Nuclear magnetic resonance equipment and use method thereof

Abstract

The present invention relates to providing a nuclear magnetic resonance (NMR) device adapted for measuring NMR signals within a body part of a subject. The present invention provides a lightweight and portable nuclear magnetic resonance (NMR) apparatus suitable for measuring a measurement NMR signal using a plurality of magnets arranged in an array to produce a first non-uniform magnetic field (B0) having a B0 static field gradient, a plurality of radio frequency coils, and an acquisition device; a plurality of radio frequency coils arranged to generate an independent non-uniform magnetic field (B1) substantially perpendicular to the first non-uniform magnetic field (B0), the plurality of radio frequency coils configured to generate a plurality of different radio frequencies and bandwidths; the acquisition device is configured to acquire NMR signal data from different bandwidths in B0 and B1 gradients and process the NMR signal data to provide spatial localization. Methods of collecting NMR data and diagnosing brain injury are also provided.

Description

Technical Field

[0001] This invention relates to providing nuclear magnetic resonance (NMR) equipment suitable for measuring NMR signals within body parts of a subject. Background Technology

[0002] Conventional magnetic resonance imaging (MRI) equipment is large, expensive, and located in specialized hospitals or imaging facilities. These traditional devices require trained technicians, and the patient must travel to the device for imaging. If the patient is immobile or has experienced a medical event such as a stroke, movement may be unsafe. Due to these limitations, patients often cannot receive a diagnosis quickly enough, and treatment may be delayed.

[0003] The purpose of this invention is to overcome some of these limitations, or at least to provide the public with a useful alternative. Summary of the Invention

[0004] In one aspect, the present invention provides a nuclear magnetic resonance (NMR) device suitable for measuring NMR signals in a target region of a body part of an object, comprising: (a) A plurality of magnets arranged in an array, the magnet array being configured to contain the body part of the object; the magnet array being configured to generate a first non-uniform magnetic field (B0) having a B0 static field gradient within the body part of the object undergoing inspection; wherein the magnet array comprises a plurality of spaced-apart magnet rings, each ring being configured to extend around the body part. (b) A plurality of radio frequency coils arranged in an array and configured, in use, between and around the body part of the object, each coil configured to generate an independent non-uniform magnetic field (B1) substantially perpendicular to the first non-uniform magnetic field (B0), the plurality of radio frequency coils configured to generate a plurality of different radio frequencies and bandwidths across the volume of the body part of the object; and (c) Acquisition device, the acquisition device being used to acquire NMR signal data from different bandwidths within the B0 and B1 gradients, and to process the magnetic resonance signal data to provide spatial localization of the volume across the body part; (d) wherein the magnet array and the radio frequency coil array are configured to ensure that fields B0 and B1 provide substantially full volume coverage of the target area within the body portion of the device.

[0005] In one example, the magnet array may include a plurality of spaced-apart yokes, each yoke supporting at least one pair of spaced-apart magnets, the yokes and magnets being arranged in an array such that the magnets define a ring, the ring defining an aperture within the device.

[0006] In one example, the spaced-apart yokes may be linear, and each yoke supports at least one pair of magnets. In another example, the spaced-apart yokes may be substantially curved around the magnet array to form the magnet loop.

[0007] In one example, the device may have three or more magnet rings.

[0008] In one example, the radio frequency coil array includes a plurality of coils configured to extend between and around the body part of the magnet array, the radio frequency coil array being configured to provide spatial information about the volume spanning the target region.

[0009] In one example, each RF coil is sensitive to RF spin within a specific sector of the aperture.

[0010] In one example, the RF coil array is configured to provide a transmit-only coil and multiple receive-only coils.

[0011] In one example, the radio frequency coil array is configured to provide multiple radio frequency coils capable of transmitting and receiving.

[0012] In one example, the plurality of radio frequency coils are configured to transmit simultaneously.

[0013] In one example, the plurality of radio frequency coils are configured to receive simultaneously.

[0014] In one example, the cross-section of the hole defined by the magnet ring can be substantially elliptical.

[0015] In one example, the side profile of each of the magnet rings may be non-planar.

[0016] In one example, the magnets in the array can be spaced irregularly.

[0017] In one example, the magnet array can be configured to provide a first controlled non-uniform magnetic field (B0) with a field strength of about 80 mT to about 120 mT, preferably about 100 mT, within the aperture.

[0018] In one example, the magnet array can be configured to provide a magnetic field gradient of about 15 mT to about 20 mT across the target region.

[0019] In one example, the device is portable. In one example, the portable device may weigh less than about 30 kg, preferably less than about 25 kg.

[0020] In one example, the body part could be the head of an object, and in another example, the object could be a person.

[0021] On the other hand, a method for collecting NMR data using the device described above is provided, the method comprising the following steps: (a) A controlled non-uniform magnetic field B0 is applied to the volume of the target region spanning the body parts of the object to generate a series of acquisition frequency bands with different resonant frequencies. (b) In each of a set of acquisition frequency bands that commonly cover the target area of ​​the body part, nuclear spins are excited by generating and emitting radio frequency pulses from multiple radio frequency coils, thereby causing the spins to generate multiple unique radio frequency signals. (c) Receiving, by using the unique spatial sensitivity of each radio frequency coil, the plurality of unique radio frequency signals emitted by nuclear spin from an acquisition frequency band that collectively provides spatial information across the target region spanning the body part; and (d) Process the received radio frequency signal to provide data representing the magnetic resonance characteristics of the target region.

[0022] In another aspect, a method for diagnosing brain injury using a device as defined above is provided, the method comprising the following steps: (a) A controlled non-uniform magnetic field B0 is applied across the volume of the object’s head to generate a series of acquisition bands with different resonant frequencies. (b) Within each of a set of acquisition frequency bands that commonly cover the head, nuclear spins are excited by generating and emitting radio frequency pulses from multiple radio frequency coils, thereby causing the spins to generate multiple unique radio frequency signals. (c) By using the unique spatial sensitivity of each radio frequency coil, receiving the plurality of unique radio frequency signals emitted by nuclear spins from a common acquisition frequency band that provides spatial information across the head; and (d) Processing the received radio frequency signals to provide data representing the magnetic resonance characteristics of the target region; and (e) Interpret the data to diagnose the presence or absence of brain injury.

[0023] In one example, the brain injury could be an ischemic stroke.

[0024] In one example, the brain injury could be a hemorrhagic stroke.

[0025] In one example, the brain injury could be neonatal hydrocephalus.

[0026] In the method defined above, in one example of step (d), the data representing the magnetic resonance characteristics of the target region can be further processed into an image.

[0027] In the method defined above, in one example, steps (a) through (d) can be performed in less than about 20 minutes; or in less than 15 minutes or less than about 10 minutes.

[0028] In the method defined above, in one example, at least multiple RF coils can be used to receive independent signals simultaneously.

[0029] In the method defined above, in one example, in step (b), the generated radio frequency pulse may have an excitation bandwidth of about 40 kHz to about 60 kHz.

[0030] In the method defined above, in one example, in step (a), the resulting series of acquisition bands may include at least 5 acquisition bands.

[0031] In one example of the method defined above, the magnetic resonance property of the target region can be diffusion.

[0032] In the method defined above, the magnetic resonance characteristics of the target region can be perfusion.

[0033] In the method defined above, the magnetic resonance characteristic of the target region can be T2.

[0034] In the method defined above, the body part can be the head of the object.

[0035] In the method defined above, the object can be a person.

[0036] In one example of the methods defined above, the method can be performed in an environment far from a hospital.

[0037] The present disclosure is described below with reference to specific examples. However, other examples besides those described above may also fall within the scope of this disclosure. Method steps, performed by hardware or software, different from the method steps described, may be provided within the scope of this disclosure. Different features and steps of this disclosure may be combined in combinations other than those described.

[0038] Further aspects of this disclosure will become apparent from the following disclosure.

[0039] In this specification, references to external sources of information, including patent specifications and other documents, are generally intended to provide context for illustrating the described features. Unless otherwise stated, references to such sources should not be construed as an admission that such sources are prior art or constitute part of general knowledge in any jurisdiction.

[0040] definition

[0041] As used in this article, the device-related term "hole" refers to the volume within a device, particularly the volume that accommodates a body part.

[0042] As used herein, the term “about” in relation to a referenced numerical indicator means the referenced numerical indicator plus or minus up to 10% of that referenced numerical indicator. For example, the language “about 30” kg covers a range of 33 kg to 27 kg.

[0043] As used herein, the term “and / or” means “and” or “or” both. As used herein, the “(s)” following a noun indicates the plural and / or singular form of the noun. The term “comprising” as used in this specification means “including” or “consisting of at least part of”. When interpreting statements in this specification that include this term, the feature beginning with that term in each statement must be present, but other features may also be present. Related terms such as “comprise” and “comprised” will be interpreted in the same context. The full disclosure of all applications, patents, and publications (if any) cited above and below is incorporated herein by reference.

[0044] As used in this specification, the terms "comprises," "comprising," "includes," and "including" should be understood as inclusive and open-ended, rather than exclusive. Specifically, when used in this specification (including the claims), the terms "comprises," "comprising," "includes," and "including," and variations thereof, mean to include the specified features, steps, or components. These terms should not be construed as excluding the presence of other features, steps, or components.

[0045] As used herein, the terms “approximately” or “about” mean almost or nearly, or approximately or approximate. Alternatively, “approximately” or “about” means estimated or imprecise.

[0046] As used in this article, the term “substantially” means most, or almost all, or generally, or to a great or significant degree. Attached Figure Description

[0047] One or more examples of this disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 This is a perspective view of an NMR device, schematically showing the head of the object located inside the aperture.

[0048] Figure 2 A further perspective view of the NMR device (with a portion of the magnet removed) is shown, schematically illustrating the position and proximity of the radio frequency coil relative to the magnet and the head of an object located within the aperture.

[0049] Figure 3 A schematic diagram showing a series of spaced-out magnet rings that together form a magnet array is shown.

[0050] Figure 4 (a) shows a top view of an array of magnet rings arranged in an elliptical pattern.

[0051] Figure 4 (b) shows a side view of an array of magnet rings arranged in a planar manner.

[0052] Figure 4 (c) in the figure shows an array of magnet rings with a non-planar arrangement.

[0053] Figure 5 Figures 5(a) and 5(b) show cross-sectional views of spaced-out pairs of magnets located at the ends of the yoke, which together provide the magnetic field described by B0, and the radio frequency coil provides a substantially perpendicular magnetic field B1.

[0054] Figure 6 Figures 6(a) to 6(e) show the magnetic field strength in different planes. Figure 6(a) shows the magnetic field strength in the XZ plane. Figure 6(b) shows the magnetic field strength in the YZ plane. Figure 6 Figures 6(c), 6(d), and 6(e) show the magnetic field strength in the XY plane and at different heights.

[0055] Figure 7 The magnetic field strength on the X-axis of five different magnet rings with radii ranging from 110 mm to 130 mm is shown.

[0056] Figure 8 Image 8(a) shows a three-dimensional view of an RF array with several RF coils.

[0057] Figure 8 Figure 8(b) shows a two-dimensional plan view of an RF array with several RF coils.

[0058] Figure 8 Figures 8(c) through 8(f) show the RF intensity of each coil across the aperture and in different planes.

[0059] Figure 9 Figures 9(a) to 9(d) show different planes that indicate areas where ischemic stroke may occur.

[0060] Figure 10 The pair of acquisition frequency bands generated by the magnet arrays (a) and (c) are shown, and their respective target area coverages are shown in the corresponding pair of thermal slices (b) and (d).

[0061] Figure 11 This shows a series of acquisition bands acquired from multiple radio frequency coils spanning different sectors of the target region / brain.

[0062] Figure 12 A graph showing the difference in simulated diffusion-weighted signal between the left and right hemispheres of a patient with ischemic areas.

[0063] Figure 13 A rendering of the portable NMR device containing a magnet array and radio frequency coils described in this article is shown. Detailed Implementation

[0064] Magnet array 1 suitable for nuclear magnetic resonance (NMR) systems Figure 1 As shown in the diagram, a magnet array 1 is configured and shown to accommodate the skull 2 ​​of an object. The magnet array includes a frame configured to define an opening through which a body part (e.g., the skull of an object) enters during use. The frame includes one or more spaced-apart rings 3 and 4 to support a plurality of magnets 5 (e.g., two or more concentric rings) configured in the array. Figure 3 As shown, the rings are spaced apart and fixed by multiple yokes 6, which position the concentric rings in a spaced manner, and each yoke 6 supports one or more magnets to form a magnet array 1.

[0065] When used to form a nuclear magnetic resonance (NMR) system, a magnet array 1 is combined with a series of radio frequency (RF) coils 7 arranged between the magnet array and the skull. The RF coils 7 are as follows: Figure 2 As shown.

[0066] refer to Figure 3 Another example is shown, illustrating a magnet array configured with three spaced-apart magnet rings 8, 9, and 10, showing each ring including a spaced-apart magnet 5. The distance between the individual magnet rings is called the z-pitch distance. This magnet array example differs from others by including the inner ring 9 of the magnet. Figure 1 and Figure 2Example of a magnet array shown.

[0067] refer to Figure 4 See Figure 4 In Figure (a), the magnet array is configured in an elliptical shape with a planar side section (see Figure 1). Figure 4 (See Figure (b) in the text). However, it should be understood that any shape surrounding the target region can be used, and depending on the shape of the target region, non-planar side sections (see Figure (b) in the text) can be used. Figure 4 Figure (c) in the middle may also be appropriate.

[0068] In this example, the NMR system uses a constant magnetic field B0 provided by a magnet array, but also relies on a weaker oscillating field B1. This oscillating field is provided by a series of radio frequency coils, such as coil 7 of the magnet array, and is used to generate the magnetic field B1 to excite the spin and detect the signal from the spin.

[0069] Uniform B0 and B1 fields (combined with pulse gradients) in conventional NMR and MRI systems can excite, detect, and spatially localize NMR signals from nuclear spins within the NMR system. In contrast, the NMR system configured and described herein performs measurements in a non-uniform field generated by its B0 magnet array. The spin is in a resonant state when its resonant frequency (depending on its location, B0) falls within the excitation frequency bandwidth of the B1 field. Spinns in a non-resonant state are essentially insensitive to excitation from the B1 field. Therefore, measurements in a non-uniform B0 field are limited by the B1 excitation frequency and bandwidth, which restricts the coverage area: the region where signals can be excited and detected. However, the spatial sensitivity of the NMR device has been configured through the design of the magnet array and RF coil array to ensure that the B0 and B1 fields still cover substantially the entire volume of the target region within the device.

[0070] Furthermore, the device is configured to minimize the mass of the magnet array and improve its efficiency: the magnetic field strength inside the aperture per unit weight of the magnet array. Since the intensity of the NMR signal depends on the field strength, configuring the magnet array to maximize the strength of the B0 field is important. However, the weight of the device is a significant consideration for its portability, especially in pre-hospital or field environments. Weight reduction is necessary because it makes the device easier to transport and use. By designing and optimizing the number, size, and position of the magnets in the magnet array (as discussed in Example 1 below), the efficiency of the design is improved while maintaining coverage across the target area.

[0071] refer to Figure 5Images 5(a) and 5(b) provide cross-sectional views of a pair of magnets 11 located on the yoke 12, showing an optional inner magnet 13. Curve 15 represents a contour line of the magnetic field strength B0 extending between the magnets, with the direction of the magnetic field indicated by the arrow B0. The magnetic field strength decreases as the line moves away from the magnets, forming a static magnetic gradient. The B0 magnetic field extends beyond the target area, i.e., the shaded area 16 in the middle. Figure 5 Image 5(b) shows the effect of the additional magnet ring 17, which is configured to straighten the contour line 15 of the B0 magnetic field strength across the target region. Numerous such arrangements are provided throughout the device by the magnet array and RF coil assembly. Figure 1 In the example shown, 18 pairs of magnets each generate their own magnetic field. RF coil 14 is shown positioned between the magnets and spaced apart from both the magnets and the yoke. An oscillating magnetic field B1 is generated by the current flowing through the RF coil and is substantially perpendicular to B0. This arrangement was determined to be substantially optimized. It should be understood that each RF coil is positioned independently of the magnetic pair, and Figure 5 What is shown is to be understood as a simplification of the overall device.

[0072] Magnetic field coverage depends on the non-uniform B0 and B1 fields generated by the magnet array and RF coils. The non-uniform B0 field forms a controlled gradient across the aperture, where spins at different locations experience a series of B0 field strengths corresponding to a series of resonant frequencies. Performing multiple NMR measurements with a series of B1 frequencies and bandwidths corresponding to different locations across the aperture allows the device to excite and detect signals from multiple different regions across the non-uniform B0 field, thereby increasing coverage. This controlled gradient, or controlled non-uniform magnetic field B0, is essential for the functionality of an NMR system.

[0073] In addition to the magnet array and RF coil array, additional hardware is required to acquire NMR signals from the spins in the aperture. This includes a spectrometer (e.g., those provided by Resonint, Wellington NZ) for performing the NMR pulse sequence and an RF amplifier (e.g., those provided by TOMCO, Stepney, SA Australia) for transmitting and receiving. This hardware is similar to the electronics used in other low-field NMR instruments. The spectrometer processes the timing in the pulse sequence, generating RF pulses of various frequencies, powers, and durations, and acquires the NMR signals. The spectrometer can operate in multi-channel mode, acquiring RF signals from all RF coils simultaneously, or in multiplexed mode, where signals are acquired from only a subset of the RF coils simultaneously.

[0074] refer to Figure 13The image shows an example of a envisioned commercial NMR device. The device is packaged in a housing with a handle for easy portability. The device may also include one or two windows to allow the user to look out for greater comfort and reduce feelings of claustrophobia.

[0075] Example 1: Simulation of a Magnet Array

[0076] The B0 magnetic field generated by the magnetic array described above defines the spatial sensitivity and coverage of the system. To understand the efficiency and gradient produced by different types of magnet array designs, a series of magnet assemblies with various designs were produced, and the magnetic fields they produced were simulated. A range of parameters, such as the number of magnets, magnet dimensions, ring diameter, eccentricity, and z-spacing, were tested in each design to understand how they affect the field strength and gradient. These parameters were used to generate a list of magnet positions and magnetization directions that served as inputs to the simulation process.

[0077] In the selected method, the finite element method (FEM), the complete geometry of the magnet array, including the shapes of the magnet blocks and yoke plates, is generated. The simulation uses the open-source gmsh / GetDP software. This generates a three-dimensional volume of the magnetic field, from which the amplitude is calculated as the B0 magnetic field.

[0078] The geometry was meshed using the software gmsh, and the coercive field, remanent magnetization, and magnetic permeability of the magnet and yoke regions were set using material properties. The fields were then solved using the scalar magnetic potential method with the software package GetDP.

[0079] This method is used because it simplifies the analysis while capturing the effects of changes in the material's magnetic permeability. The magnetic field is calculated and then interpolated onto a regular mesh to produce a 2D map or 3D volume of the magnetic field across the aperture.

[0080] It was determined that the most efficient design for axial field was the inner-outer ring or Aubert ring design, modified to add a yoke connecting the main rings. This design produced a radial magnetic field gradient, where the field was weakest along the bore axis at r = 0 and increased with increasing r inside the bore. The results related to the magnetic field strength of this design are as follows: Figure 6 As shown in the series of contour maps.

[0081] The magnet array defines the aperture based on two magnet rings, with an additional magnet ring between these two rings to further modify the magnetic field as needed. For example... Figure 3As shown, one of the main rings has a block arranged to have a magnetization intensity pointing radially outward from the bore axis, and the other has a block with a magnetization intensity facing the bore axis. Figure 3 As shown, these magnet rings generate a magnetic field oriented along the hole axis z inside the array.

[0082] One or two additional magnet rings may be present between the inner and outer magnet rings to further control the magnetic field gradient inside the aperture. The magnets in the additional rings are magnetized to point towards -z to increase the field strength inside the aperture. The magnet size can vary according to the desired magnetic field gradient. Preferably, the size of the magnet is the same as or smaller than that of the inner and outer ring magnets to avoid reducing the aperture size.

[0083] Furthermore, the yoke bars of a high-permeability metal (such as steel) connect the inner and outer rings, forming a yoke that redirects and concentrates the magnetic field inside the aperture. This increases the magnetic field strength inside the aperture, improves the efficiency of the magnet array, and consequently reduces stray magnetic fields outside the device. It also provides mechanical support for the inner and outer rings.

[0084] Through inner-outer magnet ring design, various simulations have shown that increasing the diameter reduces the field strength inside the aperture (for the same number of magnets). This trend is expected, as the magnetic field generated by a magnet of the same volume is distributed over a larger volume. This suggests that a smaller aperture volume would provide higher efficiency; however, the body size to be measured still limits the minimum aperture size.

[0085] It was also determined that stretching the magnet ring into a near-elliptical shape along the y-axis helps maintain field strength and coverage, as well as minimize the x-axis diameter and enclose the aperture volume. This is desirable because the preferred body part to be studied within the aperture volume is the skull, where the skull length is typically greater than the skull width, meaning the front-to-back length is greater than the left-to-right width. The larger size of the skull limits the minimum size of the device in order to house it within the aperture. Surprisingly, it was found that stretching the magnet ring along the y-axis helps maintain field strength and coverage, as well as minimize the x-axis diameter and enclose the aperture volume.

[0086] It was also found that the z-spacing of the rings affects the magnetic field strength and magnetic field gradient. For a pair of inner-outer magnet rings, the maximum field strength and efficiency are obtained when the z-spacing is approximately equal to the diameter of the magnet rings. However, this also significantly increases the radial gradient, limiting the magnetic field coverage. At the cost of field strength, making the z-spacing larger than the diameter reduces the radial gradient. This parameter was determined to be very important for the coverage of the control system.

[0087] Another parameter of interest is the shape of the ring along the y-axis. While this shape can be a flat plane that remains constant along the y-axis at the z-position (e.g., ... Figure 4(as shown in (b)), but the effect of distorting the z-position of the magnet along the front-rear axis to conform to the contour lines of the target region was also investigated. The contour lines can be obtained by averaging the shape of the target region, or alternatively by a mathematical expression (e.g., y = cz). z 2 (y < 0) The position of the magnet ring is obtained by twisting it. This paper describes a plane with a curved region facing the back of the magnet ring, thereby improving the coverage of the target area.

[0088] Further optimization of the magnet array could include altering the spacing between the magnets around the ring, such as increasing the spacing between adjacent magnets within the ring, or removing one or more magnets from certain locations within the ring. This could further reduce weight and increase patient comfort by alleviating claustrophobia.

[0089] Depending on the z-pitch of the magnet rings, the magnetic field contains an ellipse with a maximum B0. A saddle point is observed; see [link to relevant documentation]. Figure 6 In diagram 6(d), the dashed line 19 indicates that the magnetic gradient is essentially zero at the saddle point. To ensure a continuous magnetic gradient covering the aperture volume and the target region, the saddle point and the area outside the saddle point must be located outside the aperture volume or any region of interest.

[0090] Because the z-spacing of the rings is larger compared to the size of the magnet, the inner-outer ring ( Figure 3 Add an internal magnet ring ( ) between the spacing of 8 and 10) Figure 3 (9 in the original text). They are magnetized along the z-axis to increase the field strength inside the array. The design with a yoke restricts the inner rings to be smaller than the main inner-outer rings. The number and position of the rings are free to vary. It has been observed that adding one or two smaller magnets in the middle of the outer magnet rings provides a way to control the field gradient, particularly the field gradient at the edge of the target region / hole. By controlling the radius of the inner magnet rings, the gradient across the target region can be made more constant, thereby eliminating any influence from the ring with the largest field strength mentioned above.

[0091] Another consideration in magnet array design is the shape and gradient of the magnetic field contour lines. As described in Example 3 below, the non-uniformity of the B0 field is used to select spins from different radial depths within the aperture. This technique allows the NMR signal to be localized to different radii by varying the B1 excitation frequency. Figure 5 As shown in Figures 5(a) and 5(b), the contour lines of the B0 magnetic field strength reflect the volume of the excited spin at each excitation frequency and the volume of the spin forming the acquisition band (e.g., as shown in Figure 5(a) and Figure 5(b), Figure 5(b)). Figure 6 (As shown).

[0092] In addition to maintaining the target area ( Figure 5The coverage of 5(a) and 5(b), specifically 16), and the control of the shape of these contour lines for each acquisition band are important. This is because highly curved acquisition bands make it more difficult to locate the detected NMR signal in the radial direction. In curved acquisition bands, the radius of the acquisition band depends on z, which can make it difficult to locate the signal on a single radius. Preferably, the magnet array is designed such that the field contour lines cross the target area in essentially straight lines. This can be achieved by adding more magnet rings above the top of the magnet array to surround one side, such as... Figure 5 As shown in 5(b) of Figure 17, the additional magnet ring appears to increase the magnetic field in the upper half of the hole, thus making the magnetic field contour lines across the target area straight.

[0093] Example 2: Coil Simulation Example

[0094] In another example, the contribution of a non-uniform B1 field generated by an array of RF coils to device coverage was simulated. Due to the non-uniformity of the B1 field generated by each coil, each coil has a sensitivity pattern that reflects its sensitivity to spin at different locations.

[0095] The B1 field generated by these coils is simulated using Biot-Savart's law (see Griffiths). Low RF B1 means the coil current can be considered quasi-static. The RF coil array is parameterized to control the position and size of the RF coils. Therefore, a series of elliptical wire paths around the surface of an elliptical cylinder are determined to fit the edges of the holes (e.g., ...). Figure 8 (As shown in 8(a) and 8(b)) is optimal.

[0096] Similar to the B0 design, the RF field generated by each coil is calculated at grid points to simulate a 3D image of the B1 field generated by each RF coil with a current of 1 Amp. A slice of the 3D image is shown below. Figure 8 As shown in 8(c) and 8(d), the B1 field amplitude on the xy plane was used because it controls the spatial sensitivity of the RF coil to the NMR signal. The B1 field amplitude was selected within a specified range corresponding to the region where the RF pulse might cause a 180-degree excitation of the B0 bandwidth. For these simulations, B1 amplitudes from 1.5 microtesla to 6 microtesla were selected as the "detectable" region. Figure 8 The slices shown in 8(c) and 8(d) are shaded in gray.

[0097] The B1 detectable region maps a series of sectors spanning the aperture volume, aligned with the RF coil. The angular size of the sector is controlled by the width of the RF coil, and the attenuation of B1 with distance from the RF coil also depends on the width and size of the RF coil.

[0098] In one embodiment, the coil array is configured as a plurality of RF coils that transmit and receive RF pulses within an aperture volume. In this configuration, pulses from the individual RF coils excite sectors of the aperture because the resulting B1 field is non-uniform. The plurality of RF coils are used to detect signals from the excited sectors. In this embodiment, this arrangement has been found to provide good spatial resolution because the non-uniformity of B1 controls both the excitation and detection regions.

[0099] In another embodiment, the coil array is configured as an RF receive-only coil array with individual volumetric transmit coils. The transmit coils are configured to excite the entire acquisition band in a single experiment, essentially exciting the loop. Due to the B1 non-uniformity of each receive coil, the receive coil array still provides spatial information to different sectors. This provides the benefit of faster acquisition over the target region because repeated NMR measurements are not required for each individual coil and frequency combination. It also reduces the need for high-power switching between different coils. The transmit coils can follow designs used in conventional MRI and NMR systems, such as birdcage coil designs or saddle coil designs, which generate transverse B1 within the volume.

[0100] It is envisioned that, for practical applications, the power and / or duration of the RF pulse transmitted through the B1 RF coil will need to vary depending on the target area within the aperture. Furthermore, the sensitivity across the detectable area will also vary depending on the distance from the RF coil.

[0101] Example 3: Data Acquisition Method, Target Area Identification, and Coverage

[0102] The coverage of the device depends on the spatial distribution of the B0 and B1 fields; therefore, it is necessary to ensure that the target region for a specific indicator is within the coverage area and within the volume of the aperture. Non-uniform B0 and B1 fields hinder the acquisition and localization of NMR signals across the aperture using conventional MRI imaging techniques and pulse sequences. Conventional NMR experiments only detect signals from a small region of the aperture, without providing coverage of the target region.

[0103] To address this issue, a static gradient magnetic resonance imaging (SMR) method was introduced. A non-uniform B0 field is segmented along a gradient into a series of frequency bands with varying magnetic field strengths, thus generating a series of resonant frequencies. Different frequency bands reflect different radial depths within the aperture. The spatial thickness of these frequency bands is determined by the bandwidth of the RF excitation pulse generated by the spectrometer. By setting the excitation frequency to the resonant frequency of each individual band, a series of NMR measurements were performed, yielding signals from each band. Combining the results from different frequency bands increases the coverage across the aperture.

[0104] The RF coil array provides further spatial localization. As described in Example 2 above, each coil has a sensitivity pattern due to the non-uniform B1 field generated by each coil. A series of measurements using the different RF coils in the array allows the signal to be localized to a specified sector of the aperture.

[0105] Spatial localization techniques can be combined with a series of pulse sequences to enable conventional MRI contrasts. This includes T1-weighted, T2-weighted, and diffusion-weighted imaging. Measurements from different coil and frequency band combinations allow for comparison of signal intensity from different locations within a body part, thus providing information about the location and size of potential lesions.

[0106] To simulate the coverage of spatial positioning technology, a coverage study was conducted using simulated B0 magnetic field images of the magnets described in Example 6 below. The B0 field images were segmented into a series of 16 frequency bands, defined by a series of center frequencies (ranging from 4.1 MHz to 4.9 MHz) and an excitation bandwidth for each band (assumed to be 50 kHz). The bandwidth and number of frequency bands were chosen to match the limitations of the spectrometer hardware, which can tune and acquire signals over a limited frequency range. Each simulated acquisition band reflects the volume within the magnetic field excited at a specified B1 frequency and bandwidth, and the overall coverage of the system is obtained by combining the volume of the frequency bands with different excitation frequencies. It is envisioned that in practical applications, the number, frequency, and bandwidth of the acquisition bands will be set based on the limitations of the specified spectrometer and RF acquisition hardware, as well as the specified field strength and gradient generated by the magnet array in each band and the required resolution.

[0107] Because the coverage area and resolution produced by spatial localization techniques differ from those of conventional MRI images, it is important to design the magnet array and RF coil array so that the device's B0 and B1 fields allow coverage of the most important areas of the body part targeted for a specific impairment. While the device can be used for a variety of indications or impairments, ischemic stroke is a particular area of ​​interest, and the inventors conducted research activities to observe ischemic stroke in order to identify target areas. According to the background art, ischemic stroke is caused by blockage of the vascular system; therefore, statistically, due to vascular anatomy, ischemic stroke is more likely to occur in some locations than others (see Bonkhoff et al.). In contrast, some areas may have a lower risk of ischemia. Statistical heatmaps were generated using images from stroke neuroimaging studies (Titan Neuroscience, Australia). Patient images were normalized to the standard MNI space, and stroke lesions were segmented to show the brain regions affected by the stroke. Combining lesions and averaging over all patients yielded a statistical heatmap showing the brain regions most likely to be affected by stroke, such as... Figure 99(a) (shown in the XY plane) and Figure 9 As shown in 9(b) (displayed in the XZ plane), the values ​​in the 3D image correspond to the probability that voxels in the patients in the dataset are affected by stroke.

[0108] The heatmap showed that ischemic stroke was most common in the middle cerebral artery (MCA) region, meaning other lesion types were not well represented in the final heatmap. To address this, a weight was added to clinically significant strokes, artificially increasing the heatmap intensity in stroke-affected areas outside the MCA and proportionally reducing the heatmap intensity in the rest of the brain. This additional weighting produced a second heatmap, which was used for system optimization and design; see [link to heatmap]. Figure 9 The heat in Figure 9 (c) (Displayed in the XY plane) and Figure 9 The heat in Figure 9 (d) (Displayed in the XZ plane).

[0109] The heatmap is thresholded to identify voxels with a significant probability of containing stroke lesions. Voxels above the threshold are combined to define the target region. Although this process allows for the identification and quantification of target regions for ischemic stroke within a pore volume, this method can also be applied to other conditions.

[0110] To evaluate the potential performance of the NMR device, the aforementioned target regions and frequency bands were combined. The acquisition frequency bands were overlaid with the target regions using a matching grid, and the number of voxels in the target regions within the acquisition frequency bands was counted. This generated a geometric coverage score, which can be used to inform the design and optimization of the magnet array.

[0111] As an example of this method, the plane calculated based on the magnet coverage score described in Example 6 is as follows: Figure 10 As shown. Figure 10 Image 10(a) shows the XY plane (z = 0 mm) passing through the center of the magnet array, with its contour lines indicating frequency bands. The planes of the aligned and superimposed target regions from the weighted heatmaps described above are shown... Figure 10 As shown in 10(b) in the image, the entire target area in the slice is within the acquisition frequency band. Figure 10 Images 10(c) and 10(d) show a second XY plane further below the aperture, illustrating the target area and coverage. The result of this process is a coverage score of 88% for the weighted heatmap and the magnet array. The coverage score for the magnet array and the unweighted heatmap is 93%. These coverage scores provide confidence that the B0 field distribution generated by the magnet array has the potential to detect signals from most stroke-prone areas.

[0112] Example 4: Measurement simulation using diffusion-weighted imaging with data from stroke patients.

[0113] One goal of the device is to provide a method for rapid diagnosis of whether a subject has been affected by stroke. To understand the sensitivity of the NMR device to stroke, we simulated the signal acquired by the device in a set of individual MRI images of stroke patients using the Australian TITAN Neuroscience Stroke Imaging Database. Based on real-world stroke data, the results provide guidance for the potential performance of the device.

[0114] The simulation was performed using diffusion-weighted imaging (DWI). DWI contrast imaging is highly sensitive to microstructural changes in ischemic stroke and is commonly used in the clinical diagnosis of stroke. Reduced diffusion during a stroke produces lesions with increased signal intensity in MRI images. The device design selected for this embodiment is described in Example 6 below.

[0115] To simulate the signals acquired by the system and estimate the signal patterns for different injuries, the B0 and B1 field maps are combined to create a series of 3D acquisition bands. Each combination of the coil and the B0 band produces what we call an “acquisition band.” The acquisition bands are then overlaid and aligned with existing 3D MRI imaging data of the individual subject. The total intensity of the MRI image voxels within each acquisition band provides the simulated signal for the measurements within that band. While the simulation focuses on DWI, other signals can be studied, including those known to MRI imaging technicians, such as T2, T2 Flair, DWI, etc. Examples of a series of acquisition bands are shown below. Figure 11 As shown (overlaid on the heatmap described above for anatomical reference), the frequency bands for the left and right hemispheres are displayed in the frequency bands of the left and right column slices, respectively. Furthermore, the two slices below show the acquisition frequency bands corresponding to the left and right posterior coils, which allows for the detection of signals from the indicated brain sectors.

[0116] The study used b=1000 s / μm 2 The process begins with diffusion-weighted images obtained from stroke subjects and including lesions acquired using a standard clinical MRI system. Images are normalized to the standard MNI space and brain volume is extracted. Intracerebral lesions are manually annotated to test intersections with a series of acquisition bands. The bands are then intersected with the brain volume images, and the DWI intensity of voxels within each band is summed. This simulates the device's acquisition of diffusion-weighted signals for each band.

[0117] Analog signals are fed into a simple classifier to identify the degree of ischemia and the specific hemisphere within the brain. By comparing DWI signals from acquisition bands of different hemispheres, hemispheres with ischemic lesions can be identified by higher diffusion-weighted signal strength. Unaffected hemispheres serve essentially as controls. The signal differences between the two hemispheres, based on variations in the volume and diffusion coefficient of the ischemic lesion, can be used to identify ischemia.

[0118] This process was performed on 120 stroke images, and the resulting data is as follows: Figure 12 As shown. Figure 12 It is clearly demonstrated that the difference in DWI signal between the two hemispheres is related to the size of ischemic lesions between the two hemispheres, and that the device and measurement simulation have predictive value for stroke detection and diagnosis.

[0119] Example 5: Signal positioning for image output

[0120] As discussed above in Example 3, the non-uniform B0 and B1 fields generated by the device can be used to localize the NMR signals acquired by the device. It is advantageous to demonstrate this to clinicians in an intuitive way; therefore, the inventors have proposed a method for generating images from NMR signals measured by the device. This method relies on prior knowledge of the B0 and B1 fields designed in Examples 1 and 2. To generate an image in real space, the contribution of the spin at each location in the aperture must be known for each coil and frequency band combination. This is discovered using the simulation methods described in Examples 1 and 2, but can also be measured directly by mapping the field in space with a gaussmeter or by measuring a known calibration sample. To generate the output image, the measured NMR signals from each frequency band of each coil are processed to produce weighted values ​​reflecting the desired signal contrast from each frequency band of each coil. This includes common MRI contrasts such as T1, T2, or diffusion-weighted contrast. The values ​​of the frequency bands are used to set the image intensity of each pixel within the band. The image intensity of overlapping frequency bands is set using a weighted average of the sensitivity maps at each pixel. The resulting image is a projection through the target region, convolved with the shape of the acquisition band to obtain an effective point spread function. Further image post-processing techniques commonly used in conventional MRI can be applied to the image output to alter image contrast.

[0121] Example 6 NMR Equipment Structure

[0122] An example of a device is as follows Figure 1As shown, it contains a magnet array designed using the method described above, comprising an inwardly magnetized ring, an outwardly magnetized ring, and an additional ring in the center. It is stretched 1.1× along the y-axis, and the rings are bent to conform to the plane of the target region. It generates a field of 96 mT to 115 mT in the brain volume. It weighs approximately 30 kg, including a soft steel yoke. It provides sufficient clearance for the 99th percentile largest adult head. It is combined with 12 RF coils in the array, wherein the coils are arranged at equal intervals around the head.

[0123] Each ring is constructed using 18 magnetic blocks, preferably 1.5 Tesla (T) NdFeB-N 42 grade, with each block measuring 35 mm × 35 mm × 50 mm. These blocks are magnetized along a 35 mm axis with a remanent magnetic field of 1.3 T. Source: Shanghai JinMagnet. The yoke plates are machined from 8 mm thick mild steel sheets with a length dimension of 300 mm × 35 mm. Mild steel was chosen because of its high permeability, which concentrates the magnetic field within the array. The magnets and yoke are attached to an aluminum frame using stainless steel fasteners. The RF coil is formed from several turns of enameled copper wire with a diameter of approximately 150 mm. The magnet array is housed within a plastic shell (not shown), with the RF coil located inside the shell, close to the opening and the body part to be measured. The final weight of the magnet array is approximately 32 kg, more preferably less than approximately 25 kg.

[0124] Advantages

[0125] Due to the integrated design of the magnet array, RF coil array, NMR acquisition method, and application, the NMR device offers several advantages over existing technologies. Conventional NMR and MRI systems rely on strong and homogeneous B0 fields > 1.5 T. In contrast, this device does not require a homogeneous field but uses a non-uniform field designed to provide coverage and localization across brain volume. The magnet array used to generate the non-uniform B0 field is significantly simpler and lighter than the magnets used in conventional systems to generate the B0 field. This device is also cheaper because the magnetic field is designed primarily in the target region, requiring less magnetic material in the array.

[0126] The low magnetic field (< 120 mT) generated by this device is less risky and safer to use than the strong magnetic fields (> 1.5 T) used in conventional MRI systems. The lower field exerts less force on nearby ferromagnetic objects. The magnet design with a yoke also reduces stray magnetic fields outside the device. Furthermore, at this field strength, the B1 excitation frequency is lower, resulting in less RF power deposition and heat at the body site.

[0127] Static gradient technology means that additional hardware such as gradient coils and amplifiers used in conventional scanners is also unnecessary. This reduces the power required to operate the system, allowing it to be powered by a portable battery or power outlet. This makes the device significantly smaller, lighter, and more portable.

[0128] Inexpensive, lightweight, quiet, and portable devices enable new applications, such as in ambulances or remote areas. Portable devices for diagnosing stroke, based on specific indications for ischemic stroke, can improve patient outcomes by accelerating the diagnostic process.

[0129] While the apparatus and methods of this disclosure have been described with reference to embodiments included herein, it will be apparent to those skilled in the art that variations may be applied to the features or overall character of the apparatus and / or methods described herein without departing from the concept, spirit, and scope of this disclosure. All such similar alternatives and modifications that are obvious to those skilled in the art are considered to be within the scope and concept of this disclosure as defined by the appended claims.

[0130] References

[0131] Anna K. Bonkhoff, Tianbo Xu, Amy Nelson, Robert Gray, Ashwani Jha,Jorge Cardoso, Sebastien Ourselin, Geraint Rees, Hans Rolf Jäger, ParashkevNachev, Reclassifying stroke lesion anatomy, Cortex, Volume 145, 2021, DJ Griffiths (2007). Introduction to Electrodynamics (3rd ed.).Pearson Education. p. 276. ISBN 978-81-7758-293-2.

Claims

1. A nuclear magnetic resonance (NMR) device suitable for measuring NMR signals in a target area of ​​a body part of a subject, said device comprising: (a) A plurality of magnets arranged in an array, the magnet array being configured to accommodate the body part of the object; The magnet array is configured to generate a first non-uniform magnetic field (B0) with a B0 static field gradient within the body part of the object being examined; wherein the magnet array comprises a plurality of spaced-apart magnet rings, each ring being configured to extend around the body part; (b) A plurality of radio frequency coils arranged in an array and configured, in use, between and around the body part of the object, each coil configured to generate an independent non-uniform magnetic field (B1) substantially perpendicular to the first non-uniform magnetic field (B0), the plurality of radio frequency coils configured to generate a plurality of different radio frequencies and bandwidths across the volume of the body part of the object; and (c) Acquisition device, the acquisition device being used to acquire NMR signal data from different bandwidths within the B0 and B1 gradients, and to process the magnetic resonance signal data to provide spatial localization of the volume across the body part; (d) wherein the magnet array and the radio frequency coil array are configured to ensure that fields B0 and B1 provide substantially full volume coverage of the target area within the body portion of the device.

2. The device of claim 1, wherein the magnet array comprises a plurality of spaced-apart yokes, each yoke supporting at least one pair of spaced-apart magnets, the yokes and magnets being arranged in an array such that the magnets define a ring, the ring defining an aperture within the device.

3. The device of claim 2, wherein the spaced-apart yokes are linear, and each of the yokes supports at least one pair of magnets.

4. The device of claim 2, wherein the spaced-apart magnetic yokes are substantially curved around the magnet array to form the magnet ring.

5. The device according to any one of claims 1 to 4, wherein it has three or more magnet rings.

6. The device according to any one of claims 1 to 5, wherein the radio frequency coil array comprises a plurality of coils configured to extend between and around the body part of the magnet array, the radio frequency coil array being configured to provide spatial information of the volume spanning the target region.

7. The device of claim 6, wherein each radio frequency coil is spin-sensitive within a specific sector of the aperture.

8. The device of claim 6, wherein the radio frequency coil array is configured to provide a transmit-only coil and a plurality of receive-only coils.

9. The device of claim 6, wherein the radio frequency coil array is configured to provide a plurality of radio frequency coils capable of transmitting and receiving.

10. The device of claim 6, wherein the plurality of radio frequency coils are configured to transmit simultaneously.

11. The device of claim 6, wherein the plurality of radio frequency coils are configured to receive simultaneously.

12. The device according to any one of the preceding claims, wherein the cross-section of the hole defined by the magnet ring is substantially elliptical.

13. The device according to any one of the preceding claims, wherein the side profile of each of the magnet rings is non-planar.

14. The device according to any one of the preceding claims, wherein the magnets in the array are irregularly spaced apart.

15. The device according to any one of the preceding claims, wherein the magnet array is configured to provide a first controlled non-uniform magnetic field (BO) having a field strength of about 80 mT to about 120 mT, preferably about 100 mT, within the aperture.

16. The device according to any one of the preceding claims, wherein the magnet array is configured to provide a gradient of a magnetic field B0 of about 15 mT to about 20 mT across the target region.

17. The device of claim 15, wherein the gradient of the magnetic field B0 is primarily in the radial direction across the target region.

18. The device of claim 16, wherein the magnet array is configured to generate a magnetic field contour line B0 that crosses the target region in a substantially straight line.

19. The device according to any one of the preceding claims, wherein the device is portable.

20. The NR device according to any one of the preceding claims, wherein the portable system weighs less than about 30 kg, preferably less than about 25 kg.

21. The device according to any one of the preceding claims, wherein the body part is the head of the object.

22. The device according to any one of the preceding claims, wherein the object is a person.

23. A method for collecting NMR data using the device as described in any one of claims 1 to 22; the method comprising the following steps: (a) A controlled non-uniform magnetic field B0 is applied to the volume of the target region spanning the body parts of the object to generate a series of acquisition frequency bands with different resonant frequencies. (b) In each of a set of acquisition frequency bands that commonly cover the target area of ​​the body part, nuclear spins are excited by generating and emitting radio frequency pulses from one or more radio frequency coils, thereby causing the spins to generate multiple unique radio frequency signals. (c) By using the unique spatial sensitivity of each radio frequency coil, the plurality of unique radio frequency signals emitted by nuclear spins from the acquisition frequency band that together provide spatial information across the target region of the body part are received; and (d) Process the received radio frequency signal to provide data representing the magnetic resonance characteristics of the target region.

24. The method of claim 23, wherein in step (d), the data representing the magnetic resonance characteristics of the target region is further processed into an image.

25. The method of claim 23 or 24, wherein steps (a) to (d) are performed in less than about 20 minutes.

26. The method according to any one of claims 23 to 25, wherein steps (a) to (d) are performed in less than about 15 minutes.

27. The method according to any one of claims 23 to 26, wherein steps (a) to (d) are performed in less than about 10 minutes.

28. The method according to any one of claims 23 to 27, wherein at least a plurality of radio frequency coils are used simultaneously to receive independent signals.

29. The method according to any one of claims 23 to 28, wherein in step (b), the generated radio frequency pulse has an excitation bandwidth of about 40 kHz to about 60 kHz.

30. The method according to any one of claims 23 to 29, wherein in step (a), the generated series of acquisition frequency bands includes at least 5 acquisition frequency bands.

31. The method according to any one of claims 23 to 30, wherein the magnetic resonance characteristic of the target region is diffusion.

32. The method according to any one of claims 23 to 31, wherein the magnetic resonance characteristic of the target region is perfusion.

33. The method according to any one of claims 23 to 32, wherein the magnetic resonance characteristic of the target region is T2.

34. The method according to any one of claims 23 to 33, wherein the body part is the head of the object.

35. The method according to any one of claims 23 to 34, wherein the object is a person.

36. The method according to any one of claims 23 to 35, wherein the object is in an environment far from the hospital.

37. The method of claim 24, wherein the data is processed into an image in real space by combining signals from each coil using a sensitivity map of each coil in real space.

38. The method of claim 24, wherein the image is presented as a projection through the target region.

39. A method for diagnosing brain injury using the device according to any one of claims 1 to 22; the method comprising the following steps: (a) A controlled non-uniform magnetic field B0 is applied across the volume of the object’s head to generate a series of acquisition bands with different resonant frequencies. (b) Within each of a set of acquisition frequency bands that commonly cover the head, nuclear spins are excited by generating and emitting radio frequency pulses from one or more radio frequency coils, thereby causing the spins to generate multiple unique radio frequency signals. (c) By using the unique spatial sensitivity of each radio frequency coil, the plurality of unique radio frequency signals emitted by nuclear spins that together provide spatial information across the head are received; and (d) Process the received radio frequency signals to provide data representing the magnetic resonance characteristics of the target region; and (e) Interpret the data to diagnose the presence or absence of brain injury.

40. The method of claim 39, wherein in step (d), the data representing the magnetic resonance characteristics of the target region is further processed into an image.

41. The method according to claim 39 or 40, wherein steps (a) to (d) are performed in less than about 20 minutes.

42. The method according to any one of claims 39 to 41, wherein steps (a) to (d) are performed in less than about 15 minutes.

43. The method according to any one of claims 39 to 42, wherein steps (a) to (d) are performed in less than about 10 minutes.

44. The method according to any one of claims 39 to 43, wherein at least a plurality of radio frequency coils are used simultaneously to receive independent signals.

45. The method according to any one of claims 39 to 44, wherein in step (b), the generated radio frequency pulse has an excitation bandwidth of about 40 kHz to about 60 kHz.

46. ​​The method according to any one of claims 39 to 45, wherein in step (a), the generated series of acquisition frequency bands includes at least 5 acquisition frequency bands.

47. The method according to any one of claims 39 to 46, wherein the magnetic resonance characteristic of the head is diffusion.

48. The method according to any one of claims 39 to 47, wherein the magnetic resonance characteristic of the head is perfusion.

49. The method according to any one of claims 39 to 48, wherein the magnetic resonance characteristic of the head is T2.

50. The method according to any one of claims 39 to 49, wherein the object is a person.

51. The method according to any one of claims 39 to 50, wherein the object is in an environment far from the hospital.

52. The method according to any one of claims 39 to 51, wherein the brain injury is ischemic stroke.

53. The method according to any one of claims 39 to 52, wherein the brain injury is a hemorrhagic stroke.

54. The method according to any one of claims 39 to 53, wherein the brain injury is neonatal hydrocephalus.

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