A method is provided for homogenizing a magnetic field profile of a superconductor magnet system having a cryostat with a room temperature bore, a superconductor bulk magnet with at least three axially stacked bulk sub-magnets, arranged coaxially with the room temperature bore, and a cryogenic cooling system for cooling the superconductor bulk magnet. The cryogenic cooling system independently controls the temperature of each bulk sub-magnet to provide different respective temperatures to the sub-magnets and thereby provide the sub-magnets with different relative currents such that a first subset of the bulk sub-magnets are almost magnetically saturated, and a second subset of the bulk sub-magnets are significantly away from magnetic saturation. By controlling a heating power and/or a cooling power at the bulk sub-magnets without measuring the temperatures of the bulk sub-magnets, the respective currents of the bulk sub-magnets are changed to increase a homogeneity of the field profile.

The present invention provides a method for compensation of periodic B.sub.0 modulations from a periodic motion of a cold head (212) of a main magnet (114) of a magnetic resonance (MR) imaging system (110), whereby main windings (200) of the main magnet (114) are cooled to superconductivity by the cold head (212), which exerts a repetitive motion, the method comprising the steps of measuring a periodic occurrence of spatial field components of the B-field based on a motion of the cold head (212) as a function of time, performing a sensor measurement of a periodic, auxiliary parameter of the MR imaging system (110), which is not the periodic occurrence of spatial field components, synchronizing the periodic occurrence of spatial field components of the B-field with the measured periodic, auxiliary parameter of the MR imaging system (110), and triggering based on the measured periodic sensor measurement of the MR imaging system (110) a periodic application of compensation signals to compensate the periodic occurrence of spatial field components of the B-field based on a motion of the cold head (212). Furthermore, the present invention provides a MR imaging system (110) for providing an image representation of a region of interest (142) of a subject of interest (120) positioned in an examination space (116) of the MR imaging system (110), wherein the MR imaging system (110) is adapted to perform the above method.

Methods and apparatus for determining at least one metabolic state of a subject using a nuclear magnetic resonance (NMR) monitoring device. The NMR monitoring device comprises at least one magnet configured to generate a primary magnetic field, a transceiver coil arranged within the primary magnetic field, wherein the transceiver coil is configured to apply a time series of radiofrequency (RF) pulses to a portion of a subject located within the primary magnetic field and detect an NMR signal generated in response to application of the time series of RF pulses, and an NMR spectrometer communicatively coupled to the transceiver coil. The NMR spectrometer is configured to process the detected NMR signal to determine at least one metabolic state of the subject.

An apparatus for controlling at least one gradient coil of a magnetic resonance imaging (MRI) system. The apparatus may include at least one computer hardware processor; and at least one computer-readable storage medium storing processor executable instructions that, when executed by the at least one computer hardware processor, cause the at least one computer hardware processor to perform a method. The method may include receiving information specifying at least one target pulse sequence; determining a corrected pulse sequence to control the at least one gradient coil based on the at least one target pulse sequence and a hysteresis model of induced magnetization in the MRI system caused by operation of the at least one gradient coil; and controlling, using the corrected gradient pulse sequence, the at least one gradient coil to generate one or more gradient pulses for imaging a patient.

A magnetic resonance arrangement with a permanent magnet system and having magnet elements, pole piece elements and yoke elements of magnetic material arranged cylinder-symmetrically with respect to the z axis. The yoke elements have a first lid (11′) and a second lid (11″) and also a hollow cylindrical drum (12) arranged axially between the lids. The yoke elements enclose the measuring volume in the axial and radial direction. The magnet elements each include a pair of cylinder-symmetrical axial magnets (13′, 13″) and also radial magnet rings (14′, 14″). The axial magnets are each arranged axially adjoining the lids and are arranged radially within the radial magnet rings and respectively axially further away from the measuring volume than the radial magnet rings. The outer diameter of the axial magnets is less than or equal to the inner diameter of the radial magnet rings.

A magnetic resonance arrangement with a permanent magnet system and having magnet elements, pole piece elements and yoke elements of magnetic material arranged cylinder-symmetrically with respect to the z axis. The yoke elements have a first lid (11′) and a second lid (11″) and also a hollow cylindrical drum (12) arranged axially between the lids. The yoke elements enclose the measuring volume in the axial and radial direction. The magnet elements each include a pair of cylinder-symmetrical axial magnets (13′, 13″) and also radial magnet rings (14′, 14″). The axial magnets are each arranged axially adjoining the lids and are arranged radially within the radial magnet rings and respectively axially further away from the measuring volume than the radial magnet rings. The outer diameter of the axial magnets is less than or equal to the inner diameter of the radial magnet rings.

A magnetic resonance imaging (MRI) system having a resistive, solenoidal electromagnet for whole-body MRI may include ferromagnetic material within an envelope of the electromagnet. The system can be configured to have a field strength of at least 0.05 Tesla and its main electromagnetic field can be generated by layers of conductors instead of bundles. Certain electromagnet designs may be fabricated using non-metallic formers, such as fiberglass, and can be constructed to form a rigid object with the layers of conductors by fixing all together with an epoxy. The electromagnet may be configured to have two separated halves, which may be held apart by a fixation structure such as carbon fiber. The power supply for certain electromagnets herein may have current fluctuations, at frequencies of 180 Hz or above, of at least one part per ten thousand without requiring an additional current filter.

Magnetic field sensor, in particular for measuring magnetic noise fields caused by environmental magnetic noise in combination with MRI apparatus, the magnetic field sensor being further provided with field compensation coils assembly and with a compensation circuit driving the field compensation coils assembly to generate a magnetic field compensating the static magnetic field dissipating outside from the static magnetic field generator or from the gantry of the MRI apparatus at the position of the magnetic sensor. A method for operating the magnetic field sensor and a method and a system for compensation magnetic noise caused by environmental noise are also provided. An MRI apparatus is also disclosed comprising such a system and carrying out such a method for compensating magnetic noise fields.

An apparatus and method for dynamically stabilizing the fields in a permanent magnet assembly, including a nuclear magnetic resonance machine. One or more magnetically active elements affect the fields of the magnet assembly. A mechanism controls and changes the position(s) of the magnetically active element(s) to affect and adjust the magnetic field strength in the working volume of the assembly. A sensor provides a control signal indicating the status of the magnetic field strength, and an algorithm is executed for determining, based on the signal, the manner in which the adjustment should be made. The adjustment may be continuous and dynamic, and stabilization of the field may occur during operation of the permanent magnet assembly. The adjustments of the position of the magnetically active element stabilize the field without unduly degrading the field homogeneity, even for high homogeneity magnets.

An apparatus and method for dynamically stabilizing the fields in a permanent magnet assembly, including a nuclear magnetic resonance machine. One or more magnetically active elements affect the fields of the magnet assembly. A mechanism controls and changes the position(s) of the magnetically active element(s) to affect and adjust the magnetic field strength in the working volume of the assembly. A sensor provides a control signal indicating the status of the magnetic field strength, and an algorithm is executed for determining, based on the signal, the manner in which the adjustment should be made. The adjustment may be continuous and dynamic, and stabilization of the field may occur during operation of the permanent magnet assembly. The adjustments of the position of the magnetically active element stabilize the field without unduly degrading the field homogeneity, even for high homogeneity magnets.