A number of repetitions of a magnetic resonance measurement sequence and a number of repetitions of a navigator magnetic resonance measurement sequence are executed in a interleaved manner. Each repetition of the magnetic resonance measurement sequence includes the time-parallel creation of gradient echoes for measurement of magnetic resonance data. Each repetition of the navigator magnetic resonance measurement sequence includes the radiating of RF excitation pulse, the activation of at least one gradient pulse train for time-sequential creation of gradient echoes, and the read out of the gradient echoes as navigator magnetic resonance data. The magnetic resonance data are modified based on the navigator magnetic resonance data. This enables an N/2 ghosting artifact and/or a constant magnetic field drift and/or a movement artifact to be reduced. Such techniques can be applied in conjunction with simultaneous multi-slice echo planar magnetic resonance imaging, SMS EPI. Diffusion-weighted magnetic resonance imaging also is possible.

In order to reduce inaccuracy of a hemodynamic visualization image acquired when a blood flow is labeled before blood flow visualization imaging, an MRI apparatus uses a blood flow velocity to control pulse sequences including a sequence of applying a high-frequency pulse for labeling the blood flow and imaging the subsequent blood flow or display of the hemodynamic visualization image. For example, the blood flow velocity is used for controlling application positions of one or more high-frequency pulses from among a plurality of the high-frequency pulses for labeling. The MRI apparatus controls time between labeling the blood flow and starting imaging and/or the application positions of high-frequency pulses for labeling the blood flow. A threshold value for color display of a blood flow visualization image is controlled.

An apparatus for correcting distortion in medical images comprises a data receiving unit for receiving first medical image data, second medical image data and third medical image data, wherein the first medical image data has a first distortion of a first distortion type and the second medical image data has the first distortion and a second distortion of a second distortion type wherein the first distortion and the second distortion are cumulative, a representation unit for determining a representation of the first type of distortion by comparing the first medical image data to third medical image data, and for determining a second representation of the second distortion in the absence of the first distortion, and an image correction unit for correcting the second type of distortion in the second medical image data using the representation of the first type of distortion and the representation of the second type of distortion.

In an EPI acquisition sequence for magnetic resonance signals k-space is scanned along sets of lines in k-space along opposite propagation directions, e.g. odd and even lines in k-space. Phase errors that occur due to the opposite propagation directions are corrected for in a SENSE-type parallel imaging reconstruction. The phase error distribution in image space may be initially estimated, calculated form the phase difference between images reconstructed from magnetic resonance signals acquired from the respective sets of k-space lines, or from an earlier dynamic.

In order to provide a magnetic resonance imaging apparatus that can acquire an image capable of quantitative assessment of fat and a method for generating water-fat separation images, echo signals are acquired during application of a frequency encoding gradient magnetic field of positive and negative polarities at the same echo time, a correction amount for correcting an adverse effect of reception frequency characteristics is evaluated from the pair of correcting echo signals, and then the correction amount is used for removing the adverse effect of reception frequency characteristics of positive- and negative-polarity images acquired by inverting a polarity of the frequency encoding gradient magnetic field.

In PROPELLER utilizing EPI k-space sampling, phase errors arising primarily from eddy currents can considerably degrade image quality. The phase errors include spatially constant phase errors, spatially linear phase errors, and oblique phase errors. Methods to measure and correct for these phase errors are disclosed. Two or three reference scans are acquired, each reference scan being mutually orthogonal along the orthogonal physical gradient axes in a MRI system. A spatially constant phase error and a spatially linear phase error are determined from each of the reference scans for each relevant physical gradient axis. These phase errors can be used to predict the constant, linear, and oblique phase errors in each blade of an EPI PROPELLER k-space data set. With the known phase errors for each blade, constant, linear, and/or oblique phase correction is applied prior to or during PROPELLER image reconstruction, producing an image with substantially reduced artifacts.

A magnetic resonance method and system are provided for providing improved simultaneous multislice echo planar imaging (EPI) with navigator-based correction of image data for B0 drift and N/2 ghosting. The correction is based on two types of multi-echo phase-encoded navigator sequences having opposite readout gradient polarities, and optionally also uses a non-phase-encoded navigator sequence. One or more navigator sequences can be generated between each RF excitation pulse and the subsequent EPI readout sequence. A dynamic off-resonance in k-space technique can be used to correct for B0 drift, and a modified slice GRAPPA technique that is based on odd and even kernels can provide slice-specific correction for N/2 ghosting effects for the EPI MR image data sets. Various patterns of navigator sequences and/or interpolation of navigator data can be used to improve accuracy of the image data corrections.

A magnetic resonance imaging apparatus according to an embodiment includes sequence controlling circuitry and image generating circuitry. The sequence controlling circuitry executes a pulse sequence which applies a excitation pulse and then continuously applies a readout gradient magnetic field with alternating polarity thereof and acquires echo signals continuously generated by the pulse sequence from a plurality of receive channels. The image generating circuitry corrects the echo signals so as to generate an image, correcting the echo signals for all of the receive channels collectively on the basis of phase differences between echo signals corresponding to even lines of k-space and echo signals corresponding to odd lines of k-space, and corrects the echo signals for each of the receive channels individually on the basis of magnitude differences between echo signals corresponding to the even lines of k-space and echo signals corresponding to the odd lines of k-space.

A system and method are provided for generating at least one confidence map indicating the accuracy of a quantitative map generated from magnetic resonance (MR) data acquired from a subject. The method includes accessing at least one of proton density fat fraction (PDFF) or R.sub.2* maps of a region of interest (ROI) of a subject produced using chemical-shift encoded magnetic resonance (MR) data acquired from the ROI in the subject, generating at least one confidence map that indicates an accuracy of the at least one of the PDFF or R.sub.2* maps, and outputting at least one of (i) the at least one confidence map or (ii) a corrected PDFF or R.sub.2* map that is corrected using the at least one confidence map.

In a method for recording measurement data of an examination object, by a MR system using an echo planar recording technique that is segmented into at least two segments in the readout direction that also records navigator data (ND) for each of its segments, sampling patterns are changed during recordings of ND, so that the ND can be recorded overall such that reference data for determining further information for improving the recorded measurement data can be generated from the ND. The navigator phases of the recording technique segmented in the readout direction may be used to determine further information. The sampling patterns can be changed depending on the type of desired information and associated reference data. Separate measurements for reference measurements that are otherwise necessary for determining the desired information can be omitted, whereby a time period that is required for the entire measurement can be reduced.