Systems and methods for ultralow field relaxation dispersion

Abstract

To provide a system of field-cycled magnetic resonance system, and a method of operating the field-cycled magnetic resonance system.SOLUTION: In accordance with various embodiments, the disclosed system includes: a static field magnet configured to provide a low static external magnetic field to a given field of view; a radio frequency coil; and a field cycling magnet. In accordance with various embodiments, the method includes: providing a static field magnet configured to image a tissue sample 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 produce a cycling radio frequency field; providing a field cycling magnet; altering the low static external magnetic field within the given field of view; and collecting images from the system.SELECTED DRAWING: None

Description

Technical Field

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

[0002] The embodiments disclosed herein generally relate to systems and methods for imaging tissue specimens and patients, for example, by magnetic resonance imaging (MRI).

Background Art

[0003] As is well known, the effectiveness of an MRI system is strongly correlated with its ability to generate high-quality contrast in an image, thereby better distinguishing between different types of tissues and / or 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, it is a well-known desire in the industry to develop a system that can enhance contrast as much as possible. Contrast depends on the relaxation time of the tissue. Extending this, since the relaxation times of different tissues vary as a function of the magnetic field, if an MRI system provides a varying magnetic field, the contrast of the image can be better maximized.

[0004] It is also well known that it is generally impossible to generate field cycled MRI using conventional means. For this reason, various methods are available to facilitate field cycling. One such method for generating different magnetic fields is spin locking. Most MRI systems can spin lock portions of tissue, but doing so is not always practical. Further, current MRI systems generally spin lock excised tissue rather than in vivo tissue. Spin locking requires that the magnetization be affected by a magnetic field greater than any offset the tissue may experience, and as a result, a large amount of energy can be accumulated in the tissue. At high magnetic fields, the strength required for spin locking becomes greater than what the specific absorption rate (SAR) standard allows, and there is a potential to expose 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 peripheral devices to vary the static magnetic field within the field of view. In that case, for example, an insert into the bore of an already cramped conventional MRI scanner is required. It is known to be difficult to simply insert an electromagnet, which is often ferromagnetic (a ferromagnetic core can increase the strength of an electromagnet), into an MRI scanner room without destroying the scanner. Conventional MRI scanners generally exert extremely large forces on ferromagnetic materials. It is even difficult to remove something as small as a steel wrench from the scanner, and there may be a need to turn off the magnetic field, which is an expensive process.

[0006] Due to these drawbacks, there is a need to develop MRI systems and methods that are not currently feasible, such as maximizing contrast within an image by effectively cycling the magnetic field using methods such as spin locking or adding peripheral devices. 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 to 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. The magnetic resonance system further includes a field cycling magnet disposed proximate to the static magnetic field magnet 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 to a given field of view, and a field cycling magnet disposed proximate to the static magnetic field magnet and concentric with the static magnetic field magnet. The magnetic resonance system further includes a radio frequency coil configured to apply a pulsed circulating 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 to a given field of view, a radio frequency coil, and a field cycling magnet. The radio frequency coil is configured to apply a pulsed circulating 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 a 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 magnetic field circulation 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 circulating radio frequency magnetic field, applying a pulsed circulating radio frequency magnetic field to the low static external magnetic field, and collecting an image from the system. The method further includes providing a magnetic field circulation 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 magnetic field circulation 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 magnetic field circulation magnet, varying the low static external magnetic field within the given field of view, and collecting an image from the system. The method further includes 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. The magnetic resonance system is a single-sided magnetic resonance imaging system.

[0012] According to various embodiments, a method of operating a magnetic field circulation 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 circulating radio frequency magnetic field, providing a magnetic field circulation magnet, varying the low static external magnetic field within the given field of view, and collecting an image from the system. The method further includes applying a pulsed circulating 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 include illustrative examples of various aspects and implementations, and provide an overview or framework for understanding the nature and features of the aspects and implementations recited in the claims. The drawings provide illustration and further understanding of the various aspects and implementations, and are incorporated herein 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 numerals and signs in the various drawings indicate like elements. For clarity, not every component is labeled in every drawing.

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[0025] It should be understood that the figures are not necessarily drawn to scale, and the 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. Whenever possible, the same reference numbers are used to refer to the same or similar parts throughout the drawings. Furthermore, it should be recognized that the drawings are not intended to limit the scope of the present teachings in any way.

DETAILED DESCRIPTION OF THE INVENTION

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

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

[0028] All publications mentioned in this specification are hereby incorporated by reference for the purpose of disclosing and describing the devices, compositions, formulations, and methods described therein and useful in connection with the present disclosure.

[0029] As used herein, "comprises," "contains," "has," "includes," and variations thereof are not intended to be limiting, but rather are inclusive or non - limiting 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 only to those features, but may include other features not explicitly recited or inherent to such process, method, system, composition, kit, or apparatus.

[0030] The nuclear magnetic resonance (NMR) relaxation of isotope hydrogen - 1 is mainly the result of the random modulation of the dipole - dipole coupling between spins within the object of interest. The relaxation rate depends on the type of relaxation being measured and the motion contributing to the relaxation. In magnetic resonance imaging (MRI), the signal is mainly generated by water in the body. The random rotational diffusion that characterizes the relaxation of this water can vary on its time scale. Free water, such as that found in cerebrospinal fluid, urine, or blood, rotates and diffuses with a correlation time 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 in fact, there can be bound water in the human body.

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

[0032] This bound water relaxes at a rate much slower than that of free water. This bound water also undergoes exchange 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 water and free water, and these two populations are exchanging with each other. As a result, the slowly relaxing free water is constantly mixing with the rapidly relaxing bound water. Since free water and bound water cannot be distinguished spectrally or spatially, 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 protein to which the water binds and is in the range of tens to hundreds of nanoseconds.

[0033] Thus, there is a large difference in rotational correlation time 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 on the order of tens of nanoseconds. This difference in correlation time affects the relaxation dispersion of water and thus the relaxation dispersion of tissue. To further clarify the effect of relaxation dispersion, Figures 1, 2, and 3 shown below present various measurements of exemplary relaxation dispersions for different tissue types and specimens.

[0034] Figure 1 is a plot diagram 100 showing the relaxation dispersion of various types of tissues according to various embodiments. As shown in the figure, the plot diagram 100 shows the relaxation dispersion of various types of tissues. As seen in Figure 1, the relaxation time of tissues can change rapidly as a function of the Larmor frequency (the precession frequency of the magnetic moment of protons or electrons around a magnetic field). It can be useful to vary the Larmor frequency so that tissues with similar relaxation times can be distinguished. The variation of 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. Further, as also shown in Figure 1, some tissues may be closely similar to each other at high frequencies (i.e., high magnetic fields) and thus difficult to distinguish, but those same tissues may be more different at lower frequencies and thus a greater contrast is expected, so the ability to distinguish between tissues with seemingly similar relaxation times is greater.

[0035] Next, referring to Figure 2, Figure 2 is a plot diagram 200 showing the relaxation dispersion of various types of tissues according to various embodiments. As shown in the figure, the plot diagram 200 shows the relaxation dispersion of various types of tissues. However, the plot diagram 200 shows the variation of relaxation time over various magnetic field frequencies by comparing healthy tissue and tumorous tissue for the same tissue type in order to discuss this concept in more detail. Referring to Figure 2, the relaxation times of tumorous muscle tissue and healthy muscle tissue can be compared, and the same is true for healthy spleen tissue and tumorous spleen tissue. As is immediately apparent, the relaxation of a certain tissue type can vary depending on its health (healthy or tumorous), and those differences converge at higher frequencies (i.e., high magnetic fields). Therefore, the identification of the difference between healthy tissue and tumorous tissue can be improved by collecting magnetic resonance images at lower frequencies, or lower magnetic fields.

[0036] FIG. 3 is a plot 300 showing the relaxation dispersion of molecules having different rotational correlation times according to various embodiments. As shown in the figure, the plot 300 shows the relaxation rates at different rotational correlation times. Free water molecules have a short correlation time, while bound water has a longer correlation time. From this, it is possible to obtain both the result that free water has a long relaxation time and that this time is stable over various magnetic fields. On the other hand, the relaxation time of bound water has a more sensitive dependence on the magnetic field.

[0037] As described above, the effectiveness of an MRI system can be strongly correlated with its ability to generate high-quality contrast in an image, thereby better distinguishing between different types of tissues and / or changes 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. The intensity of a voxel in MRI depends, for example, on the relaxation characteristics of water in the portion of space associated with that voxel. Voxels having similar relaxation times have similar intensities, depending on the imaging protocol selected. Voxels having different relaxation times form contrast with each other. Many variables contribute to making one voxel different from another in intensity. For example, the difference in tissue composition of each voxel is an important contribution to the contrast.

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

[0039] Static magnetic field cycling is the most direct method of measuring 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 varied as part of a scan. Magnetic field cycling is generally performed using an electromagnet that can generate a relatively uniform magnetic field across the region of interest, and the magnetic field can be set to various magnitudes. These devices generally have a single magnetic field used for signal acquisition, and other possible magnetic fields are reserved for encoding some information onto the signal.

[0040] An exemplary experiment performed using 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 polarization magnetic field, which increases the nuclear spin polarization of the specimen and thus increases the signal-to-noise ratio. After the specimen is polarized, the external magnetic field is decreased to a value that puts the relaxation dispersion of the specimen in the desired state. Then, the specimen can be relaxed for a time sufficient for the magnitudes of the signals from different parts of the specimen to branch according to their different relaxation times. After the specimen is encoded with their relaxation times, the external magnetic field is increased again to any frequency at which the resonance radio frequency coil used in conjunction with the magnet is tuned. This process is repeated several times, each time changing the encoding magnetic field until the overall relaxation dispersion curve is sampled. However, this method requires a powerful electromagnet designed to rapidly increase and decrease the external magnetic field by hundreds of millitesla (mT).

[0041] There is also a method of circulating the magnitude of the magnetic field used for relaxation encoding that does not require changing an external magnetic field. All magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) scanners have a tuned radio frequency coil as part of the scanning apparatus. These coils apply a resonant magnetic field to the specimen and change the effective strength and direction of the magnetic field. For example, a conventional MRI has a static magnetic field equal to 3 tesla (T) and a radio frequency coil capable of generating an oscillating magnetic field on the order of several tens of microtesla (μT). However, when the radio frequency coil is turned on and set to generate a magnetic field oscillating at the Larmor frequency of the specimen, the specimen receives an effective magnetic field equal to the magnitude of the radio frequency magnetic field. The static magnetic field is canceled by the pulsed radio frequency magnetic field. Using this, certain relaxation dispersions can be measured. The specimen or patient can be relaxed with the effective magnetic field generated by the radio frequency coil. The magnitude of the radio frequency magnetic field can be changed to circulate the magnetic field in the same way as the magnetic field of an electromagnet, making it possible to examine the relaxation dispersion of the specimen. This requires considerably less hardware modification than installing an electromagnet in the scanner, and in addition, the magnetic field range is much more limited. In the case of an MRI scanner, the magnetic field range is 1 to 1000 μT. An NMR spectrometer can reach several tens of mT.

[0042] There are several other methods for magnetic field cycling that are used in some cases. Newer NMR spectrometers generally have the ability to move a sample in and out of the fringe field of a magnet. The magnets used in NMR can be varied in the range of 7.9T to 23T. Each magnet sold with a scanner is said to be at one magnetic field and is generally converted to the Larmor frequency of protons. However, the magnetic field generated by a superconducting magnet has a strong gradient. This gradient can be called the fringe field and changes from the defined magnetic field of the magnet to the Earth's magnetic field as it moves away from the field of view of the magnet. Some newer spectrometers have the function of utilizing this fringe field. The spectrometer can move a sample from the field of view into the fringe field, where the sample can relax at a much lower magnetic field. Then the sample is returned back into the field of view for detection.

[0043] Another method for magnetic field cycling is simply to 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). It is possible to collect images of the same part of the body using each scanner and derive information regarding relaxation dispersion therefrom. Although most of the dispersion occurs below 10 MHz and thus may not be readily identified, the contrast differences are significant. However, this requires considerable time and cost due to performing multiple scans and having the financial resources to purchase and maintain multiple scanners at multiple magnetic field strengths.

[0044] As noted above and as demonstrated by some of the known exemplary methods above, it is generally not possible to generate magnetic field cycling MRI using conventional means. In the case of an MRI system, a potentially effective method for generating different magnetic fields is the process of spin locking.

[0045] Spin locking can be generated when magnetization is retained along the same axis as the applied resonance 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 a phase as long as the spin locking pulse is applied. This also changes the relaxation characteristics of the spin-locked magnetization. The relaxation characteristics of magnetization change in two ways, one of which is important for low magnetic field systems. The important change for relaxation is that the spin-locked magnetization relaxes as if it were in a static magnetic field with the same magnitude as the oscillating magnetic field used for spin locking. Since radio frequency pulses are generally in microtesla (μT) units and the magnetic fields used for polarization are generally from several tens of millitesla (mT) to several tens of tesla, spin locking makes it possible to relax tissues at magnetic fields with much greater contrast than can be accessed by other means. The relaxation time measured using the spin locking pulse is called T1rho.

[0046] Most MRI systems can spin lock portions of tissue, but doing so is not always practical. Furthermore, current MRI systems can sometimes effectively spin lock excised tissue rather than tissue in vivo. Spin locking requires that the magnetization be affected by a magnetic field greater than any offset the tissue may experience. At high magnetic fields, the strength required for spin locking becomes greater than what the specific absorption rate (SAR) standard allows, and there is a possibility of exposing the human body to extremely large amounts of energy during an MRI scan. The higher the external magnetic field, the more energy is accumulated by the radio frequency coil. The scaling of SAR is shown below.

Number

[0047] Again, as described above and as demonstrated by some of the known exemplary methods above, it is generally not possible to generate magnetic field cycling MRI using conventional means. In the case of an MRI system, another potentially effective way to generate different magnetic fields is to provide an insert (or peripheral device) in the bore of the MRI scanner, where the bore is, for example, an opening within a whole body MRI scanner that houses a patient during the scan process, or an opening within a portable or point-of-care scanner that houses a particular body part.

[0048] Applicants have found that by providing a specific MRI (or spectrometer) design (e.g., a single-sided MRI design) for a low-field MRI scanner to facilitate magnetic field cycling, image contrast can be improved by effective spin locking. Thus, spin locking can be performed without exposing the body to large amounts of energy corresponding to such spin locking methods in standard MRI machines, where the amount of energy often exceeds the SAR criteria as described above. Applicants have further found that by providing a specific MRI (or spectrometer) design (e.g., a single-sided MRI design) for a low-field MRI scanner, an insert or peripheral device can be effectively added within the bore at a distance close enough to assist magnetic field cycling and improve image contrast.

[0049] Figure 4 is a schematic diagram of a magnetic field circulation magnetic resonance system 400 according to various embodiments. According to various embodiments, system 400 is a single-sided magnetic resonance imaging system. According to various embodiments, system 400 may include a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer. As shown in FIG. 4, 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 being examined. According to various embodiments, the static magnetic field magnet 420 may include a plurality of cylindrical permanent magnets in a parallel 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 diameters 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 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 diameters 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 may have a length of approximately 2 inches to 20 inches. According to various embodiments, the cylindrical field of view may have lengths of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0050] As shown in FIG. 4, 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, system 400 may include a magnetic field circulation magnet 460. According to various embodiments, the magnetic field circulation magnet 460 may be disposed proximate to a low static external magnetic field. According to various embodiments, the magnetic field circulation magnet 460 may be disposed proximate to the static magnetic field magnet 420. For example, the magnetic field circulation magnet 460 may be disposed in front of, behind, or in the center of the static magnetic field magnet 420. According to various embodiments, the magnetic field circulation magnet 460 may be concentric with the static magnetic field magnet 420. According to various embodiments, the magnetic field circulation 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 a low static external magnetic field. According to various embodiments, the magnetic field circulation 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, and relaxation encoding in different magnetic fields is expected.

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

[0053] Figures 5A and 5B are perspective views of an exemplary magnetic field circulation 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, system 500 includes a housing 510 that can house various components for generating a radio frequency magnetic field, such as, but not limited to, magnets, electromagnets, coils, and various electronic components for, but not limited to, control, power supply, and / or monitoring of system 500. According to various embodiments, housing 510 may house, for example, a static magnetic field magnet 420, a radio frequency coil 440, and / or a magnetic field circulation magnet 460 within housing 510. According to various embodiments, system 500 also includes a bore 520 at the center of its magnetic components, such as, but not limited to, static magnetic field magnet 420, radio frequency coil 440, and / or magnetic field circulation magnet 460. According to various embodiments, magnetic field circulation magnet 460 may be inserted into bore 520. According to various embodiments, magnetic field circulation magnet 460 may be disposed proximate to bore 520. For example, magnetic field circulation magnet 460 may be disposed in front of, behind, or at the center of bore 520. According to various embodiments, magnetic field circulation magnet 460 may be disposed proximate to or at the entrance of bore 520. According to various embodiments, bore 520 may have a diameter of 1 inch to 20 inches. According to various embodiments, bore 520 may have diameters of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches. According to various embodiments, system 500 may not include a bore.

[0055] According to various embodiments, system 500 can be configured to image a tissue specimen within a given field of view 530 as shown in FIG. 5B. According to various embodiments, a given field of view 530 is a three-dimensional (3D) volumetric measurement space where a tissue specimen, including but not limited to any anatomical part of a human, is subject to examination, evaluation, and / or imaging. According to various embodiments, a given field of view 530 can be a spherical or cylindrical field of view. According to various embodiments, a spherical field of view can have a diameter of from 2 inches to 20 inches. According to various embodiments, a spherical field of view can have diameters of from 1 inch to 4 inches, from 4 inches to 8 inches, and from 10 inches to 20 inches. According to various embodiments, a cylindrical field of view has a length of approximately from 2 inches to 20 inches. According to various embodiments, a cylindrical field of view can have lengths of from 1 inch to 4 inches, from 4 inches to 8 inches, and from 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 circulation magnet 460, are configured to generate and / or enhance during examination, evaluation, and / or imaging within a given field of view 530.

[0056] As shown in FIG. 5B, a given field of view 530 is proximate to the bore 520 of system 500 or is located near the surface 515 in front of the bore 520. According to various embodiments, the surface 515 is a curved surface, a flat surface, a concave surface, a convex surface, or some other contoured surface.

[0057] FIG. 6A is a side view of an exemplary magnetic field circulation magnetic resonance system 600 according to various embodiments. FIG. 6B is a front view of the exemplary magnetic field circulation magnetic resonance system 600. According to various embodiments, 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 FIGS. 6A and 6B, system 600 includes a housing 610 that can house various components for generating a radio frequency magnetic field, such as but not limited to magnets, electromagnets, coils, and various electronic components for, but not limited to, control, power supply, and / or monitoring of system 600. According to various embodiments, housing 610 can house, for example, a static magnetic field magnet 420 and / or a radio frequency coil 440 therein. According to various embodiments, system 600 also includes a bore 620 at its center. As shown in FIGS. 6A and 6B, housing 610 also includes a front portion 612, a rear portion 614, and a surface 615 of system 600. According to various embodiments, surface 615 is a curved surface, a flat surface, a concave surface, a convex surface, or some other curved surface.

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

[0060] As shown in FIGS. 6A and 6B, system 600 includes a magnetic field circulation magnet 660 disposed near surface 615 on the front portion 612 of system 600. According to various embodiments, magnetic field circulation magnet 660 is disposed proximate to the center of surface 615 on the front portion 612 of system 600. According to various embodiments, magnetic field circulation magnet 660 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 a low static external magnetic field. According to various embodiments, magnetic field circulation magnet 660 can be a solenoid coil configured to generate a magnetic field that is added to or subtracted from the magnetic field generated by the static magnetic field magnet, and relaxation encoding at different magnetic fields is expected.

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

[0062] As shown in FIG. 6A, system 600 also includes a rack 680 for housing various auxiliary components such as, for example, a computer configured to control system 600, one or more power supplies, data acquisition equipment, and the like. As shown in FIG. 6A, system 600 also includes a conduit 685 for connecting the various components within housing 610 to the various components housed within rack 680. As shown in FIG. 6A, magnetic field circulation magnet 660 is connected to conduit 685 via connection 665. According to various embodiments, connection 665 can be any suitable power cable 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 can 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 can vary from about 10 mT to about 1 T, from about 15 mT to about 900 mT, from about 20 mT to about 800 mT, from about 25 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 45 mT to about 300 mT, from about 50 mT to about 200 mT, from about 50 mT to about 100 mT, from about 45 mT to about 100 mT, from about 40 mT to about 100 mT, from about 35 mT to about 100 mT, from about 30 mT to about 100 mT, from about 25 mT to about 100 mT, from about 20 mT to about 100 mT, and from 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 a spherical or cylindrical field of view. 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 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 with respect to the diameter and length. The field of view can also vary 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 with respect to the diameter and length.

[0066] According to various embodiments, the system is configured to apply magnetic field circulation to a low static external magnetic field radiated by a magnet. According to various embodiments, the system is configured to provide magnetic field circulation to the low static external magnetic field provided by the magnet by applying a spin locking magnetic field, and the spin locking magnetic field uses radio frequency pulses to spin lock the magnetization radiated by the magnet. According to various embodiments, the system is further configured to provide magnetic field circulation to the low static external magnetic field radiated by the magnet by further including a peripheral device (e.g., a magnetic field circulation magnet) for changing the static magnetic field within a given field of view. Spin locking is executable when the peripheral device is not active. According to various embodiments, the given low magnetic field is substantially below the SAR standard. According to various embodiments, the system is a single-sided MRI system.

[0067] According to various embodiments, the above describes a magnetic resonance system configured to, for example, magnetically circulate an external magnetic field by addition of, for example, spin locking or an insert (e.g., a peripheral device such as a magnetic field circulation magnet as described herein) to a magnet (e.g., a static magnetic field magnet), but the present disclosure also contemplates a method of imaging tissue within a field of view. The method can include, for example, providing a magnetic resonance system equipped with a magnet, providing a tissue specimen within the field of view, applying a low static external magnetic field to a given field of view, magnetically circulating that low static external magnetic field, and collecting an image from the system. Magnetically circulating can 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 at the Larmor frequency of a desired slice after excitation. When the spin locking magnetic field is collinear with the magnetization, the magnetization is spin locked. This requires only a transmit coil.

[0068] By spin locking at low magnetic fields provided by a system in which the magnitude and duration of the magnetic field are not limited by SAR for low-level external fields, a magnetic resonance system can perform relaxation dispersion experiments on tissue without circulating the external field. The external field may be static, but the strength of the spin locking magnetic field can vary. The system can apply a spin locking magnetic field in the range from about 450 μT to about 550 μT, from about 400 μT to about 600 μT, from about 350 μT to about 650 μT, from about 300 μT to about 700 μT, from about 250 μT to about 750 μT, from about 200 μT to about 800 μT, from about 150 μT to about 850 μT, from about 100 μT to about 900 μT, from about 50 μT to about 950 μT, from about 10 μT to about 990 μT, and from about 1 μT to about 1 mT. The range of the spin locking magnetic field can also span 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 550 μT, from about 550 μT to about 600 μT, from about 600 μT to about 650 μT, from about 650 μT to about 700 μT, from about 700 μT to about 750 μT, from about 750 μT to about 800 μT, from about 800 μT to about 850 μT, from about 850 μT to about 900 μT, from about 900 μT to about 950 μT, and from about 950 μT to about 1 mT. According to various embodiments, the system can apply a spin locking magnetic field from about 0.5 μT to about 1 mT.

[0069] With this spin locking method, it becomes possible to change the contrast of an image by changing the intensity of the spin locking magnetic field. By performing a plurality of spin locking experiments and fitting the collected relaxation times to a simple model, the rotational correlation time can be extracted. Thereby, by examining tissues under many different conditions, deeper insights into the tissues can be obtained. Changes to tissues such as an increase in cell packing density associated with cancer can be visualized by changing the relaxation dynamics of the system without major hardware changes. By using spin locking relaxation dispersion, a distribution of multiple relaxation times, rather than just the binary time values T1 and T2, becomes available to the radiologist.

[0070] In addition to what has been disclosed above, there are many advantages to spin locking at lower magnetic fields. For example, at high magnetic fields, during the period of spin locking, there are at least two major contributions to relaxation: relaxation due to dipole-dipole coupling and relaxation due to chemical exchange. The contribution from 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 T1rho relaxation disappears. As a result, if there is interest in collecting dipole relaxation dispersion using spin locking, doing so at high magnetic fields is difficult because the dispersion gets mixed with the chemical exchange contribution to relaxation. Sampling lower magnetic fields with spin locking at high static magnetic fields is also extremely difficult because the contribution from chemical exchange also scales with the magnitude of the spin locking magnetic field.

[0071] According to various embodiments, the magnetic resonance system can further include an insert or a peripheral device, or can be configured to house an insert or a peripheral device. According to various embodiments, the insert or the peripheral device is an electromagnet. The electromagnet can be, for example, an air core, a ferromagnetic core, or a dielectric core. As described above, for example, due to the low static magnetic field, the possibility of changing the static magnetic field of the system with an electromagnet is much higher. Different from the superconducting magnets used for conventional MRI, the system herein has a much weaker permanent magnetic field. Bringing the hardware required for a powerful electromagnet, i.e., the hardware that can have ferromagnetic components, closer to the system herein is significantly safer than bringing a device similar to a superconducting magnet closer. Further, as described above and as shown, for example, in FIGS. 4, 5A, 5B, 6A, and 6C, since the field of view can be provided at the surface of the magnet rather than the bore, access becomes much easier. A similar device (insert or peripheral device) would need to be inserted into the bore in a conventional MRI, which already has little room and is often occupied by the patient. Thus, incorporating an electromagnet into the system enables changing the static magnetic field. The electromagnet can reduce the static magnetic field within the field of view, and within that field of view, tissues are relaxed in a magnetic field where the relaxation times of different tissues differ most significantly. This allows, in some situations, expanding the range of the magnetic field more than spin locking.

[0072] Assume that for the range of the magnetic field accessible by a magnetic field circulation magnet (e.g., magnetic field circulation magnet 420), the magnetic field circulation magnet is designed to reduce or increase the static magnetic field. According to various embodiments, the range of the magnetic field accessible by the magnetic field circulation magnet can be 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 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 the magnetic field accessible by the magnetic field circulation magnet can also 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, 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, assuming that the magnetic field circulation magnet is designed to reduce or increase the static magnetic field.According to various embodiments, the range of the magnetic field accessible by the magnetic field circulation magnet, assuming that the magnetic field circulation magnet is 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 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 magnetic field circulation magnet does not generate a uniform magnetic field. Image encoding is not performed while the magnetic field circulation magnet is on. The magnetic field circulation magnet slowly shifts the external field slowly enough to meet the adiabatic conditions. According to some embodiments, the magnetic resonance system can be configured to provide magnetic field circulation to the low static external magnetic field provided by the magnet, both by applying a spin locking magnetic field and by housing an insert or a peripheral device. According to some embodiments, the magnetic resonance system can be configured to provide magnetic field circulation to the low static external magnetic field provided by the magnet, either by applying a spin locking magnetic field or by housing an insert or a peripheral device.

[0074] According to various embodiments, the magnetic field circulation magnet can be in the shape of a donut-shaped ring, a cylindrical ring, an oval-shaped ring, or any other suitable shape or form having an opening in the magnet. According to various embodiments, the magnetic field circulation magnet can include a set of magnets, and these magnets are arranged in the form of a ring or any other suitable shape or form surrounding the perimeter. According to various embodiments, the magnetic field circulation magnet is disposed proximate to the magnet, for example, in front of, behind, or at the center of the magnet. According to various embodiments, the magnetic field circulation magnet is concentric with the magnet. The magnetic field circulation magnet may be disposed around the patient.

[0075] Possible applications of an MRI scanner capable of magnetic field cycling include, for example, multimodal imaging. Conventional MRI scanners have a limited number of types of contrast available. Generally, the types of contrast include T1, T2, T1rho (under special circumstances), and diffusion. A magnetic field cycling MRI scanner makes available a range of T1 and T1rho contrast. If no contrast is visible at a certain magnetic field, the user may vary the magnetic field and retry. Another application of this technology is, for example, that the user can collect a form of contrast dispersion image. The contrast dispersion image can be an image repeatedly collected with different relaxation encoding magnetic fields. Tissues can be characterized by how their contrast varies as a function of the magnetic field. And the analyzed image can be an image such that the value of each voxel is extracted from the fitting of the amplitude variation as a function of the magnetic field strength. The value of this fitting can roughly correspond to the rotational correlation time of water within that pixel. A series of images are generated using non-linear reconstruction, one for each magnetic field strength used for relaxation encoding. The value of each pixel of these images is fitted using a simple model that describes 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 water pools. One pool is free water that relaxes slowly, and the other is bound water that relaxes rapidly. These two pools mix at a characteristic exchange rate. The parameters that describe relaxation using this simple model, namely the rotational correlation times of free water and bound water and the exchange rate between them, are found by fitting the model to the data.

Number

[0076] FIG. 7 is a flowchart of an exemplary method S100 of operating a magnetic field circulation 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, 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 part of a subject under examination. According to various embodiments, the static magnetic field magnet can include a plurality of cylindrical permanent magnets in a parallel 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 diameters 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 can be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view can have a diameter of 2 inches to 20 inches. According to various embodiments, the spherical field of view can have diameters 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 can have a length of approximately 2 inches to 20 inches. According to various embodiments, the cylindrical field of view can have lengths of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0077] As shown in FIG. 7, method S100 includes, at step S120, applying a low static external magnetic field to the 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 a low magnetic field strength.

[0079] In step S140, method S100 includes applying a pulsed circulating radio frequency magnetic field to a 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, method S100 optionally includes providing a magnetic field circulating magnet. According to various embodiments, the magnetic field circulating magnet can be disposed in proximity to the low static external magnetic field. According to various embodiments, the magnetic field circulating magnet can be disposed in proximity to the static magnetic field magnet, for example, in front of, behind, or at the center of the static magnetic field magnet, and is concentric with the static magnetic field magnet. According to various embodiments, the magnetic field circulating 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 circulating magnet can include an opening at the center of the magnet. According to various embodiments, the magnetic field circulating magnet can be a donut-shaped ring, a cylindrical ring, or an oval-shaped ring. According to various embodiments, the magnetic field circulating magnet can include a plurality of magnets, and these plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around them. According to various embodiments, the magnetic field circulating magnet has a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the magnetic field circulating magnet has a magnetic field strength of 5 mT to 195 mT.

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

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

[0083] FIG. 8 is a flowchart of an exemplary method S200 for operating a magnetic field circulation 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, method S200 includes, in 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 a plurality of cylindrical permanent magnets in a parallel 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 diameters 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 can have a diameter of 2 inches to 20 inches. According to various embodiments, the spherical field of view can have diameters 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 has a length of approximately 2 inches to 20 inches. According to various embodiments, the cylindrical field of view can have lengths of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0084] As shown in FIG. 8, method S200 includes, at 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] At step S230, method S200 includes providing a magnetic field circulation magnet. According to various embodiments, the magnetic field circulation magnet can be disposed proximate to the low static external magnetic field. According to various embodiments, the magnetic field circulation magnet can be disposed proximate to the static magnetic field magnet, for example, in front of, behind, or at the center of the static magnetic field magnet, and be concentric with the static magnetic field magnet. According to various embodiments, the magnetic field circulation 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 circulation magnet can include an opening at the center of the magnet. According to various embodiments, the magnetic field circulation magnet can be a donut-shaped ring, a cylindrical ring, or an oval-shaped ring. According to various embodiments, the magnetic field circulation magnet can include a plurality of magnets, and these plurality of magnets can be arranged in a ring configuration or any other suitable shape or configuration formed around these plurality of magnets. According to various embodiments, the magnetic field circulation magnet has a magnetic field strength of from 0.5 mT to 1 T. According to various embodiments, the magnetic field circulation magnet has a magnetic field strength of from 5 mT to 195 mT.

[0086] At step S240, method S200 includes changing the low static external magnetic field within a given field of view. According to various embodiments, changing the low static external magnetic field can include at least one of an increase, a decrease, or a change in 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, method S200 optionally includes applying a pulsed circulating radio frequency magnetic field to a 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, method S200 includes collecting an image from the magnetic resonance system.

[0090] FIG. 9 is a flowchart of an exemplary method S300 for operating a magnetic field circulation 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, 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 a plurality of cylindrical permanent magnets in a parallel 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 diameters 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 can be a spherical or cylindrical field of view. According to various embodiments, the spherical field of view can have a diameter of 2 inches to 20 inches. According to various embodiments, the spherical field of view can have diameters 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 can have a length of approximately 2 inches to 20 inches. According to various embodiments, the cylindrical field of view can have lengths of 1 inch to 4 inches, 4 inches to 8 inches, and 10 inches to 20 inches.

[0091] As shown in FIG. 9, method S300 includes, at step S320, applying a low static external magnetic field to the 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, 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 a low magnetic field strength.

[0093] In step S340, method S200 includes providing a magnetic field circulation magnet. According to various embodiments, the magnetic field circulation magnet can be disposed in proximity to a low static external magnetic field. According to various embodiments, the magnetic field circulation magnet can be disposed in proximity to the static magnetic field magnet, for example, in front of, behind, or at the center of the static magnetic field magnet, and is concentric with the static magnetic field magnet. According to various embodiments, the magnetic field circulation 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 for adjusting and shaping a low static external magnetic field. According to various embodiments, the magnetic field circulation magnet can include an opening at the center of the magnet. According to various embodiments, the magnetic field circulation magnet can be a donut-shaped ring, a cylindrical ring, or an oval-shaped ring. According to various embodiments, the magnetic field circulation magnet can include a plurality of magnets, and these plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around these plurality of magnets. According to various embodiments, the magnetic field circulation magnet has a magnetic field strength of 0.5 mT to 1 T. According to various embodiments, the magnetic field circulation magnet has a magnetic field strength of 5 mT to 195 mT.

[0094] In step S350, method S300 includes changing a low static external magnetic field within a given field of view. According to various embodiments, changing the low static external magnetic field can include at least one of an increase, a decrease, or a change in direction of the low static external magnetic field.

[0095] In step S360, method S300 optionally includes applying a pulsed circulating radio frequency magnetic field to a 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, method S300 includes collecting an image from a 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 to 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 one of embodiments 1-2, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is from 1 inch to 20 inches.

[0100] 4. The system of any one of embodiments 1-3, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view has a diameter from 2 inches to 20 inches, or the cylindrical field of view has a length of approximately 2 inches to 20 inches.

[0101] 5. The system of any one of embodiments 1-4, further comprising a magnetic field circulation magnet disposed proximate to the static magnetic field magnet and concentric with the static magnetic field magnet.

[0102] 6. The system of any one of embodiments 1-4, further comprising a magnetic field circulation magnet disposed proximate to the low static external magnetic field.

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

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

[0105] 9. The system according to any one of embodiments 5-8, wherein the magnetic field circulation magnet is 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.

[0106] 10. The system according to any one of embodiments 5-9, wherein the magnetic field circulation magnet includes an opening at the center of the magnet.

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

[0108] 12. The system according to any one of embodiments 5-11, wherein the magnetic field circulation magnet includes a plurality of magnets, and the plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around the plurality of magnets.

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

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

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

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

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

[0114] 18. The system according to any one of Embodiments 1 to 17, wherein the magnetic field intensity of the magnetic field circulating magnet is from 0.5 mT to 1 T.

[0115] 19. The system according to any one of Embodiments 1 to 18, wherein the magnetic field intensity of the magnetic field circulating magnet is from 5 mT to 195 mT.

[0116] 20. The system according to any one of Embodiments 1 to 19, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system including a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0117] 21. A magnetic resonance system including a static magnetic field magnet configured to provide a low static external magnetic field for a given field of view, and a magnetic field circulating magnet disposed adjacent to the static magnetic field magnet and concentric with the static magnetic field magnet.

[0118] 22. The system according to Embodiment 21, wherein the magnetic field circulating magnet is disposed adjacent to the low static external magnetic field.

[0119] 23. The system according to any one of Embodiments 21 to 22, wherein the static magnetic field magnet includes a plurality of cylindrical permanent magnets in a parallel configuration.

[0120] 24. The system according to any one of Embodiments 21 to 23, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is from 1 inch to 20 inches.

[0121] 25. A system according to any one of embodiments 21 to 24, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view having a diameter of 2 inches to 20 inches, or the cylindrical field of view having a length of approximately 2 inches to 20 inches.

[0122] 26. A system according to any one of embodiments 21 to 25, wherein the magnetic field circulation magnet is configured to vary the low static magnetic field within the given field of view.

[0123] 27. A system according to any one 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. A system according to any one of embodiments 26 to 27, wherein the magnetic field circulation magnet is configured to vary the low static external magnetic field when the radio frequency coil is not in use.

[0125] 29. A system according to any one of embodiments 21 to 28, wherein the magnetic field circulation magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material for adjusting and shaping the low static external magnetic field.

[0126] 30. A system according to any one of embodiments 21 to 29, wherein the magnetic field circulation magnet includes an opening at the center of the magnet.

[0127] 31. A system according to any one of embodiments 21 to 30, wherein the magnetic field circulation magnet is a donut-shaped ring, a cylindrical ring, or an oval-shaped ring.

[0128] 32. A system according to any one of embodiments 21 to 31, wherein the magnetic field circulation magnet includes a plurality of magnets, the plurality of magnets being arranged in a ring configuration or any other suitable shape or configuration formed around the plurality of magnets.

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

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

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

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

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

[0134] 38. A system according to any one of embodiments 21 to 37, wherein the magnetic field strength of the magnetic field circulating magnet is from 0.5 mT to 1 T.

[0135] 39. A system according to any one of embodiments 21 to 38, wherein the magnetic field strength of the magnetic field circulating magnet is from 5 mT to 195 mT.

[0136] 40. A system according to any one of embodiments 21 to 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 to a given field of view, a radio frequency coil, and a magnetic field circulating 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 according to any one of embodiments 41 to 42, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is from 1 inch to 20 inches.

[0140] 44. The system according to any one of embodiments 41 to 43, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view has a diameter of from 2 inches to 20 inches, or the cylindrical field of view has a length of approximately from 2 inches to 20 inches.

[0141] 45. The system according to any one 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 according to any one of embodiments 41 to 45, wherein the magnetic field circulating magnet is disposed adjacent to the static magnetic field magnet and is concentric with the static magnetic field magnet.

[0143] 47. The system according to any one of embodiments 41 to 46, wherein the magnetic field circulating magnet is disposed adjacent to the low static external magnetic field.

[0144] 48. The system according to any one of embodiments 41 to 47, wherein the magnetic field circulating magnet is configured to change the low static external magnetic field within the given field of view.

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

[0146] 50. The system according to any one of embodiments 41 to 49, wherein the magnetic field circulating magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material for adjusting and shaping the low static external magnetic field.

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

[0148] 52. A system according to any one of Embodiments 41 to 51, wherein the magnetic field circulation magnet is a donut-shaped ring, a cylindrical ring, or an oval-shaped ring.

[0149] 53. A system according to any one of Embodiments 41 to 52, wherein the magnetic field circulation magnet includes a plurality of magnets, and the plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around the plurality of magnets.

[0150] 54. A system according to any one of Embodiments 41 to 53, wherein the low static magnetic field ranges from 10 mT to 1 T.

[0151] 55. A system according to any one of Embodiments 41 to 54, wherein the low static magnetic field ranges from 20 mT to 100 mT.

[0152] 56. A system according to any one of Embodiments 41 to 55, wherein the circulating radio frequency magnetic field ranges from 1 μT to 1 mT.

[0153] 57. A system according to any one of Embodiments 41 to 56, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

[0154] 58. A system according to any one of Embodiments 41 to 57, wherein the magnetic field intensity of the magnetic field circulation magnet is from 0.5 mT to 1 T.

[0155] 59. A system according to any one of Embodiments 41 to 58, wherein the magnetic field intensity of the magnetic field circulation magnet is from 5 mT to 195 mT.

[0156] 60. A system according to any one of Embodiments 41 to 59, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system including a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0157] 61. A method of operating a magnetic 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 collecting an image from the system.

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

[0159] 63. The method according to any one of embodiments 61 to 62, wherein varying the low static external magnetic field includes at least one of an increase, a decrease, or a change in direction of the low static external magnetic field.

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

[0161] 65. The method according to any one of embodiments 61 to 64, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is from 1 inch to 20 inches.

[0162] 66. The method according to any one of embodiments 61 to 65, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view has a diameter of from 2 inches to 20 inches, or the cylindrical field of view has a length of approximately from 2 inches to 20 inches.

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

[0164] 68. The method according to any one of embodiments 61 to 67, wherein the magnetic field cycling magnet is disposed in proximity to and concentric with the static magnetic field magnet.

[0165] 69. The method according to any one of embodiments 61 to 68, wherein the magnetic field circulation magnet is an electromagnetic magnet, 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.

[0166] 70. The method according to any one of embodiments 61 to 69, wherein the magnetic field circulation magnet includes an opening at the center of the magnet.

[0167] 71. The method according to any one of embodiments 61 to 70, wherein the magnetic field circulation magnet is a donut-shaped ring, a cylindrical ring, or an oval-shaped ring.

[0168] 72. The method according to any one of embodiments 61 to 71, wherein the magnetic field circulation magnet includes a plurality of magnets, and the plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around the plurality of magnets.

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

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

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

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

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

[0174] 78. The method according to any one of embodiments 61 to 77, wherein the magnetic field strength of the magnetic field circulation magnet is from 0.5 mT to 1 T.

[0175] 79. A method according to any one of Embodiments 61 to 78, wherein the magnetic field strength of the magnetic field circulation magnet is 5 mT to 195 mT.

[0176] 80. A method according to any one of Embodiments 61 to 79, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system including a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0177] 81. A method of operating a magnetic field circulation 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 magnetic field circulation magnet; changing the low static external magnetic field within the given field of view; and collecting an image from the system.

[0178] 82. The method of Embodiment 81, wherein changing the low static external magnetic field includes at least one of an increase, a decrease, or a change in direction of the low static external magnetic field.

[0179] 83. The method according to any one of Embodiments 81 to 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 according to any one of Embodiments 81 to 83, wherein the magnetic field circulation magnet is disposed close to the low static external magnetic field.

[0181] 85. The method according to any one of Embodiments 81 to 84, wherein the magnetic field circulation magnet is disposed close to the static magnetic field magnet and is concentric with the static magnetic field magnet.

[0182] 86. The method according to any one of Embodiments 81 to 85, wherein the static magnetic field magnet includes a plurality of cylindrical permanent magnets in a parallel configuration.

[0183] 87. The method according to any one of Embodiments 81 to 86, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is from 1 inch to 20 inches.

[0184] 88. The method according to any one of Embodiments 81 to 87, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view has a diameter of from 2 inches to 20 inches, or the cylindrical field of view has a length of approximately from 2 inches to 20 inches.

[0185] 89. The method according to any one of Embodiments 81 to 88, wherein the magnetic field circulation magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material for adjusting and shaping the low static external magnetic field.

[0186] 90. The method according to any one of Embodiments 81 to 89, wherein the magnetic field circulation magnet includes an opening at the center of the magnet.

[0187] 91. The method according to any one of Embodiments 81 to 90, wherein the magnetic field circulation magnet is a donut-shaped ring, a cylindrical ring, or an oval-shaped ring.

[0188] 92. The method according to any one of Embodiments 81 to 91, wherein the magnetic field circulation magnet includes a plurality of magnets, and the plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around them.

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

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

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

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

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

[0194] 98. The method according to any one of Embodiments 81 to 97, wherein the magnetic field intensity of the magnetic field circulating magnet is from 0.5 mT to 1 T.

[0195] 99. The method according to any one of Embodiments 81 to 98, wherein the magnetic field intensity of the magnetic field circulating magnet is from 5 mT to 195 mT.

[0196] 100. The method according to any one of Embodiments 81 to 99, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system including a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0197] 101. A method for operating a magnetic field circulating magnetic resonance system, comprising preparing 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, preparing a radio frequency coil configured to generate a circulating radio frequency magnetic field, preparing a magnetic field circulating magnet, changing the low static external magnetic field within the given field of view, and collecting an image from the system.

[0198] 102. The method according to Embodiment 101, wherein changing the low static external magnetic field includes at least one of an increase, a decrease, or a change in direction of the low static external magnetic field.

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

[0200] 104. The method according to any one of Embodiments 101 to 103, wherein the static magnetic field magnet includes a plurality of cylindrical permanent magnets in a parallel configuration.

[0201] 105. The method according to any one of Embodiments 101 to 104, wherein the static magnetic field magnet has a bore at its center, and the diameter of the bore is 1 inch to 20 inches.

[0202] 106. The method according to any one of Embodiments 101 to 105, wherein the given field of view is a spherical or cylindrical field of view, the spherical field of view has a diameter of 2 inches to 20 inches, or the cylindrical field of view has a length of approximately 2 inches to 20 inches.

[0203] 107. The method according to any one of Embodiments 101 to 106, wherein the magnetic field circulation magnet is arranged close to the low static external magnetic field.

[0204] 108. The method according to any one of Embodiments 101 to 107, wherein the magnetic field circulation magnet is arranged close to the static magnetic field magnet and is concentric with the static magnetic field magnet.

[0205] 109. The method according to any one of Embodiments 101 to 108, wherein the magnetic field circulation magnet is an electromagnet, a permanent magnet configured to move relative to the main magnet, or a permanent magnet including a ferromagnetic or magnetizable material for adjusting and shaping the low static external magnetic field.

[0206] 110. The method according to any one of Embodiments 101 to 109, wherein the magnetic field circulation magnet includes an opening at the center of the magnet.

[0207] 111. The method according to any one of Embodiments 101 to 110, wherein the magnetic field circulation magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

[0208] 112. The method according to any one of Embodiments 101 to 111, wherein the magnetic field circulation magnet includes a plurality of magnets, and the plurality of magnets are arranged in a ring configuration or any other suitable shape or configuration formed around the plurality of magnets.

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

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

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

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

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

[0214] 118. The method according to any one of Embodiments 101 to 117, wherein the magnetic field strength of the magnetic field circulation magnet is from 0.5 mT to 1 T.

[0215] 119. The method according to any one of Embodiments 101 to 118, wherein the magnetic field strength of the magnetic field circulation magnet is from 5 mT to 195 mT.

[0216] 120. The method according to any one of Embodiments 101 to 119, wherein the magnetic resonance system is a single-sided magnetic resonance imaging system including a magnetic resonance imaging scanner or a magnetic resonance imaging spectrometer.

[0217] This specification includes details of many specific implementations, but these should not be construed as limitations on the scope of any implementation or subject matter that may become the scope of the claims, but rather as descriptions and interpretations of features specific to the particular implementation of a particular implementation. Some features described herein in the context of individual implementations may also be implemented in combination in a single implementation. Conversely, the various features described in the context of a single implementation may also be implemented individually in multiple implementations, or in any suitable partial combination. Further, although the features are described above as acting in some combinations and may thus be initially recited in the claims, one or more features from the combinations of the claims may in some cases be deleted from that combination, and the combinations of the claims may be directed to partial combinations or variations of partial combinations.

[0218] Similarly, operations are illustrated in the drawings in a particular order, but this should not be understood as requiring that such operations be performed in the particular order or sequential order shown, or that all of the illustrated operations be performed, in order to achieve the desired result. In some circumstances, multitasking and parallel processing may be advantageous. Further, the separation of various system components in the above implementations should not be understood as requiring such separation in all implementations, and 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 in that any terms described using "or" may indicate any of the singular, plural, and all of the terms described. Labels such as "first," "second," "third," etc. do not necessarily mean to indicate an order and are generally used merely to distinguish between similar or like items or elements.

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

Claims

1. 1. 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 said given field of view; Providing a radio frequency coil configured to generate a circulating radio frequency magnetic field; applying a pulsed cyclic radio frequency magnetic field to the low static external magnetic field; acquiring an image from the system; A method of operating a field cycling magnetic resonance system comprising:

2. Providing a magnetic field circulating magnet; Varying the low static external magnetic field within the given field of view; The method of claim 1 further comprising:

3. The method of claim 2 , wherein varying the low static external magnetic field comprises at least one of increasing, decreasing, or changing the direction of the low static external magnetic field.

4. The method of claim 1 , wherein the static magnetic field magnet comprises a plurality of cylindrical permanent magnets in a parallel configuration.

5. 2. The method 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.

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

7. The method of claim 2 , wherein the field-cycling magnet is positioned in close proximity to the low static external magnetic field.

8. The method of claim 2 , wherein the field cycling magnet is disposed proximate to and concentric with the static magnetic field magnet.

9. 3. The method of claim 2, wherein the field-cycling magnet is an electromagnet, a permanent magnet configured to move relative to a main magnet, or a permanent magnet that includes ferromagnetic or magnetizable material that adjusts and shapes the low static external magnetic field.

10. The method of claim 2 , wherein the field-circulating magnet includes an opening in the center of the magnet.

11. The method of claim 2 , wherein the field-circulating magnet is a donut-shaped ring, a cylindrical ring, or an egg-shaped ring.

12. 3. The method of claim 2, wherein the 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.

13. The method of claim 1 , wherein the low static magnetic field ranges from 10 mT to 1 T.

14. The method of claim 1 , wherein the low static magnetic field ranges from 20 mT to 100 mT.

15. The method of claim 1 , wherein the low static magnetic field ranges from 35 mT to 75 mT.

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

17. 10. The method of claim 1, wherein the circulating radio frequency magnetic field ranges from 100 μT to 900 μT.

18. The method of claim 2 , wherein the magnetic field cycling magnet has a magnetic field strength between 0.5 mT and 1 T.

19. The method of claim 2 , wherein the magnetic field cycling magnet has a magnetic field strength between 5 mT and 195 mT.

20. The method of claim 1 , 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.

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