Abstract: An NMR apparatus provided with a lock device having improved monotonicity without reducing a control range. In a lock device including a lock transmitter, a lock receiver, a lock detector, a lock corrector, a lock power supply and a lock coil, the lock detector performs complex detection of a detection signal and outputs to the lock corrector an absorption signal SA which is a real number component of the detection signal and a dispersion signal SD which is an imaginary number component of the detection signal; the lock corrector obtains a value SC by multiplying together SD/(SD2+SA2) and a value G, and the lock power supply performs adjustment so that a current flowing through the lock coil is proportional to SC. Different constants G are selectively used according to the value of SD/(SD2+SA2).

Abstract: The present invention provides a magnet assembly (30a, 30b) comprising a pair of drive coils (31a, 31b; 32a, 32b; 33a, 33b) symmetrically disposed with respect to a reference plane. The reference plane is located approximately equidistant between the drive coils. Each of the drive coils has a current flowing through it which is in the opposite sense to the current flowing through the other drive coil, such that a primary magnetic field is generated in a plane which is parallel to and substantially coincident with the reference plane. The assembly may comprise further compensating coils (44a, 45a, 46a) which are configured to generate a magnetic field to improve homogeneity of the primary magnetic field. The drive coils and the compensating coils are generally in the shape of a racetrack and are preferably superconducting coils.

Abstract: The invention concerns a superconducting high-field magnet system (1) for a high-resolution magnetic resonance spectrometer, comprising a magnet coil (4) which is superconductingly short-circuited during operation, and generates a homogeneous temporally stable magnetic field during operation that meets the requirements for taking a high-resolution magnetic resonance spectrum. The magnet coil (4) comprises an LTS partial coil (4b, 4c) and an HTS partial coil (4a, 4d). The LTS partial coil (4b, 4c) can be separately short-circuited in a pure LTS circuit (14b) via an LTS switch (15b), and the HTS partial coil (4a, 4d) can be separately short-circuited in a pure HTS circuit (14) via an HTS switch (15a) and both partial coils (4a, 4d; 4b, 4c) are connected via an LTS-HTS joint (20) and are charged by the same power supply.

Abstract: A Magnetic Resonance Imaging system includes a plurality of auxiliary magnets that are disposed around the main magnets to adjust the interval between the main magnet and the auxiliary magnets and the interval between the main magnet and the auxiliary magnets respectively.

Abstract: A permanent magnet assembly comprising a fixed permanent magnet body and a movable permanent magnet body which is movable relative to the fixed permanent magnet body.

Abstract: Systems, methods and apparatus are provided through which inhomogeneity in a magnetic field is reduced by invoking electromagnetic mutual inductance between a main coil and another coil.

Abstract: A magnetic field generator comprises a pair of plate yokes connected by a column yoke. The pair of plate yokes has a pair of opposed surfaces each provided with a permanent magnet including a plurality of neodymium magnets. In a method in which the neodymium magnets are demagnetized and adhesive is ground, the magnetic field generator is heated to 200° C.˜350° C. After the neodymium magnets are demagnetized, the adhesive is removed and the neodymium magnets are removed and collected from the magnetic field generator. In a method in which the adhesive is carbonized, the magnetic field generator is heated to 350° C.˜1000° C. After carbonizing the adhesive, the neodymium magnets are removed and collected. Surfaces of the collected neodymium magnets are polished and the neodymium magnets are reused. Further, the collected neodymium magnets are re-aged and reused.

Abstract: To access a measurement space located at the center of the magnet, an access port is provided in the direction of the magnet's axis, a clearance is provided in the coil winding portion, and another access port passes through the clearance so that a sample can be positioned perpendicularly to the coil axis. According to this configuration, an access port passing through the coil winding portion can be smaller than the access port passing through the coil axis, a sample is inserted from the access port, and a probe is inserted from the access port passing through the magnet axis, and thus the clearance can be minimized.

Abstract: A generator of time-variable magnetic fields of a magnetic resonance apparatus, said apparatus having an examination space for imaging of at least one area of an examination subject to be examined, incorporates the following features: the conductors of a gradient coil arrangement of the generator extent over an essentially disk-shaped area, the area includes at least one sub-area which is free from conductors of the gradient coil arrangement and within which are arranged conductors of a high-frequency antenna of the generator, and a field backflow space, which is available inter alia for fields of the high-frequency antenna, extends away from the examination space, starting from the sub-area.

Abstract: A voltage compensation unit reduces the effects of induced voltages upon a device having a single wire line. The single wire line has balanced characteristic impedance. The voltage compensation unit includes a tunable compensation circuit connected to the wire line. The tunable compensation circuit applies supplemental impedance to the wire line. The supplemental impedance causes the characteristic impedance of the wire line to become unbalanced, thereby reducing the effects of induced voltages caused by changing magnetic fields.

Abstract: A multi-tune radio frequency (RF) coil for concurrent magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) is disclosed. The multi-tune RF coil includes a first end ring having a generally annular opening and a first plurality of elongated segments coupled to and positioned circumferentially around the first end ring. The first plurality of elongated segments are azimuthally offset from one another by a substantially equal angular distance. A second RF coil includes a second end ring having a generally annular opening and a second plurality of elongated segments coupled to and positioned circumferentially around the second end ring. The second plurality of elongated segments are azimuthally offset from one another by a substantially equal angular distance.

Abstract: The projection of magnetic gradient fields useful in Magnetic Resonance Imaging where projection of a gradient outside of a field generating assembly allows imaging of samples which will not physically fit inside the coil confines. The linearity of the projected gradient field is improved by arranging the position of the magnetic field generating coil conductors such that the second derivative of a gradient component is equal to zero. In one practical example the linearity is improved by providing a first circular coil which is positioned so that its center is offset along the axis of the field generating coil assembly by a distance equal to half the radius of the coil. In another example a pair of current carrying wires are selectively positioned offset from a region of interest.

Abstract: The MRI apparatus has ring-shaped superconducting coils arranged to vertically oppose each other. The superconducting coils are installed in ring-shaped cooling containers. The cooling containers are accommodated in radiation shield plates. The radiation shield plates are accommodated in vacuum vessels. The cooling containers are connected together at at least two locations. Support members are arranged between an outer wall surface of the lower cooling container and an inner wall surface of the lower vacuum vessel to support the lower cooling container on the lower vacuum vessel. The upper cooling container is free, supported only by the connecting tubes connecting the upper and lower cooling containers.

Abstract: A method for tuning a radio frequency coil of a magnetic resonance imaging system includes disposing a plurality of probes at selected portions of a fixture, disposing the fixture proximate to the radio frequency coil at a first location, and obtaining a first set of measurements of an output of the radio frequency coil using an automated test equipment.

Abstract: The present invention discloses a permanent magnet for magnetic resonance, which is used for a magnetic resonance imaging apparatus for medical diagnosis. The permanent magnet of the present comprises permanent magnetic material; pole heads; plates for eliminating vortex (i.e. eddy currents); rings for homogenizing the magnetic field; gradient coils; and a yoke, said yoke of the permanent magnet has an integral and substantially C-shaped structure formed with two columns and is an open type configuration. This invention fully ensures the parallelism of the lower and upper poles, greatly improves the mechanical strength of the yoke, and results in a good magnetic uniformity and a consistent magnetic current.

Abstract: A magnetic field generator (10) capable of generating a more intense magnetic field, and an MRI apparatus (200) using it are provided. Permanent magnets (12a), (12b), (14a), (14b), (16a), (16b), (18a), (18b), (20a), (20b), (22) and (24) are disposed annularly for formation of a magnetic field generation space (30). Ferromagnetic materials (26a) and (26b) are provided near the magnetic field generation space (30), at places passed by a magnetic flux. Each of the permanent magnets (12a), (14a), (16a), (18a) and (20a) surrounding the ferromagnetic material (26a) is magnetized so as to make an S pole on the side of the ferromagnetic material (26a). Each of the permanent magnets (12b), (14b), (16b), (18b) and (20b) surrounding the ferromagnetic material (26b) is magnetized so as to make an N pole on the side of the ferromagnetic material (26b). An MRI apparatus (200) is obtained by using the magnetic field generator (10).

Abstract: A distortion-corrected magnetic resonance examination with a magnetic resonance device is undertaken by use of a distortion correction algorithm which uses coefficients to describe a magnetic field used in a measurement. In this case, after an examination area has been selected, by including the distortion correction algorithm and the coefficients for description of the magnetic field, a measurement area needed for correction is determined. Subsequently a magnetic resonance measurement is performed in the measurement area. Subsequently a distortion-corrected magnetic resonance image of the examination area is created with the aid of the distortion correction algorithm. In addition to the examination area, the measurement area and also any necessary measurement times can be shown on a display of the magnetic resonance device. This type of magnetic resonance examination does not include in the magnetic resonance image any picture elements which were not measured because of distortion.

Abstract: Disclosed is a method and system for steady state free precession based magnetic resonance thermometry that measures changes in temperature on a pixel by pixel basis. The method comprises generating an RF pulse sequence used to find the proton resonance frequency shift, which is proportional to temperature change, processing the resultant MRI data to measure the proton frequency shift, and converting the measured proton frequency shift into change in temperature data. Further disclosed is a method for identifying and compensating for temperature drifts due to core heating of the gradient magnet.

Abstract: A magnetic resonance imaging apparatus generates an MR signal from an object to be examined by applying a gradient field pulse generated by a gradient field coil and a high-frequency magnetic field pulse generated by a high-frequency coil to the object in a static field generated by a static field magnet, and reconstructs an image on the basis of the MR signal. The gradient field coil is housed in a sealed vessel. Numerous techniques are disclosed to reduce adverse effects of vibrations caused by rapidly changing gradient coil currents. By judicious use of non-conducting connection components between gantry components at some joint portions requiring electrical contact and at some other portions not requiring electrical contact, the generation of adverse B waves, and/or induced electron flow in response to physical vibration between joint components can be reduced.

Abstract: An apparatus and method for providing RF shielding for performing nuclear magnetic resonance (“NMR”) procedures, comprising a radio-opaque holder in combination with radio-opaque magnet components to form an RF shield around a patient undergoing an NMR procedure. In embodiments, a radio-opaque holder having a radio-opaque bottom portion and a radio-opaque canopy is adjoined to an NMR magnet having a radio-opaque cryostat and a radio-opaque service end cap to form an RF shield. A patient is placed on a patient support unit located in the holder bottom portion. The patient support unit, including the patient, is then inserted into the cavity of the NMR magnet and a canopy is placed on top of the bottom portion of the holder. An RF shield is thus created comprising the canopy, the bottom portion, the cryostat of the magnet, and an end cap on the service end of the magnet.

Abstract: A method and apparatus for magnetic field drift compensation for a superconducting magnet system includes electrically coupling a micro-flux injection system to a secondary B0 superconducting coil in a secondary compensation circuit; magnetically coupling the secondary compensation circuit to the superconducting magnet via the secondary B0 superconducting coil; switching the micro-flux injection system on and off either thermally or magnetically to induce a first current from a flux coil of the secondary compensation circuit into the secondary B0 superconducting coil producing a secondary field to compensate magnet field drift of the superconducting magnet.

Abstract: A time-varying magnetic fields generator for a magnetic resonance apparatus has at least one gradient coil and one radio-frequency antenna, gradient coil being formed by two essentially hollow-cylindrical units that are axially separated from one another and that contain conductors of the gradient coil, and that each have at least one axial free space proceeding therethrough to accommodate a shim device, and at least one hollow conductor of the radio-frequency antenna is disposed between the units such that its hollow interior axially communicates with and continues at least one of the free spaces.

Abstract: A nuclear magnetic resonance diagnosing apparatus for continuously taking tomograms in a space formed between a pair of magnets includes a cylindrical table top support of a gantry side, a pair of magnets vertically arranged, a table top support of the gantry side being interposed between the pair of magnets; and a column for supporting at least the magnet arranged in an upper side between the pair of magnets. The column is formed so that between a gantry and an examining table body, a width between a bridge construction, which is provided between the column and the table top support of the gantry side, and the table top support of the gantry side may be smaller than an examination width L determined by lines R? passing through a center of the table top support of the gantry side perpendicular to a center line R.

Abstract: A recycling method for a magnetic field generator, which includes a plate yoke, and a permanent magnet provided on the plate yoke, the magnetic field generator further including a plurality of neodymium magnets bonded together by an adhesive. The magnetic field generator is heated to 200° C.˜1000° C., then at least one of the plurality of neodymium magnets is removed; and a surface of the removed neodymium magnet is polished for reusing the neodymium magnet.

Abstract: A magnetic resonance system has a primary RF transmitting antenna and at least one secondary RF transmitting antenna. Both antennas generate RF excitation fields in an examination volume. At least one of the primary and secondary transmitting antennas has a control element connected thereto, which allows an amplitude ratio and/or a phase difference of the respective excitation currents in the antennas to be set by a control and evaluation device. The control and evaluation device causes the excitation current in the secondary transmitting antenna to have a smaller amplitude than the excitation current in the primary transmitting antenna, so that the excitation field generated by the secondary transmitting antenna has a smaller spatial extent in the examination volume than the excitation field generated by the primary transmitting antenna.

Abstract: A split type magnet device configured for a high-sensitivity NMR apparatus and used for solution analysis generates a uniform magnetic field at the center portion of the magnet device of at least 11 T, which is used for determining a sample. The NMR magnet device has left and right solenoid superconducting magnets, which face each other with a predetermined distance being provided therebetween. The left solenoid superconducting magnets and the right solenoid superconducting magnets are substantially coaxial to a central axis, and constituted respectively by a plurality of outermost magnets and a separate plurality of innermost magnets. When a sample energizing current generates a main magnetic NMR detection field in the vicinity of a center portion of the apparatus the current direction in at least one of the plurality of innermost magnets is minus while the current direction in at least one of the plurality of outermost magnets is plus.

Abstract: A structure for superconducting magnets is provided. The structure includes a thermally conductive electrically resistive composite bobbin, a superconducting coil disposed around the thermally conductive electrically resistive composite bobbin for conducting current in a superconductive state. The structure also includes an electrically open cryogenic coil disposed on the thermally conductive composite electrically resistive bobbin, which can receive a flow of cryogenic fluid to maintain the superconducting coil in the superconductive state by transfer of heat from the superconducting coil to the electrically open cryogenic coil through the thermally conductive electrically resistive composite bobbin.

Abstract: A magnetic resonance tomography device, wherein vibrations of device components, particularly in the low frequency range, are attenuated, as a magnet body surrounded by a magnet shell, which surrounds and defines an inner area. A gradient coil system is disposed in the inner area and an inner encapsulation cylinder also is disposed therein. The magnetic shell and the gradient coil system are externally and acoustically sealed from the inner encapsulation cylinder, and from a capsule. The capsule is formed as a three-layer system, including a cover layer, a full foam layer and a partial foam layer.

Abstract: A coil and method for a medical imaging are provided. The coil includes a first section and a second section. The first and second sections form a loop and are configured in a diagonal arrangement.

Abstract: In a superconductive magnet device comprising upper and lower vacuum vessels coupled by a coupling conduit, the upper and lower vacuum vessels 9 and the coupling conduit 24 coupling them are made of a high electric-resistance material so that the magnetic flux of gradient magnetic field coils reaches the upper and lower pair of a second heat shields 8 and a coupling conduit 23 coupling the pair of the second heat shields 8. The coupling conduit 23 coupling the upper and lower pair of the second heat shields 8 is provided with a slit (cut) 41 extending in the vertical direction so that no eddy currents occur and thus eddy currents generated asymmetrically in the coupling conduit 23 are reduced. Artifacts caused by asymmetrical eddy currents can by reduced in an MRI apparatus using such a magnet device.

Abstract: The invention concerns an apparatus for generating and/or detecting radio frequency (RF)-B1 fields in an investigational volume (10) of a magnetic resonance (MR) device, wherein the apparatus comprises a tubular surface coil (1; 20; 30; 41–44; 51–54; 61) which is formed from a conducting strip and is capacitively closed at least two neighboring ends, wherein the ratio between length L and width W of the strip is ?30, and wherein the volume under investigation (10) is disposed outside of the space surrounded by the strip, bordering an outer surface (9) of the surface coil (1; 20; 30; 41–44; 51–54; 61) such that the B1 field lines, generated by the surface coil (1; 20; 30; 41–44; 51–54; 61) in the volume under investigation (10) extend substantially parallel to this outer surface (9) thereby producing an NMR transmitting and receiving apparatus with improved properties, in particular, one permitting precise influence of the distribution of the RF-B1 field.

Abstract: A phased-array knee coil is provided and includes a transmit coil array and a receive coil array having a plurality of coils configured to provide a first imaging mode and a second imaging mode.

Abstract: An MRI apparatus having an open structure includes a static magnetic field generating magnet including magnetic field generating sources arranged above and below an imaging space and magnetic field fluctuation reducing plates arranged inside the magnet. Gradient magnetic field coils are fixed to the static magnetic field generating magnet so as to not be in contact with the magnetic field fluctuation reducing plates. When the strength of the magnetic field generated by the static magnetic field generating magnet fluctuates due to vibration of the gradient magnetic field coils or other devices during an imaging operation of the MRI apparatus, an eddy current is generated on the magnetic field fluctuation reducing plates in response to the magnetic field fluctuation components. Magnetic flux which cancels the static magnetic field fluctuation components is generated due to this eddy current, and consequently, a time-sequentially stable static magnetic field can be obtained.

Abstract: A driver for use in applying an oscillating stress to a subject undergoing a magnetic resonance elastography (MRE) examination includes a passive actuator located in the bore of the magnet and in contact with the subject. A remotely located acoustic driver produces acoustic energy in response to an applied current and this energy is coupled therethrough a flexible tube to the passive actuator. A movable element in the passive actuator vibrates in response to this acoustic energy.

Abstract: The present invention provides a magnetic field generator for MRI in which, by simplifying the component parts of the pole pieces incorporated therein, the magnetic field generator for MRI can be manufactured at a lower cost without detracting from its magnetic characteristics. Specifically, the present invention provides an inclined magnetic field generation coil for use in a magnetic field generator for MRI, the coil comprising a plurality of magnetic field regulating holes (17), an electric conductor in coiled form, and a resin base.

Abstract: A magnetic field generator for producing a homogenous magnetic field region. The magnetic field generator comprises: a plurality of main magnet coils arranged in a cylindrical fashion; a plurality of shielding coils arranged in a cylindrical fashion, and located radially outward of the plurality of magnets; and wherein the main magnet coils and shielding coils are configured to shape a magnetic field which comprises at least one low fringe field region when in operation. A method for designing an MRI system that produces a low fringe field region. The method comprises: defining a solution space; defining a field of view, a center field and homogeneity requirements; defining fringe field requirements; and running an optimization algorithm to determine coil positions.

Abstract: In a magnetic resonance tomography apparatus employing a FISP pulse sequence, the pulse sequence is repeated with a repetition time TR with different phase-coding gradient directions and with an alternating operational sign of the flip angle ?. The gradient pulse trains are thereby completely balanced. A phase increment ??=? is generated in addition to the alternating operational sign of the flip angle ? between successive excitation pulses, so that the steady state signals for a first and a second spin ensemble optionally have either identical or reversed signal polarities. A first dataset on the basis of identical signal polarities and a second dataset on the basis of reversed signal polarities are obtained by means of the free selection of the mutual signal polarities. A pure image of the first and the second spin ensembles is thus obtained by the addition and/or subtraction of the first and second datasets.

Abstract: The present invention provides for a cooling system for circulating a coolant to cool the patient bore. In one embodiment, that patient bore consists of two concentric cylinders separated by spacers running either longitudinally or helically. In another embodiment of the present invention, fluid may be passed either helically or longitudinally through tubes bonded to the outer diameter of the patient bore such that the parts of the bore that are exposed to the patient are directly cooled. In a third embodiment, the RF coil could form part of the patient bore, with the helical or longitudinal fluid channels surrounding the patient bore.

Abstract: A radio-frequency antenna for a magnetic resonance system has a number of antenna rods and two rings. The antenna rods are regularly arranged around an antenna axis and are each connected at their rod ends with one of the rings per rod end. When the antenna rods proceed substantially parallel to the antenna axis, they exhibit, in a middle region of the antenna axis, a rod spacing from the antenna axis that is larger than the ring spacing from the antenna axis for at least one of the ferules. Either the antenna rods, with regard to their total length, are bent radially inwardly only in the area of the last 10%, or they proceed radially inwardly from their middle region over at least 20%, whereby in the outermost 10% no inward change ensues, or the rings, in their connection regions, are directed radially outwardly toward the antenna rods.

Abstract: Wireline NMR well logging measurements suffer from disadvantages of poor vertical resolution, logging speeds less than 20 ft/min, and power consumption in excess of 200 W. In spite of these disadvantages, NMR well logging is used because it is capable of providing estimates for a number of petrophysical parameters that are difficult to obtain from other wireline data. These include estimates of the bulk volume irreducible (BVI) of fluids in the formation. The present invention targets BVI and clay bound water (CBW) measurements. Logging speeds of up to 60 ft/min are attainable with little or no loss of resolution. In one preferred embodiment, the tool has four sensors circumferentially distributed around the logging tool and in contact with the borehole wall. A horseshoe like magnet is used to generate the static magnetic field.

Abstract: A magnetic resonance device HAS a cavity and with a gradient coil system arranged in the cavity, that, in a middle region, exhibits a lower mechanical stiffness than in edge regions connected to the middle region, and has a supporting arrangement to support the middle region against a boundary surface of the cavity.

Abstract: A cryogen pressure vessel assembly for a superconducting magnet comprises an inner former, an outer former, and an outer shell. The inner former has a plurality of superconducting magnet coils wound thereon, and the outer former has a plurality of bucking coils wound thereon. The inner former, the outer former, and the outer shell form a fluid boundary for a cryogen. In one aspect, a pressure face is formed on at least one of the coil formers, and a radial slot for receiving wires entering and exiting a coil is disposed in the pressure face. A plurality of wire clamps are positioned in the radial slot, with each wire clamp in the plurality of wire clamps including: a front face extending coplanar with the pressure face, a rear face opposite the front face, the rear face contacting a back surface of the radial slot, and a recess formed in the rear face, the recess forming a channel for passage of the wires.

Abstract: A system composed of multiple transmit coils with corresponding RF pulse synthesizers and amplifiers is disclosed. A method of designing RF pulses specific to each transmit coil to dynamically control RF power deposition across an imaging volume is also disclosed, where parallel excitation with the transmit coils allows for management of RF power deposition on a subject while facilitating faithful production of a desired excitation profile. The present invention also supports reduction in scan time and is applicable to any coil array geometry.

Abstract: The invention concerns a method for charging an actively shielded magnet coil arrangement (20) comprising a first partial region (21) which can be superconductingly short-circuited using an additional switch (23), and a second partial region (22), wherein the two partial regions (21, 22) generate dipole moments of different signs. The magnetic fringe field B* is measured close to the desired operating state of the arrangement (20) and operating currents are determined for each of the two partial regions (21, 22) at which the overall magnetic field B is free from an additional dipole moment caused by production tolerances to permit setting of the theoretically optimum fringe field, irrespective of production tolerances.

Abstract: An MRI system includes an array of series resonant transmit elements 6 and 65 including individual control of RF current in all elements 106, 108, 110, 114, 116, 118, 120. The array 6 and 65 adjusts scan homogeneity during a scan or prescan phase by adjusting amplitude and phase. The array 6 and 65 also selectively excites areas of interest, thus avoiding major power dissipation and avoiding heating in the patient.

Abstract: A secondary coil circuit for use with a multi-section protected superconductive magnet coil circuit is disclosed herein. The secondary coil circuit includes two circuit nodes, a ramping switch electrically connected between the two circuit nodes, and a number of secondary coils electrically connected between the two circuit nodes. The secondary coils are made of wire having substantially superconductive capability when cooled below a characteristic critical temperature level and conducting electric current below a characteristic critical current level. The secondary coils are sized and positioned relative to the superconductive magnet coils situated in the individual sections of the multi-section protected superconductive magnet coil circuit so as to functionally cooperate with the multi-section protected superconductive magnet coil circuit in producing and maintaining a magnetic field that is substantially homogeneous.

Abstract: A configurable matrix receiver comprises a plurality of antennas that detect one or more signals. The antennas are coupled to a configurable matrix comprising a plurality of amplifiers, one or more switches that selectively couple the amplifiers in series fashion, and one or more analog-to-digital converters (ADCs) that convert the output signals generated by the amplifiers to digital form. For example, in one embodiment, a matrix comprises a first amplifier having a first input and a first output, and a second amplifier having a second input and a second output, a switch to couple the first output of the first amplifier to a the second input of the second amplifier, a first ADC coupled to the first output of the first amplifier, and a second ADC coupled to the second output of the second amplifier. In one embodiment, the signals detected by the antennas include magnetic resonance (MR) signals.

Abstract: A magnetic resonance imaging apparatus and method having a magnet assembly, which provides substantially flat surfaces of constant magnetic field outside the assembly and a set of magnetic field gradients. One-, two-, and three-dimensional images are rendered. The static magnetic field is virtually uniform within horizontal degrees of freedom and decreases monotonically in a direction away from the surface. An RF probe, for example, a coil, located adjacent the surface, produces a field substantially perpendicular to the static magnetic field. A magnetic field gradient is set to horizontally scan a given level within the sensitive volume. Received magnetic resonance signals are detected by the coil for a depth corresponding to the excitation frequency. As the tuning and excitation frequency is switched to lower values, signals are generated for layers progressively farther from the surface. The RF probe is automatically tuned.

Abstract: Magnet assembly for use in medical magnetic resonance imaging includes means for increasing flux generation in the gap region to provide the capability of scanning smaller volume regions of a patient at increased levels of scanning resolution. The means for increasing flux generation is mechanical or electromagnetic, is coupled to each of the polar regions and maintains the gap region sufficiently large and unobstructed to allow for access to the patient by several persons during scanning. Tapered outer walls of the polar region proximate the gap region further enhance accessibility to the patient during scanning.

Abstract: Asymmetric, compact superconducting magnets for magnetic resonance imaging are provided. The magnets have a homogeneous region (the “dsv”) which can be located close to one end of the magnet so as to reduce the sensation of claustrophobia experienced by patients undergoing MRI procedures. The magnets can be designed using a hybrid process in which current density analysis is performed to obtain an initial coil configuration which is then refined using non-linear optimization techniques to obtain a final coil configuration. The hybrid method can incorporate various constraints, including, the location and size of the dsv, the uniformity and strength of the B0 field, stray field strengths outside of the superconducting magnet, and field strengths within the magnet's coils. The hybrid technique can also be used to design compact symmetric superconducting magnets.