In a method and magnetic resonance (MR) apparatus for acquiring MR data from a volume of an object in which first and second excitable spin types are present that differ in their Larmor frequencies by a chemical shift, an MR sequence with at least one radio-frequency pulse sequence selectively excites the first spin type or selectively suppresses MR signals of the second spin type. A B0 map describing the basic field distribution in a region of interest of the volume is established. First and second items of distribution information, which respectively describe the spectral distribution of Larmor frequencies of the first and second spin types, are derived from the B0 map. A pulse sequence parameter that describes the excitation spectrum of the radio-frequency pulse sequence is optimized based on the items of distribution information, with regard to a quality criterion that optimizes selective excitation and/or suppression.

In a method and magnetic resonance (MR) apparatus for acquisition of MR data from a slice in a subject, a first slice selection gradient is activated in a first direction perpendicular to the slice, and an RF excitation pulse then selectively excites nuclear spins in the slice. A second slice selection gradient is activated along the first direction, and a refocusing pulse is radiated. A first phase encoding gradient along the first direction is activated, and a second phase encoding gradient is activated along a second direction perpendicular to the first direction. A selection gradient is activated along a third direction perpendicularly to the first and second directions, during which MR data are acquired from the slice. The acquired MR data are entered into multiple k-space lines that are selected starting from the refocusing pulse, without a further RF pulse being radiated.

The invention provides for a medical instrument (100, 500) comprising a magnetic resonance imaging system (102) for acquiring magnetic resonance data (142) from a subject (118) within an imaging zone (108). The magnetic resonance imaging system comprises: a main magnet (104) for generating a B0 magnetic field within the imaging zone; a memory (134, 136) containing machine executable instructions (160, 162, 164, 166) and pulse sequence commands (140); a processor (130) for controlling the medical instrument. Execution of the machine executable instructions causes the processor to: acquire (200) the magnetic resonance data by controlling the magnetic resonance imaging system with the pulse sequence commands; receive (202) a subject magnetic susceptibility map (144) of the subject; calculate (204) a B0 inhomogeneity map (146) from the magnetic resonance data; calculate (206) a subject B0 magnetic field perturbation (148) from the subject magnetic susceptibility map; calculate (208) a residual B0 magnetic field perturbation (150) by subtracting the subject B0 magnetic field perturbation from the B0 inhomogeneity map; and calculate (210) a bone map (152) from the residual B0 magnetic field perturbation.

Systems and methods for quantitative susceptibility mapping (QSM) using magnetic resonance imaging (MRf) and a localized processing technique are described. A field-shift map is processed based on localized regions of local field perturbations. These localized field-shift regions are processed using established QSM algorithms, or using direct dipole inversion techniques, to compute regional susceptibility distributions from the localized field shift information. When the localized regions correspond to subvolumnes of the field-shift map, local susceptibility maps can be generated and combined to form a composite quantitative susceptibility map. By computing regional susceptibility distributions based on localized field-shift information, residual streaking artifacts in the susceptibility map are constrained to the individual volumes from which they originate, thereby eliminating their propagation through the image.

Accelerated 3D multispectral imaging (MSI) on a magnetic resonance imaging (MRI) system uses phase-encoding in two dimensions and frequency-encoding in the third. The method generates randomized k-space undersampling patterns that vary between different spectral bins to determine k-space samples to be acquired in each spectral bin; orders k-space samples into echo trains that determine gradient waveforms; initializes the gradient waveforms, RF waveforms, and timing information; plays the gradient and RF waveforms using the timing information to excite and refocus different spatial and spectral bin regions; acquires undersampled MRI signal data on the MRI system from the spatial and spectral bin regions; uses robust principal component analysis to reconstruct on-resonance images and off-resonance images represented as sets of low rank and sparse matrices from the undersampled MRI signal data; combines the on-resonance images and off-resonance images to yield a final image; and presents the final image on a display.

In a method and apparatus for acquiring a magnetic resonance (MR) data set from a target area of a patient containing at least one metal object that distorts the basic magnetic field due to susceptibility differences, a slice selection gradient that rises in one direction is used to select a slice from which MR data are to be acquired. At least for at least one outermost edge slice on one side of the slice stack from which the MR data are to be acquired, the polarity of the slice selection gradient is selected as a function of a primary direction of distortion in the edge slice.

A system and method for accelerated magnetic resonance imaging (MRI) includes controlling an RF system of an MRI system to acquire coil calibration data from a subject including a material causing inhomogeneities in a static magnetic field of the MRI system when arranged in the bore of the MRI system. After acquiring the coil calibration data, the RF system is controlled to acquire imaging data from the subject at multiple different resonance frequency offsets. The spectral bin images relate specific resonance frequencies to distinct spatial locations in the static magnetic field of the MRI system. An image of the subject is reconstructed from the imaging data using coil calibration data and the spectral bin data to provide spatial encoding of the image.

Systems and methods for performing diffusion-weighted multi-spectral imaging (MS!) with a magnetic resonance imaging (MRI) system are provided, Diffusion-weighted images can thus be acquired from a subject in which a metallic object, such as an implant or other device, is present. In general, a two-dimensional or three-dimensional diffusion-weighted PROPELLER acquisition is performed to acquire data from multiple different spectral bins. Images from the spectral bins are reconstructed and combined to form diffusion-weighted composite images. Non-CPMG phase-cycling and split-blade PROPELLER techniques are combined with PROPELLER MSI metal artifact mitigation principles to this end.

Example apparatus and methods provide improved resolution over conventional magnetic resonance imaging (MRI) that is affected by the presence of metal (e.g., prosthetic hip) in the MRI field of view (FOV). Embodiments may excite a slice that is affected by a susceptibility effect produced by metal. Embodiments may excite the slice using a first pre-determined frequency and a plurality of scout frequency encodings. Embodiments may acquire nuclear magnetic resonance (NMR) signal data from the slice in response to the first pre-determined frequency and the plurality of scout frequency encodings and select frequency encodings to use to image the slice as a function of an amplitude of the NMR signal data. Frequency encodings are selected to produce data that will help account for distortions caused by the susceptibility effect.

In a SEMAC-like magnetic resonance imaging, MR data of multiple readout partitions of a target slice are used in order to reduce image artifacts due to magnetic field inhomogeneities. Slice-selectively excited nuclear spins are refocused via radiation of multiple refocusing pulses. For each refocusing pulse, at least one kz-phase coding gradient is respectively applied along a first direction (to define a readout partition) and at least one ky-phase coding gradient is applied along a second direction to acquire MR data, wherein the first and second directions are orthogonal to one another. The multiple refocusing pulses have at least two different flip angles.