An apparatus for providing a B.sub.0 magnetic field for a magnetic resonance imaging system. The apparatus includes at least one first B.sub.0 magnet configured to produce a first magnetic field to contribute to the B.sub.0 magnetic field for the magnetic resonance imaging system, the at least one first B.sub.0 magnet comprising a first plurality of permanent magnet rings including at least two rings with respective different heights.

According to some aspects, a portable magnetic resonance imaging system is provided, comprising a Bo magnet configured to produce a Bo magnetic field for an imaging region of the magnetic resonance imaging system, a noise reduction system configured to detect and suppress at least some electromagnetic noise in an operating environment of the portable magnetic resonance imaging system, and electromagnetic shielding provided to attenuate at least some of the electromagnetic noise in the operating environment of the portable magnetic resonance imaging system, the electromagnetic shielding arranged to shield a fraction of the imaging region of the portable magnetic resonance imaging system. According to some aspects, the electromagnetic shield comprises at least one electromagnetic shield structure adjustably coupled to the housing to provide electromagnetic shielding for the imaging region in an amount that can be varied. According to some aspects, substantially no shielding of the imaging region is provided.

Flow measurement of hydrogen density, volumetric concentrations, and longitudinal relaxation times and transverse relaxation times have all n components in pairs different to each other. The method has the steps of: enclosing a mixture inside a probe volume and polarizing the mixture with a magnetic field; measuring the mixture enclosed inside the probe volume in terms of its longitudinal or transverse relaxation behaviour by means of pulsed electromagnetic waves at least n times with a different volumetric share of its components to measure at least n different relaxation curves; obtaining the relaxation times from the relaxation curves; obtaining the thermal equilibrium magnetizations M.sub.0 of the individual components from the relaxation curves; and correlating yielded thermal equilibrium magnetizations M.sub.0 of the individual components to calculate the hydrogen densities and the volumetric share of the components for each relaxation curve.

At least one example embodiment provides a magnetic resonance imaging system comprising a field generation unit and a supporting structure for providing structural support for the field generation unit, wherein the field generation unit comprises at least one magnet for generating a B0 magnetic field and an opening configured to provide access to an imaging volume positioned in the B0 magnetic field along at least one direction and wherein the at least one direction is angled with respect to a main direction of magnetic field lines of the B0 magnetic field in the imaging volume.

According to some aspects, a method of suppressing noise in an environment of a magnetic resonance imaging system is provided. The method comprising estimating a transfer function based on multiple calibration measurements obtained from the environment by at least one primary coil and at least one auxiliary sensor, respectively, estimating noise present in a magnetic resonance signal received by the at least one primary coil based at least in part on the transfer function, and suppressing noise in the magnetic resonance signal using the noise estimate.

In one embodiment, a receiving coil includes at least one coil element that can simultaneously receive a plurality of magnetic resonance signals having different frequencies, wherein a resonance structure for the different frequencies is provided in a single plane in each of the at least one coil element.

In one embodiment, an MRI apparatus includes: a current-driven magnet configured to generate a magnetic field that predominantly determine a magnetic resonance frequency; a detector configured to detect a position of an object to be imaged in a movable state in the magnetic field; and control circuitry configured to set an imaging region of the object depending on a motion of the object by controlling a drive current of the current-driven magnet based on the detected position of the object.

A radiation therapy system comprises a magnetic resonance imaging (MRI) system combined with an irradiation system, which can include one or more linear accelerators (linacs) that can emit respective radiation beams suitable for radiation therapy. The MRI system includes a split magnet system, comprising first and second main magnets separated by gap. A gantry is positioned in the gap between the main MRI magnets and supports the linac(s) of the irradiation system. The gantry is rotatable independently of the MRI system and can angularly reposition the linac(s). Shielding can also be provided in the form of magnetic and/or RF shielding. Magnetic shielding can be provided for shielding the linac(s) from the magnetic field generated by the MM magnets. RF shielding can be provided for shielding the MRI system from RF radiation from the linac.

A method of producing a permanent magnet shim configured to improve a profile of a B.sub.0 magnetic field produced by a B.sub.0 magnet is provided. The method comprises determining deviation of the B.sub.0 magnetic field from a desired B.sub.0 magnetic field, determining a magnetic pattern that, when applied to magnetic material, produces a corrective magnetic field that corrects for at least some of the determined deviation, and applying the magnetic pattern to the magnetic material to produce the permanent magnet shim. According to some aspects, a permanent magnet shim for improving a profile of a B.sub.0 magnetic field produced by a B.sub.0 magnet is provided. The permanent magnet shim comprises magnetic material having a predetermined magnetic pattern applied thereto that produces a corrective magnetic field to improve the profile of the B.sub.0 magnetic field.

An apparatus for providing a B.sub.0 magnetic field for a magnetic resonance imaging system. The apparatus includes at least one first B.sub.0 magnet configured to produce a first magnetic field to contribute to the B.sub.0 magnetic field for the magnetic resonance imaging system, the at least one first B.sub.0 magnet comprising a first plurality of permanent magnet rings including at least two rings with respective different heights.