The disclosure relates to techniques for perming chemical exchange saturation transfer (CEST) imaging correction. The present disclosure improves the speed of correcting CEST images.

To achieve a uniform magnetic field in an MRI system, fitting can be performed using a partially differentiated residue phase map, differentiated shim functions, radial weights, a regularization factor, a discontinuity mask, and/or a signal intensity mask to determine coefficients for shim functions. The fitting can be performed iteratively, where the regularization factor is stronger and the radial weights focus on areas of higher confidence during earlier iterations. During later iterations, the regularization factor gradually gets weaker and the radial weights gradually focus on areas of lower confidence.

A method for providing magnetic field data includes receiving image data as input data of a trained function, and applying the trained function to the image data. The trained function is trained based on a data fidelity of image data corrected using the magnetic field data, and based on at least one assumption about at least one attribute of the magnetic field data. The method includes providing the magnetic field data as output data of the trained function.

A navigator echo is acquired during imaging, and when frequency is corrected based on phase change, the correction is performed with high accuracy without being affected by an offset caused by variations with time. An MRI apparatus including a navigation controller is configured to control an imaging unit acquiring an NMR signal, generate the navigator echo and collect navigation data during a predetermined measurement time, prior to collection of nuclear magnetic resonance signals for reconstructing an image of a subject. The phase change of the navigator echo is analyzed during the measurement time to calculate a correction value for correcting misalignment due to the phase change with a navigation analyzer that calculates a phase change amount relative to a reference, based on a difference between the phase change of the navigator echo and the phase change of the navigator echo serving as the reference during the measurement time.

Example embodiments associated with characterizing a sample using NMR fingerprinting are described. One example NMR apparatus includes an NMR logic that repetitively and variably samples a (k, t, E) space associated with an object to acquire a set of NMR signals that are associated with different points in the (k, t, E) space. Sampling is performed with t and/or E varying in a non-constant way. The NMR apparatus may also include a signal logic that produces an NMR signal evolution from the NMR signals and a characterization logic that characterizes a tissue in the object as a result of comparing acquired signals to reference signals. Example embodiments facilitate distinguishing diseased tissue from healthy tissue based on tissue component fractions identified using the NMR fingerprinting.

A method for the compensation of magnetic field inhomogeneity in magnetic resonance spectroscopic imaging comprising the steps of using dynamic k-space expansion in combination with parallel imaging.

Magnetic resonance (MR) data are acquired from a volume segment of an examination object and an MR image composed of multiple image pixels is reconstructed therefrom. For a magnetic field assumed to have been generated by the scanner, a summed field deviation is calculated, from which a respective displacement vector is calculated for each image pixel. A signal portion is assigned to each image pixel that has been displaced with the respective displacement vector from the respective image pixel. The summed field deviation is the sum of deviations caused by at least two of: non-linearities in gradient coils, Maxwell fields, field inhomogeneities independent of the gradients, and dynamic field disturbances.

Provided are MRI images with excellent image quality and in which the occurrence of artifacts is suppressed by effectively removing a secondary error magnetic field, generated by compensation current (additional current), of eddy current that is caused by applying a gradient magnetic field. The present invention measures and analyzes, in advance, a secondary error magnetic field generated due to the applying of compensation current and saves the results as compensation parameters (secondary compensation parameters), uses the secondary compensation parameters to calculate a correction magnetic field output to be applied to each of a gradient magnetic field coil and a correction coil, and supplies this correction magnetic field output to the gradient magnetic field coil and the correction coil to compensate for (cancel out) the secondary error magnetic field.

A system and method of mapping and correcting the inhomogeneity of a magnetic field within an object using an Magnetic Resonance Imaging (MRI) system where there is a single dominant resonance. The method includes acquiring at least three MRI images, each at different echo times (TE). At least two ΔTE images (ΔTE.sub.i=1 . . . N) are generated based on the at least three MRI images, wherein the subscripts I=1 N refer to images with sequentially increasing ΔTE times. Aliasing in the ΔTE.sub.1 image is permitted. The ΔTE times of ΔTE.sub.1 and ΔTE.sub.2 are set such that the alias points at which wrapping occurs in ΔTE.sub.1 does not overlap with the alias points of ΔTE.sub.2. Each ΔTE image is unwrapped. A final B0 map is set to the unwrapped ΔTE.sub.N image.

The invention relates to a method for carrying out post-processing on a first set of samples measuring the magnitude of a WASAB1 signal delivered by a magnetic-resonance medical-imaging apparatus. Such a method comprises a step of detecting the samples of a first set Z, for which samples the respective polarities of the values of the measured signal are known, and of constructing a second set Y of “polarised” samples. Such a method further comprises a step of fitting a determined model to said second set Y, the two parameters of the determined model describing the static magnetic field B0 and excitation magnetic field B1 of the magnetic-resonance medical-imaging apparatus, respectively, and of producing an estimation of the parameters B0 and B1 of the model. Such a method relates to any magnetic-resonance-imaging application in which a correction for inhomogeneities in the fields B0 and B1 is required.