Systems and methods for ultra-low magnetic field relaxation dispersion - Patents.com

Abstract

A field cycling magnetic resonance system and a method of operating a field cycling magnetic resonance system are described. According to various embodiments, the disclosed system includes a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, a radio frequency coil, and a field cycling magnet. According to various embodiments, the method includes providing a static magnetic field magnet configured to image a tissue specimen in the given field of view, applying the low static external magnetic field to the given field of view, providing a radio frequency coil configured to generate a cycling radio frequency magnetic field, providing the field cycling magnet, varying the low static external magnetic field in the given field of view, and acquiring an image from the system.

Description

[Technical field]

[0001] Related Applications This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 806,664, filed February 15, 2019, entitled “SYSTEMS AND METHODS FOR ULTRALOW FIELD RELAXATION DISPERSION,” the entire contents of which are incorporated herein by reference for all purposes.

[0002] SUMMARY OF THE DISCLOSURE The embodiments disclosed herein are generally directed to systems and methods for imaging tissue specimens and patients, for example by magnetic resonance imaging (MRI). [Background technology]

[0003] As is well known, the effectiveness of an MRI system can be strongly correlated with the system's ability to produce high quality contrast in an image, thereby better distinguishing between different types of tissue and / or between variations within a single type of tissue. The greater the difference in contrast between different individual voxels, the easier it is for a physician to make a diagnosis. Therefore, there is a well-known desire in the industry to develop systems that can enhance contrast as much as possible. Contrast depends on the relaxation time of the tissue. By extension, since the relaxation times of different tissues change as a function of the magnetic field, the contrast of the image can be better maximized if the MRI system is provided with a varying magnetic field.

[0004] It is also well known that it is generally not feasible to generate field cycled MRI using conventional means. For this reason, various methods are available to facilitate field cycling. One such method of generating distinct magnetic fields is spin locking. Although the majority of MRI systems can spin lock portions of tissue, it is not always practical to do so. Furthermore, current MRI systems generally spin lock excised tissue, rather than in vivo. Spin locking requires that magnetization be affected by a magnetic field that is greater than any offset that the tissue may experience, and as a result, large amounts of energy can be deposited in the tissue. At high magnetic fields, the strength required for spin locking can be greater than Specific Absorption Rate (SAR) standards allow, potentially exposing the human body to extremely large amounts of energy during an MRI scan.

[0005] Another way to generate a circulating magnetic field is to use a peripheral device to vary the static magnetic field in the field of view. This would require, for example, the insertion of an object into the already cramped bore of a conventional MRI scanner. It is notoriously difficult to simply insert an electromagnet, which is often ferromagnetic (a ferromagnetic core can increase the strength of the electromagnet), into an MRI scanner room without destroying the scanner. Conventional MRI scanners generally exert extremely large forces on ferromagnetic materials. Even removing something as small as a steel wrench from the scanner can be difficult and requires turning off the magnetic field, which is an expensive process.

[0006] These shortcomings require the development of MRI systems and methods that maximize contrast in images by effectively cycling the magnetic field using methods such as spin locking or the addition of peripheral devices, which is not currently feasible. Summary of the Invention

[0007] According to various embodiments, a magnetic resonance system is provided. The magnetic resonance system includes a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, and a radio frequency coil configured to apply a pulsed cycling radio frequency magnetic field to the low static external magnetic field. The magnetic resonance system further includes a field cycling magnet disposed proximate to and concentric with the static magnetic field magnet. The field cycling magnet is configured to vary the low static external magnetic field. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0008] According to various embodiments, a magnetic resonance system is provided. The magnetic resonance system includes a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, and a magnetic field cycling magnet disposed proximate to and concentric with the static magnetic field magnet. The magnetic resonance system further includes a radio frequency coil configured to apply a pulsed cycling radio frequency magnetic field to the low static external magnetic field. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0009] According to various embodiments, a magnetic resonance system is provided. The magnetic resonance system includes a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, a radio frequency coil, and a field cycling magnet. The radio frequency coil is configured to apply a pulsed cycling radio frequency magnetic field to the low static external magnetic field. The field cycling magnet is configured to vary the low static external magnetic field within the given field of view. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0010] According to various embodiments, a method of operating a field cycling magnetic resonance system is provided. The method includes providing a static magnetic field magnet configured to image a tissue specimen within a given field of view, applying a low static external magnetic field to the given field of view, providing a radio frequency coil configured to generate a cycling radio frequency magnetic field, applying a pulsed cycling radio frequency magnetic field to the low static external magnetic field, and acquiring an image from the system. The method further includes providing a field cycling magnet and varying the low static external magnetic field within the given field of view. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0011] According to various embodiments, a method of operating a field cycling magnetic resonance system is provided. The method includes providing a static magnetic field magnet configured to image a tissue specimen within a given field of view, applying a low static external magnetic field to the given field of view, providing a field cycling magnet, varying the low static external magnetic field within the given field of view, and acquiring an image from the system. The method further includes providing a radio frequency coil configured to generate a cycling radio frequency magnetic field, and applying a pulsed cycling radio frequency magnetic field to the low static external magnetic field. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0012] According to various embodiments, a method of operating a field cycling magnetic resonance system is provided. The method includes providing a static magnetic field magnet configured to image a tissue specimen within a given field of view, applying a low static external magnetic field to the given field of view, providing a radio frequency coil configured to generate a cycling radio frequency magnetic field, providing a field cycling magnet, varying the low static external magnetic field within the given field of view, and acquiring an image from the system. The method further includes applying a pulsed cycling radio frequency magnetic field to the low static external magnetic field. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0013] These and other aspects and implementations are described in detail below. The above information and the following detailed description, including illustrative examples of the various aspects and implementations, provide an overview or framework for understanding the nature and characteristics of the claimed aspects and implementations. The drawings provide illustration and a further understanding of the various aspects and implementations, and are incorporated in and constitute a part of this specification. [Brief description of the drawings]

[0014] The accompanying drawings are not intended to be drawn to scale. Like reference numbers and designations in the various drawings indicate like elements. For clarity, every component may not be labeled in every drawing.

[0015] [Figure 1] 1 is a plot illustrating relaxation dispersion for various types of tissue, in accordance with various embodiments.

[0016] [Diagram 2] 1 is a plot illustrating relaxation dispersion for various types of tissue, in accordance with various embodiments.

[0017] [Diagram 3] 1 is a plot illustrating relaxation dispersion of molecules with different rotational correlation times in accordance with various embodiments.

[0018] [Figure 4] 1 is a schematic diagram of a field cycling magnetic resonance system, in accordance with various embodiments.

[0019] [Figure 5A-5B] FIG. 5 is a perspective view of an exemplary magnetic field cycling magnetic resonance system 500, in accordance with various embodiments.

[0020] [Figure 6A] 1 is a side view of an exemplary field cycling magnetic resonance system, in accordance with various embodiments.

[0021] [Figure 6B] 6B is a front view of the exemplary magnetic resonance imaging system of FIG. 6A, in accordance with various embodiments.

[0022] [Figure 7] 1 is a flowchart of an exemplary method of operating a field cycling magnetic resonance system in accordance with various embodiments.

[0023] [Figure 8] 5 is another flow chart of an exemplary method of operating a field cycling magnetic resonance system in accordance with various embodiments.

[0024] [Figure 9] 5 is another flow chart of an exemplary method of operating a field cycling magnetic resonance system in accordance with various embodiments.

[0025] It should be understood that the figures are not necessarily drawn to scale, and that objects in the figures are not necessarily drawn to scale in relation to each other. The figures are illustrations intended to bring clarity and understanding to various embodiments of the devices, systems, and methods disclosed herein. Wherever possible, the same reference numbers will be used throughout the figures to refer to the same or similar parts. Additionally, it should be appreciated that the drawings are not intended to limit the scope of the present teachings in any way. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following description of various embodiments is exemplary and explanatory only and should not be construed as limiting or restrictive in any sense. Other embodiments, features, objects, and advantages of the present teachings will become apparent from this description and the accompanying drawings, and from the claims.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which their various embodiments belong.

[0028] All publications mentioned herein are incorporated by reference for the purpose of describing and disclosing the devices, compositions, formulations and methods that are described in the publications and that can be used in connection with the present disclosure.

[0029] As used herein, "comprising," "containing," "having," "including," and variations thereof are not intended to be limiting and are inclusive or open-ended and do not exclude additional, unrecited additives, components, integers, elements, or method steps. For example, a process, method, system, composition, kit, or apparatus that includes a list of features is not necessarily limited to only those features and may include other features not expressly recited or inherent to such process, method, system, composition, kit, or apparatus.

[0030] Nuclear magnetic resonance (NMR) relaxation of the isotope hydrogen 1 is primarily the result of random modulation of dipolar coupling between spins in the object of interest. The rate of relaxation depends on the type of relaxation being measured and the motions that contribute to the relaxation. In magnetic resonance imaging (MRI), the signal is generated primarily by water in the body. The random rotational diffusion that characterizes this water relaxation can vary on the time scale. Free water, such as that found in cerebrospinal fluid, urine, or blood, diffuses rotationally with correlation times on the order of 10 picoseconds, although the exact value varies with the viscosity of the fluid. Not all water in the body is free, and there can in fact be bound water in the human body.

[0031] When water is in contact with a tissue, a certain percentage of the water may interact with the tissue. This interaction may take the form of binding to proteins that make up the tissue. These proteins often have cavities that can accommodate water molecules. These cavities are generally small enough to constrain the motion of the water bound within them. The motion of water within a cavity may be constrained enough to change the overall rotational correlation time of the water molecules within the associated cavity. Thus, the rotational correlation time of bound water approaches the rotational correlation time of the protein to which it is bound.

[0032] This bound water relaxes at a much slower rate than the free water. This bound water also exchanges with free water. The time scale of this exchange is on the order of microseconds. Thus, in any given tissue specimen, there are two populations of water, bound and free, which exchange with each other. As a result, the slowly relaxing free water is constantly mixing with the rapidly relaxing bound water. Since free and bound water are spectrally or spatially indistinguishable, the water measured by the scanner relaxes with an overall relaxation time constant. This relaxation time constant is characterized by the rotational correlation time of the proteins that bind the water and can range from tens to hundreds of nanoseconds.

[0033] Thus, there is a large difference in rotational correlation times between free water, which has a rotational correlation time on the order of tens of picoseconds, and bound water, which has a rotational correlation time of tens of nanoseconds. This difference in correlation time affects the relaxation dispersion of water, and therefore the relaxation dispersion of tissue. To further clarify the effect of relaxation dispersion, Figures 1, 2, and 3 shown below show various measurements of exemplary relaxation dispersion for different tissue types and specimens.

[0034] FIG. 1 is a plot 100 showing the relaxation dispersion of various types of tissues according to various embodiments. The plot 100 shows the relaxation dispersion of various types of tissues as shown in the figure. As seen in FIG. 1, the relaxation time of tissues can change rapidly as a function of the Larmor frequency (the precession frequency of the magnetic moment of the proton or electron around the magnetic field). It can be useful to vary the Larmor frequency so that tissues with similar relaxation times can be distinguished. The variation in relaxation time as a function of the Larmor frequency is known as relaxation dispersion. Measuring the relaxation dispersion of a specimen is a sensitive way to characterize its dynamics and distinguish it from other types of specimens. Furthermore, as FIG. 1 also shows, some tissues can be closely similar to each other at high frequencies (i.e., high magnetic fields) and therefore difficult to distinguish, while those same tissues can be more different at lower frequencies and therefore allow for greater contrast, thus allowing for greater ability to distinguish between tissues with seemingly similar relaxation times.

[0035] Referring now to FIG. 2, FIG. 2 is a plot 200 showing the relaxation dispersion of various types of tissues according to various embodiments. The plot 200 shows the relaxation dispersion of various types of tissues as shown in the figure. However, the plot 200 shows the variation of relaxation time over various magnetic field frequencies by comparing healthy and neoplastic tissues for the same tissue type to discuss this concept in more detail. Referring to FIG. 2, the relaxation times of neoplastic muscle tissue and healthy muscle tissue can be compared, as well as healthy and neoplastic spleen tissue. As is immediately evident, the relaxation of a tissue type may vary depending on its healthiness (healthy or neoplastic), and the differences between them converge at higher frequencies (i.e., higher magnetic fields). Thus, the identification of the difference between healthy and neoplastic tissues can be improved by acquiring magnetic resonance images at lower frequencies or lower magnetic fields.

[0036] 3 is a plot 300 showing the relaxation dispersion of molecules with different rotational correlation times according to various embodiments. Plot 300 shows the relaxation rates at different rotational correlation times as shown. Free water molecules have a short correlation time, whereas bound water has a longer correlation time. This results in both a long relaxation time for free water and a time that is stable across different magnetic fields. On the other hand, the relaxation time for bound water has a sharper dependence on the magnetic field.

[0037] As mentioned above, the effectiveness of an MRI system can be strongly correlated with the system's ability to generate high quality contrast in images, thereby better distinguishing between different types of tissue and / or changes within a single type of tissue. The greater the contrast difference between different individual voxels, the easier it is for a physician to make a diagnosis. The intensity of a voxel in an MRI depends, for example, on the relaxation properties of water in the portion of space associated with that voxel. Voxels with similar relaxation times have similar intensities, depending on the imaging protocol selected. Voxels with different relaxation times contrast with each other. Many variables contribute to making one voxel different in intensity from another voxel. For example, differences in the tissue composition of each voxel are an important contributor to contrast.

[0038] There are many existing methods for measuring relaxation dispersion in specimens and patients. These methods can be broadly divided into two types: static field cycling and effective field cycling, both of which are difficult to implement in conventional MRI scanners.

[0039] Static magnetic field cycling is the most direct way to measure the relaxation dispersion of a specimen or patient. Magnetic field cycling is a technique in magnetic resonance where the magnitude of the external field is changed over part of the scan. Magnetic field cycling is typically performed with electromagnets that can generate a relatively uniform magnetic field over the region of interest, and the magnetic field can be set to a variety of magnitudes. These devices generally have a single magnetic field that is used for signal acquisition, and other possible magnetic fields are reserved for encoding some information onto the signal.

[0040] An exemplary experiment performed with a magnetic field cycling spectrometer can be realized in several steps. First, the external magnetic field is increased to the highest value that the electromagnet can reach and maintain. This is considered the polarizing magnetic field, which increases the nuclear spin polarization of the specimen and therefore increases the signal-to-noise ratio. After the specimen is polarized, the external magnetic field is decreased to a value that brings the relaxation dispersion of the specimen to the desired state. The specimen is then allowed to relax for a sufficient time for the signal magnitudes of different parts of the specimen to diverge according to their different relaxation times. After the specimen is encoded with their relaxation times, the external magnetic field is increased again to whatever frequency the resonant radio frequency coil used with the magnet is tuned to. This process is repeated several times, changing the encoding magnetic field each time, until the entire relaxation dispersion curve has been sampled. However, this method requires powerful electromagnets designed to rapidly increase and decrease the external magnetic field by several hundred milliteslas (mT).

[0041] There are also methods to cycle the magnitude of the magnetic field used for relaxation encoding that do not require changing an external magnetic field. All magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) scanners have tuned radio frequency coils as part of the scanning device. These coils apply a resonant magnetic field to the specimen and change the effective strength and orientation of the magnetic field. For example, a conventional MRI has a static magnetic field equal to 3 Tesla (T) and a radio frequency coil that can generate an oscillating magnetic field on the order of tens of microteslas (μT). However, when the radio frequency coil is turned on and set to generate a magnetic field that oscillates at the specimen's Larmor frequency, the specimen experiences an effective magnetic field equal to the magnitude of the radio frequency field. The static magnetic field is countered by a pulsed radio frequency magnetic field. This can be used to measure some type of relaxation dispersion. The specimen or patient can be allowed to relax with the effective magnetic field generated by the radio frequency coil. The magnitude of the radio frequency magnetic field can be changed to cycle the magnetic field in a manner similar to that of an electromagnet, making it possible to examine the relaxation dispersion of the specimen. In addition to requiring significantly less hardware modification than installing an electromagnet in the scanner, the range of the magnetic field is much more limited. For MRI scanners, the magnetic field ranges from 1 to 1000 µT. NMR spectrometers can reach tens of mT.

[0042] There are several other methods for magnetic field cycling that are sometimes used. Newer NMR spectrometers generally have the ability to move the specimen in and out of the magnet's fringe field. Magnets used in NMR can vary from 7.9T to 23T. Each magnet sold with the scanner is said to be in one field, and is generally converted to the Larmor frequency of the protons. However, the magnetic field produced by superconducting magnets has a strong gradient. This gradient can be called the fringe field, and it changes from the magnet's normal field to the earth's magnetic field as you move away from the magnet's field of view. Some newer spectrometers have the ability to take advantage of this fringe field. The spectrometer moves the specimen out of the field of view and into the fringe field, where it can relax in a much lower field. The specimen is then brought back into the field of view again for detection.

[0043] Another method for magnetic field cycling is to simply perform MRI scans at different magnetic fields using different scanners. Some facilities may have access to 1T, 3T and 7T scanners, which are generally considered the most common magnetic fields. Images of the same part of the body can be acquired with each scanner, and information about relaxation dispersion can be derived therefrom. Since most of the dispersion occurs below 10 MHz, not much dispersion may be identified, but the contrast differences are noticeable. However, this requires significant time and cost to perform multiple scans and to have the financial resources to purchase and maintain multiple scanners at multiple magnetic field strengths.

[0044] As noted above, and as evidenced by some of the known exemplary methods above, it is generally not feasible to generate magnetic field cycling MRI using conventional means. For MRI systems, a potentially effective method of generating distinct magnetic fields is the process of spin locking.

[0045] Spin locking can be produced when the magnetization is held along the same axis as the applied resonant magnetic field. This can be done by applying a radio frequency pulse along the same axis as the magnetization. As a result, this can prevent the transverse magnetization from acquiring phase as long as the spin locking pulse is applied. This also changes the relaxation properties of the spin locked magnetization. The relaxation properties of the magnetization change in two ways, one of which is important for low field systems. The change that is important for relaxation is that the spin locked magnetization relaxes as if it were in a static magnetic field equal in magnitude to the oscillating magnetic field used for spin locking. Since the radio frequency pulses are typically in the microtesla (μT) range and the magnetic fields used for polarization are typically tens of milliteslas (mT) to tens of Tesla, spin locking allows tissue to relax in magnetic fields with much greater contrast than would be accessible otherwise. The relaxation time measured with the spin locking pulse is called T1rho.

[0046] While the majority of MRI systems can spin lock portions of tissue, it is not always practical to do so. Furthermore, current MRI systems may generally be able to effectively spin lock excised tissue, but not in vivo tissue. Spin locking requires that magnetization be affected by a magnetic field that is greater than any offset that the tissue may experience. At high magnetic fields, the strength required for spin locking can be greater than Specific Absorption Rate (SAR) standards allow, potentially exposing the body to extremely large amounts of energy during an MRI scan. The higher the external magnetic field, the more energy is deposited by the radio frequency coil. Scaling of SAR is shown below:

number

[0047] Again, as noted above, and as evidenced by some of the known exemplary methods above, it is generally not feasible to generate magnetic field cycling MRIs using conventional means. In the case of MRI systems, another potentially effective method of generating distinct magnetic fields is to provide an insert (or peripheral device) in the bore of the MRI scanner, for example the opening in a whole-body MRI scanner that houses the patient during the scanning process, or the opening in a portable or point-of-care scanner that houses a particular body part.

[0048] Applicant has found that by providing a specific MRI (or spectrometer) design (e.g., single-sided MRI design) for a low-field MRI scanner to facilitate magnetic field circulation, image contrast can be improved by effective spin locking. Thus, spin locking can be performed without exposing the body to large amounts of energy associated with such spin locking methods in standard MRI machines, the amount of energy of which can often exceed the SAR criteria as described above. Applicant has further found that by providing a specific MRI (or spectrometer) design (e.g., single-sided MRI design) for a low-field MRI scanner, inserts or peripheral devices can be effectively added within the bore at a close enough distance to also assist in magnetic field circulation and improve image contrast.

[0049] FIG. 4 is a schematic diagram of a magnetic field cycling magnetic resonance system 400 according to various embodiments. According to various embodiments, the system 400 is a single-sided magnetic resonance imaging system. According to various embodiments, the system 400 may include a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer. As shown in FIG. 4, the system 400 includes a static magnetic field magnet 420. According to various embodiments, the static magnetic field magnet 420 may be configured to image a tissue specimen within a given field of view. According to various embodiments, the tissue specimen may be any anatomical part of the subject. According to various embodiments, the static magnetic field magnet 420 may include multiple cylindrical permanent magnets in a side-by-side configuration. According to various embodiments, the static magnetic field magnet 420 may include a bore at its center. According to various embodiments, the static magnetic field magnet 420 may not include a bore. According to various embodiments, the bore may have a diameter of 1 inch to 20 inches. According to various embodiments, the bore may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, a given field of view may be spherical or cylindrical. According to various embodiments, a spherical field of view may have a diameter of 2 inches to 20 inches. According to various embodiments, a spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, a cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, a cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0050] As shown in FIG. 4, the system 400 may include a radio frequency coil 440. According to various embodiments, the radio frequency coil 440 may be configured to generate a circulating radio frequency magnetic field. According to various embodiments, the radio frequency coil 440 may be used for spin locking. According to various embodiments, the radio frequency coil 440 may be configured to apply a pulsed circulating radio frequency magnetic field to a low static external magnetic field. According to various embodiments, the circulating radio frequency magnetic field may range from 1 μT to 1 mT. According to various embodiments, the circulating radio frequency magnetic field may range from 100 μT to 900 μT.

[0051] As shown in FIG. 4, the system 400 may include a magnetic field cycling magnet 460. According to various embodiments, the magnetic field cycling magnet 460 may be positioned in proximity to a low static external magnetic field. According to various embodiments, the magnetic field cycling magnet 460 may be positioned in proximity to the static magnetic field magnet 420. For example, the magnetic field cycling magnet 460 may be positioned in front of, behind, or in the middle of the static magnetic field magnet 420. According to various embodiments, the magnetic field cycling magnet 460 may be concentric with the static magnetic field magnet 420. According to various embodiments, the magnetic field cycling magnet 460 may be an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet 460 may be a solenoid coil configured to generate a magnetic field that adds to or subtracts from the magnetic field generated by the static magnetic field magnet, allowing for relaxation encoding in different magnetic fields.

[0052] According to various embodiments, the magnetic field cycling magnet 460 may include an opening in the center of the magnet. According to various embodiments, the magnetic field cycling magnet 460 may be a donut-shaped ring, a cylindrical ring, or an egg-shaped ring. According to various embodiments, the magnetic field cycling magnet 460 may include a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed. According to various embodiments, the magnetic field cycling magnet 460 may have a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the magnetic field cycling magnet 460 may have a magnetic field strength of 5 mT to 195 mT.

[0053] 5A and 5B are perspective views of an exemplary magnetic field cycling magnetic resonance system 500, according to various embodiments. According to various embodiments, the system 500 can be any MRI system, including, for example, a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer as disclosed herein.

[0054] As shown in FIGS. 5A and 5B, the system 500 includes a housing 510 that can house various components, including but not limited to, magnets, electromagnets, coils, for generating a radio frequency magnetic field, and various electronic components, for example, but not limited to, for controlling, powering, and / or monitoring the system 500. According to various embodiments, the housing 510 can house, for example, the static magnetic field magnet 420, the radio frequency coil 440, and / or the magnetic field cycling magnet 460 within the housing 510. According to various embodiments, the system 500 also includes a bore 520 at the center of its magnetic components, such as, for example, the static magnetic field magnet 420, the radio frequency coil 440, and / or the magnetic field cycling magnet 460. According to various embodiments, the magnetic field cycling magnet 460 can be inserted within the bore 520. According to various embodiments, the magnetic field cycling magnet 460 can be positioned proximate to the bore 520. For example, the magnetic field cycling magnet 460 can be positioned in front of, behind, or in the center of the bore 520. According to various embodiments, the field cycling magnet 460 may be located proximate to the bore 520 or at the entrance to the bore 520. According to various embodiments, the bore 520 may have a diameter between 1 inch and 20 inches. According to various embodiments, the bore 520 may have a diameter between 1 inch and 4 inches, between 4 inches and 8 inches, and between 10 inches and 20 inches. According to various embodiments, the system 500 may not include a bore.

[0055] According to various embodiments, the system 500 may be configured to image a tissue specimen within a given field of view 530, as shown in FIG. 5B. According to various embodiments, the given field of view 530 is a three-dimensional (3D) volumetric space in which a tissue specimen, including but not limited to any anatomical part of a person, is to be examined, evaluated, and / or imaged. According to various embodiments, the given field of view 530 may be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view may have a diameter of 2 inches to 20 inches. According to various embodiments, the spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, the cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, magnetic components, such as, for example, static magnetic field magnet 420, radio frequency coil 440, and / or magnetic field circulating magnet 460, are configured to generate and / or enhance during inspection, evaluation, and / or imaging in a given field of view 530.

[0056] 5B, a given field of view 530 resides near a surface 515 that is proximate to or in front of a bore 520 of the system 500. According to various embodiments, the surface 515 may be curved, flat, concave, convex, or otherwise curved.

[0057] 6A is a side view of an exemplary magnetic field cycling magnetic resonance system 600, according to various embodiments. FIG. 6B is a front view of the exemplary magnetic field cycling magnetic resonance system 600. According to various embodiments, the system 600 can be any MRI system, including, for example, a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer as disclosed herein.

[0058] As shown in Figures 6A and 6B, the system 600 includes a housing 610 that can house various components including, but not limited to, magnets, electromagnets, coils for generating a radio frequency magnetic field, and various electronic components for, but not limited to, controlling, powering, and / or monitoring the system 600. According to various embodiments, the housing 610 can house, for example, the static magnetic field magnet 420 and / or the radio frequency coil 440 therein. According to various embodiments, the system 600 also includes a bore 620 at its center. As shown in Figures 6A and 6B, the housing 610 also includes a front 612, a rear 614, and a surface 615 of the system 600. According to various embodiments, the surface 615 is curved, flat, concave, convex, or otherwise curved.

[0059] According to various embodiments, the system 600 may be configured to image a tissue specimen within a given field of view 630 as shown in FIG. 6B. According to various embodiments, the given field of view 630 is a three-dimensional (3D) volumetric space in which a tissue specimen, including but not limited to any anatomical part of a person, is being examined, evaluated, and / or imaged. According to various embodiments, the given field of view 630 may be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view may have a diameter of 2 inches to 20 inches. According to various embodiments, the spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, the cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0060] As shown in Figures 6A and 6B, the system 600 includes a field cycling magnet 660 disposed near the surface 615 on the front 612 of the system 600. According to various embodiments, the field cycling magnet 660 is disposed proximate to the center of the surface 615 on the front 612 of the system 600. According to various embodiments, the field cycling magnet 660 can be an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet that includes a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field. According to various embodiments, the field cycling magnet 660 can be a solenoid coil configured to generate a magnetic field that adds or subtracts from the magnetic field generated by the static magnetic field magnet, allowing for relaxation encoding at different magnetic fields.

[0061] As shown in FIG. 6B, the given field of view 630 is at the center of the surface 615 at the front 612 of the system 600. According to various embodiments, the magnetic field cycling magnet 660 is disposed within the given field of view 630. According to various embodiments, the magnetic field cycling magnet 660 is disposed concentrically with the given field of view 630. According to various embodiments, the magnetic field cycling magnet 660 may be inserted into the bore 620. According to various embodiments, the magnetic field cycling magnet 660 may be disposed proximate to the bore 620. For example, the magnetic field cycling magnet 660 may be disposed in front of, behind, or in the middle of the bore 620. According to various embodiments, the magnetic field cycling magnet 660 may be disposed proximate to the bore 620 or at the entrance of the bore 620.

[0062] As shown in Figure 6A, system 600 also includes a rack 680 for housing various ancillary components such as, for example, a computer configured to control system 600, one or more power supplies, data acquisition equipment, etc. As shown in Figure 6A, system 600 also includes a conduit 685 for connecting various components in housing 610 to the various components housed in rack 680. As shown in Figure 6A, field cycling magnet 660 is connected to conduit 685 via connection 665. According to various embodiments, connection 665 can be any suitable power cable that is shielded from the magnet.

[0063] According to various embodiments, a magnetic resonance system (also referred to herein as a field cycling magnetic resonance system) is provided that includes a static magnetic field magnet (e.g., static magnetic field magnet 420) configured to provide a low static external magnetic field. The magnetic field can vary for a given field of view from about 50 mT to about 60 mT, from about 45 mT to about 65 mT, from about 40 mT to about 70 mT, from about 35 mT to about 75 mT, from about 30 mT to about 80 mT, from about 25 mT to about 85 mT, from about 20 mT to about 90 mT, from about 15 mT to about 95 mT, and from about 10 mT to about 100 mT. The magnetic field may vary from about 10 mT to about 15 mT, from about 15 mT to about 20 mT, from about 20 mT to about 25 mT, from about 25 mT to about 30 mT, from about 30 mT to about 35 mT, from about 35 mT to about 40 mT, from about 40 mT to about 45 mT, from about 45 mT to about 50 mT, from about 50 mT to about 55 mT, from about 55 mT to about 60 mT, from about 60 mT to about 65 mT, from about 65 mT to about 70 mT, from about 70 mT to about 75 mT, from about 75 mT to about 80 mT, from about 80 mT to about 85 mT, from about 85 mT to about 90 mT, from about 90 mT to about 95 mT, and from about 95 mT to about 100 mT. According to various embodiments, the magnetic field may vary from about 10 mT to about 1 T, about 15 mT to about 900 mT, about 20 mT to about 800 mT, about 25 mT to about 700 mT, about 30 mT to about 600 mT, about 35 mT to about 500 mT, about 40 mT to about 400 mT, about 45 mT to about 300 mT, about 50 mT to about 200 mT, about 50 mT to about 100 mT, about 45 mT to about 100 mT, about 40 mT to about 100 mT, about 35 mT to about 100 mT, about 30 mT to about 100 mT, about 25 mT to about 100 mT, about 20 mT to about 100 mT, and about 15 mT to about 100 mT.

[0064] According to various embodiments, the magnetic resonance system is an MRI scanner or a spectrometer.

[0065] According to various embodiments, the field of view is spherical or cylindrical. According to various embodiments, the field of view is approximately 4 inches in diameter and / or 4 inches in length. The field of view can vary in diameter and length from about 10 to about 11 inches, from about 9 to about 12 inches, from about 8 to about 13 inches, from about 7 to about 14 inches, from about 6 to about 15 inches, from about 5 to about 16 inches, from about 4 to about 17 inches, from about 3 to about 18 inches, from about 2 to about 19 inches, from about 1 to about 20 inches, from about 1 to about 30 inches, and from about 1 to about 40 inches. The field of view may vary in diameter and length from about 1 to about 2 inches, from about 2 to about 3 inches, from about 3 to about 4 inches, from about 4 to about 5 inches, from about 5 to about 6 inches, from about 6 to about 7 inches, from about 7 to about 8 inches, from about 8 to about 9 inches, from about 9 to about 10 inches, from about 10 to about 11 inches, from about 11 to about 12 inches, from about 12 to about 13 inches, from about 13 to about 14 inches, from about 14 to about 15 inches, from about 15 to about 16 inches, from about 16 to about 17 inches, from about 17 to about 18 inches, from about 18 to about 19 inches, from about 19 to about 20 inches, from about 3 to about 5 inches, from about 2 to about 6 inches, from about 1 to about 7 inches, from about 1 to about 5 inches, and from about 1 to about 4 inches.

[0066] According to various embodiments, the system is configured to apply magnetic field cycling to the low static external magnetic field emitted by the magnet. According to various embodiments, the system is configured to provide magnetic field cycling to the low static external magnetic field provided by the magnet by applying a spin locking magnetic field, which spin locks the magnetization emitted by the magnet using radio frequency pulses. According to various embodiments, the system is configured to provide magnetic field cycling to the low static external magnetic field emitted by the magnet by further including a peripheral device (e.g., a magnetic field cycling magnet) for varying the static magnetic field within a given field of view. The spin locking can be performed when the peripheral device is inactive. According to various embodiments, the applied low magnetic field is substantially below the SAR criteria. According to various embodiments, the system is a single-sided MRI system.

[0067] According to various embodiments, while the above describes a magnetic resonance system configured to cycle, e.g., an external magnetic field, e.g., by adding an insert (e.g., a peripheral device such as a field cycling magnet as described herein) to a magnet (e.g., a static magnetic field magnet), the present disclosure also contemplates a method of imaging tissue in a field of view. The method may include, e.g., providing a magnetic resonance system with a magnet, providing a tissue specimen in the field of view, applying a low static external magnetic field to a given field of view, cycling the low static external magnetic field, and acquiring an image from the system. The cycling may further include applying a spin locking magnetic field and / or adding an insert or peripheral device to the magnet. Spin locking may be performed by continuously applying a magnetic field resonant with the Larmor frequency of the desired slice after excitation. If the spin locking magnetic field is collinear with the magnetization, the magnetization is spin locked. This requires only a transmission coil.

[0068] The low field spin locking provided by the system, where the magnitude and duration of the magnetic field is not limited by SAR due to the low level of the external field, allows the magnetic resonance system to perform relaxation dispersion experiments on tissue without cycling the external field. The external field may be static, but the strength of the spin locking field may vary. The system may apply a spin locking field in the range of about 450 μT to about 550 μT, about 400 μT to about 600 μT, about 350 μT to about 650 μT, about 300 μT to about 700 μT, about 250 μT to about 750 μT, about 200 μT to about 800 μT, about 150 μT to about 850 μT, about 100 μT to about 900 μT, about 50 μT to about 950 μT, about 10 μT to about 990 μT, and about 1 μT to about 1 mT. The range of the spin locking magnetic field is from about 1 μT to about 50 μT, from about 50 μT to about 100 μT, from about 100 μT to about 150 μT, from about 150 μT to about 200 μT, from about 200 μT to about 250 μT, from about 250 μT to about 300 μT, from about 300 μT to about 350 μT, from about 350 μT to about 400 μT, from about 450 μT to about 500 μT, from about 500 μT to about 600 μT, from about 600 μT to about 700 μT, from about 700 μT to about 800 μT, from about 800 μT to about 900 μT, from about 900 μT to about 1000 μT, from about 1000 μT to about 1100 μT, from about 1100 μT to about 1200 μT, from about 1200 μT to about 1300 μT, from about 1300 μT to about 1400 μT, from about 1400 μT to about 1500 μT, from about 1500 μT to about 2000 μT, from about 1500 μT to about 2500 μT, from about 1500 μT to about 2000 μT, from about 1500 μT to about 2500 μT, from about 1500 μT to about 3000 μT, from about 1500 μT to about 3 ...400 μT, from The spin locking magnetic field may range from about 0.5 μT to about 1 mT, about 550 μT to about 600 μT, about 600 μT to about 650 μT, about 650 μT to about 700 μT, about 700 μT to about 750 μT, about 750 μT to about 800 μT, about 800 μT to about 850 μT, about 850 μT to about 900 μT, about 900 μT to about 950 μT, and about 950 μT to about 1 mT. According to various embodiments, the system may apply a spin locking magnetic field of from about 0.5 μT to about 1 mT.

[0069] The spin locking technique allows the contrast of the image to be varied by varying the strength of the spin locking field. By performing multiple spin locking experiments, the rotational correlation time can be extracted by fitting the collected relaxation times to a simple model. This allows deeper insight into the tissue to be gained by studying the tissue under many different conditions. Changes to the tissue, such as increased cellularity associated with cancer, can be visualized by changing the relaxation dynamics of the system without major hardware modifications. Using spin locking relaxation dispersion, a distribution of multiple relaxation times is available to the radiologist, rather than just a binary time value T1 and a time value T2.

[0070] Besides those disclosed above, spin locking at lower magnetic fields has many advantages. For example, at high magnetic fields, there are at least two major contributions to the relaxation during spin locking: relaxation due to dipolar coupling and relaxation due to chemical exchange. The contribution of chemical exchange increases with the square of the external magnetic field. The stronger the magnetic field, the more the chemical exchange contribution dominates the T1rho relaxation (the relaxation time measured with the spin locking pulse). At lower magnetic fields, the chemical exchange contribution to the T1rho relaxation disappears. As a result, if one is interested in using spin locking to collect dipolar relaxation dispersion, doing so at high magnetic fields becomes difficult because the dispersion mixes with the chemical exchange contribution to the relaxation. Using spin locking to sample lower magnetic fields at high static magnetic fields also becomes extremely difficult because the contribution from chemical exchange also scales with the magnitude of the spin locking field.

[0071] According to various embodiments, the magnetic resonance system may further include or be configured to accommodate an insert or peripheral device. According to various embodiments, the insert or peripheral device is an electromagnet. The electromagnet may be, for example, air-core, ferromagnetic core, or dielectric core. As described above, for example, due to the low static magnetic field, the feasibility of changing the static magnetic field of the system with an electromagnet is much higher. Unlike the superconducting magnets used for conventional MRI, the systems herein have a much weaker permanent magnetic field. Bringing the hardware required for a strong electromagnet, i.e., hardware that may have ferromagnetic components, closer to the systems herein is significantly safer than bringing a similar device closer to a superconducting magnet. Furthermore, as described above and shown, for example, in Figures 4, 5A, 5B, 6A, and 6C, the field of view can be provided at the surface of the magnet rather than in the bore, making access much easier. A similar device (insert or peripheral device) would need to be inserted into the bore of a conventional MRI, which is already tight and may often be occupied by the patient. Thus, incorporating an electromagnet into the system allows for changing the static magnetic field. Electromagnets can reduce the static magnetic field in a field of view where tissues relax at the field where the relaxation times of different tissues differ most significantly, allowing in some circumstances a greater range of fields than spin locking.

[0072] Regarding the range of magnetic fields accessible with a field cycling magnet (e.g., field cycling magnet 420), assuming that the field cycling magnet is designed to reduce or increase the static magnetic field, according to various embodiments, the range of magnetic fields accessible with the field cycling magnet is from about 95 mT to about 105 mT, from about 90 mT to about 110 mT, from about 85 mT to about 115 mT, from about 80 mT to about 120 mT, from about 75 mT to about 125 mT, from about 70 mT to about 130 mT, from about 65 mT to about 135 mT, from about 60 mT to about 140 mT, from about 55 mT to about 145 mT, from about 50 mT to about 5 ... It can be from 0 mT to about 150 mT, from about 45 mT to about 155 mT, from about 40 mT to about 160 mT, from about 35 mT to about 165 mT, from about 30 mT to about 170 mT, from about 25 mT to about 175 mT, from about 20 mT to about 180 mT, from about 15 mT to about 185 mT, from about 10 mT to about 190 mT, from about 5 mT to about 195 mT, and from about 0.5 mT to about 200 mT. The range of magnetic fields accessible with a field cycling magnet, assuming the field cycling magnet is designed to reduce or increase the static magnetic field, may be from about 0.5 mT to about 10 mT, from about 10 mT to about 20 mT, from about 20 mT to about 30 mT, from about 30 mT to about 40 mT, from about 40 mT to about 50 mT, from about 50 mT to about 60 mT, from about 60 mT to about 70 mT, from about 70 mT to about 80 mT, from about 80 mT to about 90 mT, It can also be from about 90 mT to about 100 mT, from about 100 mT to about 110 mT, from about 110 mT to about 120 mT, from about 120 mT to about 130 mT, from about 130 mT to about 140 mT, from about 140 mT to about 150 mT, from about 150 mT to about 160 mT, from about 160 mT to about 170 mT, from about 170 mT to about 180 mT, from about 180 mT to about 190 mT, and from about 190 mT to about 200 mT.According to various embodiments, the range of magnetic fields accessible with the field cycling magnets, assuming that the field cycling magnets are designed to reduce or increase the static magnetic field, can be from about 0.5 mT to about 1 T, from about 5 mT to about 900 mT, from about 10 mT to about 800 mT, from about 20 mT to about 700 mT, from about 30 mT to about 600 mT, from about 35 mT to about 500 mT, from about 40 mT to about 400 mT, from about It can be from 45 mT to about 300 mT, from about 50 mT to about 200 mT, from about 50 mT to about 100 mT, from about 40 mT to about 200 mT, from about 40 mT to about 100 mT, from about 30 mT to about 200 mT, from about 30 mT to about 100 mT, from about 20 mT to about 200 mT, from about 20 mT to about 100 mT, from about 10 mT to about 200 mT, and from about 10 mT to about 100 mT.

[0073] According to various embodiments, the field cycling magnet does not generate a uniform magnetic field. No image encoding takes place while the field cycling magnet is turned on. The field cycling magnet shifts the external field slowly enough to satisfy the adiabatic condition. According to some embodiments, the magnetic resonance system may be configured to provide field cycling to the low static external magnetic field provided by the magnet, both by application of the spin locking magnetic field and by retraction of the insert or peripheral device. According to some embodiments, the magnetic resonance system may be configured to provide field cycling to the low static external magnetic field provided by the magnet, either by application of the spin locking magnetic field or by retraction of the insert or peripheral device.

[0074] According to various embodiments, the magnetic field cycling magnet can be a donut-shaped ring, a cylindrical ring, an egg-shaped ring, or any other suitable shape or form with an opening in the magnet. According to various embodiments, the magnetic field cycling magnet can include a set of magnets, which are arranged in the form of a ring, or any other suitable shape or form around the circumference. According to various embodiments, the magnetic field cycling magnet is placed in close proximity to the magnet, for example in front of, behind, or in the middle of the magnet. According to various embodiments, the magnetic field cycling magnet is concentric with the magnet. The magnetic field cycling magnet may be placed around the patient.

[0075] Possible applications of MRI scanners capable of field cycling include, for example, multimodal imaging. Conventional MRI scanners have a small number of contrast types available. In general, the contrast types include T1, T2, T1rho (under special circumstances), and diffusion. Field cycling MRI scanners allow a range of T1 and T1rho contrasts to be available. If contrast is not visible at one field, the user may change the field and try again. Another application of this technique is, for example, allowing the user to collect a form of contrast dispersion image. The contrast dispersion image may be an image repeatedly collected at different relaxation encoding fields. Tissues may be characterized by how their contrast varies as a function of the magnetic field. The analyzed image may then be one in which the value of each voxel is extracted from a fit of the amplitude variation as a function of magnetic field strength. The value of this fit may roughly correspond to the rotational correlation time of the water in that pixel. A series of images is generated using nonlinear reconstruction, one for each magnetic field strength used for relaxation encoding. The values ​​of each pixel in these images are fitted with a simple model that describes the relaxation as a function of the external magnetic field, similar to the model used to describe the paramagnetic enhancement of relaxation. This can be done by using a model in which each pixel in the image is assumed to have two exchanging pools of water. One pool is free water, which relaxes slowly, and the other is bound water, which relaxes rapidly. These two pools mix with a characteristic exchange rate. The parameters that describe the relaxation using this simple model, namely the rotational correlation times of the free and bound water and the exchange rates between them, are found by fitting the data to the model.

number

[0076] FIG. 7 is a flow chart of an exemplary method S100 of operating a field cycling magnetic resonance system (e.g., system 400, 500, or 600) according to various embodiments. According to various embodiments, the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer. As shown in FIG. 7, the method S100 includes, at step S110, providing a static magnetic field magnet configured to image a tissue specimen within a given field of view. According to various embodiments, the tissue specimen can be any anatomical portion of an examined subject. According to various embodiments, the static magnetic field magnet can include multiple cylindrical permanent magnets in a side-by-side configuration. According to various embodiments, the static magnetic field magnet includes a bore at its center. According to various embodiments, the bore can have a diameter of 1 inch to 20 inches. According to various embodiments, the bore can have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the given field of view can be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view may be 2 inches to 20 inches in diameter. According to various embodiments, the spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, the cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0077] 7, the method S100 includes, in step S120, applying a low static external magnetic field to a given field of view. According to various embodiments, the low static external magnetic field can range from 10 mT to 1 T. According to various embodiments, the low static external magnetic field can range from 20 mT to 100 mT. According to various embodiments, the low static external magnetic field can range from 35 mT to 75 mT.

[0078] In step S130, method S100 includes providing a radio frequency coil configured to generate a circulating radio frequency magnetic field. According to various embodiments, the radio frequency coil is used for spin locking at low magnetic field strengths.

[0079] In step S140, the method S100 includes applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field. According to various embodiments, the circulating radio frequency magnetic field can range from 1 μT to 1 mT. According to various embodiments, the circulating radio frequency magnetic field can range from 100 μT to 900 μT.

[0080] In step S150, the method S100 optionally includes providing a magnetic field cycling magnet. According to various embodiments, the magnetic field cycling magnet can be located in proximity to the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can be located in proximity to the static magnetic field magnet, for example, in front of, behind, or in the middle of the static magnetic field magnet, and is concentric with the static magnetic field magnet. According to various embodiments, the magnetic field cycling magnet can be an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can include an opening in the center of the magnet. According to various embodiments, the magnetic field cycling magnet can be a donut-shaped ring, a cylindrical ring, or an egg-shaped ring. According to various embodiments, the magnetic field cycling magnet can include a plurality of magnets, the plurality of magnets being arranged in a ring configuration, or any other suitable shape or configuration with the plurality of magnets formed around it. According to various embodiments, the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the field cycling magnet has a field strength between 5 mT and 195 mT.

[0081] In step S160, method S100 optionally includes varying the low static external magnetic field within the given field of view. According to various embodiments, varying the low static external magnetic field may include at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0082] In step S170, the method S100 includes acquiring an image from the magnetic resonance system. According to various embodiments, the radio frequency coil and the field cycling magnet are switched before the start of image acquisition to encode the desired contrast.

[0083] FIG. 8 is a flow chart of an exemplary method S200 of operating a field cycling magnetic resonance system (e.g., system 400, 500, or 600) according to various embodiments. According to various embodiments, the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer. As shown in FIG. 8, the method S200 includes, at step S210, providing a static magnetic field magnet configured to image a tissue specimen within a given field of view. According to various embodiments, the tissue specimen can be any anatomical part of the person being examined. According to various embodiments, the static magnetic field magnet can include multiple cylindrical permanent magnets in a side-by-side configuration. According to various embodiments, the static magnetic field magnet includes a bore at its center. According to various embodiments, the bore can have a diameter of 1 inch to 20 inches. According to various embodiments, the bore can have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the given field of view can be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view may be 2 inches to 20 inches in diameter. According to various embodiments, the spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, the cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0084] 8, the method S200 includes, in step S220, applying a low static external magnetic field to a given field of view. According to various embodiments, the low static external magnetic field can range from 10 mT to 1 T. According to various embodiments, the low static external magnetic field can range from 20 mT to 100 mT. According to various embodiments, the low static external magnetic field can range from 35 mT to 75 mT.

[0085] In step S230, the method S200 includes providing a magnetic field cycling magnet. According to various embodiments, the magnetic field cycling magnet can be located in proximity to the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can be located in proximity to the static magnetic field magnet, for example, in front of, behind, or in the middle of the static magnetic field magnet, and is concentric with the static magnetic field magnet. According to various embodiments, the magnetic field cycling magnet can be an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can include an opening in the center of the magnet. According to various embodiments, the magnetic field cycling magnet can be a donut-shaped ring, a cylindrical ring, or an egg-shaped ring. According to various embodiments, the magnetic field cycling magnet can include a plurality of magnets, the plurality of magnets being arranged in a ring configuration, or any other suitable shape or configuration with the plurality of magnets formed around it. According to various embodiments, the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the field cycling magnet has a field strength between 5 mT and 195 mT.

[0086] In step S240, the method S200 includes varying the low static external magnetic field within the given field of view. According to various embodiments, varying the low static external magnetic field may include at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0087] In step S250, method S200 optionally includes providing a radio frequency coil configured to generate a circulating radio frequency magnetic field. According to various embodiments, the radio frequency coil is used for spin locking at low magnetic field strengths.

[0088] In step S260, the method S200 optionally includes applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field. According to various embodiments, the circulating radio frequency magnetic field can range from 1 μT to 1 mT. According to various embodiments, the circulating radio frequency magnetic field can range from 100 μT to 900 μT.

[0089] In step S270, the method S200 includes acquiring an image from the magnetic resonance system.

[0090] FIG. 9 is a flow chart of an exemplary method S300 of operating a field cycling magnetic resonance system (e.g., system 400, 500, or 600) according to various embodiments. According to various embodiments, the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer. As shown in FIG. 9, the method S300 includes, at step S310, providing a static magnetic field magnet configured to image a tissue specimen within a given field of view. According to various embodiments, the tissue specimen can be any anatomical part of the person being examined. According to various embodiments, the static magnetic field magnet can include multiple cylindrical permanent magnets in a side-by-side configuration. According to various embodiments, the static magnetic field magnet includes a bore at its center. According to various embodiments, the bore can have a diameter of 1 inch to 20 inches. According to various embodiments, the bore can have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the given field of view can be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view may be 2 inches to 20 inches in diameter. According to various embodiments, the spherical field of view may have a diameter of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, the cylindrical field of view is approximately 2 inches to 20 inches in length. According to various embodiments, the cylindrical field of view may have a length of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0091] 9, the method S300 includes, at step S320, applying a low static external magnetic field to a given field of view. According to various embodiments, the low static magnetic field can range from 10 mT to 1 T. According to various embodiments, the low static magnetic field can range from 20 mT to 100 mT. According to various embodiments, the low static magnetic field can range from 35 mT to 75 mT.

[0092] In step S330, the method S300 includes providing a radio frequency coil configured to generate a circulating radio frequency magnetic field. According to various embodiments, the radio frequency coil is used for spin locking at low magnetic field strengths.

[0093] In step S340, the method S200 includes providing a magnetic field cycling magnet. According to various embodiments, the magnetic field cycling magnet can be placed in proximity to the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can be placed in proximity to the static magnetic field magnet, for example, in front of, behind, or in the middle of the static magnetic field magnet, and is concentric with the static magnetic field magnet. According to various embodiments, the magnetic field cycling magnet can be an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field. According to various embodiments, the magnetic field cycling magnet can include an opening in the center of the magnet. According to various embodiments, the magnetic field cycling magnet can be a donut-shaped ring, a cylindrical ring, or an egg-shaped ring. According to various embodiments, the magnetic field cycling magnet can include a plurality of magnets, the plurality of magnets being arranged in a ring configuration, or any other suitable shape or configuration with the plurality of magnets formed around it. According to various embodiments, the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the field cycling magnet has a field strength between 5 mT and 195 mT.

[0094] In step S350, the method S300 includes varying the low static external magnetic field within the given field of view. According to various embodiments, varying the low static external magnetic field may include at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0095] In step S360, the method S300 optionally includes applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field. According to various embodiments, the circulating radio frequency magnetic field can range from 1 μT to 1 mT. According to various embodiments, the circulating radio frequency magnetic field can range from 100 μT to 900 μT.

[0096] In step S370, the method S300 includes acquiring an image from the magnetic resonance system.

[0097] Enumeration of embodiments 1. A magnetic resonance system comprising: a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view; and a radio frequency coil configured to apply a pulsed circulating radio frequency magnetic field to the low static external magnetic field.

[0098] 2. The system of embodiment 1, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0099] 3. The system of any of embodiments 1-2, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0100] 4. The system of any of embodiments 1-3, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between approximately 2 inches and 20 inches in length.

[0101] 5. The system of any of embodiments 1 to 4, further comprising a magnetic field circulating magnet positioned adjacent to and concentric with the static magnetic field magnet.

[0102] 6. The system of any of embodiments 1-4, further comprising a magnetic field cycling magnet positioned in proximity to the low static external magnetic field.

[0103] 7. The system of any of embodiments 5-6, wherein the magnetic field cycling magnet is configured to vary the low, static external magnetic field within the given field of view.

[0104] 8. The system of any of embodiments 7, wherein the field cycling magnet is configured to vary the low static external magnetic field when the radio frequency coil is not in use.

[0105] 9. The system of any of embodiments 5-8, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to a main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0106] 10. The system of any of embodiments 5-9, wherein the magnetic field circulating magnet includes an opening in the center of the magnet.

[0107] 11. The system of any of embodiments 5 to 10, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0108] 12. The system of any of embodiments 5 to 11, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0109] 13. The system of any of embodiments 1-12, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0110] 14. The system of any of embodiments 1-13, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0111] 15. The system of any of embodiments 1-14, wherein the low static magnetic field ranges from 35 mT to 75 mT.

[0112] 16. The system of any of embodiments 1-15, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0113] 17. The system of any of embodiments 1-16, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0114] 18. The system of any of embodiments 1 to 17, wherein the magnetic field circulating magnet has a magnetic field strength of 0.5 mT to 1 T.

[0115] 19. The system of any of embodiments 1 to 18, wherein the magnetic field circulating magnet has a magnetic field strength of 5 mT to 195 mT.

[0116] 20. The system of any of embodiments 1-19, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0117] 21. A magnetic resonance system comprising a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, and a magnetic field circulating magnet positioned adjacent to and concentric with said static magnetic field magnet.

[0118] 22. The system of embodiment 21, wherein the field-cycling magnet is positioned in close proximity to the low static external magnetic field.

[0119] 23. The system of any of embodiments 21-22, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0120] 24. The system of any of embodiments 21-23, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0121] 25. The system of any of embodiments 21-24, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between approximately 2 inches and 20 inches in length.

[0122] 26. The system of any of embodiments 21-25, wherein the field cycling magnet is configured to vary the low static magnetic field within the given field of view.

[0123] 27. The system of any of embodiments 21 to 26, further comprising a radio frequency coil configured to apply a pulsed circulating radio frequency magnetic field to the low static external magnetic field.

[0124] 28. The system of any of embodiments 26-27, wherein the magnetic field cycling magnet is configured to vary the low static external magnetic field when the radio frequency coil is not in use.

[0125] 29. The system of any of embodiments 21-28, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0126] 30. The system of any of embodiments 21-29, wherein the magnetic field circulating magnet includes an opening in the center of the magnet.

[0127] 31. The system of any of embodiments 21-30, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0128] 32. The system of any of embodiments 21 to 31, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0129] 33. The system of any of embodiments 21-32, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0130] 34. The system of any of embodiments 21-33, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0131] 35. The system of any of embodiments 21-34, wherein the low static magnetic field ranges from 35 mT to 75 mT.

[0132] 36. The system of any of embodiments 21-35, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0133] 37. The system of any of embodiments 21-36, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0134] 38. The system of any of embodiments 21 to 37, wherein the magnetic field circulating magnet has a magnetic field strength of 0.5 mT to 1 T.

[0135] 39. The system of any of embodiments 21 to 38, wherein the magnetic field circulating magnet has a magnetic field strength of 5 mT to 195 mT.

[0136] 40. The system of any of embodiments 21-39, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0137] 41. A magnetic resonance system comprising a static magnetic field magnet configured to provide a low static external magnetic field in a given field of view, a radio frequency coil, and a field cycling magnet.

[0138] 42. The system of embodiment 41, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0139] 43. The system of any of embodiments 41-42, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0140] 44. The system of any of embodiments 41-43, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between approximately 2 inches and 20 inches in length.

[0141] 45. The system of any of embodiments 41 to 44, wherein the radio frequency coil is configured to apply a pulsed circulating radio frequency magnetic field to the low static external magnetic field.

[0142] 46. ​​The system of any of embodiments 41 to 45, wherein the magnetic field circulation magnet is positioned adjacent to and concentric with the static magnetic field magnet.

[0143] 47. The system of any of embodiments 41-46, wherein the magnetic field cycling magnet is positioned in close proximity to the low static external magnetic field.

[0144] 48. The system of any of embodiments 41-47, wherein the magnetic field cycling magnet is configured to vary the low, static, external magnetic field within the given field of view.

[0145] 49. The system of embodiment 48, wherein the field cycling magnet is configured to vary the low static external magnetic field when the radio frequency coil is not in use.

[0146] 50. The system of any of embodiments 41-49, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0147] 51. The system of any of embodiments 41 to 50, wherein the magnetic field circulating magnet includes an opening in the center of the magnet.

[0148] 52. The system of any of embodiments 41-51, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0149] 53. The system of any of embodiments 41-52, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0150] 54. The system of any of embodiments 41-53, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0151] 55. The system of any of embodiments 41-54, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0152] 56. The system of any of embodiments 41-55, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0153] 57. The system of any of embodiments 41-56, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0154] 58. The system of any of embodiments 41 to 57, wherein the magnetic field circulating magnet has a magnetic field strength of 0.5 mT to 1 T.

[0155] 59. The system of any of embodiments 41 to 58, wherein the magnetic field circulating magnet has a magnetic field strength of 5 mT to 195 mT.

[0156] 60. The system of any of embodiments 41-59, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0157] 61. A method of operating a field cycling magnetic resonance system, comprising: providing a static magnetic field magnet configured to image a tissue specimen within a given field of view; applying a low static external magnetic field to the given field of view; providing a radio frequency coil configured to generate a circulating radio frequency magnetic field; applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field; and acquiring an image from the system.

[0158] 62. The method of embodiment 61, further comprising providing a field cycling magnet and varying the low static external magnetic field within the given field of view.

[0159] 63. The method of any of embodiments 61-62, wherein varying the low static external magnetic field includes at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0160] 64. The method of any of embodiments 61-63, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0161] 65. The method of any of embodiments 61-64, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0162] 66. The method of any of embodiments 61-65, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being approximately between 2 inches and 20 inches in length.

[0163] 67. The method of any of embodiments 61-66, wherein the field-cycling magnet is positioned in close proximity to the low static external magnetic field.

[0164] 68. The method of any of embodiments 61-67, wherein the magnetic field cycling magnet is positioned adjacent to and concentric with the static magnetic field magnet.

[0165] 69. The method of any of embodiments 61-68, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to a main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0166] 70. The method of any of embodiments 61-69, wherein the field-circulating magnet includes an opening in the center of the magnet.

[0167] 71. The method of any of embodiments 61-70, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0168] 72. The method of any of embodiments 61-71, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0169] 73. The method of any of embodiments 61-72, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0170] 74. The method of any of embodiments 61-73, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0171] 75. The method of any of embodiments 61-74, wherein the low static magnetic field ranges from 35 mT to 75 mT.

[0172] 76. The method of any of embodiments 61-75, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0173] 77. The method of any of embodiments 61-76, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0174] 78. The method of any of embodiments 61-77, wherein the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T.

[0175] 79. The method of any of embodiments 61-78, wherein the magnetic field cycling magnet has a magnetic field strength of 5 mT to 195 mT.

[0176] 80. The method of any of embodiments 61-79, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0177] 81. A method of operating a field cycling magnetic resonance system, comprising: providing a static magnetic field magnet configured to image a tissue specimen within a given field of view; applying a low static external magnetic field to the given field of view; providing a field cycling magnet; varying the low static external magnetic field within the given field of view; and acquiring an image from the system.

[0178] 82. The method of embodiment 81, wherein varying the low static external magnetic field includes at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0179] 83. The method of any of embodiments 81-82, further comprising providing a radio frequency coil configured to generate a circulating radio frequency magnetic field, and applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field.

[0180] 84. The method of any of embodiments 81-83, wherein the field-cycling magnet is positioned in close proximity to the low static external magnetic field.

[0181] 85. The method of any of embodiments 81-84, wherein the field-circulating magnet is positioned proximate to and concentric with the static magnetic field magnet.

[0182] 86. The method of any of embodiments 81-85, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0183] 87. The method of any of embodiments 81-86, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0184] 88. The method of any of embodiments 81-87, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being approximately between 2 inches and 20 inches in length.

[0185] 89. The method of any of embodiments 81-88, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to a main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0186] 90. The method of any of embodiments 81-89, wherein the magnetic field circulating magnet includes an opening in the center of the magnet.

[0187] 91. The method of any of embodiments 81-90, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0188] 92. The method of any of embodiments 81-91, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0189] 93. The method of any of embodiments 81-92, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0190] 94. The method of any of embodiments 81-93, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0191] 95. The method of any of embodiments 81-94, wherein the low static magnetic field ranges from 35 mT to 75 mT.

[0192] 96. The method of any of embodiments 81-95, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0193] 97. The method of any of embodiments 81-96, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0194] 98. The method of any of embodiments 81-97, wherein the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T.

[0195] 99. The method of any of embodiments 81-98, wherein the magnetic field strength of the magnetic field cycling magnet is between 5 mT and 195 mT.

[0196] 100. The method of any of embodiments 81-99, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0197] 101. A method of operating a field cycling magnetic resonance system, comprising: providing a static magnetic field magnet configured to image a tissue specimen within a given field of view; applying a low static external magnetic field to the given field of view; providing a radio frequency coil configured to generate a cycling radio frequency magnetic field; providing a field cycling magnet; varying the low static external magnetic field within the given field of view; and acquiring an image from the system.

[0198] 102. The method of embodiment 101, wherein varying the low static external magnetic field includes at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

[0199] 103. The method of any of embodiments 101-102, further comprising applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field.

[0200] 104. The method of any of embodiments 101-103, wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

[0201] 105. The method of any of embodiments 101-104, wherein the static magnetic field magnet has a bore at its center, the diameter of the bore being between 1 inch and 20 inches.

[0202] 106. The method of any of embodiments 101-105, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between approximately 2 inches and 20 inches in length.

[0203] 107. The method of any of embodiments 101-106, wherein the field-circulating magnet is positioned in close proximity to the low static external magnetic field.

[0204] 108. The method of any of embodiments 101-107, wherein the magnetic field circulation magnet is positioned adjacent to and concentric with the static magnetic field magnet.

[0205] 109. The method of any of embodiments 101-108, wherein the magnetic field cycling magnet is an electromagnet, a permanent magnet configured to move relative to a main magnet, or a permanent magnet comprising a ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

[0206] 110. The method of any of embodiments 101-109, wherein the magnetic field circulating magnet includes an opening in the center of the magnet.

[0207] 111. The method of any of embodiments 101-110, wherein the magnetic field circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0208] 112. The method of any of embodiments 101-111, wherein the magnetic field circulating magnet comprises a plurality of magnets arranged in a ring configuration or any other suitable shape or configuration around which the plurality of magnets are formed.

[0209] 113. The method of any of embodiments 101-112, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0210] 114. The method of any of embodiments 101-113, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0211] 115. The method of any of embodiments 101-114, wherein the low static magnetic field ranges from 35 mT to 75 mT.

[0212] 116. The method of any of embodiments 101-115, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0213] 117. The method of any of embodiments 101-116, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0214] 118. The method of any of embodiments 101-117, wherein the magnetic field cycling magnet has a magnetic field strength of 0.5 mT to 1 T.

[0215] 119. The method of any of embodiments 101-118, wherein the magnetic field cycling magnet has a magnetic field strength of 5 mT to 195 mT.

[0216] 120. The method of any of embodiments 101-119, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system comprising a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0217] Although this specification contains many specific implementation details, these should not be interpreted as limitations on the scope of any embodiment or possible claims, but as descriptions of features specific to a particular implementation of a particular embodiment. Some features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Furthermore, although features may be described above as acting in some combinations and may initially be claimed as such, one or more features from the combination of the claims can be deleted from the combination in some cases, and the combination of the claims may be directed to a subcombination or a variation of the subcombination.

[0218] Similarly, although operations are illustrated in the figures in a particular order, this should not be understood as requiring that such operations be performed in the particular or sequential order illustrated, or that all of the illustrated operations be performed, to achieve desirable results. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the above implementations should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems may generally be integrated into a single software product or packaged into multiple software products.

[0219] References to "or" may be construed as inclusive such that any term described with "or" may refer to either the single, the plural, and all of the described terms. Labels such as "first," "second," "third," etc. do not necessarily imply an ordering, but are generally used merely to distinguish between like or similar items or elements.

[0220] Various modifications to the implementations described in this disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with the present disclosure, i.e., the principles and novel features disclosed herein.

Claims

1. a static magnetic field magnet configured to provide a static external magnetic field in a given field of view; a radio frequency coil configured to apply a pulsed circulating radio frequency magnetic field to the static external magnetic field; a magnetic field cycling magnet disposed in proximity to the static external magnetic field; 1. A magnetic resonance system comprising: A magnetic resonance system, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system.

2. 10. The system of claim 1, wherein said static magnetic field magnet has a bore at its center, said bore having a diameter between 1 inch and 20 inches.

3. 10. The system of claim 1, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between 2 inches and 20 inches in length.

4. The system of claim 1 , wherein the static external magnetic field ranges from 10 mT to 1 T.

5. The system of claim 1 , wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

6. The system of claim 1 , wherein the magnetic resonance system comprises a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

7. a static magnetic field magnet configured to provide a static external magnetic field in a given field of view; a magnetic field circulation magnet disposed adjacent to and concentric with the static magnetic field magnet; 1. A magnetic resonance system comprising: A magnetic resonance system, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system.

8. 8. The system of claim 7, further comprising a radio frequency coil configured to apply a pulsed circulating radio frequency magnetic field to the static external magnetic field.

9. The system of claim 8 , wherein the field-cycling magnet is configured to vary the static external magnetic field when the radio frequency coil is not in use.

10. The system of claim 7 , wherein the static external magnetic field ranges from 10 mT to 1 T.

11. The system of claim 7 , wherein the magnetic field cycling magnet has a magnetic field strength between 0.5 mT and 1 T.

12. The system of claim 7 , wherein the magnetic resonance system comprises a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

13. a static magnetic field magnet configured to provide a static external magnetic field in a given field of view; A radio frequency coil; A magnetic field circulating magnet; 1. A magnetic resonance system comprising: A magnetic resonance system, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system.

14. 14. The system of claim 13, wherein the static magnetic field magnet has a bore at its center, the bore having a diameter between 1 inch and 20 inches.

15. 14. The system of claim 13, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view being between 2 inches and 20 inches in diameter, or the cylindrical field of view being between 2 inches and 20 inches in length.

16. The system of claim 13 , wherein the field-cycling magnet is configured to vary the static external magnetic field when the radio frequency coil is not in use.

17. The system of claim 13 , wherein the static external magnetic field ranges from 10 mT to 1 T.

18. The system of claim 13 , wherein the static external magnetic field ranges from 20 mT to 100 mT.

19. The system of claim 13 , wherein the magnetic resonance system comprises a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

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