Resistance electromagnet system

Abstract

The invention relates to a resistive electromagnet system. An MRI system having a resistive solenoid electromagnet for whole body magnetic resonance imaging (MRI) may include ferromagnetic material within the envelope of the electromagnet, i.e., a conductor generating a primary electromagnetic field around a volume region of the electromagnet. The system may be configured to have a field strength of at least 0.05 Tesla, and its primary electromagnetic field may be generated by the conductor layer rather than the conductor bundle. Certain electromagnet designs may be manufactured using non-metallic formers, such as glass fibers, and may be configured to form rigid objects together with conductor layers by securing them together with epoxy. The electromagnet may be configured to have two separate halves, which may be held apart by a securing structure such as carbon fibers. Power supplies for certain electromagnets herein may have current fluctuations of at least one ten thousandth at frequencies of 180 Hz or more without the need for additional current filters.

Description

[0001] This application is a divisional application of the invention patent application with the application date of November 5, 2018, application number 201880095675.5, and invention name “Resistive Electromagnetic System”.

[0002] Related Applications

[0003] This application claims priority to and the benefit of U.S. Provisional Application No. 62 / 672,525, filed on May 16, 2018, entitled “Resistive Electromagnet Systems and Methods,” and U.S. Provisional Application No. 62 / 677,546, filed on May 29, 2018, entitled “Resistive Electromagnet Design and Construction,” the contents of each of which are hereby incorporated by reference in their entirety. Technical Field

[0004] The present invention relates to a resistance electromagnet system. Background Art

[0005] Magnetic resonance imaging (MRI) or nuclear magnetic resonance imaging is a non-invasive imaging technique that uses the interaction between radio frequency pulses, strong magnetic fields (modified by weak gradient fields applied across them to locate and encode or decode phase and frequency) and body tissues to acquire projections, spectral signals, and planar or volumetric images from within a patient. Magnetic resonance imaging is particularly useful in soft tissue imaging and can be used in the diagnosis of disease. Real-time or cine MRI can be used to diagnose medical conditions that require imaging of moving structures within a patient. Real-time MRI can also be used in conjunction with interventional procedures (such as radiation therapy or image-guided surgery) and can also be used when planning such procedures. Summary of the invention

[0006] Disclosed are electromagnet designs that can be utilized in magnetic resonance imaging systems. Certain embodiments may include a resistive solenoid electromagnet for whole-body MRI that includes a conductor and a ferromagnetic material within the envelope of the electromagnet. The electromagnet may be gapped and the ferromagnetic material may be steel. In some variations, the electromagnet may be configured for flowing current in only one circumferential direction within the electromagnet.

[0007] The electromagnet can be configured as a resistive solenoid electromagnet for whole body MRI having a field strength of at least 0.05 Tesla, comprising a conductor for generating a main electromagnetic field of the electromagnet, wherein the main electromagnetic field is not generated by a bundle of conductors. In some variations, the main electromagnetic field can be generated by layers (e.g., less than ten layers) of conductors.

[0008] The electromagnet designs disclosed herein can utilize non-metallic formers to support the conductors, such as fiberglass formers. The layers of non-metallic formers and conductors can be configured to form a rigid object by fixing them together with epoxy resin. The electromagnet can have two halves, and the two halves can be kept apart by a fixing structure, which can be made of carbon fiber. In one embodiment, a conductor having a cross-sectional area greater than 0.5 square centimeters can be utilized.

[0009] In another embodiment, a magnetic resonance imaging system may include a resistive solenoidal electromagnet for whole body MRI having a field strength of at least 0.05 Tesla, wherein a conductor is used to generate a main electromagnetic field of the electromagnet that covers at least 50% of the electromagnet envelope.

[0010] In certain systems disclosed herein, the power supply used to power the resistive electromagnet may have a current fluctuation of more than one part in ten thousand at a frequency of 180 Hz or higher, and may not include a current filter itself separate from the filtering provided by the resistive electromagnet itself. The power supply may also be a single channel power supply and may not include active current control. In certain embodiments, the system may include a battery, wherein the resistive electromagnet may be connected to the battery, and the system may be configured so that the battery can be charged by the power supply. The system may also include a fuel cell, wherein the system may be configured so that the fuel cell is located between the power supply and the resistive electromagnet.

[0011] Implementations of the current subject matter may include, but are not limited to, methods consistent with the description provided herein, and articles including tangibly implemented machine-readable media that can be operatively caused to produce one or more machines (e.g., computers, etc.) to implement operations that implement one or more of the above-mentioned features. Similarly, a computer system that may include one or more processors and one or more memories coupled to the one or more processors is also contemplated. The memory that may include a computer-readable storage medium may include, encode, store, etc., one or more programs that cause one or more processors to perform one or more operations described herein. Computer-implemented methods consistent with one or more implementations of the current subject matter may be implemented by one or more data processors residing 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., by one or more connections-including but not limited to connections through a network (e.g., the Internet, a wireless wide area network, a local area network, a wide area network, a wired network, etc.), by direct connections between one or more of the multiple computing systems, etc.

[0012] 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 be apparent from the specification and drawings, and from the claims. Although certain features of the subject matter disclosed herein are described for illustrative purposes related to specific embodiments, it should be readily understood that these features are not intended to be limiting. The claims that follow this disclosure are intended to define the scope of the protected subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, help explain some principles associated with the disclosed embodiments.

[0014] Figure 1 is a diagram showing a simplified perspective view of an exemplary magnetic resonance imaging system according to certain aspects of the present disclosure.

[0015] Figure 2 is shown for Figure 1 A simplified cross-sectional view of an exemplary electromagnet with a bandgap solenoidal magnet generating a main magnetic field is shown.

[0016] Figure 3 is a diagram showing simplified cross-sectional and simplified perspective views of layers of an electromagnet according to certain aspects of the present disclosure.

[0017] Figure 4 is a diagram showing a simplified cross-sectional view of an electromagnet including additional ferromagnetic material for reducing fringe fields in accordance with certain aspects of the present disclosure.

[0018] Figure 5 is a diagram showing a simplified perspective view of an exemplary magnetic resonance imaging system incorporating an exemplary interventional apparatus for radiation therapy according to certain aspects of the present disclosure.

[0019] Figure 6 is a diagram showing a simplified perspective view of the conductors of two exemplary halves of a bandgap solenoidal electromagnet, according to certain aspects of the present disclosure.

[0020] Fig. 7A is a diagram illustrating a simplified exemplary configuration of a portion of an electromagnet in accordance with certain aspects of the present disclosure.

[0021] Figure 7B is a diagram showing a simplified perspective view of one half of an electromagnet with an indirect cooling system including a serpentine passage, according to certain aspects of the present disclosure.

[0022] Figure 7Cis a diagram showing a simplified perspective view of an indirect cooling system including serpentine passages between electromagnet layers, according to certain aspects of the present disclosure.

[0023] Fig. 8A are diagrams showing two exemplary arrangements of conductors in adjacent levels for use within an electromagnet, according to certain aspects of the present disclosure.

[0024] Figure 8B is a diagram illustrating a simplified exemplary configuration of a portion of an electromagnet having a radial S-shaped bend, in accordance with certain aspects of the present disclosure.

[0025] Figure 8C is a diagram illustrating a simplified example configuration of an electromagnet in accordance with certain aspects of the present disclosure.

[0026] Fig. 9 is a diagram illustrating a simplified example alternative configuration of a portion of an electromagnet in accordance with certain aspects of the present disclosure.

[0027] Fig.10 is a simplified circuit diagram illustrating an exemplary electromagnet and associated power supply with filtering in accordance with certain aspects of the present disclosure.

[0028] Fig.11 is a diagram illustrating a simplified implementation for using multiple batteries in conjunction with powering an electromagnet, in accordance with certain aspects of the present disclosure.

[0029] Fig.12 is a diagram showing a simplified implementation of a fuel cell between a power source and an electromagnet, according to certain aspects of the present disclosure. DETAILED DESCRIPTION

[0030] The present disclosure relates to techniques that can be utilized in various systems, devices, methods, and computer software for use with electromagnets. Certain embodiments of the techniques described herein may be beneficially employed in conjunction with magnets for magnetic resonance imaging (MRI), but it is contemplated that these techniques may also be implemented in electromagnets for other applications.

[0031] One specific type of MRI magnet discussed herein that benefits from these techniques is a solenoid (i.e., cylindrical) resistive electromagnet (as distinguished from, for example, permanent magnets, superconducting electromagnets, and non-solenoidal electromagnets, such as dipole electromagnets). When the term "solenoid" or "solenoidal" is used herein to describe a magnet, it refers only to the so-called configuration of certain MRIs (i.e., cylindrical); it is in no way limited to magnet configurations that can generally be described as ideal solenoids (e.g., a single helically wound conductor). Although these techniques herein can be used for MRI electromagnets of any size, the main embodiments discussed herein relate to magnets for whole-body MRI systems. When the term "whole-body" is used herein, it refers to magnetic resonance imaging systems of typical sizes (e.g., the Siemens Healthineers Magnetom Aera and GE Signa), rather than small MRIs used for imaging specific body parts (e.g., the Esaote O-Scan), or those used for veterinary applications, research, etc.

[0032] In the case of whole body MRI electromagnets, it is contemplated that the techniques herein can be used at any MRI field strength, although imaging may be compromised below 0.05 Tesla, and power requirements may be high for resistive electromagnets above 0.5 Tesla. Two specific embodiments of resistive solenoid electromagnets discussed herein have field strengths of 0.12T and 0.2T.

[0033] The disclosed techniques can be used in conventional solenoid MRI systems for diagnostic purposes, but in bandgap solenoid systems (e.g., Figure 1 When the present disclosure refers to a "bandgap" magnet, the magnet is intended to include a magnet having a gap (e.g., Figure 1 ) of a solenoid electromagnet. Bandgap systems such as those discussed herein may be used for interventional applications such as MRI-guided radiation therapy, MRI-guided surgery, etc. Examples of such radiation therapy systems are shown in Figure 5 , which shows a gantry in the gap, on which a magnetic shielding structure containing components of a linear accelerator is mounted.

[0034] Although the techniques described herein apply primarily to electromagnets used with MRI, these features may also be used with suitable magnet designs for whatever purpose. For example, more general magnet systems may include magnet systems used in scientific, industrial, or practical applications such as magnetic switches, motors, generators, relays, speakers, magnetic separation devices, etc.

[0035] Figure 1One embodiment of a magnetic resonance imaging system (MRI) 100 consistent with certain aspects of the present disclosure is shown. Figure 1 In FIG. 1 , MRI 100 includes a main electromagnet 102, a gradient coil assembly 104, and an RF coil system 106. Within MRI 100 is a patient couch 108 on which a human patient 110 may lie.

[0036] The main electromagnet 102 of the MRI 100 may be a bandgap solenoid electromagnet separated by legs 114 having gaps 116, such as Figure 1 The term "gap" as used herein refers to Figure 1 and 2 The type of solenoid magnet gap 116 depicted in FIG. 1 is not the open space in the dipole magnet arrangement in which the patient is placed for imaging. In one embodiment contemplated herein, Figure 1 The gap 116 shown in FIG. 1 is 28 cm.

[0037] The gradient coil assembly 104 contains the coils necessary to add a small varying magnetic field on top of the magnetic field of the main electromagnet 102 to allow for spatial encoding of the imaging data. The gradient coil assembly 104 may be a continuous cylindrical assembly such as Figure 1 Separate gradient coil assemblies are shown, or other designs may be necessitated by the particular MRI configuration being used.

[0038] The RF coil system 106 is responsible for exciting the spins of hydrogen protons within the patient 110 and receiving subsequent signals emanating from the patient 110. The RF coil system 106 thus includes an RF transmitter portion and an RF receive portion. Figure 1 The embodiments in include a single body coil that performs both RF transmit and RF functionality. The RF coil system 106 may alternatively divide transmit and receive functionality between the body coil and the surface coil, or may provide both transmit and receive functionality within the surface coil.

[0039] The magnetic resonance imaging system includes a control system configured to acquire and process magnetic resonance imaging data (including image reconstruction) from a patient 110. Such a control system may include many subsystems, such as those that control the operation of the gradient coil assembly 104, the RF coil system 106, parts of the system itself, and those that process data received from the RF coil system 106 and perform image reconstruction. For example, when an interventional device (e.g., a radiotherapy device) is integrated with the MRI 100, additional control system functionality may be included.

[0040] Figure 2 Shows Figure 1A simplified cross section of the main electromagnet 102 is shown in FIG. 1 , including the gap 116 . The gradient coil 104 and the RF coil 106 are not shown in this figure. Figure 2 All four visible cross-sections of the main electromagnet 102 surrounding the aperture 200 and the imaging region or field of view 202 of the MRI 100 are shown in FIG.

[0041] Figure 2 shows an important concept that will be referenced throughout this disclosure, specifically, the "magnet envelope". As this term is used herein, the concept of the magnet envelope can be referred to by reference Figure 2 , B, C, and D in the magnet envelope. The term refers to the outer boundaries of the conductor used to generate the main magnetic field of the electromagnet. In the case where the outer boundaries of the conductor of the magnet are not rectangular, the magnet envelope should be understood to refer to the smallest rectangle (or, for irregular shapes, a tightly fitting convex polygon) that can be used to enclose the conductor. For example, no conductor is used near the corner marked "C" in the electromagnet 102, but the magnet envelope extends all the way to the corner "C" rather than following the exact boundaries of the conductor to form a rectangle. Although the magnet envelope is shown in a two-dimensional cross-section in the accompanying drawings, it should be understood that the magnet envelope actually contains the entire three-dimensional volume corresponding to the (multiple) cross-sections (i.e., roughly, the volume area defined by sweeping the cross-section around the Z-axis of the solenoidal magnet at a constant radius).

[0042] In bandgap magnets, such as Figure 2 As shown in , "within the magnet envelope" means within the magnet envelope created by the conductors in the two halves of the magnet. Figure 2 In the example shown, the magnet envelope is understood to include the area bounded by points A, B, C, D and also the area bounded by points E, G, F, H, but it does not include the area within the magnet gap 116. If Figure 2 If the electromagnet is of no-gap design, the magnet envelope will be defined by the letters E, B, F and D.

[0043] Figure 3 Focus on Figure 1 and 2 The right half of the electromagnet 102 shown in FIG. Figure 2 This figure is increased in size in the exemplary embodiment to show the distance along the Z axis of the magnet to the center field of view on the x-axis and the radial distance from the Z axis of the solenoidal magnet on the y-axis.

[0044] exist Figure 3 In the exemplary design of FIG. 1 , conductor 302 is represented by the cross-hatched area, ferromagnetic material 304 is represented by the solid black area, and the absence of conductor or ferromagnetic material is represented by white space 306 .

[0045] Electromagnets are of course made of conductors, such as loops of copper wire. As used herein, the term "conductor" refers to any conductive loop, coil, or other structure used to generate the main magnetic field of an electromagnet. When the plural form of the word is used herein, it is intended to cover not only multiple conductors (e.g., separate coils or bundles of wires), but multiple "conductors" may also refer to structures that are technically one continuous conductor but may include, for example, multiple conductive loops, turns, or other structures.

[0046] A particularly advantageous embodiment of the present disclosure has a ferromagnetic material included within the envelope of the electromagnet. An example of this is Figure 3 The ferromagnetic material 304 is shown in the figure and may include materials such as iron, steel alloys, and even martensitic stainless steel (but not low permeability austenitic stainless steel). For example, a ferromagnetic material having an initial relative permeability greater than 20 may be used. Although ferromagnetic materials with lower initial relative permeabilities are acceptable, such as martensitic and ferritic stainless steels, it is preferred to use materials with higher initial relative permeabilities, such as non-stainless steels (e.g., SAE 1006 steel).

[0047] Figure 3 A specific embodiment is shown, which includes ferromagnetic material within the envelope of the electromagnet. This specific magnet configuration includes six layers, Figure 3 The top and bottom of the magnet are marked L1, L2, L3, L4, L5 and L6. A layer is understood to refer to the part of the electromagnet located at a given radial distance from the magnet axis. Figure 3 In the example of , layers L1 to L6 are each designed to be 4 cm high. Thus, this example includes a 4 cm x 4 cm conductor wrapped in a generally cylindrical shape at layers L1, L2, L4, L5 and L6, and a 4 cm thick generally cylindrical piece of ferromagnetic material (e.g., steel) at L4 ( Figure 3 The ferromagnetic material is not shown in the lower half of the ).

[0048] Although Figure 3 The examples used relatively large and evenly distributed conductors, but the beneficial techniques described herein can also be used in electromagnet designs that include "bundles" of conductors. For example, the ferromagnetic material within the envelope may be beneficial for an electromagnet designed with, for example, 10 bundles of smaller conductors that are coiled together and placed at specific locations within the magnet to produce a desired magnetic field.

[0049] This disclosure contemplates similar Figure 3 The layers of the electromagnet design need not all have the same height, nor do the ferromagnetic material layers have to be the same height as any of the conductor layers. For example, in one embodiment, the conductor layer is 4 cm high, while the ferromagnetic layer is only 2 cm high.

[0050] The present disclosure contemplates many different configurations of ferromagnetic material within the envelope of the electromagnet. Figure 3 Examples of include a single and complete layer of ferromagnetic material, but electromagnets may similarly be designed to have more than one layer of ferromagnetic material or partial layers (one or more) of ferromagnetic material. Although the examples discussed so far contemplate cylindrical layers of ferromagnetic material, it is contemplated that the ferromagnetic material within the envelope of the electromagnet need not be cylindrical. Furthermore, if a portion of the ferromagnetic element is within the envelope and a portion thereof protrudes from the envelope, such a design is considered to satisfy the configuration of "ferromagnetic material within the envelope" because a portion is still within the envelope and will provide the beneficial results sought. In other words, if in Figure 3 Although the ferromagnetic material depicted at layer 3 of extends further outward along the magnet axis Z, beyond the envelope defined by the conductor, such embodiments will still be understood herein as having ferromagnetic material "within the envelope" of the electromagnet.

[0051] The present disclosure specifically contemplates that its technology be used in magnet designs without yokes and magnet designs without flux returns. The "ferromagnetic material within the electromagnet envelope" magnet designs discussed herein are distinguishable from flux returns and yokes. For example, for a solenoid magnet (such as Figure 2 ), the flux return or yoke will be located within the bore 200 of the magnet, rather than within the "envelope" of the magnet (described by the letters A, B, C, D, E, F, G, H as described previously). Similarly, conventional dipole magnet designs that utilize flux returns or yokes are likewise distinguishable from the designs of the present disclosure.

[0052] The present disclosure also specifically distinguishes magnets in which the primary magnetic field is primarily generated by one or more permanent magnets. Although such systems appear to contain ferromagnetic materials within the envelope of their magnets, they are different from the technology disclosed herein, which involves electromagnets and defines "within the envelope" as within the envelope of the conductor used to generate the primary magnetic field of the electromagnet.

[0053] exist Figure 3In the exemplary design depicted, it can be seen that the amount of ferromagnetic material is about one-sixth of the volume of the entire electromagnet, or about one-fifth of the volume of the conductor. In another embodiment, the height of the ferromagnetic layer can be cut in half, and the total volume of ferromagnetic material is reduced to only about one-tenth of the volume of the conductor. In other embodiments, the volume of ferromagnetic material can be as small as one-twentieth of the volume of the conductor. In particular, the volume and configuration of the ferromagnetic material may vary greatly and can be determined by modeling a specific magnet design using software such as Comsol MultiPhysics or Faraday (from Integrated Engineering Solutions, Inc.), thereby deriving a configuration that induces a magnetizing current in the ferromagnetic material that is sufficient to improve the uniformity of the main magnetic field without requiring additional power (e.g., driving a negative current loop).

[0054] It should be noted that the electromagnet designs contemplated herein may include additional ferromagnetic material outside the envelope of the electromagnet configured to reduce the fringe fields of the electromagnet. Examples of such fringe field reducing materials 402 are shown in Figure 4 . For example, the additional ferromagnetic material 402 can be designed as a 1-2 cm thick L-shaped cross-section steel structure. When including this additional passive shielding in the design, it should be considered together with the conductors and ferromagnetic materials within the envelope of the electromagnet in the above-mentioned magnet modeling.

[0055] It should also be noted that when electromagnets are used in conjunction with interventional applications that may require the placement of ferromagnetic materials in or near the magnets, the modeling and optimal uniformity of the design should also take such materials into account. Figure 5 Such an interventional application is depicted, specifically, an MRI-guided radiation therapy system. In addition to the electromagnet 102, Figure 5 A gantry 502 is depicted on which a magnetic shield 504 is mounted to protect a portion of a linear accelerator 508 from the main magnetic field of the electromagnet. As shown, the linear accelerator portion 508 can be connected using an RF waveguide 506. In such an exemplary design, the magnetic shield 504 includes a large amount of ferromagnetic material, which should also be taken into account when designing the electromagnet along with the conductors and ferromagnetic materials contained in the envelope of the electromagnet.

[0056] Thus, one embodiment of the present disclosure is a magnetic resonance imaging (MRI) system comprising a resistive solenoid electromagnet for whole-body MRI, the electromagnet comprising a conductor and a ferromagnetic material within the envelope of the electromagnet. The electromagnet may be bandgap, and the ferromagnetic material may comprise steel. In various embodiments, the volume of the ferromagnetic material may be at least one-sixth of the volume of the conductor or at least one-twentieth of the volume of the conductor. In certain designs, the electromagnet may comprise a plurality of cylindrical layers, and the ferromagnetic material may comprise a layer in the plurality of cylindrical layers. Alternatively, the ferromagnetic material may comprise a portion of a layer in the plurality of cylindrical layers. In yet other embodiments, the ferromagnetic material may comprise a plurality of layers in the plurality of cylindrical layers or a plurality of portions of a layer.

[0057] Many existing magnet designs, particularly for bandgap solenoid magnets, require that the current within the electromagnet flow in both the positive and negative directions in order to obtain the desired magnetic field uniformity. As used herein, a "positive" current is one that flows in a direction that makes a positive contribution to the main magnetic field Bo of the magnet (see, e.g. Figure 1 The "negative" current is in the opposite direction of the main magnetic field Bo of the magnet (see e.g. Figure 1 These circumferential flow patterns are easy to understand based on the right-hand law of physics.

[0058] In an electromagnet that relies on bundles of conductors to produce its main magnetic field, some bundles may have positive currents and others may have negative currents. Figure 3 The electromagnet design depicted at the bottom can replace the S-shaped bends of the many conductors incorporated into it with U-shaped bends, allowing current to flow in the negative direction.

[0059] Using the techniques of the present disclosure, for example, magnet designs that include ferromagnetic material in the magnet envelope allow magnet designs containing only positive currents to produce a satisfactorily uniform magnetic field, even in a bandgap magnet configuration.

[0060] In some embodiments of the present disclosure, a magnetic resonance imaging system may thus include a resistive solenoid electromagnet for whole body MRI, the electromagnet including a conductor and a ferromagnetic material within the envelope of the electromagnet, wherein the system may be bandgap, and the electromagnet may be configured to flow current in only one circumferential direction within the magnet. For example, each beam driving the main magnetic field may have a positive current direction, or in the case of a non-beam design, each conductor (e.g., such as Figure 3 ) is configured, bent or formed to provide current flowing only in the forward direction.

[0061] In other embodiments, the electromagnet may be configured for less than 5% negative current or less than 10% negative current. Figure 3In an embodiment, less than 5% or 10% of the conductors may be configured or formed in a manner that results in negative current. In other words, less than 5% or 10% of the current loops are configured for negative flow (e.g., loops representing a single turn around the circumference of the magnet).

[0062] Reducing or eliminating negative current allows for lower power requirements in certain magnet designs. Certain embodiments of such systems are discussed below, and exemplary power supply sizes are provided. It should be understood that these specific system designs and associated power supply sizes are exemplary only, and other designs and power supply sizes or size ranges are contemplated.

[0063] Certain embodiments herein of a magnetic resonance imaging system may include a resistive solenoid electromagnet for whole body MRI, comprising a conductor and a ferromagnetic material within the envelope of a bandgap electromagnet, wherein the conductor is made of copper. The conductor in such embodiments may be directly cooled (e.g., a coolant flows through the center of the conductor). Certain embodiments may be configured to have a field strength of at least 0.12 Tesla and a power supply of less than 30 kW or less than 45 kW, while other embodiments may be configured to have a field strength of at least 0.2 Tesla and a power supply of less than 100 kW or less than 145 kW, while still other embodiments may be configured to have a field strength of at least 0.3 Tesla and a power supply of less than 210 kW or less than 300 kW. In embodiments where the conductors are indirectly cooled (e.g., a coolant flows around the conductors or the conductors are naturally cooled by the environment around them), such electromagnets may be configured for a field strength of at least 0.12 Tesla and a power supply of less than 35 kW or less than 50 kW, while other electromagnets may be configured for a field strength of at least 0.2 Tesla and a power supply of less than 105 kW or less than 150 kW, while still other electromagnets may be configured for a field strength of at least 0.3 Tesla and a power supply of less than 230 kW or less than 330 kW.

[0064] Other embodiments herein of magnetic resonance imaging systems may include a resistive solenoid electromagnet for whole body MRI, comprising a conductor and a ferromagnetic material within the envelope of a bandgap electromagnet, wherein the conductor is made of aluminum. The conductor in such embodiments may be directly cooled (e.g., a coolant flows through the center of the conductor). Certain embodiments may be configured for a field strength of at least 0.12 Tesla and a power supply of less than 45 kW or less than 65 kW, while other embodiments may be configured for a field strength of at least 0.2 Tesla and a power supply of less than 155 kW or less than 220 kW, while still other embodiments may be configured for a field strength of at least 0.3 Tesla and a power supply of less than 335 kW or less than 480 kW. In embodiments where the conductors are indirectly cooled (e.g., a coolant flows around the conductors or the conductors are naturally cooled by the environment around them), such electromagnets may be configured with a field strength of at least 0.12 Tesla and a power supply of less than 50 kW or less than 70 kW, while other electromagnets may be configured with a field strength of at least 0.2 Tesla and a power supply of less than 170 kW or less than 245 kW, and still other electromagnets may be configured with a field strength of at least 0.3 Tesla and a power supply of less than 365 kW or less than 520 kW.

[0065] As described above, the techniques of the present disclosure can reduce power requirements and can result in reduced forces between the two halves of a bandgap solenoid electromagnet. With prior art, a bandgap solenoid electromagnet requires a substantially fixed structure to separate the two halves of the magnet, which are attracted to each other with considerable force. This must be done in a manner that avoids any relative motion that could affect field uniformity.

[0066] exist Figure 1 An example of such a substantially fixed structure is depicted as a strut 114 in FIG. Such a strut would typically need to be made of a strong and typically metallic material, such as steel or aluminum. However, the techniques of the present disclosure enable implementations of a magnetic resonance imaging system that includes a resistive solenoid electromagnet for whole body MRI, the resistive solenoid electromagnet comprising a conductor and ferromagnetic material within the envelope of a bandgap electromagnet, wherein the two halves of the electromagnet are held apart by a fixed structure, wherein, in some embodiments, the fixed structure may be substantially non-metallic. "Substantially" non-metallic is understood to describe a fixed structure that relies primarily on non-metallic materials to resist the forces applied by the two magnet halves. To the extent that metallic materials are included in such a structure but are not primarily responsible for bearing the load, such a structure is intended to fall within the term "substantially non-metallic."

[0067] In certain embodiments, the securing structures contemplated herein may include carbon fibers or zero CTE carbon fibers.

[0068] When the above technology is combined with a radiotherapy device, the combined system can be configured so that the radiotherapy device is oriented for treatment through a fixed structure. For example, the fixed structure can be a 0.5 cm thick uniform carbon fiber cylinder between the two magnet halves, which has a substantially zero coefficient of thermal expansion and provides minimal and uniform attenuation of the radiotherapy beam.

[0069] In yet another embodiment, the securing structure may be a single cylinder or continuous former that extends not only between the two magnet halves, but also into the electromagnet assembly itself (eg, as a former between conductor layers).

[0070] The disclosed techniques can reduce the current demand and heating of the electromagnet, and can also reduce the forces applied to the conductors of the magnet and the structures supporting them. Therefore, these techniques can promote certain types of beneficial magnet design and configuration methods. For example, in a specific embodiment, a magnetic resonance imaging system with a resistive solenoid electromagnet for whole-body MRI (with a magnetic field strength of at least 0.05 Tesla) can include a conductor for forming the main magnetic field of the electromagnet, wherein the main magnetic field is not generated by a conductor bundle, but can be generated by a conductor layer.

[0071] While cylindrical MRI systems typically use bundles (i.e., conductors wrapped together and placed at specific distinct locations) to generate their main magnetic field, certain embodiments of the present disclosure provide for a more distributed arrangement of conductors, e.g., across layers. Examples of such layered conductor arrangements are shown in FIG. Figure 3 , and the details of this design are discussed further below. Because such layered arrangements can produce highly uniform fields and can facilitate beneficial new manufacturing methods, they can provide an alternative to using conductor bundles to generate the main magnetic field. When the present disclosure refers to a design in which "the main magnetic field is not generated by a conductor bundle", this means that the main magnetic field is completely or primarily generated by a more distributed conductor configuration (e.g., similar to the one described with respect to FIG. Figure 3 Those described). However, the present disclosure contemplates that a small number of conductor bundles may be used in conjunction with these designs. Thus, the term "the main magnetic field is not generated by the bundle" contemplates some minimal use of the bundle herein, for example, where the bundle is used but the bundle does not contribute more than 10% to the generation of the main magnetic field.

[0072] When the present disclosure refers to using conductors configured as "layers" to generate the main magnetic field, for example, this refers to conductor loops or coils arranged in a generally cylindrical shape at the radius of the electromagnet, which traverse a majority of the length of the electromagnet (or in the case of a bandgap magnet, a majority of half the length of the electromagnet). Figure 3One example of a layered design for a bandgap solenoidal magnet is illustrated in which the conductor layers extend or traverse approximately one meter across the Z-axis of the magnet - from approximately 0.2 m away from the center of the imaging field to approximately 1.2 m away from the center of the imaging field.

[0073] like Figure 3 As depicted, the main magnetic field can be generated by multiple layers of conductors, and an electromagnet having such a design can include ferromagnetic material within the magnet envelope, also as Figure 3 As depicted and described above.

[0074] Figure 6 Depicted Figure 3 , and additional design views from the opposite angle. Figure 6 Five separate layers of conductors for generating the main magnetic field are shown, with level L3 being reserved for the insertion of the ferromagnetic cylinder. The present disclosure contemplates various numbers of layers being used, which may depend, for example, on the particular conductor size selected. Figure 6 In an embodiment, a relatively large conductor is used (e.g., 4 cm by 4 cm with an open core for direct cooling).

[0075] In another embodiment, a 2 cm x 2 cm conductor may be used. In a specific embodiment of a resistive solenoid electromagnet for whole body MRI having a field strength of at least 0.05 Tesla and a conductor for generating a main magnetic field of the electromagnet, the main magnetic field is generated by a conductor layer, wherein the conductor has a field strength greater than 0.50 cm 2 or greater than 0.75cm 2 cross-sectional area.

[0076] In some embodiments, a portion of the conductors may have a smaller cross-sectional area than the cross-sectional area of ​​the other conductors. For example, a layer of smaller conductors may have a cross-sectional size that is approximately half that of a layer of larger conductors (e.g., one layer of conductors may have a cross-sectional size of 40 mm x 40 mm, while another layer may have a conductor with a cross-sectional size of 20 mm x 20 mm). In some embodiments, the conductors may be at or near the outer radial layer, or at the ferromagnetic layer (e.g., Figure 6 One or more layers of smaller conductors are implemented at or near L3) shown in FIG.

[0077] Layered designs using the techniques of the present disclosure can avoid the need for substantial / solid metal formers that are typically used with bundle designs and designs with higher current requirements. Thus, in some embodiments, the conductors of the designs contemplated herein can be supported by lower strength materials such as fiberglass or plastic cylindrical formers. For example, the conductor layers can be supported by 1 mm thick cylindrical fiberglass formers between the layers, and the conductor layers and formers can be combined into a single rigid object by using epoxy or other insulating materials.

[0078] Fig. 7A A cross section of a particular embodiment is shown in which the conductor layers L1, L2, L4, L5, L6 and the ferromagnetic material layer L3 are separated by a former 702 which may be composed of a non-metallic material such as a glass reinforced polymer. Fig. 7A An embodiment is shown in which the electromagnet may also include side cheeks 704, which may be made of a similar non-metallic material, and an outer former 706, which may optionally be made of a stronger metallic material such as aluminum.

[0079] In one particular embodiment, a resistive solenoid electromagnet for whole-body MRI having a field strength of at least 0.05 Tesla may include a conductor for generating a main magnetic field of the electromagnet, wherein the main magnetic field is generated by a layer of conductors, and wherein the electromagnet supports the conductors using a non-metallic former, such as a fiberglass former. One embodiment includes at least two solenoid layers of conductors separated by a non-metallic former. Another embodiment may include less than ten layers of conductors. In yet another embodiment, the layers of conductors and non-metallic formers may be configured to form a rigid object, such as by fixing them together using epoxy. In yet another embodiment, the rigid object may also include at least a portion of a gradient coil. For example, only a slice selection coil may be included, or, alternatively, the entire gradient coil may be formed into a single rigid object together with the main magnet by epoxy bonding.

[0080] Fig. 7A An example of a conductor 708 having a generally square cross-section is shown with a cylindrical, hollow core 710 that may be used for direct cooling (eg, water or coolant flowing through the core 710).

[0081] Figure 7B An example of an electromagnet with an indirect cooling system provided by a serpentine coolant channel is shown. In some embodiments, the indirect cooling system can provide sufficient cooling for the electromagnet so that some or all of the conductors in the electromagnet can be solid conductors, rather than Fig. 7A The direct cooling example shown has a hollow core 710.

[0082] The present disclosure contemplates indirect cooling systems having various types of cooling channels, such as saddle-shaped circular rings, spiral rings, serpentine shapes, etc. Figure 7B As shown, the serpentine channel 720 may include one or more linear portions 722 and one or more curved portions 724, which may combine to form an "S-shaped" or "serpentine" channel 720. In some embodiments, the serpentine channel 720 may be adjacent to (or wrapped around) one or more conductors or ferromagnetic layers to provide indirect cooling. Figure 7C Shows such as Figure 7B An exemplary indirect cooling system is depicted in FIG. , wherein serpentine channels are interspersed between layers of conductor and / or ferromagnetic material.

[0083] The serpentine passage 720 will include an inlet and an outlet (e.g., 726) for flowing coolant through the passage. In some embodiments, the inlet and / or outlet may be located at a specific end 730 of the electromagnet that may be more easily accessible to establish a cooling connection. For example, the inlet and outlet may be located at the patient end or the service end of the electromagnet.

[0084] When the present disclosure refers to a solenoid electromagnet or to a solenoid layer of a conductor in an electromagnet, it is contemplated that the conductor may vary slightly from an ideal solenoid (i.e., a uniform, helically wound coil). For example, the conductor layer may include an S-shaped bend (in Figure 6 602).

[0085] The S-bend configuration is an alternative to the spiral configuration. In addition to having a different manufacturing process, they can be modeled more efficiently during magnet design if the software used for modeling simplifies the current loops into pure current "loops" (in which case the S-bend design will match the model more closely than the spiral design).

[0086] As referred to herein, an "S-shaped bend" may take the form of an elongated letter S, as shown in the figures, but the term is intended to encompass any gradual or sharp transition (even a 90 degree turn) to a subsequent loop that results in current continuing in the same circumferential direction in the subsequent loop. An S-shaped bend is distinct from a spiral arrangement, and also distinct from a U-shaped bend, which results in current in the subsequent loop flowing in the opposite direction.

[0087] As previously discussed, certain electromagnet designs may contain negative currents therein (i.e., those currents that produce a magnetic field that is opposite in direction to the main magnetic field). If such negative currents are desired, they may be implemented in the coils of the present disclosure using a U-shaped bend. However, as noted, using the techniques of the present disclosure - including including ferromagnetic material within the envelope of the electromagnet, negative currents may be avoided.

[0088] In some embodiments, the conductors may also be arranged so that they traverse the layers in a direction parallel to the axis of the solenoid electromagnet. Figure 6 This arrangement is depicted as 604 in FIG. 1 and can be used when magnet modeling and design indicate that a current loop is not required at a particular axial position within the layer. Figure 3 Such a location is depicted as element 306 in the exemplary design of .

[0089] In a specific embodiment, a resistive solenoidal electromagnet for whole body MRI having a field strength of at least 0.05 Tesla may include a conductor for generating a main magnetic field of the electromagnet, wherein the main magnetic field is generated by a multilayer conductor, and wherein the multilayer conductor includes at least one layer, the at least one layer including the following: wherein the conductor traverses in a direction parallel to the axis of the solenoidal electromagnet, and wherein the conductor may have a magnetic field greater than 0.50 cm 2 or greater than 0.75cm 2 cross-sectional area.

[0090] In some embodiments, the multilayer conductor may include a first layer, which is a helically wound conductor having a first helical tilt, and a second layer adjacent to the first layer, which includes a helically wound conductor having a second helical tilt, wherein the second helical tilt is opposite to the first helical tilt. In other words, some embodiments may have a layer that is a helically wound conductor tilted to the right, and the layer inside or outside of the layer (i.e., the layer adjacent to the smaller or larger radius) is a helically wound conductor tilted to the left.

[0091] In other embodiments similarly designed to facilitate the generation of a uniform magnetic field, the conductor layer may include a first layer of a wrapped conductor having a first S-shaped bend that bends in a first direction and a second layer adjacent to the first layer, the wrapped conductor having a second S-shaped bend that bends in a second direction, wherein the first S-shaped bend and the second S-shaped bend overlap, and wherein the second direction is opposite to the first direction. Examples of such configurations are described in Fig. 8A , where an outer layer 808 has an S-shaped bend in one direction, and an adjacent layer 810 has an S-shaped bend in the opposite direction, and where the S-shaped bends of each layer overlap at location 812. Fig. 8A An alternative arrangement is depicted at the top of FIG, in which the S-shaped bends overlap but do not bend in opposite directions.

[0092] Figure 8B 826 is a diagram showing a simplified exemplary configuration of a portion of an electromagnet having a radial S-shaped bend according to certain aspects of the present disclosure. In some embodiments, adjacent layers of conductors can be connected (e.g., in a generally radial direction) by one or more S-shaped bends 826. Examples of such configurations are shown in FIG. Figure 8B , which shows two adjacent layers of conductors, wherein a first layer 820 of wound conductors is connected to a second layer 822 of wound conductors by an S-shaped bend 826. An expanded view 824 of the S-shaped bend connection is also shown. In some embodiments, either or both of the adjacent layers can be helical (e.g., not include an S-shaped bend in the axial direction), or they can include an S-shaped bend in the axial direction without a helical pitch.

[0093] Figure 8C is a diagram illustrating a simplified exemplary configuration of an electromagnet in accordance with certain aspects of the present disclosure. The exemplary configuration comprises a bandgap electromagnet design and depicts exactly a cylinder disposed in the gap that may be used in radiation therapy applications to shield components of a linear accelerator. In certain embodiments, the magnet halves (830, 832) may be "rotated" so that their radial connections 834 (e.g., S-bends) between adjacent layers of conductors are not at the same azimuth angle. This may have the beneficial effect of reducing residual tessera l harmonics that may result from the radial S-bend connections. As Figure 8C As shown in the example shown in , the magnet halves can be rotated approximately 180 degrees relative to each other, but other rotation angles can be achieved, such as 30°, 45°, 60°, 90°, 135°, 150°, 165°, etc. One of the magnet halves can be designated as the "patient end" (the location where the patient enters the bore 200 of the MRI system) and the other magnet half can be designated as the "service end". In one embodiment, the patient end radial connection 834 can be on the bottom (i.e., at the lowest point of the patient end magnet half 830) and the service end radial connection 836 can be on the top (i.e., at the highest point 832 of the service end magnet half). In other embodiments, the angles of the magnet halves can be different (e.g., with an overall rotation of 30°, 45°, 60°, 90°, 135°, 150°, 165° relative to vertical so that the radial connections are not at the top and bottom), while still maintaining a spacing of approximately 180 degrees between the radial connections of the two magnet halves.

[0094] In the exemplary magnet designs of the present disclosure, multiple layers of conductors (e.g., Figure 3 The electromagnets may be configured to operate with a single supplied current. The connections between the layers may be made so that the current will be positive in each layer and so each layer will make a positive contribution to the generation of the main magnetic field. In the case of a bandgap magnet, the two magnet halves may be connected in series and thus still operate with a single supply current (or they may be operated in a parallel circuit but with the same ampere value). This beneficial configuration may utilize a simplified power supply compared to typical beam magnet designs which typically require different ampere values ​​for different beams (and typically require negative current in one or more beams).

[0095] Fig. 9 An alternative electromagnet design is depicted that is not based on a conductor layer, but similarly has a more distributed conductor arrangement for generating the main magnetic field. Exemplary embodiments of such a design include conductors covering, for example, at least 40%, 50%, 60% or 70% of the magnet envelope. Fig. 9The particular exemplary embodiment depicted in has conductors covering more than 50% of the magnet envelope and utilizes conductor bundles 902 in generating the main magnetic field. While many electromagnet designs that utilize bundles to generate their main magnetic field may utilize very small conductors, the present disclosure also contemplates utilizing larger conductors in bundles. Fig. 9 In one particular example depicted in , a single conductor 904 has a cross-section of 1 cm x 1 cm.

[0096] Implementations of this type of design may also include ferromagnetic material within the magnet envelope, as previously discussed. An example of this is Fig. 9 906, and can configure the electromagnet to flow current in only one circumferential direction within the magnet. For example, each beam driving the main magnetic field may have a positive current direction. In other embodiments, the electromagnet may be configured for less than 5% negative current or less than 10% negative current. In one embodiment, the beams may be connected by conductors that traverse in a direction parallel to the axis of the electromagnet to essentially form a single current path and allow the electromagnet to be powered with a single supply of current.

[0097] Electromagnets, particularly those used in magnetic resonance imaging, may be required to produce a highly uniform and stable magnetic field. Typically, such stability is facilitated by using a complex DC power supply that maintains a highly stable voltage and current output (e.g., fluctuations on the order of only a few parts per million). However, the techniques of the present disclosure can provide a uniform and stable magnetic field without the need for such a complex power supply design. These techniques are applicable to different magnet configurations, such as conventional solenoid (gapless) magnets, gapped solenoid systems, dipole magnets, and the like.

[0098] When the present disclosure relates to electromagnets for magnetic resonance imaging, it is assumed that such magnets and their power supplies are configured to result in the necessary imaging field uniformity and stability (e.g., on the order of parts per million) required for such MR imaging. When reference is made herein to a "power supply," the term is intended to encompass the electronics responsible for providing the electromagnet with its necessary power, including any associated electronics for rectification, filtering, control, etc. It is contemplated that such electronics may reside in a single unit, or may be dispersed in different locations or modules. It is also understood herein that the power supply may be configured to provide a single current, or may be a multi-channel power supply to provide multiple, possibly different currents.

[0099] Although power supplies for MRI systems are typically designed to provide DC current with fluctuations on the order of only a few parts per million, the techniques of the present disclosure can provide the necessary field uniformity and stability using power supplies with, for example, only a few parts per million stability. In one example, the stability metric can relate to the DC current ripple present at the original AC frequency and its harmonics after rectification. For example, embodiments of the present disclosure can utilize power supplies with current fluctuations of at least one part per ten thousand at 180 Hz or higher, or at 600 Hz or higher. Other embodiments can even utilize power supplies with current fluctuations of at least one part per thousand at 180 Hz or higher, or at 600 Hz or higher.

[0100] In various electromagnetic designs disclosed herein, relatively high current fluctuations in such power supplies can be filtered substantially by the complex impedance of the wound metal conductor. In one specific example discussed below, an exemplary electromagnet can filter current fluctuations of 15 parts per ten thousand at 600 Hz to a level of -90 dB. Thus, embodiments of the present disclosure may include a magnetic resonance imaging system that does not include a current filter separate from the filtering provided by the resistive electromagnet itself. In other words, such a system does not include additional elements added for the purpose of reducing current fluctuations (e.g., adding an inductor).

[0101] Alternative embodiments may include current filters, but may limit such filters to having an inductance of, for example, less than 5 mH, 2 mH, or 1 mH. Thus, one particular embodiment of a magnetic resonance imaging system may include a resistive electromagnet for whole body MRI having a field strength of at least 0.05 Tesla, and a power supply for powering the resistive electromagnet having a current fluctuation of at least one part in ten thousand at a frequency of 180 Hz or higher, and no current filter separate from the filtering provided by the resistive electromagnet itself or a current filter having an inductance of less than 2 mH.

[0102] Some embodiments of the technology described herein also enable the use of a single-channel power supply. For example, some electromagnet designs described herein as having ferromagnetic materials within their magnet envelopes can be provided with a single current. As described above, for example, these magnet designs can be optimized to avoid the need for negative currents and / or conductor bundles that must provide different amounts of current. Therefore, a simplified single-channel power supply can be used, which does not require a complex control system to synchronize multiple power supply channels with each other. In addition, compared with fluctuations from a multi-channel power supply, it is considered that the MRI control system of this variant can more easily handle low-frequency current fluctuations from a single-channel power supply. For example, a spectrometer of an MRI can be used to compensate for low-frequency drifts of current or voltage by correction of the main magnetic field strength.

[0103] In certain embodiments, these power supplies can be used with the exemplary bandgap solenoidal magnet designs discussed above. For example, in an embodiment utilizing directly cooled aluminum conductors where the field strength of the electromagnet is at least 0.12 Tesla, the power supply can be designed to provide only 45 kW or less of power. Alternatively, a 155 kW or less power supply can be used with such a design with a field strength of at least 0.2 Tesla. Other configurations taught or specifically discussed herein are contemplated.

[0104] Even single-channel power supplies for MRI typically require complex control systems to minimize current and voltage fluctuations, but the present disclosure contemplates the use of power supplies that do not include active current control (eg, utilizing a current feedback loop).

[0105] Embodiments of the present disclosure contemplate adding a simple filter to control voltage fluctuations, such as an LC filter. In one exemplary embodiment, similar to the designs disclosed above, consider a solenoid electromagnet with a gap of 28 cm, configured for whole body MRI, having a field strength of at least 0.12 Tesla, and made of ferromagnetic material within the magnet envelope and directly cooled by aluminum conductors. Fig.10 An exemplary filter for this design is depicted in . Fig.10 This exemplary electromagnet is depicted with a resistance of 40 mΩ and an inductance of 40 mH. The power supply used may be configured to provide 1000 A of current at 40 V and may have a ripple of 1760 ppm at 600 Hz and 57.6 kHz. In this example, a filter with Li n=1 mH, Ri n=1 mΩ, Ct=50 mF and Rt=0.1 mΩ may be used. The characteristics of such a filter may be determined with the aid of the following formula:

[0106]

[0107] These equations represent the transfer function (dynamic response) of the system. A Bode plot of the magnitude can show the magnitude response as a function of frequency (high frequency components are effectively filtered). Such a plot (or an equivalent calculation of the transfer function) can be implemented to design a filter to reduce the ripple amplitude at unwanted frequencies above the low frequency cutoff frequency.

[0108] In alternative embodiments, one or more batteries may be utilized in the system to at least partially limit power supply fluctuations. These may be utilized in addition to or in lieu of the filters discussed above. In one embodiment, the electromagnet may be connected to and substantially powered by the battery, and the system may be configured so that the battery may be charged by the power supply.

[0109] Other embodiments utilizing multiple batteries (e.g., two or more) can avoid power fluctuations in the electromagnet that may be caused by the power source charging the batteries. In such embodiments, the battery responsible for powering the electromagnet can be avoided from being charged while it is powering the magnet, and then, when the battery powering the electromagnet needs to be charged, the power source for the electromagnet can be switched to another battery that has already been charged. In other words, the system can be configured so that the resistive electromagnet can be connected to one of the multiple batteries while another of the multiple batteries can be charged by the power source.

[0110] exist Fig.11 Another example of a multi-battery embodiment is depicted in FIG, and this example uses at least three batteries. Fig.11 As shown at the top of , a switch can be opened and closed so that a single battery powers the electromagnet (but not charged at the same time) while other batteries can be charged. When it is necessary to charge the initial battery, the switch position can be changed in a manner that allows the electromagnet to be switched to be powered by another battery that has been cut off from the power supply. For example, a switch that connects a second battery for charging can be opened before the switch between the second battery and the electromagnet is closed to power the magnet. Such a system with three or more batteries can therefore be configured to facilitate a smooth transition between two batteries that are not charged and are not affected by power supply fluctuations. In other words, the system can include at least three batteries, and can be configured so that a resistive electromagnet can be connected to a first battery while a second battery is being charged, and the system can be further configured so that the connection for the resistive electromagnet is switched to a third battery that is not charged when the connection is switched.

[0111] If necessary, such as Fig.11 As shown at the bottom, all batteries can be charged and connected to the electromagnet to keep it warm when the electromagnet is not in use (e.g., when MRI imaging is not occurring, such as between patients).

[0112] Although a battery or batteries may be used to protect the electromagnet from power fluctuations, the present disclosure also contemplates the use of fuel cells in a similar manner. Fig.12 As shown, the system can be configured so that the fuel cell is located between the power source and the resistive electromagnet to substantially filter out voltage fluctuations seen at the power source.

[0113] project:

[0114] 1. A magnetic resonance imaging (MRI) system, comprising:

[0115] A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet comprising a conductor; and

[0116] A ferromagnetic material is contained within the envelope of the electromagnet.

[0117] 2. The system of item 1, wherein the electromagnet is bandgap.

[0118] 3. The system of claim 2, wherein the ferromagnetic material comprises steel.

[0119] 4. A system according to item 2, wherein the volume of the ferromagnetic material is at least one sixth of the volume of the conductor.

[0120] 5. A system according to item 2, wherein the volume of the ferromagnetic material is at least one twentieth of the volume of the conductor.

[0121] 6. The system of item 2, wherein the electromagnet comprises a plurality of cylindrical layers and the ferromagnetic material comprises a layer of the plurality of cylindrical layers.

[0122] 7. The system of item 2, wherein the electromagnet comprises a plurality of cylindrical layers and the ferromagnetic material comprises a portion of a layer in the plurality of cylindrical layers.

[0123] 8. A system according to item 2, wherein the electromagnet includes a plurality of cylindrical layers and the ferromagnetic material includes a plurality of layers or portions of layers in the plurality of cylindrical layers.

[0124] 9. The system of item 2, further comprising additional ferromagnetic material outside the envelope of the electromagnet configured to reduce the fringe fields of the electromagnet.

[0125] 10. The system of item 2, wherein the electromagnet is configured to flow current in only one circumferential direction within the electromagnet.

[0126] 11. The system of item 2, wherein the electromagnet is configured for a negative current of less than 5%.

[0127] 12. The system of item 2, wherein the electromagnet is configured for a negative current of less than 10%.

[0128] 13. The system of item 2, wherein the conductor is directly cooled.

[0129] 14. The system of item 13, wherein the conductor is copper.

[0130] 15. The system of item 14, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 25 kW.

[0131] 16. The system of item 14, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 55 kW.

[0132] 17. The system of item 13, wherein the conductor is aluminum.

[0133] 18. The system of item 17, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 40 kW.

[0134] 19. The system of claim 17, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 90 kW.

[0135] 20. The system of item 2, wherein the conductor is indirectly cooled.

[0136] 21. The system of item 20, wherein the conductor is copper.

[0137] 22. The system of claim 21, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 20 kW.

[0138] 23. The system of claim 21, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 45 kW.

[0139] 24. The system of item 20, wherein the conductor is aluminum.

[0140] 25. The system of claim 24, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 35 kW.

[0141] 26. The system of item 24, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 70 kW.

[0142] 27. The system of item 2, wherein the electromagnet has two halves and the two halves are held apart by a fixed structure.

[0143] 28. The system of claim 27, wherein the fixed structure is substantially non-metallic.

[0144] 29. The system of item 28, wherein the fixing structure comprises carbon fiber.

[0145] 30. The system of item 29, wherein the fixed structure comprises zero CTE carbon fiber.

[0146] 31. The system according to item 28 further includes a radiotherapy device, wherein the system is configured so that the radiotherapy device is oriented for treatment through the fixed structure.

[0147] 32. A magnetic resonance imaging (MRI) system comprising:

[0148] A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet having a field strength of at least 0.05 Tesla, comprising:

[0149] a conductor for generating a main electromagnetic field of the electromagnet;

[0150] Wherein, the main electromagnetic field is not generated by a conductor bundle.

[0151] 33. A system according to item 32, wherein the main electromagnetic field is generated by a conductor layer.

[0152] 34. A system according to item 33, wherein the electromagnet has less than 10 layers of conductors.

[0153] 35. The system of item 33, further comprising a ferromagnetic material within the envelope of the electromagnet.

[0154] 36. The system of item 33, wherein the electromagnet is configured to flow current in only one circumferential direction within the electromagnet.

[0155] 37. A system according to item 33, wherein the electromagnet is configured to operate with a single supply of current.

[0156] 38. The system of item 33, wherein the electromagnet is bandgap.

[0157] 39. The system of claim 33, wherein the electromagnet utilizes a non-metallic former to support the conductor.

[0158] 40. The system of claim 33, wherein the electromagnet utilizes a fiberglass former to support the conductor.

[0159] 41. The system of item 39, wherein the conductor layer and the non-metallic former are configured to form a rigid object.

[0160] 42. The system of item 41, wherein the conductor and non-metallic former layers are configured to form a rigid object by being secured together using epoxy.

[0161] 43. A system according to item 41, wherein the rigid object includes at least a portion of a gradient coil.

[0162] 44. A system according to item 33, wherein the conductor has a cross-sectional area greater than 0.5 square centimeters.

[0163] 45. A system according to item 44, wherein the conductor comprises at least two spiral layers of conductor separated by a non-metallic former.

[0164] 46. ​​The system of item 33, wherein the conductor is directly cooled.

[0165] 47. The system of item 46, wherein the conductor is aluminum.

[0166] 48. The system of claim 47, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 40 kW.

[0167] 49. The system of claim 47, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 90 kW.

[0168] 50. The system of item 33, wherein the conductor layer comprises:

[0169] a first layer comprising a helically wound conductor having a first helical tilt; and

[0170] a second layer adjacent to the first layer, the second layer comprising a helically wound conductor having a second helical tilt;

[0171] The second spiral inclination is opposite to the first spiral inclination.

[0172] 51. The system of item 33, wherein the conductor layer comprises:

[0173] a first layer comprising a wrapped conductor having a first S-shaped bend that bends in a first direction; and

[0174] A second layer adjacent to the first layer includes a wrapped conductor having a second S-shaped bend that bends in a second direction.

[0175] 52. A system according to item 51, wherein the first S-shaped bend and the second S-shaped bend overlap, and the second direction is opposite to the first direction.

[0176] 53. The system of item 33, wherein the conductor layer comprises:

[0177] At least one layer includes a portion through which the conductor traverses in a direction parallel to the axis of the solenoidal electromagnet.

[0178] 54. A system according to item 53, wherein the conductor traversing in a direction parallel to the axis of the solenoid electromagnet has a cross-sectional area greater than 0.5 square centimeters.

[0179] 55. The system of claim 33, wherein the electromagnet has two halves and the two halves are held apart by a fixed structure.

[0180] 56. A system according to item 55, wherein the fixed structure is substantially non-metallic.

[0181] 57. The system of item 56, wherein the fixing structure comprises carbon fiber.

[0182] 58. The system according to item 56 further includes a radiotherapy device, wherein the system is configured so that the radiotherapy device is oriented for treatment through the fixed structure.

[0183] 59. A magnetic resonance imaging (MRI) system comprising:

[0184] A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet having a field strength of at least 0.05 Tesla, comprising:

[0185] a conductor for generating a main electromagnetic field of the electromagnet;

[0186] Wherein, the main electromagnetic field is generated by the conductor layer.

[0187] 60. The system of item 59, wherein the electromagnet has less than 10 layers of conductors.

[0188] 61. The system of item 59, further comprising ferromagnetic material within the envelope of the electromagnet.

[0189] 62. The system of item 59, wherein the electromagnet is configured to flow current only in one circumferential direction within the electromagnet.

[0190] 63. A system according to item 59, wherein the electromagnet is configured to operate with a single supply of current.

[0191] 64. The system of item 59, wherein the electromagnet is bandgap.

[0192] 65. The system of claim 59, wherein the electromagnet utilizes a non-metallic former to support the conductor.

[0193] 66. The system of claim 59, wherein the electromagnet utilizes a fiberglass former to support the conductor.

[0194] 67. A system according to item 65, wherein the layers of conductor and non-metallic former are configured to form a rigid object.

[0195] 68. The system of item 67, wherein the conductor layer and the non-metallic former are configured to form a rigid object by being secured together using epoxy.

[0196] 69. A system according to item 67, wherein the rigid object includes at least a portion of a gradient coil.

[0197] 70. The system of claim 59, wherein the conductor has a cross-sectional area greater than 0.5 square centimeters.

[0198] 71. A system according to item 70, wherein the conductor comprises at least two spiral layers of conductor separated by a non-metallic former.

[0199] 72. The system of item 59, wherein the conductor is directly cooled.

[0200] 73. The system of item 72, wherein the conductor is aluminum.

[0201] 74. A system according to item 73, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 40 kW.

[0202] 75. The system of claim 73, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 90 kW.

[0203] 76. The system of item 59, wherein the conductor layer comprises:

[0204] a first layer comprising a helically wound conductor having a first helical tilt; and

[0205] a second layer adjacent to the first layer, the second layer comprising a helically wound conductor having a second helical tilt;

[0206] The second spiral inclination is opposite to the first spiral inclination.

[0207] 77. The system of item 59, wherein the conductor layer comprises:

[0208] a first layer comprising a wrapped conductor having a first S-shaped bend that bends in a first direction; and

[0209] A second layer adjacent to the first layer includes a wrapped conductor having a second S-shaped bend that bends in a second direction.

[0210] 78. A system according to item 77, wherein the first S-shaped bend and the second S-shaped bend overlap, and the second direction is opposite to the first direction.

[0211] 79. The system of item 59, wherein the conductor layer comprises:

[0212] At least one layer includes a portion through which the conductor traverses in a direction parallel to the axis of the solenoidal electromagnet.

[0213] 80. A system according to item 79, wherein the conductor traversing in a direction parallel to the axis of the solenoid electromagnet has a cross-sectional area greater than 0.5 square centimeters.

[0214] 81. A system according to item 59, wherein the electromagnet has two halves and the two halves are held apart by a fixed structure.

[0215] 82. A system according to item 81, wherein the fixed structure is substantially non-metallic.

[0216] 83. The system of item 82, wherein the fixing structure comprises carbon fiber.

[0217] 84. The system of item 82, further comprising a radiotherapy device, wherein the system is configured such that the radiotherapy device is oriented through the fixed structure for treatment.

[0218] 85. A magnetic resonance imaging (MRI) system comprising:

[0219] A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet having a field strength of at least 0.05 Tesla, comprising:

[0220] a conductor for generating a main electromagnetic field of the electromagnet;

[0221] Therein, the main electromagnetic field is generated by a conductor covering at least 50% of the envelope of the electromagnet.

[0222] 86. The system of item 85 further comprises a ferromagnetic material within the envelope of the electromagnet.

[0223] 87. A system according to item 85, wherein the electromagnet is configured to flow current only in one circumferential direction within the electromagnet.

[0224] 88. A system according to item 85, wherein the electromagnet is configured to operate with a single supply of current.

[0225] 89. The system of item 85 further comprises a conductor that traverses in a direction parallel to the axis of the solenoid electromagnet.

[0226] 90. The system of claim 85, wherein the electromagnet is bandgap.

[0227] 91. A system according to item 85, wherein the conductor has a cross-sectional area greater than 0.5 square centimeters.

[0228] 92. The system of claim 85, wherein the conductor is directly cooled.

[0229] 93. The system of item 91, wherein the conductor is aluminum.

[0230] 94. A system according to item 85, wherein the electromagnet has two halves and the two halves are held apart by a fixed structure.

[0231] 95. A system according to item 94, wherein the fixed structure is substantially non-metallic.

[0232] 96. The system of item 95, wherein the fixed structure comprises carbon fiber.

[0233] 97. The system according to item 95 also includes a radiotherapy device, wherein the system is configured so that the radiotherapy device is oriented for treatment through the fixed structure.

[0234] 98. A magnetic resonance imaging (MRI) system comprising:

[0235] A resistive electromagnet for whole body magnetic resonance imaging, the resistive electromagnet having a field strength of at least 0.05 Tesla and comprising a conductor for generating a main magnetic field of the resistive electromagnet; and

[0236] A power source for powering the resistance electromagnet, the power source having a current fluctuation of at least one part in ten thousand at a frequency of 180 Hz or higher.

[0237] 99. The system of item 98, wherein the resistive electromagnet is a non-bandgap solenoid electromagnet.

[0238] 100. The system of item 98, wherein the system does not include a current filter separate from the filtering provided by the resistive electromagnet itself.

[0239] 101. The system of item 98, further comprising a current filter separate from the filtering provided by the resistive electromagnet itself, and comprising an inductor having an inductance less than 2 mH.

[0240] 102. The system of claim 98, wherein the power supply is a single channel power supply.

[0241] 103. A system according to item 102, wherein the system is configured to compensate for low-frequency current drift or low-frequency voltage drift by main magnetic field strength correction.

[0242] 104. The system of claim 98, wherein the power supply does not include active current control.

[0243] 105. The system of item 98, further comprising a filter for controlling voltage fluctuations.

[0244] 106. A system according to item 105, wherein the filter for controlling voltage fluctuations is an LC filter.

[0245] 107. The system of item 98, further comprising a battery, wherein the resistive electromagnet is connected to the battery and the system is configured such that the battery can be charged by the power source.

[0246] 108. The system of item 98, further comprising a plurality of batteries, wherein the system is configured such that the resistive electromagnet can be connected to one of the plurality of batteries, while another of the plurality of batteries can be charged by the power source.

[0247] 109. The system according to item 98 further includes at least three batteries, wherein the system is configured so that the resistance electromagnet can be connected to the first battery when the second battery is charged, and the system is also configured for the resistance electromagnet connection to be switched to a third battery that is not charged when the connection is switched.

[0248] 110. The system of item 98, further comprising a fuel cell, wherein the system is configured such that the fuel cell is located between the power source and the resistive electromagnet.

[0249] 111. The system of item 98, wherein the resistive electromagnet is solenoid and bandgap and contains ferromagnetic material within the envelope of the resistive electromagnet.

[0250] 112. A system according to item 111, wherein the conductor is directly cooled.

[0251] 113. The system of item 111, wherein the conductor is copper.

[0252] 114. A system according to item 113, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 30kW.

[0253] 115. A system according to item 113, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 100 kW.

[0254] 116. A system according to item 113, wherein the electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 210 kW.

[0255] 117. The system of item 111, wherein the conductor is aluminum.

[0256] 118. The system of item 117, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 45 kW.

[0257] 119. The system of item 117, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 155 kW.

[0258] 120. The system of item 117, wherein the electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 335 kW.

[0259] 121. A system according to item 111, wherein the conductor is indirectly cooled.

[0260] 122. The system of item 121 further comprising a serpentine coolant passage adjacent to at least one of the conductors to provide indirect cooling.

[0261] 123. According to the system of item 122, the serpentine coolant channel includes an inlet and an outlet, both of which are located at the service end or the patient end of the magnetic resonance imaging system.

[0262] 124. The system of item 121, wherein the conductor is copper.

[0263] 125. A system according to item 124, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 35 kW.

[0264] 126. A system according to item 124, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 105 kW.

[0265] 127. A system according to item 124, wherein the electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 230 kW.

[0266] 128. The system of claim 121, wherein the conductor is aluminum.

[0267] 129. The system of claim 128, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 50 kW.

[0268] 130. The system of item 128, wherein the electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 170 kW.

[0269] 131. A system according to item 128, wherein the electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 365kW.

[0270] One or more aspects or features of the subject matter described herein can be implemented in digital electronic circuits, integrated circuits, specially designed application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) computer hardware, firmware, software, and / or combinations thereof. These various aspects or features can include implementations in one or more computer programs, which can be executed and / or interpreted on a programmable system including at least one programmable processor, which can be dedicated or general purpose, coupled to receive data and instructions from a storage system, at least one input device, and at least one output device, and to send data and instructions to a storage system, at least one input device, and at least one output device. A programmable system or computing system can include a client and a server. The client and the server are usually far away from each other, and usually interact through a communication network. The relationship between the client and the server is generated by a computer program that runs on a corresponding computer and has a client-server relationship with each other.

[0271] These computer programs—which may also be referred to as programs, software, software applications, applications, components, or code, include machine instructions for programmable processors 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, device, and / or apparatus, such as, for example, disks, optical disks, memories, and programmable logic devices (PLDs), for providing 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 for providing machine instructions and / or data to a programmable processor. The machine-readable medium may be a non-transitory machine-readable medium that may store such machine instructions non-transitorily, such as, for example, a non-transitory solid-state memory or a magnetic hard drive or any equivalent storage medium would do. The machine-readable medium may alternatively or additionally store such machine instructions in a temporary manner, such as, for example, a processor cache or other random access memory associated with one or more physical processor cores would do.

[0272] In order to provide interaction with a user, one or more aspects or features of the subject matter described herein can be implemented on a computer having a display device such as, for example, a cathode ray tube (CRT) or a liquid crystal display (LCD) or a light emitting diode (LED) monitor for displaying information to the user, as well as a keyboard and a pointing device (such as, for example, a mouse or a trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user. For example, the feedback provided to the user can be any form of sensory feedback, such as, for example, visual feedback, auditory feedback, or tactile feedback, and input from the user can be received in any form, including but not limited to sound, voice, or tactile input. Other possible input devices include, but are not limited to, touch screens or other touch-sensitive devices, such as single-point or multi-point resistive or capacitive touch pads, voice recognition hardware and software, optical scanners, optical indicators, digital image capture devices and related interpretation software, etc.

[0273] In the above description and claims, phrases such as "at least one" or "one or more" may appear before a list of combinations of elements or features. The term "and / or" may also appear in a list of two or more elements or features. Unless implicitly or obviously contradictory to the context in which it is used, the phrase is intended to represent any listed element or feature alone, or in combination with any other recited element or feature to represent any recited element or feature. For example, the phrases "at least one of A and B"; "one or more of A and B"; and "A and / or B" respectively mean "A alone, B alone, or A with B together". A similar interpretation also applies to lists containing three or more items. For example, the phrases "at least one of A, B, and C"; "one or more of A, B, and C"; "A, B, and / or C" are respectively intended to mean "A alone, B alone, C alone, A with B together, A with C together, B with C together, or A with B with C together". The use of the term "based on" above and in the claims is intended to mean "based at least in part on", thereby also allowing unrecited features or elements.

[0274] Depending on the desired configuration, the subject matter described herein may be embodied in a system, device, method, computer program and / or article. Any method or logic flow depicted in the drawings and / or described herein does not necessarily require the specific order or sequential order shown to achieve the desired results. The embodiments described in the foregoing description do not represent all embodiments consistent with the subject matter described herein. On the contrary, they are only some examples consistent with the aspects related to the described subject matter. Although some variations have been described in detail above, other modifications or additions are possible. In particular, in addition to those features and / or variations described herein, other features and / or variations may also be provided. The above embodiments may be directed to various combinations and subcombinations of the disclosed features and / or combinations and subcombinations of the other features mentioned above. In addition, the above advantages are not intended to limit the application of any issued claims to the process and structure that achieve any or all advantages.

[0275] In addition, section headings should not limit or characterize the invention(s) that may be presented in any claims that may issue from this disclosure. Furthermore, the description of a technology in the “Background” should not be construed as an admission that the technology is prior art to any invention(s) in this disclosure. Nor should the “Summary” be considered a characterization of the invention(s) presented in the issued claims. Furthermore, any reference to the disclosure as a whole or use of the word “invention” in the singular is not intended to imply any limitation on the scope of the claims presented. Multiple inventions may be presented based on the limitations of multiple claims that issue from this disclosure, and these claims accordingly define the invention(s) and their equivalents that are protected thereby.

Claims

1. A magnetic resonance imaging (MRI) system, comprising: A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet comprising a conductor; and A ferromagnetic material is contained within the envelope of the electromagnet.

2. The system according to claim 1, wherein: The electromagnet is bandgap.

3. The system according to claim 2, wherein: The ferromagnetic material comprises steel.

4. The system according to claim 2, wherein: The volume of the ferromagnetic material is at least one sixth of the volume of the conductor.

5. The system according to claim 2, wherein: The volume of the ferromagnetic material is at least one twentieth of the volume of the conductor.

6. The system according to claim 2, wherein: The electromagnet includes a plurality of cylindrical layers, and the ferromagnetic material includes a layer of the plurality of cylindrical layers.

7. The system according to claim 2, wherein: The electromagnet includes a plurality of cylindrical layers, and the ferromagnetic material includes a portion of a layer of the plurality of cylindrical layers.

8. The system according to claim 2, wherein: The electromagnet includes a plurality of cylindrical layers, and the ferromagnetic material includes a plurality of layers or portions of layers of the plurality of cylindrical layers.

9. The system of claim 2, further comprising additional ferromagnetic material outside of an envelope of the electromagnet configured to reduce fringe fields of the electromagnet.

10. The system according to claim 2, wherein: The electromagnet is configured to flow current in only one circumferential direction within the electromagnet.

11. The system according to claim 2, wherein: The electromagnet is configured for a negative current of less than 5%.

12. The system according to claim 2, wherein: The electromagnet is configured for a negative current of less than 10%.

13. The system of claim 2, wherein: The conductor is directly cooled.

14. The system according to claim 13, wherein: The conductor is copper.

15. The system of claim 14, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 25 kW.

16. The system of claim 14, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 55 kW.

17. The system of claim 13, wherein: The conductor is aluminum.

18. The system of claim 17, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 40 kW.

19. The system of claim 17, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 90 kW.

20. The system of claim 2, wherein: The conductor is cooled indirectly.

21. The system of claim 20, wherein: The conductor is copper.

22. The system of claim 21, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 20 kW.

23. The system of claim 21, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 45 kW.

24. The system of claim 20, wherein: The conductor is aluminum.

25. The system of claim 24, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 35 kW.

26. The system of claim 24, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 70 kW.

27. The system of claim 2, wherein: The electromagnet has two halves, and the two halves are held apart by a fixing structure.

28. The system of claim 27, wherein: The fixing structure is substantially non-metallic.

29. The system of claim 28, wherein: The fixing structure comprises carbon fibers.

30. The system of claim 29, wherein: The fixing structure includes zero CTE carbon fibers.

31. The system of claim 28, further comprising a radiation therapy device, wherein: The system is configured such that the radiation therapy device is directed through the fixed structure to perform treatment.

32. A magnetic resonance imaging (MRI) system comprising: A resistive solenoid electromagnet for whole body magnetic resonance imaging, the resistive solenoid electromagnet having a field strength of at least 0.05 Tesla, comprising: a conductor for generating a main electromagnetic field of the electromagnet; Wherein, the main electromagnetic field is generated by the conductor layer.

33. The system of claim 32, wherein: The electromagnet has less than 10 layers of conductor.

34. The system of claim 32, further comprising a ferromagnetic material within an envelope of the electromagnet.

35. The system of claim 32, wherein: The electromagnet is configured to flow current in only one circumferential direction within the electromagnet.

36. The system of claim 32, wherein: The electromagnet is configured to operate with a single supplied current.

37. The system of claim 32, wherein: The electromagnet is bandgap.

38. The system of claim 32, wherein: The electromagnet utilizes a non-metallic former to support the conductor.

39. The system of claim 32, wherein: The electromagnet utilizes a fiberglass former to support the conductor.

40. The system of claim 38, wherein: The layers of conductor and non-metallic former are configured to form a rigid object.

41. The system of claim 40, wherein: The conductor layer and the non-metallic former are configured to form a rigid object by being secured together using epoxy resin.

42. The system of claim 40, wherein: The rigid object includes at least a portion of a gradient coil.

43. The system of claim 32, wherein: The conductor has a cross-sectional area greater than 0.5 square centimeters.

44. The system of claim 43, wherein: The conductor includes at least two spiral layers of conductor separated by a non-metallic former.

45. The system of claim 32, wherein: The conductor is directly cooled.

46. ​​The system of claim 45, wherein: The conductor is aluminum.

47. The system of claim 46, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 40 kW.

48. The system of claim 46, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 90 kW.

49. The system of claim 32, wherein: The conductor layer comprises: a first layer comprising a helically wound conductor having a first helical tilt; and a second layer adjacent to the first layer, the second layer comprising a helically wound conductor having a second helical tilt; The second spiral inclination is opposite to the first spiral inclination.

50. The system of claim 32, wherein: The conductor layer comprises: a first layer comprising a wrapped conductor having a first S-shaped bend that bends in a first direction; and A second layer adjacent to the first layer includes a wrapped conductor having a second S-shaped bend that bends in a second direction.

51. The system of claim 50, wherein: The first S-shaped bend and the second S-shaped bend overlap, and the second direction is opposite to the first direction.

52. The system of claim 32, wherein: The conductor layer comprises: At least one layer includes a portion through which the conductor traverses in a direction parallel to the axis of the solenoidal electromagnet.

53. The system of claim 52, wherein: The conductor traversing in a direction parallel to the axis of the solenoid electromagnet has a cross-sectional area greater than 0.5 square centimeters.

54. The system of claim 32, wherein: The electromagnet has two halves, and the two halves are held apart by a fixing structure.

55. The system of claim 54, wherein: The fixing structure is substantially non-metallic.

56. The system of claim 55, wherein: The fixing structure comprises carbon fibers.

57. The system of claim 55, further comprising a radiation therapy device, wherein: The system is configured such that the radiation therapy device is directed through the fixed structure to perform treatment.

58. A magnetic resonance imaging (MRI) system comprising: A resistance electromagnet for whole body magnetic resonance imaging, the resistance electromagnet having a field strength of at least 0.05 Tesla and comprising a conductor for generating a main magnetic field of the resistance electromagnet; and A power source for powering the resistance electromagnet, the power source having a current fluctuation of at least one part in ten thousand at a frequency of 180 Hz or higher.

59. The system of claim 58, wherein: The resistive electromagnet is a non-bandgap solenoid electromagnet.

60. The system of claim 58, wherein: The system does not include a current filter separate from the filtering provided by the resistive electromagnet itself.

61. The system of claim 58, further comprising a current filter separate from the filtering provided by the resistive electromagnet itself and comprising an inductor having an inductance less than 2 mH.

62. The system of claim 58, wherein: The power supply is a single channel power supply.

63. The system of claim 62, wherein: The system is configured to compensate for low frequency current drift or low frequency voltage drift by means of a main magnetic field strength correction.

64. The system of claim 58, wherein: The power supply does not include active current control.

65. The system of claim 58, further comprising a filter for controlling voltage fluctuations.

66. The system of claim 65, wherein: The filter used to control voltage fluctuations is an LC filter.

67. The system of claim 58, further comprising a battery, wherein: The resistive electromagnet is connected to the battery, and the system is configured such that the battery can be charged by the power source.

68. The system of claim 58, further comprising a plurality of batteries, wherein: The system is configured such that the resistive electromagnet can be connected to one of the plurality of batteries while another of the plurality of batteries can be charged by the power source.

69. The system of claim 58, further comprising at least three batteries, wherein: The system is configured such that the resistive electromagnet is connectable to the first battery while the second battery is being charged, and the system is further configured for the resistive electromagnet connection to be switched to a third battery that is not being charged when the connection is switched.

70. The system of claim 58, further comprising a fuel cell, wherein: The system is configured such that the fuel cell is located between the power source and the resistive electromagnet.

71. The system of claim 58, wherein: The resistive electromagnet is solenoidal and bandgap and contains ferromagnetic material within an envelope of the resistive electromagnet.

72. The system of claim 71, wherein: The conductor is directly cooled.

73. The system of claim 71, wherein: The conductor is copper.

74. The system of claim 73, wherein the electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 30 kW.

75. The system of claim 73, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 100 kW.

76. The system of claim 73, wherein: The electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 210 kW.

77. The system of claim 71, wherein: The conductor is aluminum.

78. The system of claim 77, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 45 kW.

79. The system of claim 77, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 155 kW.

80. The system of claim 77, wherein: The electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 335 kW.

81. The system of claim 71, wherein: The conductor is cooled indirectly.

82. The system of claim 81 further comprising a serpentine coolant passage adjacent at least one of the conductors to provide indirect cooling.

83. The system of claim 82, the serpentine coolant passage comprising an inlet and an outlet, both of which are located at a service end or a patient end of the magnetic resonance imaging system.

84. The system of claim 81, wherein: The conductor is copper.

85. The system of claim 84, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 35 kW.

86. The system of claim 84, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 105 kW.

87. The system of claim 84, wherein: The electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 230 kW.

88. The system of claim 81, wherein: The conductor is aluminum.

89. The system of claim 88, wherein: The electromagnet has a field strength of at least 0.12 Tesla and a power supply of less than 50 kW.

90. The system of claim 88, wherein: The electromagnet has a field strength of at least 0.2 Tesla and a power supply of less than 170 kW.

91. The system of claim 88, wherein: The electromagnet has a field strength of at least 0.3 Tesla and a power supply of less than 365 kW.

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