Systems and methods for designing and fabricating three-dimensional objects with precisely computed material compositions for use in enhancing electromagnetic fields for magnetic resonance imaging (“MRI”) are provided. As examples, the fabricated object can be designed to reduce magnetic field inhomogeneities in the main magnetic field of an MRI system, or to reduce inhomogeneities in a transmit radio frequency (“RF”) field (i.e., a B.sub.1 field). As examples, the object can be a shim; a housing or other part of an RF coil; a medical device, such as a surgical implant; or component used in a medical device, such as a housing for an implantable medical device.

Systems and methods for designing and fabricating three-dimensional objects with precisely computed material compositions for use in enhancing electromagnetic fields for magnetic resonance imaging (“MRI”) are provided. As examples, the fabricated object can be designed to reduce magnetic field inhomogeneities in the main magnetic field of an MRI system, or to reduce inhomogeneities in a transmit radio frequency (“RF”) field (i.e., a B.sub.1 field). As examples, the object can be a shim; a housing or other part of an RF coil; a medical device, such as a surgical implant; or component used in a medical device, such as a housing for an implantable medical device.

A method for ascertaining a magnetic field of at least one magnetic coil unit of a magnetic resonance apparatus, a magnetic resonance apparatus, and a computer program product are provided. According to the method, the magnetic field is generated by the at least one magnetic coil unit. A plurality of magnetic field vectors are detected at different positions of the magnetic field by a magnetic field sensor unit, where each magnetic field vector of the plurality of magnetic field vectors describes a strength, such as a magnitude, and a direction of the magnetic field at the respective position. The magnetic field is ascertained. To ascertain the magnetic field based on the plurality of magnetic field vectors, a model of a vector field is ascertained.

In a method and apparatus for acquiring a magnetic resonance image data set of a scan area of an examination subject, the image data are acquired with a magnetic resonance apparatus having a transmitter coil that emits a radio-frequency signal having at least two transmission channels so that different polarizations of the radio-frequency signal are produced, and a magnetic resonance sequence is used to acquire raw data for the magnetic resonance image data set, wherein raw data are acquired during at least two scanning operations with the magnetic resonance sequence, with different polarizations of the radio-frequency signals being used for at least two of the at least two scanning operations, following which the magnetic resonance image data set is determined by averaging the raw data.

In a method and apparatus for acquiring a magnetic resonance image data set of a scan area of an examination subject, the image data are acquired with a magnetic resonance apparatus having a transmitter coil that emits a radio-frequency signal having at least two transmission channels so that different polarizations of the radio-frequency signal are produced, and a magnetic resonance sequence is used to acquire raw data for the magnetic resonance image data set, wherein raw data are acquired during at least two scanning operations with the magnetic resonance sequence, with different polarizations of the radio-frequency signals being used for at least two of the at least two scanning operations, following which the magnetic resonance image data set is determined by averaging the raw data.

The present disclosure in some embodiments provides a method and an apparatus for processing MRI images wherein a plurality of slices of an object is applied with a spatial encoding gradient and a corrected gradient for applying a radial sampling, and radially sampled magnetic resonance signals of the slices are received, and MRI images are generated with the radial sampling applied over multi-bands.

The present disclosure in some embodiments provides a method and an apparatus for processing MRI images wherein a plurality of slices of an object is applied with a spatial encoding gradient and a corrected gradient for applying a radial sampling, and radially sampled magnetic resonance signals of the slices are received, and MRI images are generated with the radial sampling applied over multi-bands.

Techniques are disclosed for acquiring magnetic resonance data of an object with a magnetic resonance imaging apparatus. A slice group is imaged whose slices define a contiguous imaging volume and which contains a first number of slices. In a number of concatenations, the magnetic resonance data for subgroups of the slices, each containing a respective second number of slices depending on the first number of concatenations, are acquired, and shimming is performed to increase field homogeneity in the imaging volume. To define the subgroups, the imaging volume is subdivided into at least two disjoint contiguous sub-volumes, and at least two subgroups are defined for each sub-volume, each subgroup only containing non-adjacent slices in the sub-volume. During acquisition of the magnetic resonance data of each subgroup, shimming is at least restricted to the respective sub-volume.

Techniques are disclosed for acquiring magnetic resonance data of an object with a magnetic resonance imaging apparatus. A slice group is imaged whose slices define a contiguous imaging volume and which contains a first number of slices. In a number of concatenations, the magnetic resonance data for subgroups of the slices, each containing a respective second number of slices depending on the first number of concatenations, are acquired, and shimming is performed to increase field homogeneity in the imaging volume. To define the subgroups, the imaging volume is subdivided into at least two disjoint contiguous sub-volumes, and at least two subgroups are defined for each sub-volume, each subgroup only containing non-adjacent slices in the sub-volume. During acquisition of the magnetic resonance data of each subgroup, shimming is at least restricted to the respective sub-volume.

A passive magnetic field shim arrangement including a plurality of shim pairs. For shimming a number of magnetic field harmonics, each shim pair may include a first shim and a second opposite and substantially equal shim, each shim pair being configured for shimming one of the magnetic field harmonics. Each shim pair may include a first shim of order N and a second opposite and substantially equal shim of order N, the first and second shims together defining a magnetic field shim correction of order N−1. Each shim may include one or more shim elements arranged on a non-magnetic tubular support, the tubular supports being dimensioned such that the tubular supports may be arranged concentrically in relation to each other. A magnetic field may be shimmed by providing a shim pair configured for shimming a magnetic field harmonic, the shim pair including a first shim and a second opposite and substantially equal shim and symmetrically adjusting an axial position of the first shim and an axial position of the second shim to provide a desired shimming magnitude in order to shim the magnetic field harmonic.