Unilateral magnetic resonance imaging system with a hole for intervention and method of operating the same

Abstract

An imaging apparatus and method for imaging a subject using magnetic resonance imaging (MRI), wherein the imaging apparatus comprises only a unilateral device for the purpose of imaging structures within the subject.

Description

[0001] Cross-references and priority claims

[0002] This patent application claims priority to U.S. Provisional Patent Application Serial No. 62 / 516,698, filed on June 8, 2017, entitled “UNILATERAL MAGNETIC RESONANCEIMAGING SYSTEM WITH APERTURE FOR INTERVENTIONS,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The disclosed embodiments provide methods and apparatus for clinical imaging or treatment of living organisms, or for examining inanimate objects. Background Art

[0004] In conventional magnetic resonance imaging (MRI) scanners, the magnetic field used to generate images is generated by a device located around the subject. For the purposes of this specification, the term "subject" is understood to be a human or other animal with or without a disease. For example, a superconducting clinical MRI typically consists of a superconducting solenoid, the aperture of which becomes the imaging volume. The subject or patient is guided into the aperture where all imaging is performed. However, due to the limited size of the aperture, these MRI systems limit the mobility of the patient and may limit the permissible body size of the patient that can be imaged.

[0005] To achieve greater patient mobility and flexibility, open MRI systems have been developed. These systems typically consist of dual-plane magnetic field generating components that create a magnetic field within a gap between two planes. The patient is imaged within this gap. Typically, the gap distance in these systems is greater than the solenoid structure of a superconducting magnet, but the patient is still surrounded by the MR system. Summary of the Invention

[0006] The disclosed embodiments provide a novel imaging apparatus and method for imaging a subject using MRI, wherein the imaging apparatus comprises only a unilateral device for the purpose of imaging structures within the subject. For the purposes of this specification, the terms "unilateral device" and "single-sided device" are understood to mean a device that is positioned less than 360 degrees around the subject for operation. For example, a conventional cylindrical MRI bore is not considered a unilateral device.

[0007] According to at least one embodiment, such an apparatus and corresponding method may be used, for example, to image the pelvic region of a subject.

[0008] According to the disclosed embodiments, due to the non-enclosed geometry of the novel imaging device, the subject's mobility is less restricted than in conventional MRI scanners.

[0009] According to the disclosed embodiments, a unilateral MRI system is provided that includes an access port through which an intervention can be performed on a subject. For the purposes of this specification, the term "intervention" is understood to mean a biopsy or treatment method involving physical contact with a portion of a subject. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In particular, the detailed description refers to the accompanying drawings, in which:

[0011] Figure 1 An embodiment of the invention is shown wherein a magnetic field generating device is placed near the region of interest.

[0012] Figure 2 An example of the composition of one layer of a magnetic field generating device composed of magnet layers according to the disclosed embodiments is shown. DETAILED DESCRIPTION

[0013] Conventional unilateral MRI systems do not provide an access port through which interventions can be performed. Examples of such conventional systems include U.S. Patent 4,721,914 to Eiichi Fukushima, entitled "Apparatus for Unilateral Generation of a Homogeneous Magnetic Field," which is incorporated herein by reference in its entirety, and U.S. Patent 6,489,872 to the same inventor, entitled "Unilateral Magnet Having a Remote Uniform Field Region for Nuclear Magnetic Resonance," which is incorporated herein by reference in its entirety.

[0014] In contrast, according to the disclosed embodiments, a unilateral MRI system is provided that includes such an access aperture through which intervention on a subject may be performed. Figure 1 1 shows an embodiment of the present invention, wherein a magnetic field generating device 100 is placed near a region of interest 110. Figure 1 As shown in FIG, there is an access hole 120 perpendicular to the face of the magnet assembly 100 that is close to the region of interest 110.

[0015] The disclosed embodiments utilize a magnetic field generating device 100 and a radio frequency generating and recording device 130 positioned on one face of the device. The magnetic field generating device 100 can be positioned only near a single face of a region of interest 110. The geometry of the device 100 may include one or more apertures (or access holes) 120. This structure enables intervention on a subject, for example, a human or animal patient / subject can be easily repositioned. In addition, the one or more apertures (or access holes) 120 enable enhanced access to one or more structures in the subject to be imaged.

[0016] The magnetic field generating device 100 may be composed of magnetic layers, wherein one layer is composed of Figure 2 As shown. Figure 2 As shown in FIG, layer 200 includes magnets 210 and 220 oriented in a direction so as to provide a magnetic field opposite to that provided by magnets in the same layer or in other layers. Figure 2 As shown in FIG, the magnets 210 can be oriented in a position so as to provide a magnetic field opposite to the magnetic field generated by the magnets 220 in the same layer. Figure 2 Shown as hole 230.

[0017] According to disclosed embodiments, magnetic field generating device 100 may include an array of one or more magnetic components, examples of which are 210 and 220 , in one or more layers (one example of a layer is 200 ).

[0018] These layers can generate a desired magnetic profile, the uniformity of which reaches a certain degree of uniformity in terms of magnetic field strength, or has a built-in magnetic field gradient that varies linearly in space, or these layers have another characteristic magnetic field profile shape that is well-suited for imaging above region 110. According to at least one embodiment, the magnetic profile in region 110 can be uniform. Alternatively, according to at least one embodiment, the magnetic profile in region 110 can be non-uniform, in which case an appropriate algorithm for reconstruction can be used to generate an image. An example of such an algorithm is provided by Dominic Holland et al. in 2010 in the journal Neuroimage, Vol. 50, pp. 175-183, titled "Efficient correction of inhomogeneous static magnetic field-induced distortion in EchoPlanar Imaging" (incorporated herein by reference in its entirety). Other correction methods can be applied, such as using maximum likelihood reconstruction. Similarly, the generation of magnetic profiles can be performed based on patented innovations for imaging living tissue.

[0019] More specifically, the imaging system 130 may include electric coils and / or electropermanent magnets, wherein the electropermanent magnets are magnetized by a transient current flowing through the electric coils and remain activated until the magnetization is removed by another transient current flowing through the electric coils. Radio frequency, gradient, prepolarization, and / or shimming coils may also be included as may be required for forming an image.

[0020] Alternatively, ultrafast and high-amplitude gradient pulses as described in U.S. Patent 8,154,286, entitled "APPARATUS AND METHOD FOR DECREASING BIO-EFFECTS OF MAGNETIC FIELDS" to Irving Weinberg, and related patents and patent applications (related by priority claim) (all of which are incorporated herein by reference) can be used to collect multiple sets of data points to achieve high spatial resolution and signal-to-noise ratio without causing uncomfortable neural stimulation. Such high magnetic field gradient strengths can be 400 mT or higher with rise times of 10 microseconds or less. The gradient pulses can be so fast that acquisition can be performed in very short times (e.g., 10 seconds or less) so that there is little motion of the chest during acquisition, thereby reducing the loss of resolution caused by "motion blur."

[0021] Optionally, in accordance with at least one embodiment, the prepolarization coil may be activated to improve the signal-to-noise ratio as taught in U.S. patent application Ser. No. 12 / 488,105 to Weinberg, entitled “RADIOMETAL-LABELEDAMINO ACID ANALOGS, IMAGING AND THERAPEUTIC AGENTS INCORPORATING THE SAME, AND METHODS USING THE SAME,” incorporated herein by reference.

[0022] According to at least one embodiment, as taught by Urdaneta et al. in the 2011 IEEE Medical Imaging Proceedings, entitled "Good-bye Wires and Formers: 3-D Additive Manufacturing and Fractal Cooling Applied to Gradient Coils", one or more coils (or electropermanent magnets) within an MRI system can be manufactured using additive manufacturing.

[0023] The region 110 having the desired magnetic profile on one side of the device may not be adjacent to the device, for example, the region 110 may be one to one hundred centimeters away from the device 100. The magnetic component 210 may be a permanent magnet, or an electromagnet, or an electropermanent magnet. The magnetic component 210 may be a discrete magnet, or may be a portion of a magnetizable material that has been deposited by additive manufacturing and has been magnetized during or after deposition.

[0024] For the purposes of this invention, an electropermanent magnet may be defined as a combination of a hard magnetic material and a soft magnetic material with one or more current-carrying coils, wherein a current flowing through the one or more coils magnetizes the soft magnetic component, as disclosed in U.S. Patent Application No. 15 / 427,426 to Weinberg and Nacev, entitled "METHOD AND APPARATUS FOR MANIPULATING ELECTRO-PERMANENT MAGNETS FOR MAGNETIC RESONANCE IMAGING AND IMAGE GUIDED THERAPY," incorporated herein by reference. In this specification, the terms "hard magnetic material" and "soft magnetic material" are used to describe materials having different levels of magnetic coercivity, with hard magnetic materials having a higher magnetic coercivity than soft magnetic materials. It should be understood that for the purposes of this specification, we will refer to "soft magnetic materials" (e.g., Alnico) as "hard magnetic materials," as compared to some other materials (e.g., Permalloy). Thus, the terms "hard magnetic material" and "soft magnetic material" are used to generally describe many different materials without particular limitation as to whether the material is generally considered to be "hard" or "soft."

[0025] For purposes of the present invention, the term "opposite orientation" refers to an orientation that is not parallel to another orientation. It should be understood that the present invention can be used in conjunction with other components (e.g., a radio frequency electromagnetic field generator) to create magnetic resonance images of subjects or structures in region of interest 110. It should be understood that some or all of those subjects or structures can be part or all of a living animal or human or an inanimate object. It should be understood that interventions such as biopsies or treatments can be performed partially or completely using aperture 120.

[0026] It will be appreciated that the device 100 can be used in conjunction with other components, such as a computer and / or a power supply and / or coils for generating magnetic and / or electromagnetic fields, in order to obtain the desired result of a meaningful image. It will be appreciated that the image can use the principles of proton magnetic resonance imaging, or the principles of magnetic resonance imaging of other particles (e.g., electrons or sodium atoms), or other imaging principles (e.g., magnetic particle imaging or impedance imaging). It will be appreciated that the imaging device can be used to deliver therapy by manipulating a magnetizable material using a magnetic field generated by a magnetic field generating device. It will be appreciated that the manipulation can be performed at one time, and the imaging can be performed at another time to guide the manipulation.

[0027] For the purposes of the disclosed embodiments, the term "imaging" includes imaging techniques that utilize various components to form images using magnetic resonance or magnetic particle imaging. It should be understood that such components include coils or magnets (or electromagnetic permanent magnets) that polarize protons or other atomic nuclei or electrons in one or more structures to be imaged, wherein gradient coils and / or radiofrequency coils form the image. Thus, although not shown in detail herein, it should be understood that the disclosed embodiments can be used in conjunction with a support structure that can hold the imaging system and can include other components required to operate or move the imaging system, such as wheels and / or batteries.

[0028] Furthermore, it should be understood that an associated display system is not shown, but is understood to be present in order to view images produced by the imaging system.

[0029] Furthermore, it should be understood that, for one or more structures, the disclosed embodiments can image multiple segments of the one or more structures at once, as it may be difficult to achieve very good uniformity across the entirety of the structure to be imaged in unilateral MRI. It should be understood that, depending on the gradients applied during image acquisition, the spatial resolution of some portions of the one or more structures to be imaged (e.g., chest tissue) may be different than the spatial resolution of other portions, which may be useful in order to better characterize certain regions of the tissue.

[0030] It should be understood that the operations set forth herein can be implemented in conjunction with or under the control of one or more general-purpose computers that run software algorithms to provide the presently disclosed functionality and convert these computers into special-purpose computers.

[0031] Furthermore, in view of the above teachings, those skilled in the art will recognize that the exemplary embodiments described above can be based on the use of one or more programmed processors programmed by an appropriate computer program. However, hardware component equivalents (such as dedicated hardware and / or dedicated processors) can be used to implement the disclosed embodiments. Similarly, general-purpose computers, microprocessor-based computers, microcontrollers, optical computers, analog computers, dedicated processors, dedicated circuits, and / or dedicated hard-wired logic can be used to construct alternative equivalent embodiments.

[0032] Furthermore, it should be understood that control and coordination of the aforementioned components may be provided using software instructions that may be stored in a tangible, non-transitory storage device (such as a non-transitory computer-readable storage device storing instructions) that, when executed on one or more programmed processors, perform the method operations and resulting functions described above. In this context, the term "non-transitory" is intended to exclude transmitted signals and propagating waves, but does not exclude storage devices that are erasable or rely on power to retain information.

[0033] In view of the above teachings, those skilled in the art will understand that the program operations and processes for implementing certain embodiments described above, as well as the associated data, may be implemented using disk storage and other forms of storage devices, including but not limited to non-transitory storage media (where non-transitory is intended to exclude only propagating signals and not transient signals, as transient signals are erased by removal of power or an explicit erase action), such as, for example, read-only memory (ROM) devices, random access memory (RAM) devices, network storage devices, optical storage elements, magnetic storage elements, magneto-optical storage elements, flash memory, magnetic core memory, and / or other equivalent volatile and non-volatile storage technologies, without departing from the specific embodiments. Such alternative storage devices should be considered equivalents.

[0034] Although specific illustrative embodiments have been described, it is apparent that many alternatives, modifications, permutations, and variations will become apparent to those skilled in the art based on the foregoing description. Therefore, the various embodiments described above are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit and scope of the present invention.

Claims

1. A unilateral magnetic resonance apparatus (100) for performing magnetic resonance imaging of one or more structures included in a subject, the unilateral magnetic resonance apparatus comprising: One or more arrays of magnetic components (210, 220) in one or more layers (200) to generate a magnetic field on one side of the single-sided magnetic resonance device (100) having a built-in magnetic field gradient that varies linearly in space, the magnetic field having a well-characterized magnetic field profile suitable for imaging over an area, the magnetic components being permanent magnets, or electromagnets, or electropermanent magnets, wherein each electropermanent magnet is a combination of hard magnetic material and soft magnetic material and one or more current-carrying coils configured to magnetize the soft magnetic material, wherein some of the magnetic components (210) in one layer are oriented in a direction so as to provide a magnetic field opposite to that provided by other magnetic components (220) in the same layer or in other layers; and an access hole (230) disposed through the magnetic component to enable intervention on the imaged subject, Wherein, the subject is a living animal or a human.

2. The single-sided magnetic resonance apparatus (100) according to claim 1, wherein: The unilateral magnetic resonance apparatus (100) is used for imaging the pelvic region of a subject.

3. The single-sided magnetic resonance apparatus (100) according to claim 1, wherein: The magnetic field on the one side of the unilateral magnetic resonance device (100) is used to image a subject at a distance from the unilateral magnetic resonance device (100).

4. The single-sided magnetic resonance apparatus (100) according to claim 1, wherein: The axis of the access hole (230) is perpendicular to the face of the single-sided magnetic resonance device.

5. A method of imaging one or more structures included in a subject using a unilateral magnetic resonance apparatus (100) according to claim 1, the method comprising: Positioning the unilateral magnetic resonance apparatus (100) such that the one or more structures of the subject are located in a region where the magnetic field has a built-in magnetic field gradient that varies linearly in space suitable for imaging; and imaging the one or more structures using magnetic resonance imaging using the unilateral magnetic resonance device (100), Wherein, the subject is a living animal or a human.

6. The method according to claim 5, wherein: The subject's pelvic region was imaged.

7. The method according to claim 5, wherein: The axis of the access hole (230) is perpendicular to the surface of the single-sided magnetic resonance device (100).

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