following detailed description of certain embodiments will be better understood when read in conjunction with the accompanying drawings. To the extent that the accompanying drawings illustrate diagrams of the functional blocks of various embodiments, these functional blocks do not necessarily represent the partitioning between hardware. It should be understood that the various embodiments are not limited to the arrangements and tools shown in the accompanying drawings.

[0012] As used herein, an element or step recited in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is explicitly stated. Furthermore, reference to "one embodiment" is not intended to be interpreted as excluding the existence of other embodiments that also incorporate the recited features. Furthermore, unless explicitly stated to the contrary, an embodiment "comprising" or "having" an element or elements having a particular property may include additional elements not having that property.

[0013] Various embodiments provide improved control of table motion for imaging systems, such as magnetic resonance imaging (MRI) systems, and reduce the travel time of a patient table by varying the speed along the travel path based on the varying magnitude of spatial gradient fields along the travel path.

[0014] Various embodiments provide for determining a table velocity profile based on a spatial gradient field profile, and controlling the table velocity based on the table velocity profile. By using the spatial gradient field at different locations along the travel path, the velocity in various embodiments varies along the travel path to provide reduced travel time while still addressing patient comfort issues.

[0015] Technical advantages of various embodiments include improved performance of the imaging system. Technical advantages of various embodiments include maintaining patient comfort while providing reduced transport time. Technical advantages of various embodiments include providing flexibility for manual table speed control in addition to automatic table speed control.

[0016] Figure 1 A schematic block diagram of a magnetic resonance imaging (MRI) system 100 is provided according to various embodiments. The depicted MRI system 100 includes a table 110 and a processing unit 120. The table 110 is configured to support a patient 102 and is configured to travel along a length 112 in a direction of movement 113 through an imaging region 114 to at least one imaging position 115 (the imaging position 115 is located at a position 115 in the image processing area). Figure 1 14. In general, the imaging zone 114 is defined by the presence of magnets 111 for providing the field to be used for MR imaging. For example, the imaging zone 114 may be defined within a bore 117 of one or more magnets 111. It may be noted that different movements of the table 110 into and out of the imaging zone 114, or between positions in the imaging zone 114, may be utilized. For example, the movement of the table 110 may be continuous from a starting position outside the imaging zone 114 to a single discrete position (e.g., a single imaging position 115) in the imaging zone 114. As another example, in various embodiments, the movement of the table 110 may be a series of movements, such as static intensity modulated movement between multiple imaging positions 115 within the imaging zone 114 (e.g., for whole-body imaging).

[0017] It may be noted that, in reality, the magnetic field disposed within the imaging zone 114 is not uniform, but rather varies across the imaging zone 114. Therefore, the imaging zone 114 may be understood as having a spatial gradient field (e.g., a variation in the strength of the field along the length 112 in the direction of movement 113). The spatial gradient field varies for at least a portion of the imaging zone 114.

[0018] Figure 2 An exemplary graph of the spatial gradient field as a function of linear position along the direction of movement 113 is provided. Figure 2 The horizontal axis in is linear position (e.g., position along the z-axis along which the stage 110 moves), and the vertical axis is the spatial gradient field (in the illustrated embodiment, in units of Tesla / meter (T / m)). It can be noted that the field experienced by the patient 102 can vary at different lengths along the patient. Generally, the effect of the field on the brain 104 of the patient 102 is of interest in determining tolerance to field variations. Therefore, Figure 2 The positions shown can be understood as corresponding to the positions of the brain 104 of the patient 102 along the z-axis or along the length 114 of the translation direction 113. Additionally, the horizontal axis is labeled with the isocenter 250 of the field as 0, and negative and positive displacement values ​​are labeled on either side of the isocenter.

[0019] It can also be noted that the magnitude of the gradient varies with the patient's size, with larger gradients for larger patients. Figure 2, namely, a first curve 210 for larger patients, a second curve 220 for medium-sized patients, and a third curve 230 for smaller patients. Figure 2 As shown, for the illustrated example, each of the curves 210, 220, and 230 has a substantially similar shape. For example, at the inlet portion 201 from -300 cm to -200 cm, the gradient is zero or close to zero. It can be noted that, in combination with Figure 2 The specific values ​​of position and / or gradient strength provided are examples for illustrative purposes, and other embodiments may utilize other values ​​and / or curve shapes. For example, Figure 2 The curve of corresponds to the gradient of an exemplary 1.5 T system. The entry portion 201 corresponds to the range of positions of the magnetic field where the brain 104 of the patient 102 completely or almost completely exits the imaging zone 114 .

[0020] Next, the first portion 202 of each gradient curve, starting at approximately -200 cm, corresponds to the portion where the brain 104 enters the imaging region and approaches the isocenter 250. At approximately -80 cm in the illustrated example, the gradient reaches a peak 203 and then decreases as the curve approaches the isocenter 250.

[0021] The second portion 204 of each gradient curve is located within about 20 centimeters of the isocenter 250 on either side of the isocenter 250 and corresponds to a position of the patient's 102 brain 104 at or near the isocenter 250. For the second portion 204, the gradient is zero or a relatively low value.

[0022] If the brain 104 of the patient 102 is advanced further past the isocenter 250, a third portion 205 of each curve is encountered. At approximately 80 centimeters in the illustrated example, the gradient reaches a peak 206 and then decreases past the isocenter 250 as the brain 104 approaches the far edge of the field within the imaging zone 114.

[0023] like Figure 2 As shown in the example of , the gradient varies along the length 112 in the direction of movement 113. However, it can be noted that patient comfort is generally related to changes in the field over time rather than distance. Therefore, the processing unit 120 in the illustrated embodiment is configured (e.g., programmed) to control the console at varying speeds. For example, the patient 102 can move more quickly through portions of the spatial gradient field that are relatively low (e.g., the entry portion 201 and the second portion 204) and more slowly through portions of the spatial gradient field that are relatively high (e.g., the first portion 202 and the third portion 205).

[0024] More specifically, in the illustrated example, the processing unit 120 is operatively coupled to the stage 110 (e.g., communicatively coupled to the actuating portion 119 of the stage 110 and configured to provide control signals to the actuating portion 119 to move the stage 110 and / or configured to receive information from the stage 110 regarding the movement of the stage 110). The depicted processing unit 120 is further configured to: obtain a spatial gradient field curve representing the magnitude of the spatial gradient field as a function of position along a movement direction 113; determine a stage velocity curve using the spatial gradient field curve (wherein the stage velocity varies along the movement direction 113 of the stage velocity curve); and control movement of the stage 110 using the stage velocity curve.

[0025] In various embodiments, the processing unit 120 includes processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. In various embodiments, the processing unit 120 may additionally control one or more aspects of the MRI system 100 to acquire imaging information and / or reconstruct images using the imaging information acquired by the MRI system 100. It should be noted that the term "processing unit," as used herein, is not necessarily limited to a single processor or computer. For example, the processing unit 120 may include multiple processors, ASICs, FPGAs, and / or computers, which may be integrated into a common housing or unit or distributed across various units or housings. It should be noted that the operations performed by the processing unit 120 (e.g., operations corresponding to the processing flows or methods discussed herein, or aspects thereof) may be sufficiently complex that a human may not be able to perform the operations within a reasonable period of time. For example, the determination of a table velocity profile and the generation of corresponding control signals may rely on or utilize calculations that a human may not be able to complete within a reasonable period of time.

[0026] The depicted processing unit 120 includes a memory 130. The memory 130 may include one or more computer-readable storage media. For example, the memory 130 may store information regarding system characteristics (e.g., information regarding spatial gradients), pre-calculated curves (e.g., predetermined spatial gradient field curves and / or table velocity curves based on patient size), algorithms or processes for determining spatial gradient field curves and / or table velocity curves, etc. Additionally, the process flows and / or flow charts (or aspects thereof) discussed herein may represent one or more sets of instructions stored in the memory 130 for directing the operation of the MRI system 100.

[0027] Figure 2 (discussed above) provides an exemplary spatial gradient field curve, and Figure 3An exemplary table velocity curve is provided. Generally speaking, in various embodiments, a table velocity curve can be determined using a corresponding spatial gradient field curve and a target time rate of field change, or a desired (or allowed) maximum field intensity time rate change value. The field intensity time rate change can be understood as the change in the field experienced by the brain 104 of the patient 102 over time as the patient 102 moves through the imaging region 114. In various embodiments, the maximum field intensity time rate change value is a predetermined value based on an established standard (e.g., set as a standard or as a percentage of the standard). For example, a standard of 3 T / s can be used as the maximum field intensity time rate change value.

[0028] Using the spatial gradient field curve obtained by the processing unit 120 (e.g., from a previously performed or otherwise known calibration or test of the MRI system 100), the processing unit 120 can then determine a table velocity curve. For example, the table velocity curve can be determined by dividing the maximum field intensity time rate change by the spatial gradient field. Because the spatial gradient field varies with position (e.g., linear position along the z-axis), while the maximum field intensity time rate change is constant, the resulting table velocity curve also varies with position, varying inversely proportional to the spatial gradient field.

[0029] The speed curves of the three stations are Figure 3 : a first machine velocity curve 310, which corresponds to or is determined using the first curve 210 (and is therefore for larger patients); a second machine velocity curve 320, which corresponds to or is determined using the second curve 220 (and is therefore for medium-sized patients); and a third machine velocity curve 330, which corresponds to or is determined using the third curve 230 (and is therefore for smaller patients). Figure 3 As shown, the first velocity curve 310 includes lower velocities than the other curves due to the higher spatial gradient field for larger patients. Generally speaking, the velocity shown by each curve is lower when the gradient is high and higher when the gradient is low. Figure 3 The curves are shown in the range of about -150 cm to about 150 cm, and therefore, each curve 310, 320, 330 includes a curve corresponding to Figure 2 The first portion 302 of the first portion 202 of the curve, the second portion 304 corresponding to the second portion 204, and the third portion 305 corresponding to the third portion 205. (It can be noted that Figure 3 A portion corresponding to the inlet portion 201 is omitted, and the velocity can be relatively high during the inlet portion 201 because there is little or no field therein. Figure 2 and Figure 3As shown, the shape of the table velocity curve varies inversely with the shape of the spatial gradient field curve, where the table velocity is relatively high when the spatial gradient field is relatively low and relatively low when the spatial gradient field is relatively high. It can be noted that the maximum velocity can also be limited by an absolute ceiling or an upper limit that is independent of the spatial gradient field. For example, in cases where the spatial gradient field is zero or low (such as in the entry section 201), the table velocity limit can be selected based on patient comfort caused by velocity alone. It can also be noted that in conjunction with the discussion of the 1.5T MRI system Figure 3 However, the same principles can be applied, for example, to systems with stronger fields, such as 3T or 7T systems.

[0030] It should be noted that in some examples, the velocity of the table 110 throughout its range of motion may be the velocity specified by the table velocity curve for a particular position along its range of motion, or may be one or more velocities derived from the table velocity curve. It should also be noted that in various embodiments, the spatial gradient field curve and / or the table velocity curve may be obtained or determined using predetermined curves, for example, based on patient characteristics (e.g., patient size) and / or system characteristics (e.g., as determined by previously performed calibration or measurements). In some embodiments, a set of predetermined curves is stored in memory 130 or otherwise accessible to processing unit 120, and one or more appropriate curves may be selected based on the conditions of a particular imaging procedure. In some embodiments, processing unit 120 may use patient size to obtain the spatial gradient field curve, for example, by selecting the spatial gradient field curve to be used from a set of available curves (e.g., curves 210, 220, 230) based on the patient's size.

[0031] If the table velocity profile is determined, the processing unit 120 uses the table velocity profile to control movement of the table 110. For example, the processing unit 120 may send control signals to the table 110 (e.g., to the actuating portion 119 of the table 110) to move the table 110 into and out of the imaging region 114. For example, to improve or optimize movement time, the table 110 may be controlled to move faster when the spatial gradient field is low and slower when the spatial gradient field is high to keep the temporal rate of field change experienced by the patient 102 at or near a predetermined maximum.

[0032] In various embodiments, the processing unit 120 is configured to obtain user input and use the user input to control the movement of the control console 110. For example, the MRI system 100 may include an input unit 110 (e.g., a keyboard, a mouse, a touch screen, etc.) configured to allow a user to provide user input to the processing unit 120. The user input may be used to specify or change the table speed. In various embodiments, the MRI system 100 includes a display unit 150 that provides guidance to the user, thereby providing input for specifying or adjusting the table speed, which the user provides via the input unit 140. For example, the display unit 150 may be a screen. (It should be noted that the display unit 150 and the input unit 140 may be integrated into a single device, such as a touch screen.) In various embodiments, the display unit 150 is configured to display one or more curves indicating maximum speed and / or gradient, and / or one or more displays comparing the current speed and / or current spatial gradient field to the maximum allowed values, thereby allowing the user to view how close the current conditions are to the maximum allowed values. In various embodiments, the display may be color-coded (e.g., displaying a green light or image when there is a relatively large difference between the current speed and the maximum allowed value, a yellow light or image when there is a smaller difference between the current speed and the maximum allowed value, or a red light or image when there is little or no difference between the current speed and the maximum allowed value). Thus, the display unit 150 may be used to provide information or updates regarding automatically controlled stage movements and / or guidance (including warnings) regarding manual control of the stage 110.

[0033] In some embodiments, for each position along the movement of stage 110, a maximum allowed speed from the stage speed profile can be used as a limit that does not allow user input to override. As another example, user input can be used to modify a predetermined control scheme. In some embodiments, an automatically generated control scheme can be used to provide a default speed, with user input being used to override the default speed.

[0034] It should be noted that various embodiments utilize one or more control modes or operating modes to control table velocity based on the table velocity profiles discussed herein. Operating modes may include modes utilizing automatic or autonomous control of table velocity, modes utilizing user input, and / or modes utilizing a combination of autonomous and manual control. For example, in various embodiments, processing unit 120 is configured to select an operating mode for movement of the table from a plurality of operating modes. For example, a particular operating mode may be selected based on a procedure, patient characteristics, and / or user preferences. Each operating mode may utilize the velocity profile differently to determine the control scheme for moving the table.

[0035] In one exemplary mode of operation, processing unit 120 is configured to control movement of table 110 at a speed specified by a table speed curve, wherein the speed at a given location (e.g., defined by the location of the patient's brain) is the speed specified at the corresponding location on the table speed curve. Thus, the speed of table 110 can vary in the same manner as the table speed curve varies. If table 110 automatically or autonomously follows a table speed curve that specifies a maximum speed at each location along the movement, the total movement time will be minimized. Alternatively, the speed of table 110 can be modified from the value specified by the table speed curve (e.g., the table speed can be 90% or another predetermined percentage of the corresponding table speed curve value for the corresponding location).

[0036] In another exemplary mode of operation, the processing unit 120 is configured to control the movement of the table 110 at a constant speed based on a minimum speed from the table speed curve. The minimum speed can be defined as the maximum allowable speed at the location of the highest spatial gradient field, which would be the minimum speed on the table speed curve defined by the maximum allowable time rate change divided by the spatial gradient field curve. Thus, an automatic or autonomous control scheme can be provided that sets a constant speed during patient transport, thereby providing an economical control method.

[0037] In a third exemplary operating mode, the processing unit is configured to control the movement of the table 110 using a default speed specified by the table speed profile and, in response to user input, to control the movement of the table 110 at a reduced speed. This mode may be referred to as a mild table movement mode. This mode provides for manual adjustment, for example, by pressing a deceleration button. For example, this mode may be particularly useful for sensitive patients who experience dizziness and / or nausea at speeds close to permitted standards.

[0038] Figure 4 A flow chart of a method 400 (e.g., a method for moving a patient table in an MRI system) according to various embodiments is provided. For example, the method 400 can employ or be performed by structures or aspects of the various embodiments (e.g., systems and / or methods and / or process flows) discussed herein. In various embodiments, certain steps can be omitted or added, certain steps can be combined, certain steps can be performed simultaneously, certain steps can be divided into multiple steps, certain steps can be performed in a different order, or certain steps or series of steps can be re-performed in an iterative manner. In various embodiments, portions, aspects, and / or variations of the method 400 can be used as one or more algorithms to direct hardware (e.g., one or more aspects of the processing unit 120) to perform one or more operations described herein.

[0039] At 402, a patient is positioned on a table (e.g., table 110). In various embodiments, the position of the patient's brain can be placed at a predetermined portion of the table, or the position of the brain relative to landmarks on the table can be noted, such that the position of the brain relative to the field within the imaging region is referred to as the table moves through the imaging region. Thus, the effect of the spatial gradient field on the patient's brain can be determined as the patient moves through the imaging region and can be used to determine the table velocity, as discussed herein. In the illustrated embodiment, the table is configured to move along a length in a direction of motion through the imaging region to at least one imaging position.

[0040] It can be noted that for at least a portion of the imaging region, the spatial gradient field varies along the length in the direction of movement (see e.g. Figure 2 and related discussions). At 404, a spatial gradient field curve is obtained. The spatial gradient field curve represents the magnitude of the spatial gradient field as a function of position along the length in the direction of movement. The spatial gradient field curve can be obtained by calculation based on the system characteristics and / or configuration of a given procedure, and / or can be obtained from an archive file containing one or more stored curves based on previous calibration and / or measurement. In the illustrated embodiment, at 406, the spatial gradient field curve is obtained using the patient's body shape. For example, a set of spatial gradient field curves for patients of different body shapes can be stored (e.g., in the memory 130), and the patient's body shape can be input before the imaging process (e.g., via the input unit 140). The spatial gradient curve for the archived body shape that is most similar to the patient's body shape can then be selected from the curves and used.

[0041] At 408, the spatial gradient field profile is used to determine a stage velocity profile (see, e.g., Figure 3 ). The table speed specified by the table speed curve varies along the direction of movement, for example, to account for changes in the spatial gradient field. In various embodiments, the table speed curve specifies a maximum table speed along the length in the direction of movement such that the specified speed and corresponding magnitude of the spatial gradient field at each position along the length meet predetermined maximum values ​​(e.g., as listed by a standard), for example, to help ensure patient comfort. For example, in some embodiments, a predetermined maximum field strength time rate change value may be used to determine the table speed curve. In the illustrated embodiment, at 410, the table speed curve is determined by using the spatial gradient field curve and a predetermined maximum field strength time rate change value (e.g., by dividing the predetermined maximum field strength time rate change value by the spatial gradient field curve).

[0042] At 412 of the illustrated embodiment, an operating mode for movement of the console is selected from a plurality of operating modes. The particular operating mode may be selected based on the imaging protocol to be performed, patient characteristics, and / or operator preferences. For example, where reduced procedure time is a priority, an operating mode may be selected that automatically or autonomously controls the console at a maximum speed for each position along the travel length specified by the table speed profile. As another example, where the patient is known to be sensitive to field movement, an operating mode may be selected that lists default speeds but allows manual input to slow the table.

[0043] At 414, the table is moved using the table speed curve. This movement can be performed as a single movement from outside the imaging area to a single imaging position within the imaging area, or can be performed in a series of steps between multiple imaging positions. The table speed can be controlled to a table speed value specified by the table speed curve. Alternatively, one or more of the speeds specified by the table speed curve can be modified as part of an automated control scheme (e.g., by having the console move at a predetermined percentage of the speed specified by the table speed control curve, or automatically modifying the speed, for example, to comply with a maximum speed limit based on individual patient comfort or physician preference), or as part of the control scheme using manual input (e.g., by allowing manual input to override or modify the predetermined control scheme, for example, to allow for a reduction in speed if the patient exhibits discomfort during movement of the table). At 416 of the illustrated embodiment, the manual input is obtained, and at 418, the table movement is controlled using the manual input.

[0044] At 420 , with the patient positioned as desired, an MRI scan is performed, and at 422 , an image is reconstructed using the data acquired during the MRI scan performed at 420 .

[0045] As discussed herein, the various methods and / or systems described herein (and / or aspects thereof) may be implemented in conjunction with an MRI system. For example, Figure 5Various major components of an MRI system 10 formed according to various embodiments are shown. The operation of the system is controlled by an operator console 12, which includes a keyboard or other input device 13, a control panel 14, and a display 16. The console 12 communicates with a separate computer system 20 via a link 18, which enables the operator to control the generation and display of images on the screen 16. The computer system 20 includes a plurality of modules that communicate with each other via a backplane 20a. These modules include an image processor module 22, a CPU module 24, and a memory module 26 (a frame buffer for storing image data arrays as known in the art). The computer system 20 is linked to a disk storage device 28 and a recordable medium 30 for storing image data and programs, and communicates with a separate system control 32 via a high-speed serial link 34. The input device 13 may include a mouse, joystick, keyboard, trackball, touch-activated screen, light wand, voice control, or any similar or equivalent input device, and may be used for interactive geometry requirements.

[0046] The system control 32 comprises a set of modules connected together via a backplane 32a. These modules include a CPU module 36 and a pulse generator module 38, which is connected to the operator console 12 via a serial link 40. Via link 40, the system control 32 receives commands from the operator indicating the scan sequence to be executed. The pulse generator module 38 operates the system components to execute the desired scan sequence and generates data indicating the timing, intensity, and shape of the generated RF pulses, as well as the duration and length of the data acquisition window. The pulse generator module 38 is connected to a set of gradient amplifiers 42 to dictate the timing and shape of the gradient pulses generated during scanning. The pulse generator module 38 may also receive patient data from a physiological acquisition controller 44, which receives signals from a number of different sensors connected to the patient or subject, such as ECG signals from electrodes attached to the patient. Finally, the pulse generator module 38 is connected to a scan room interface circuit 46, which receives signals from various sensors related to the condition of the patient and the magnet system. A patient positioning system 48 also receives commands through the scan room interface circuit 46 to move the patient to the desired position for scanning.

[0047] The gradient waveform generated by the pulse generator module 38 is applied to the x Amplifier, G y Amplifier and G zThe system includes a gradient amplifier system 42 of amplifiers. Each gradient amplifier excites a corresponding physical gradient coil in a gradient coil assembly 50, which is generally designated to generate magnetic field gradients used to spatially encode acquired signals. The gradient coil assembly 50 and an RF shield (not shown) form part of a magnet assembly 52, which includes a polarizing magnet 54 and an RF coil assembly 56. A transceiver module 58 in the system control 32 generates pulses, which are amplified by an RF amplifier 60 and coupled to the RF coil assembly 56 via a transmit / receive switch 62. The resulting signals emitted by excited nuclei within the patient can be sensed by the same RF coil assembly 56, or portions thereof, and coupled to a preamplifier 64 via the transmit / receive switch 62. The amplified MR signals are demodulated, filtered, and digitized in the receiver portion of the transceiver 58. The transmit / receive switch 62 is controlled by signals from the pulse generator module 38 to electrically connect the RF amplifier 60 to the coil assembly 56 during transmit mode and to connect the preamplifier 64 to the coil assembly 56 during receive mode. The transmit / receive switch 62 may also enable a separate RF coil (eg, a surface coil) to be used in either transmit or receive mode.The magnet assembly 52 may be cryogenically cooled.

[0048] The MR signals picked up by the selected RF coil are digitized by the transceiver module 58 and transmitted to the memory module 66 in the system control 32. The scan is complete when an array of raw k-space data is acquired in the memory module 66. For each image to be reconstructed, the raw k-space data is rearranged into a separate k-space data array, and each of these separate k-space data arrays is input to the array processor 68, which operates to Fourier transform the data into an array of image data. The image data is transmitted to the computer system 20 via the serial link 34, from which it is stored in a memory such as the hard disk storage device 28. In response to commands received from the operator console 12, the image data can be archived in a long-term storage device, such as a tape drive 30, or can be further processed by the image processor 22 and transmitted to the operator console 12 and presented on the display 16.

[0049] It should be noted that various embodiments may be implemented with hardware, software or a combination thereof. Various embodiments and / or components (e.g., modules or components and controllers therein) may also be implemented as a part of one or more computers or processors. A computer or processor may include a computing device, an input device, a display unit and an interface, such as for accessing the Internet. A computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. A computer or processor may also include a memory. The memory may include a random access memory (RAM) and a read-only memory (ROM). A computer or processor may also include a storage device, which may be a hard drive or a removable storage drive, such as a solid-state drive, an optical drive, etc. A storage device may also be other similar devices for loading a computer program or other instructions into a computer or processor.

[0050] As used herein, the term "computer" or "module" may include any processor-based or microprocessor-based system, including systems using microcontrollers, reduced instruction set computers (RISC), ASICs, logic circuits, and any other circuits or processors capable of performing the functions described herein. The above examples are exemplary only and are therefore not intended to limit the definition and / or meaning of the term "computer" in any way.

[0051] A computer or processor executes a set of instructions stored in one or more memory elements to process input data. A memory element may also store data or other information as desired or needed. A memory element may be in the form of an information source or a physical memory element within a processor.

[0052] The instruction set may include various commands that instruct a computer or processor to perform specific operations (such as the methods and processes of various embodiments) as a processing machine. The instruction set may be in the form of a software program. The software may be in various forms, such as system software or application software, and may be embodied as a tangible and non-transitory computer-readable medium. In addition, the software may be in the form of a collection of separate programs or modules, a program module within a larger program, or a portion of a program module. The software may also include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to operator commands, or in response to the results of previous processing, or in response to a request made by another processing machine.

[0053] As used herein, a structure, constraint, or element that is "configured to" perform a task or operation is formed, constructed, or adjusted in a specific structure in a manner corresponding to the task or operation. For the purpose of clarity and avoidance of doubt, an object that can only be modified to perform a task or operation is not "configured to" perform a task or operation as used herein. In contrast, as used herein, "configured to" is used to indicate a structural adaptation or characteristic and to indicate the structural requirements of any structure, constraint, or element that is described as "configured to" perform a task or operation. For example, a processing unit, processor, or computer that is "configured to" perform a task or operation can be understood to be specifically constructed to perform the task or operation (e.g., having one or more programs or instructions stored thereon or used therewith that are customized or intended to perform the task or operation, and / or having an arrangement of processing circuits that are customized or intended to perform the task or operation). For the purpose of clarity and avoidance of doubt, a general-purpose computer (which can be "configured to" perform a task or operation if appropriately programmed) is not "configured to" perform a task or operation unless or until it is specifically programmed or structurally modified to perform the task or operation.

[0054] As used herein, the terms "software" and "firmware" are interchangeable and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only and, therefore, do not limit the types of memory that can be used to store computer programs.

[0055] It should be understood that the above description is intended to be illustrative and not restrictive. For example, the above-described embodiments (and / or aspects thereof) may be used in combination with one another. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the various embodiments without departing from the scope of the present invention. While the sizes and types of materials described herein are intended to define the parameters of the various embodiments, they are by no means limiting and are merely exemplary. Upon reviewing the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the various embodiments should be determined by reference to the appended claims and the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain Chinese equivalents of the respective terms "comprising" and "wherein." Furthermore, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels and are not intended to impose numerical requirements on their objects. Furthermore, the limitations in the following claims are not written in means-plus-function format and are not intended to be interpreted under 35 U.S.C. §112(f), and unless such limitations explicitly use the phrase "means for..." followed by a functional statement without other structure,

[0056] This written description uses examples to disclose various embodiments, including the best mode, and also to enable any person skilled in the art to practice the various embodiments, including making and using any devices or systems and performing any included methods. The patentable scope of the various embodiments is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A magnetic resonance imaging (MRI) system (100), comprising: a table (110) configured to support a patient (102), the table (110) configured to travel along a length (112) in a movement direction (113) through an imaging region (114) to at least one imaging position (115), wherein a spatial gradient field varies for at least a portion of the imaging region (114); and at least one processor (120) operatively coupled to the station (110), the at least one processor (120) being configured to: using the patient's (102) body shape to obtain a spatial gradient field curve representing the magnitude of the spatial gradient field as a function of position (115) along the movement direction (113); determining a table velocity profile using the spatial gradient field curve and a position of the patient's brain relative to the spatial gradient field, wherein a table velocity specified by the table velocity profile varies along the movement direction (113); controlling movement of the stage (110) using the stage velocity profile; and Movement of the stage is controlled at a reduced speed in response to user input.

2. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to determine the table velocity curve using the spatial gradient field curve and a predetermined maximum field intensity time rate change value.

3. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to obtain user input and control movement of the table (110) using the user input.

4. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to select an operating mode for controlling movement of the table (110) from a plurality of operating modes.

5. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to control movement of the table (110) at a speed specified by the table speed profile.

6. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to control movement of the table (110) at a constant speed based on a minimum speed from the table speed curve.

7. The MRI system (100) of claim 1, wherein the at least one processor (120) is configured to control movement of the table (110) using a default speed specified by the table speed profile.

8. A method for stage movement control, the method comprising: using the patient (102) body shape to obtain a spatial gradient field curve, the spatial gradient field curve representing a magnitude of a spatial gradient field as a function of position in a direction of movement (113) along a length (112) through an imaging zone (114) to at least one imaging position (115) of a table (110) of a magnetic resonance imaging (MRI) system (100), wherein the spatial gradient field varies for at least a portion of the imaging zone (114); determining a table velocity profile using the spatial gradient field curve and a position of the patient's brain relative to the spatial gradient field, wherein a table velocity specified by the table velocity profile varies along the movement direction (113); controlling movement of the stage (110) using the stage velocity profile; and Movement of the stage is controlled at a reduced speed in response to user input.

9. A method according to claim 8, comprising determining the stage velocity profile using the spatial gradient field profile and a predetermined maximum field intensity time rate change value.

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