A method for acquiring a basic magnetic field inhomogeneity value of a magnetic resonance imaging (MRI) system includes homogenizing an original basic magnetic field of the MRI system into a target magnetic field, providing a magnetic field compensation amount for the MRI system by a dynamic shimming method. The dynamic shimming method includes performing a 3D low-resolution dual-echo gradient echo sequence, and using a general formula to acquire the magnetic field inhomogeneity value, the general formula being: ΔB=ΔB.sub.original+ΔB.sub.compensating, wherein ΔB is the magnetic field inhomogeneity value, ΔB.sub.original is a difference value between the original magnetic field and the target magnetic field, and ΔB.sub.compensating is the magnetic field compensation amount. This method for acquiring a magnetic field inhomogeneity value for an MRI system saves considerable time to map the magnetic field again, thereby shortening the magnetic resonance imaging time, and increasing the efficiency of magnetic resonance imaging.

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.

The invention provides for a magnetic resonance system (100) for acquiring a magnetic resonance data from a subject (118) within a measurement zone (108) according to a magnetic resonance fingerprinting technique. The pulse sequence comprises a train of pulse sequence repetitions (302, 304). Each pulse sequence repetition has a repetition time chosen from a distribution of repetition times. Each pulse sequence repetition comprises a radio frequency pulse (306) chosen from a distribution of radio frequency pulses. The distribution of radio frequency pulses cause magnetic spins to rotate to a distribution of flip angles, and each pulse sequence repetition comprises a sampling event (310) at a sampling time chosen from a distribution of sampling times. Each pulse sequence repetition of the pulse sequence comprises a first 180 degree RF pulse (308) performed at a first temporal midpoint between the radio frequency pulse and the sampling event to refocus the magnetic resonance signal. Each pulse sequence repetition of the pulse sequence comprises a second 180 degree RF pulse (309) performed at a second temporal midpoint between the sampling event and the start of the next pulse repetition.

In a method for displaying quantitative magnetic resonance image data, and a processor, and a magnetic resonance (MR) apparatus that implement such a method, first quantitative MR image data of an examination object are provided to the processor, the first quantitative MR image having been obtained using an MR scanner with a first basic magnetic field strength. The first quantitative magnetic resonance image data are converted in the processor from the first basic magnetic field strength to a second basic magnetic field strength, thereby generating second quantitative MR image data, which are then displayed.

In a method and magnetic resonance (MR) apparatus for recording MR signals in a recording volume of an examination object with an imaging sequence, the recording volume has a first recording region in which at least one system component of the scanner of the MR apparatus has a first homogeneity, which is greater than a homogeneity of the at least one scanner component in a second recording region of the recording volume. A magnetization of nuclear spins in the recording volume is produced by at least one RF pulse, with the RF pulse being determined such that the magnetization produced in the first recording region by the at least one RF pulse is greater than magnetization produced in the second recording region by the at least one RF pulse.

The present disclosure discloses a method for measuring relaxation time of ultrashort echo time magnetic resonance fingerprinting. In the method, semi-pulse excitation and semi-projection readout are adopted to shorten echo time (TE) to achieve acquisition of an ultrashort T2 time signal; and image acquisition and reconstruction are based on magnetic resonance fingerprint imaging technology. A TE change mode of sinusoidal fluctuation is introduced, so that distinguishing capability of a magnetic resonance fingerprint signal to short T2 and ultrashort T2 tissues is improved, and multi-parameter quantitative imaging of the short T2 and ultrashort T2 tissues and long T2 tissues is realized. Non-uniformity of a magnetic field is modulated into phase information of the fingerprint signal through the TE of the sinusoidal fluctuation; a B0 graph is directly reconstructed according to an amplitude-modulated signal demodulation principle; and the phase change caused by a BO field is compensated in the fingerprint signal.

Described here are systems and methods for correcting magnetic resonance data for off-resonance effects arising from the use of a multi-echo echo planar imaging (“EPI”) pulse sequence. Reference data are acquired, from which phase maps are computed in a distorted coordinate space associated with geometric distortions associated with the multi-echo EPI acquisition. Images reconstructed from the magnetic resonance data are demodulated using the distorted phase maps to produce distortion free images of the subject. Advantageously, the systems and methods can be used to reconstruct distortion free images from magnetic resonance data that is otherwise prone to image distortions from off-resonance errors, including data acquired from hyperpolarized nuclear spin species such as hyperpolarized carbon-13.

A prescan is automated to the greatest extent practicable, allowing acquisition of a favorable image irrespective of skills of an operator, as well as minimizing the time related to the prescan. For a plurality of image types in imaging tasks, a comprehensive FOV including all FOVs respectively of a plurality of image types is set, and for the comprehensive FOV, it is determined whether or not an item adjusted by the prescan satisfies an allowable condition for each image type, and the prescan is executed to make an adjustment appropriate for the image type with the strictest condition, on the item not satisfying the allowable condition.

A guide map is created for use in placing a spectroscopic single voxel in a region of interest in single voxel magnetic resonance spectroscopy. An anatomical planning image of the region of interest is obtained through MRI. A spectroscopy voxel is stepped across the region of interest, characteristics of the magnetic field used in the MRI are measured at each location of the imaging voxel, and a guide-FWHM map indicative of the homogeneity/inhomogeneity of the magnetic field over the region of interest is derived using the measurements. The guide map is created by overlaying the guide-FWHM map on the anatomical planning image. A spectroscopic single voxel of a size corresponding to that of the spectroscopy voxel is placed within the region of interest as per the guide map. Then spectral data is acquired from the region of interest confined to the single voxel.

A method for generating a magnetic resonance image of an object in a magnetic resonance imaging (MRI) system, wherein the object contains at least one metallic implant is provided. The MRI system provides multiple excitations of at least part of the object. The MRI system reads out image signals from the object. The MRI system saves the readout image signals as image data. A field-map is generated from the image data using a goodness-of-fit process which uses a goodness-of-fit metric, matched-filter, and/or similar fitting techniques to fit expected signals from each excitation to the image data.