The disclosure relates to a field camera and a method for measuring a magnetic field distribution using a magnetic resonance tomograph and the field camera. The field camera has a number of samples, which are distributed over a spatial volume to be measured, and a number of receive antennas. In an act of the method, a sensitivity matrix for the receive antennas, for each sample at each receive antenna, is captured using the magnetic resonance tomograph. In another act, antenna signals of the samples in a magnetic field to be measured are captured by the receive antennas, using the magnetic resonance tomograph. Finally, magnetic resonance signals of the individual samples are determined from the antenna signals as a function of the sensitivity matrix, using a controller. In a further act, the magnetic field strength at the location of the samples may be determined from the magnetic resonance signals.

A computer-implemented method is disclosed for providing an actuation sequence which specifies transmit signals for at least one high-frequency transmit channel of an antenna arrangement of a magnetic resonance device for acquiring measurement data of an object under investigation by the magnetic resonance device. The method includes providing different actuation sequences, wherein each sequence is the result of an optimization method and which differs with regard to the value of an optimization parameter taken into account in the course of the optimization method. The method further includes providing a plurality of field distribution maps, (e.g., at least one B.sub.0 map and/or at least one B.sub.1 map), acquired by the or a further magnetic resonance device from the object under investigation. The method further includes selecting the actuation sequence to be used from the different actuation sequences depending on the field distribution maps and providing the actuation sequence to be used.

A system and method for determining a magnetic field map when using a magnetic resonance imaging (MRI) system to acquire images from a region of interest (ROI) of a subject. The method includes selecting a pulse sequence to elicit a plurality of echoes from the subject as medical imaging data from the subject. The method also includes optimizing an echo time for a dynamic range of interest during the pulse sequence (SB.sub.max), a minimum signal-to-noise ratio (SNR.sub.0) in the medical imaging data, and minimum T2* value in the ROI. The method further includes generating a magnetic field map estimation using the optimized echo times.

A method for producing an image of a subject using a magnetic resonance imaging (MRI) system includes acquiring a series of echo signals by sampling k-space along radial lines that each pass through the center of k-space. Each projection of the radial lines is divided into multiple echoes and successive projections are spaced by a predetermined angular distance. The series of echo signals are reconstructed into a plurality of images, wherein each image corresponds to a distinct echo signal.

The invention relates to a method of CEST or APT MR imaging of at least a portion of a body (10) placed in a main magnetic field B.sub.0 within the examination volume of a MR device. The method of the invention comprises the following steps: •a) subjecting the portion of the body (10) to a saturation RF pulse at a saturation frequency offset; •b) subjecting the portion of the body (10) to an imaging sequence comprising at least one excitation/refocusing RF pulse and switched magnetic field gradients, whereby MR signals are acquired from the portion of the body (10) as spin echo signals; •c) repeating steps a) and b) two or more times, wherein the saturation frequency offset and/or a echo time shift in the imaging sequence are varied, such that a different combination of saturation frequency offset and echo time shift is applied in two or more of the repetitions; •d) reconstructing a MR image and/or B.sub.0 field homogeneity corrected APT/CEST images from the acquired MR signals. Moreover, the invention relates to a MR device (1) for carrying out the method of the invention and to a computer program to be run on a MR device.

Systems and methods for quantitative susceptibility mapping (“QSM”) using magnetic resonance imaging (“MRI”) are described. Localized magnetic field information is used when performing the inversion to compute quantitative susceptibility maps. The localized magnetic field information can include multi-resolution subvolumes obtained by segmenting, or dividing, a field shift map. In some instances, a trained machine learning algorithm, such as a trained neural network, can be implemented to convert the localized magnetic field information into quantitative susceptibility data. These local susceptibility maps can be combined to form a composite quantitative susceptibility map of the imaging volume.

The present disclosure provides a system for MRI. The system may obtain a plurality of echo signals relating to a subject that are excited by an MRI pulse sequence applied to the subject. The system may perform a quantitative measurement on the subject based on the plurality of echo signals. The MRI pulse sequence may include a CEST module configured to selectively excite exchangeable protons or exchangeable molecules in the subject, an RF excitation pulse applied after the CEST module configured to excite a plurality of gradient echoes, and one or more refocusing pulses applied after the RF excitation pulse. In some embodiments, the quantitative measurement may include determining various quantitative parameters including a T1, a T2, a T2*, an R2 value, an R2* value, an R2′, a B0 field, a pH value, an MWF, and an APT simultaneously.

A magnetic resonance (MR) image may be created from MR data by receiving the MR data, applying a transform to the MR data, where a result of the applying is an image space representation of the MR data, determining a wrapped phase map of the image space representation of the MR data, obtaining an unwrapped phase map based on the wrapped phase map, scaling the unwrapped phase map into a B0 field map, reconstructing the MR image based on the MR data, correcting the MR image based on the B0 field map, and outputting the MR image. The scaling may be free of accounting for effects on the MR data by artifact sources secondary to B0 field inhomogeneities.

A control device establishes a change in a main magnetic field expected for a respective time instant and based on the established expected change in the main magnetic field, correctively adjusts the main magnetic field and/or a nominal receive frequency of the RF receive coil and/or a transmit frequency for subsequent RF transmit pulses and/or takes the expected change in the main magnetic field into account in the evaluation of the received MR signals. At least for some of the RF transmit pulses, the control device acquires, via a sensor device, a portion of the respective radiofrequency wave supplied to the RF transmit coil. The controller extracts therefrom an oscillation corresponding to a respiratory motion of the patient and based on the variation with time of the extracted oscillation, establishes the change in the main magnetic field expected for the respective time instant.

A method of processing magnetic resonance data of a sample under investigation includes the steps of provision of the MR data being collected with an MRI scanner apparatus, and machine learning based data analysis of the MR data by supplying the MR data to an artificial neural network being trained with predetermined training data, wherein at least one image parameter of the sample and additionally at least one uncertainty quantification measure representing a prediction error of the at least one image parameter are provided by output elements of the neural network. Furthermore, a magnetic resonance imaging (MRI) scanner apparatus being adapted for employing the method of processing MR data is described.