Dry eye alleviation for eyeball aberration analysis system and method

Abstract

To disclose a system, a method, and software of magnetic resonance imaging.SOLUTION: A magnetic resonance imaging system includes a low field strength main magnet, a gradient coil part, an RF coil system, and a control system configured for the acquisition and processing of magnetic resonance imaging data from a human patient while utilizing a sparse sampling imaging technique.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 62 / 353,583, entitled "Magnetic Resonance Imaging," filed June 22, 2016, the disclosure of which is incorporated herein in its entirety.

[0002] The objectives described herein relate to systems, methods and computer software for magnetic resonance imaging and various related diagnostic and interventional applications. [Background technology]

[0003] Magnetic resonance imaging (MRI), or nuclear magnetic resonance imaging, is a non-invasive imaging technique that uses the interaction between radio frequency signals, a strong magnetic field (with weak cross-directional gradient fields to localize and encode or decode phase and frequency), and body tissue to obtain projections, spectral signals, and planar or volumetric images of the inside of a patient's body. Magnetic resonance imaging is particularly useful for imaging soft tissues and can be used for diagnosing disease. Real-time MRI or cine MRI can be used for diagnosing medical conditions that require imaging of moving structures inside a patient. Real-time MRI can be used in conjunction with interventional procedures such as radiation therapy or image-guided surgery, as well as the planning of such procedures. Summary of the Invention [Problem to be solved by the invention]

[0004] A magnetic resonance imaging system, method and software are disclosed. [Means for solving the problem]

[0005] Some embodiments may be used with a main magnet having a low magnetic field strength, gradient coil assemblies, an RF coil system, and a control system for the acquisition and processing of magnetic resonance imaging data from a human patient.

[0006] In some embodiments, the magnetic field strength of the main magnet is less than 1.0 Tesla, and in other embodiments, the magnetic field strength is about 0.35 Tesla. In some embodiments, the MRI control system is configured to use low gradient magnetic field strengths (e.g., below 20 mT / m), use large flip angles (e.g., greater than 40 degrees), use RF frequency bands to keep chemical shift artifacts and susceptibility artifacts below 1 millimeter (e.g., RF frequency bands below 1800 Hz), use gradient slew rates above 75 mT / m / ms, and / or employ pulse trains that do not require dephasing or spoiler pulses. In some embodiments, the RF coil system may not include a surface coil.

[0007] The control system of the magnetic resonance imaging system is also configured to generate cine MRI (e.g., at least 4 FPS). In another embodiment, the magnetic resonance imaging system may be integrated with a radiation therapy device for radiation treatment of a human patient, and the control system may be further configured to utilize the cine MRI to track the location of tissue in the human patient. The radiation therapy device may be, for example, a linear accelerator with an energy in the range of 4-6 MV. The radiation therapy device may also be a proton therapy system, a heavy ion therapy system, or a radioisotope therapy system.

[0008] The magnetic resonance imaging system may include a split open bore magnet and may be configured to allow surgical intervention in the gap between the split magnets, for example by a robotic surgical device integrated into the system. Similarly, the gradient coil components may be split gradient coil components. The main magnet may be a superconducting magnet, a non-superconducting magnet, or a resistive magnet. The main magnet may be powered by a battery system.

[0009] Embodiments of the present subject matter may include methods according to the description provided herein, as well as articles and computer program products that include a machine-readable medium tangibly embodied therein and that cause one or more machines (e.g., computers, etc.) to perform operations that implement one or more of the described features. Similarly, it is contemplated that a computer system may include one or more processors and one or more memories coupled to the one or more processors. The memory, which may include a computer-readable storage medium, may include, encode, store, etc., one or more programs that cause one or more of the described operations to be performed. A computer-implemented method according to one or more embodiments of the present subject matter may be performed by one or more data processors present in a single computing system or across multiple computing systems. Such multiple computing systems may be connected and may exchange data and / or commands or other instructions, etc., through one or more connections, which may include, but are not limited to, connections over a network (e.g., the Internet, a wireless wide area network, a local area network, a wide area network, a wired network, etc.), connections through a direct connection between one or more of the multiple computing systems, etc.

[0010] Details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the following description. Other features and advantages of the subject matter described herein will become apparent from the description and drawings, as well as from the claims. For illustrative purposes, certain features of the presently disclosed subject matter are described with reference to specific embodiments, but it should be immediately understood that such features are not intended to be limiting. The claims following this disclosure are intended to define the scope of protection of the subject matter protected.

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, disclose certain aspects of the subject matter disclosed herein and aid in explaining some of the concepts related to the disclosed embodiments. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a simplified perspective view illustrating an example of a magnetic resonance imaging system according to certain aspects of the present disclosure. [Diagram 2] FIG. 1 is a simplified perspective view illustrating an example of a magnetic resonance imaging system incorporating an exemplary interventional device, according to certain aspects of the present disclosure. [Diagram 3] 1 is a flow chart illustrating an exemplary method of real-time MRI-guided radiation therapy, according to certain aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] This disclosure describes, inter alia, systems, methods and computer software that enable high quality magnetic resonance imaging with limited susceptibility distortion and chemical shift artifacts, coupled with sub-millimeter spatial accuracy, the ability to image at high frame rates with adequate specific absorption rates (SAR), and the ability to support real-time 2D and volumetric MRI-guided diagnostic and interventional applications.

[0014] FIG 1 illustrates one embodiment of a magnetic resonance imaging system (MRI) 100 in accordance with certain aspects of the present disclosure. In FIG 1, the MRI 100 includes a main magnet 102, a gradient coil assembly 104, and an RF coil system 106. Within the MRI 100 is a patient couch 108 on which a human patient 110 lies. The MRI 100 also includes a control system 112, which is described in more detail below.

[0015] The main magnet 102 of the MRI 100 may be a cylindrical split or open bore magnet with gap 116 as shown in FIG. 1, a closed bore cylindrical arrangement, a C-shaped arrangement, a bipolar magnet, etc. The main magnet 102 may be composed of several types of magnets, including electromagnets, permanent magnets, superconducting magnets, or combinations thereof. For example, a combined magnet or "hybrid" magnet includes a permanent magnet and an electromagnet. The main magnet 102 may be used for any commonly used magnetic field strength, but is preferably used for low magnetic field strengths. When the term "low magnetic field strength" is used herein, it refers to a magnetic field strength less than 1.0 Tesla. In particular, in certain embodiments of the present disclosure, the magnetic field strength of the main magnet 102 may be set within the range of 0.1 to 0.5 Tesla, or may be set to about 0.35 Tesla. For example, when the magnetic field strength of the main magnet is less than about 0.2 Tesla, the system may be designed to use a resistive magnet or a permanent magnet, or a combination thereof. In some embodiments, a system utilizing single or multiple resistive magnets may be powered by a DC battery system, such as a lithium-ion system such as Tesla's Powerwall® or the like.

[0016] The gradient coil assembly 104 contains the coils necessary to apply a small, variable magnetic field over and above the magnetic field of the main magnet 102 to allow spatial encoding of the imaging data. The gradient coil assembly 104 may be a continuous cylindrical assembly, a segmented gradient coil assembly as shown in FIG. 1, or other design as required for the particular MRI.

[0017] The RF coil system 106 is capable of inducing the rotation of hydrogen protons in the patient 110 and then receiving signals emanating from the patient 110. The RF coil system 106 therefore includes an RF transmitting section and an RF receiving section. The embodiment of FIG. 1 includes a single body coil performing both RF transmitting and RF receiving functions. The RF coil system 106 may alternatively split the transmitting and receiving functions into a body coil and a surface coil, or provide both transmitting and receiving functions to a surface coil. Although the RF coil system 106 shown in the embodiment of FIG. 1 has a continuous cylindrical shape, it may also be designed in a split manner such that a gap 116 opens from the patient to the outer periphery of the main magnet 102.

[0018] The control system 112 is configured to acquire and process magnetic resonance imaging data from the patient 110. The control system 112 may include multiple subsystems, such as those that control the functionality of the gradient coil assembly 104, the functionality of the RF coil system 106, or parts of the system itself, as well as those that process data received from the RF coil system 106 to perform image reconstruction.

[0019] In some useful embodiments, the control system 112 may be configured to utilize sparsely sampled image techniques rather than parallel imaging. As used herein, the term "sparsely sampled imaging techniques" refers to image acquisition and reconstruction techniques in which only a portion of the frequency space is measured (for purposes of this disclosure, less than 50% of the frequency information required to reconstruct an image using conventional backprojection techniques) and the image is reconstructed by optimizing the reconstructed image to conform to prior knowledge of the imaged subject while generally satisfying consistency between the frequency information of the reconstructed image and the measured frequency information. Sparsely sampled imaging techniques thus include techniques such as compressed sensing and volumetric imaging techniques, as disclosed in U.S. Patent Application No. 62 / 353,530, filed concurrently herewith and assigned to ViewRay Technologies, Inc.

[0020] Parallel imaging techniques are often used in magnetic resonance imaging, especially with cine MRI, to reduce the time required for data acquisition. Parallel imaging methods replace part of the time-consuming phase encoding step in the MRI process by using knowledge of the spatial distribution of signals received by multiple RF detectors (such as a surface coil with an array of "elements"). In this approach, signals are received "in parallel" from multiple coil elements, and the sampling of a smaller portion of k-space along the readout trajectory is compensated for by overlapping data from all coil elements.

[0021] However, certain embodiments of the present disclosure contemplate data acquisition and processing that do not utilize parallel imaging techniques, which in this disclosure will be referred to as "non-parallel imaging" magnetic resonance data acquisition and processing, and which also contemplate systems, methods, and computer software that incorporate a small amount of parallel imaging (possibly in an attempt to avoid infringement) that does not result in a significantly large increase in the signal-to-noise ratio, all other values ​​being designed to be constant.

[0022] In some advantageous embodiments, the MRI and control system 112 may be configured to utilize low gradient field strengths, such as below 20 mT / m, or in other cases 12 mT / m. Additionally, some advantageous embodiments may utilize relatively high gradient slew rates or rise times, such as slew rates of greater than 75 mT / m / ms. The control system 112 may be advantageously configured to utilize large flip angles, such as greater than 40 degrees. Additionally, the control system 112 may be advantageously configured to employ pulse trains that do not require dephasing pulses (herein contemplated as such pulse trains having no dephasing pulses or only a small number of dephasing or spoiling pulses such that there is no significant increase in the speed of data acquisition from a patient throughput standpoint).

[0023] In some embodiments, the control system 112 may be configured to utilize RF frequency bands to keep chemical shift artifacts and magnetic susceptibility artifacts below 1 millimeter or 0.5 millimeters. For example, the control system 112 may be configured for RF frequency bands below 1800 Hz. Estimates of potential worst-case artifacts due to magnetic susceptibility and chemical shift may be evaluated. For example, the following equation [1] may be used to estimate magnetic susceptibility artifacts for the worst case, e.g., 8 ppm, perturbation observed in human distortion estimates:

[0024]

number

[0025] where δms [mm] is the spatial distortion due to magnetic susceptibility artifacts in millimeters. Magnetic susceptibility artifacts result from magnetic susceptibility-induced magnetic field changes, where magnetic susceptibility is expressed in parts per million of the main magnetic field strength Bo [T] (in Tesla), and Ge [T / mm] is the gradient encoding strength in Tesla per millimeter.

[0026] In addition, the following equation [2] can be used to estimate the deviation due to chemical shift.

[0027]

number

[0028] Here, δcs [mm] is the spatial distortion due to chemical shift in millimeters, 3.5 [ppm] is the relative difference in parts per million in the Larmor frequency of oxygen-bonded hydrogen (OH) relative to carbon-bonded hydrogen (CH) at a pixel or voxel size (PixelSize, millimeters), fBo is the Larmor frequency of hydrogen in water, and BW [Hz / pixel] is the frequency band for a pixel or voxel in hertz per pixel or hertz per voxel.

[0029] The worst case distortion is the sum of these two distortions plus any remaining distortion due to the nonlinear components of the uncorrected gradient fields.

[0030] In one particular embodiment of a magnetic resonance imaging system 100 according to the present disclosure, the magnetic field strength of the main magnet 102 is about 0.35 Tesla, and the control system 112 is configured to utilize gradient magnetic field strengths below 12 mT / m, gradient slew rates above 75 mT / m / ms, flip angles greater than 40 degrees, an RF frequency band less than 1800 Hz, and pulse trains that do not include dephasing pulses. The control system 112 may also be configured to utilize a sparsely sampled imaging technique for non-parallel imaging.

[0031] In another embodiment of the magnetic resonance imaging system 100, the magnetic field strength of the main magnet 102 is about 0.15 Tesla, and the control system 112 may be configured to utilize gradient strengths below 10 mT / m, gradient slew rates above 75 mT / m / ms, an RF frequency band below 1000 Hz, and pulse trains that do not include dephasing pulses. In this embodiment, the control system 112 may be configured to utilize a sparsely sampled imaging technique for non-parallel imaging.

[0032] As discussed further herein, certain embodiments of the disclosed systems, methods, and computer software are beneficial for cine planar, cine biplanar, or real-time volumetric or "4D" (3D spatial plus time dimensions) magnetic resonance imaging. The control system 112 may therefore be configured to acquire and process data as necessary and reconstruct images to create cine MRI, for example, to enable cine MRI at least 4 frames per second while maintaining a certain acceptable absorption rate in the patient 110.

[0033] Conventional wisdom holds that while high main magnet field strength is always desirable for high signal-to-noise ratios, the desired field strength is limited primarily by size and cost considerations. Through higher signal-to-noise ratios, contrast, and resolution, higher field strengths typically improve a physician's ability to make a diagnosis based on the resulting images. However, embodiments of the present disclosure that utilize low main magnet field strengths (e.g., below 1.0 Tesla) result in high quality images and additionally provide several benefits.

[0034] For example, embodiments of the present disclosure can include RF frequency bands below 1800 Hz, which reduces chemical shift artifacts (i.e., hydrogen atoms in different chemical environments, such as water and oil, are partially shielded from the main magnetic field due to differences in the sharing of electrons in OH and CH chemical bonds, and therefore have different atomic magnetic resonance chemical shifts, which appear in different spatial locations when positioning the frequency encoded signal).While high field systems exhibit significant chemical shift artifacts and require high RF frequency bands (and the associated low signal to noise ratios), the low field systems disclosed herein can maintain high spatial integrity using lower RF frequency bands.

[0035] In addition, systems with high main magnetic field strengths exhibit significant magnetic sensitivity artifacts, leading to spatially distorted images, when the diamagnetic and paramagnetic (and rarely ferromagnetic) properties of the imaging subject perturb the magnetic field. While these issues in high field systems can typically be addressed through an increase in gradient field strength, embodiments of the present disclosure avoid the same level of artifacts and therefore may utilize lower gradient field strengths, leading to improved signal-to-noise ratios and lower specific absorption rates.

[0036] Furthermore, the systems, methods and software discussed herein can be implemented without parallel imaging, which would cause a decrease in signal-to-noise ratio, and therefore an increase in imaging speed is expected. Instead, the sparse sampling technique disclosed herein allows acquisition at high frame rates with a relatively high signal-to-noise ratio without significantly reducing the image acquisition speed. For example, by avoiding the use of "grid" k-space data through a priori data acquired prior to the scan, recursive optimization techniques are applied. By not using parallel imaging, the use of phased array receive coils can also be avoided. This achieves high quality imaging with less complex techniques. The number of RF receive channels used is reduced, and the number of expensive spectrometers is reduced as effectively only one RF receive channel can be employed.

[0037] Certain embodiments of the present disclosure may also be employed without a surface coil in contact with the patient, instead imaging is performed with only a body coil, including both transmit and receive coils, mounted within the bore of the MRI.

[0038] In addition, simultaneous multislice imaging techniques may be beneficially employed in which multiple imaging slices or subvolumes are stimulated simultaneously and read out simultaneously. One example of simultaneous multislice stimulation sums multiple RF waveforms with different phase modulation functions, resulting in a multiband pulse that can stimulate desired slices in the presence of a common slice selection gradient.

[0039] Additionally, embodiments of the present disclosure may utilize relatively high flip angles that would otherwise cause patient heating at high main magnetic field strengths. Large flip angles in embodiments of the present disclosure may result in improved image contrast and signal-to-noise ratios.

[0040] In addition, the low main magnetic field strength embodiments discussed herein exhibit faster RF signal decay, allowing for pulse trains that do not require dephasing pulses (with the benefit of a lower specific absorption rate).

[0041] The lower main magnetic field strength in certain embodiments of the present disclosure may also allow for lower frequency RF stimulation pulses, thereby reducing patient heating from those pulses.

[0042] Furthermore, the well-controlled specific absorption rate exhibited by the embodiments of the present disclosure allows data to be processed and acquired fast enough for high frame rate cine MRI.

[0043] Due to the numerous advantages discussed above, embodiments of the present disclosure are suitable for high quality cine MRI with acceptable patient specific absorption rates. These embodiments control magnetic susceptibility and chemical shift artifacts and provide high spatial consistency, which can be critical in certain diagnostic and interventional applications.

[0044] Embodiments of the present disclosure may be useful in numerous applications for diagnostic cine MRI, including, for example, anatomical localizers, repeated high-speed imaging for motion localization and study (e.g., vocalization), imaging of freely moving subjects (e.g., fetal MRI), cardiac imaging, etc.

[0045] The embodiments of the present disclosure are also useful for interventional applications that also benefit from high spatial alignment and controlled specific absorption rates. Examples of interventional applications include angioplasty, stent delivery, thrombolysis, aneurysm elimination, thrombolysis, fibroid embolization, and many other applications where fluoroscopy is currently used (and where the use of cine MRI reduces patient radiation exposure).

[0046] The disclosed embodiments may also be used for image-guided surgery and may provide real-time intraprocedural guidance in multiple orthogonal planes, imaging feedback regarding device position, guidance and / or warning systems, etc. An open-bore MRI embodiment similar to that shown in Fig. 1 (but with a split RF coil system 106) may be particularly beneficial for such interventional procedures. The MRI 100 may thus be configured to permit surgical intervention in a split magnet and may further include a robotic surgical device integrated into the system.

[0047] Yet another advantage of the low magnetic field strength associated with certain embodiments of the present disclosure is the reduction in magnetic forces applied to any interventional devices employed in conjunction with the MRI 100, such as robotic surgical devices, biopsy devices, cryoablation units, brachytherapy devices, radiation therapy devices, etc.

[0048] In one embodiment of the magnetic resonance imaging system 100 in combination with an interventional device (eg, a radiation therapy device such as a linac), a low field strength, non-superconducting magnet is utilized, such as, for example, a resistive magnet, a permanent magnet, or a hybrid magnet.

[0049] Another beneficial application of certain embodiments of the present disclosure is in the field of image-guided radiation therapy, which also benefits from the ability of the present disclosure to provide high frame rate cine MRI with high spatial coherence, both of which are key to accurately tracking the subject being treated and avoiding delivering large amounts of ionizing radiation to critical structures of the patient.

[0050] FIG. 2 illustrates the MRI 100 further configured to incorporate a radiation therapy device to treat the patient 110. In one embodiment, the MRI 100 may include a gantry 202 located in the gap 116 of the open bore MRI. The gantry 202 may incorporate a radiation therapy device 204 and be configured to direct a radiation therapy beam 206 to the patient 110. In one particular embodiment, the radiation therapy device 204 is a linear accelerator having an energy in the range of 4-6 MV, and as shown, the components of the linear accelerator may be separated into separate shielded containers 208 that are positioned around the gantry 202. These linac components may then be connected to an RF waveguide 210. Although FIG. 2 illustrates a particular radiation therapy device placement, the present disclosure contemplates the incorporation of any type of radiation therapy system, such as proton therapy, heavy ion therapy, radioisotope therapy, etc.

[0051] As noted above, the control system 112 of the magnetic resonance imaging system 100 may be configured for cine MRI and further configured to track the position of tissue in the human patient 110 using the cine MRI.

[0052] An additional advantage of the disclosed embodiments utilizing a lower field strength main magnet 102 is that it reduces distortions in the ionizing radiation dose distribution in the patient 110 caused by the magnetic Lorentz forces exerted by the movement of secondary electrons (and positrons). The Lorentz forces exerted by the higher field main magnet can cause the electrons (and positrons) to scatter excessively, causing them to rotate out of their natural orbits and become trapped at low density interfaces. This can potentially lead to unexpected harmful dose concentrations within the patient.

[0053] FIG. 3 illustrates an example method of real-time image-guided radiation therapy according to an embodiment of the present disclosure. At 302, magnetic resonance imaging data may be acquired from a human patient 110 through a low field strength superconducting main magnet, gradient coil assembly 104, and magnetic resonance imaging system 100. At 304, the magnetic resonance imaging data is processed. At 306, radiation therapy is administered to the human patient 110. At 308, the magnetic resonance imaging data is utilized to track the location of one or more tissues in the patient 110. Then, at 310, the radiation therapy delivery is modified based on the results of tracking the location of one or more tissues in the patient 110. The modification of the treatment may include stopping the treatment, reoptimizing the treatment, adjusting the radiation therapy beam, etc. The example method illustrated in FIG. 3 may include some or all of the features described above (e.g., low gradient field strength, large flip angle, RF frequency band for spatial coherence, etc.).

[0054] When this disclosure states that "magnetic resonance imaging systems are configured to operate in a particular manner," it means that those systems are set up to operate in that manner and are configured as intended to do so, regardless of whether they are also configured to utilize single or multiple pulse sequences or settings that do not operate in the manner described or claimed herein.

[0055] The present disclosure contemplates that the computations disclosed in the embodiments herein may be performed in any number of ways, applying the same concepts taught herein, and that such computations are equivalent to the disclosed embodiments.

[0056] One or more aspects or features of the subject matter described herein may be implemented in digital electronic circuitry, embedded circuitry, specially designed application specific embedded circuits (ASICs), field programmable gate array (FPGA) computer hardware, firmware, software, and / or combinations thereof. Various of these aspects or features include implementation in one or more computer programs executable and / or translatable on a programmable system including at least one programmable processor. The processor may be special purpose or general purpose and may be coupled to a storage system for transmitting and receiving data and instructions, at least one input device, and at least one output device. The programmable system or computing system may include clients and servers. The clients and servers are generally remote from each other and typically interact through a remote communications network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0057] These computer programs, also referred to as programs, software, software applications, applications, components, or codes, include machine instructions for a programmable processor and may be implemented in high-level procedural languages, object-oriented programming languages, functional programming languages, logic programming languages, and / or assembly / machine languages. As used herein, the term "machine-readable medium" (or "computer-readable medium") refers to any computer program product, apparatus, and / or device, such as magnetic disks, optical disks, memories, and programmable logic devices (PLDs), used to provide machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. The term "machine-readable signal" (or "computer-readable signal") refers to any signal used to transmit machine instructions and / or data to a programmable processor. A machine-readable medium may store such machine instructions non-transitoryly, such as, for example, a non-transitory solid-state memory or a magnetic hard drive, or any equivalent storage medium. The machine-readable medium may alternatively or additionally be capable of storing such machine instructions in a temporary manner, such as exemplified by a processor cache or other random access memory associated with one or more physical processor cores.

[0058] To provide for interaction with a user, one or more aspects or features of the subject matter described herein may be implemented on a computer having a display device, such as a cathode ray tube (CRT) or liquid crystal display (LCD) or light emitting diode (LED) monitor, for displaying information to a user, and a keyboard and a pointing device, such as a mouse or trackball, for allowing the user to provide input to the computer. Other types of devices may also be used to provide interaction with a user. For example, feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; input from the user may be received in any form, including, but not limited to, sound, voice, or touch input. Other possible input devices include, but are not limited to, touch screens or other contact-sensing devices, such as single-point or multi-point resistive or capacitive trackpads, voice recognition hardware and software, optical scanners, optical pointers, digital image capture devices, and associated translation software.

[0059] In the above description and in the claims, phrases like "at least one" or "one or more" may appear followed by a conjunctive list of elements or features. The term "and / or" may also appear in a list of two or more elements or features. These phrases are intended to mean any of the listed elements or features individually, or any one of the listed elements or features in combination with any one of the other listed elements or features, unless otherwise implicitly or explicitly stated by the context. For example, the phrases "at least one of A and B," "one or more of A and B," and "A and / or B" all mean "A only, B only, or both A and B." A similar interpretation is intended in lists containing more than two. For example, the phrases "at least one of A, B, and C," "one or more of A, B, and C," and "A, B, and / or C" are all intended to mean "A only, B only, C only, both A and B, both A and C, both B and C, and all of A through C." The phrase "based on" above and in the claims means "based at least in part on" and allows for unrecited features or elements.

[0060] The subject matter described herein may be implemented on systems, devices, methods, computer programs, and / or articles in any desired arrangement. The methods or logic flows illustrated in the accompanying drawings and / or described herein do not necessarily require the depicted order or procedural order to achieve the desired results. The embodiments described in the foregoing description do not represent all embodiments consistent with the subject matter described herein, but are merely some examples consistent with aspects related to the subject matter described. Although some variations have been described in detail above, other modifications or additions are possible. In particular, further features and / or variations may be provided in addition to those described herein. The embodiments described above may be directed to various combinations and subcombinations of the disclosed elements, and / or combinations and subcombinations of some of the additional features set forth above. Furthermore, the advantages described above are not intended to limit the application of any issued claims to processes or structures that achieve any or all of the advantages.

[0061] In addition, the section headings may not limit or characterize the invention or inventions set forth in any claims that may issue from this disclosure. In particular, and by way of example, even if a heading refers to a "Technical Field," such claims should not be limited by the language chosen under this heading to describe the so-called technical field. Furthermore, the description of a technology in the "Technical Background" is not to be construed as an admission that such technology is prior art to any invention or inventions in this disclosure. Nor is the "Summary of the Invention" to be recognized as a feature of the invention or inventions set forth in the claimed claims. Furthermore, a general reference to this disclosure or use of the word "invention" in the singular does not imply any limitations in the claims set forth below. Multiple inventions may be set forth by the limitations of the multiple claims asserted by this disclosure. And accordingly, such multiple claims define the invention or inventions and their equivalents that are protected thereby.

Claims

1. 1. A magnetic resonance imaging system (MRI), comprising: a main magnet having a low magnetic field strength; A gradient coil assembly; An RF coil system; and a control system configured for acquisition and processing of magnetic resonance imaging data from a human patient, the control system being configured to utilize a sparse sampling imaging technique without parallel imaging. Magnetic resonance imaging system.

2. The magnetic field strength of the main magnet is less than 1.0 Tesla.

10. The magnetic resonance imaging system of claim 1.

3. The MRI control system is further configured to utilize low gradient magnetic field strengths.

3. The magnetic resonance imaging system of claim 2.

4. The gradient magnetic field strength is less than 20 mT / m; 4. A magnetic resonance imaging system according to claim 3.

5. The control system is further configured to utilize a large flip angle.

3. The magnetic resonance imaging system of claim 2.

6. The flip angle is greater than 40 degrees.

6. A magnetic resonance imaging system as claimed in claim 5.

7. The MRI control system is further configured to utilize RF frequency bands to keep chemical shift and magnetic susceptibility artifacts below 0.5 millimeters.

3. The magnetic resonance imaging system of claim 2.

8. The RF frequency band is less than 1800 Hz.

8. A magnetic resonance imaging system according to claim 7.

9. The magnetic field strength of the MRI is about 0.35 Tesla.

3. The magnetic resonance imaging system of claim 2.

10. the control system is configured to employ a pulse train that does not require a dephasing pulse; 3. The magnetic resonance imaging system of claim 2.

11. The control system is configured to utilize a gradient slew rate of greater than 75 mT / m / ms.

3. The magnetic resonance imaging system of claim 2.

12. The control system is configured to employ a simultaneous multi-slice imaging technique.

3. The magnetic resonance imaging system of claim 2.

13. The control system is further configured to generate a cine MRI.

3. The magnetic resonance imaging system of claim 2.

14. The control system is further configured to acquire magnetic resonance imaging data at a rate enabling cine MRI of at least 4 frames per second.

14. A magnetic resonance imaging system according to claim 13.

15. The main magnet is a divided magnet.

3. The magnetic resonance imaging system of claim 2.

16. the gradient coil component is a segmented gradient coil component; 16. A magnetic resonance imaging system according to claim 15.

17. a radiation therapy device integrated into the system; The radiation therapy device is configured for radiation therapy of a human patient.

16. A magnetic resonance imaging system according to claim 15.

18. The control system is further configured to utilize cine MRI to track the location of tissue in the human patient.

20. A magnetic resonance imaging system as claimed in claim 17.

19. The radiation therapy device is a linear accelerator.

20. A magnetic resonance imaging system as claimed in claim 17.

20. the linear accelerator has an energy in the range of 4-6 MV; 20. A magnetic resonance imaging system as claimed in claim 19.

21. The radiation therapy device is selected from the group consisting of a proton therapy system, a heavy ion therapy system, and a radioisotope therapy system.

20. A magnetic resonance imaging system as claimed in claim 17.

22. and further configured to allow surgical intervention in the gap of the split magnets.

17. A magnetic resonance imaging system according to claim 16.

23. and further comprising a robotic surgical device integrated into the system.

23. A magnetic resonance imaging system as claimed in claim 22.

24. The main magnet is a superconducting magnet.

3. The magnetic resonance imaging system of claim 2.

25. The main magnet is a resistive magnet.

3. The magnetic resonance imaging system of claim 2.

26. The main magnet is powered by a battery system.

26. A magnetic resonance imaging system as claimed in claim 25.

27. The main magnet is a non-superconducting magnet.

20. A magnetic resonance imaging system as claimed in claim 17.

28. The RF coil system does not include a surface coil.

3. The magnetic resonance imaging system of claim 2.

29. When executed by at least one programmable processor, the at least one programmable processor is caused to: acquiring magnetic resonance imaging data from a human patient via a magnetic resonance imaging system (MRI) comprising a low field strength main magnet, a gradient coil assembly, and an RF coil system, said acquiring utilizing a sparse sampling imaging technique without parallel imaging; processing the magnetic resonance imaging data, the processing comprising reconstructing an image of the human patient; a non-transitory machine-readable medium storing instructions for performing operations including Computer program products.

30. The magnetic field strength of the main magnet is less than 1.0 Tesla.

30. A computer program product according to claim 29.

31. The acquiring step utilizes a low gradient magnetic field strength.

31. A computer program product according to claim 30.

32. The gradient magnetic field strength is less than 20 mT / m.

32. A computer program product according to claim 31.

33. the obtaining step utilizing a large flip angle.

31. A computer program product according to claim 30.

34. The flip angle is greater than 40 degrees.

34. A computer program product according to claim 33.

35. The acquiring step utilizes RF frequency bands to keep chemical shift and magnetic susceptibility artifacts below 0.5 millimeters.

31. A computer program product according to claim 30.

36. The RF frequency band is less than 1800 Hz.

36. A computer program product according to claim 35.

37. The magnetic field strength of the MRI is about 0.35 Tesla.

31. A magnetic resonance imaging system according to claim 30.

38. the obtaining step employs a pulse train that does not require a dephasing pulse; 31. A computer program product according to claim 30.

39. The control system is configured to utilize a gradient slew rate of greater than 75 mT / m / ms.

31. A computer program product according to claim 30.

40. The control system is configured to employ a simultaneous multi-slice imaging technique.

31. A computer program product according to claim 30.

41. said processing and reconstructing steps including generating a cine MRI; 31. A computer program product according to claim 30.

42. and generating the cine MRI includes at least 4 frames per second.

42. A computer program product according to claim 41.

43. further comprising administering radiation therapy to the human patient.

31. A computer program product according to claim 30.

44. utilizing the magnetic resonance imaging data to track the location of tissue in the human patient.

44. A computer program product according to claim 43.

45. and modifying the administration of the radiation therapy based on the tracking of the location of tissue in the human patient.

44. A computer program product according to claim 43.

46. and further comprising utilizing the magnetic resonance imaging data to monitor a surgical intervention.

31. A computer program product according to claim 30.

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