Max-planck-gesellschaft Zur F&#xf6;rderung Der Wissenschaften E. V.

Jens Frahm

Klaus-Dietmar Merboldt

Axel Haase

Martin Uecker

Dirk Voit

Wolfgang Haenicke

Dieter Matthaei

Shuo Zhang

Klausdietmar Merboldt

Wolfgang Hanicke

Oleksandr Kalentev

A method for creating multiple sequences of diffusion-weighted magnetic resonance (MR) images of an object is described, wherein each of said sequences of MR images represents the same series of contiguous cross-sectional slices covering a volume of the object. The method comprises (a) providing multiple sequences of sets of image raw data being collected with the use of at least one radiofrequency receiver coil of a magnetic resonance imaging device, wherein each set of image raw data includes data samples being generated with a combined diffusion-weighted spin-echo and single-shot stimulated-echo sequence with diffusion-encoding gradients, (b) subjecting a sequence of sets of image raw data generated with diffusion-encoding gradients of zero strength or lower strength to a regularized nonlinear inverse reconstruction process to provide a sequence of coil sensitivities and MR images with no or lower diffusion weighting, and (c) subjecting all sequences of sets of image raw data with diffusion-encoding gradients of zero or lower strength as well as of higher strength to a regularized linear inverse reconstruction process, to provide a sequence of MR images with no or lower diffusion weighting and a sequence of MR images with higher strength, each of the MR images representing one of the cross-sectional slices and being created by using the sensitivity of the at least one receiver coil determined in step (b) for the same cross-sectional slice and in dependency on a difference between a current image content estimation and an image content estimation of a neighboring cross-sectional slice. Furthermore, an MRI device for creating a sequence of diffusion-weighted MR images of an object is described.

Method and device for acquiring and reconstructing a sequence of diffusion-weighted magnetic resonance images covering a volume

A method of collecting magnetic resonance data for imaging an object with a predetermined spin density being arranged in a static magnetic field, comprises the steps subjecting said object to at least one radiofrequency pulse and magnetic field gradients for creating spatially encoded magnetic resonance signals, including at least two settings of spatially encoding phase-contrast gradients differently encoding the phase of said magnetic resonance signals in at least one field of view in a predetermined spatial dimension, acquiring at least two magnetic resonance signals, each with one of said at least two settings of different spatially encoding phase-contrast gradients, and determining at least one mean spin density position of said object along said spatial dimension by calculating the phase difference between said signals. Furthermore, a control device and a magnetic resonance imaging (MRI) device implementing the method are described.

Spatially encoded phase-contrast MRI

A method for reconstructing a sequence of magnetic resonance (MR) images of an object under investigation, includes the steps of (a) providing a series of sets of image raw data including an image content of the MR images to be reconstructed, the image raw data being collected with the use of at least one radiofrequency receiver coil of a magnetic resonance imaging (MRI) device, wherein each set of image raw data includes a plurality of data samples being generated with a gradient-echo sequence, in particular a FLASH sequence, that spatially encodes an MRI signal received with the at least one radiofrequency receiver coil using a non-Cartesian k-space trajectory, each set of image raw data includes a set of homogeneously distributed lines in k-space with equivalent spatial frequency content, the lines of each set of image raw data cross the center of k-space and cover a continuous range of spatial frequencies, and the positions of the lines of each set of image raw data differ in successive sets of image raw data, and (b) subjecting the sets of image raw data to a regularized nonlinear inverse reconstruction process to provide the sequence of MR images, wherein each of the MR images is created by a simultaneous estimation of a sensitivity of the at least one receiver coil and the image content and in dependency on a difference between a current estimation of the sensitivity of the at least one receiver coil and the image content and a preceding estimation of the sensitivity of the at least one receiver coil and the image content.

Method and device for reconstructing a sequence of magnetic resonance images

The 'spoiled FLASH' nuclear magnetic resonance (NMR) method avoids image artifacts which may be caused by transverse magnetization remaining at the end of a TR period of a partial experiment by applying an additional 'spoiler' slice gradient pulse ('SP') after the detection of a gradient echo ('Signal') and before the application of the radio frequency pulse (RF) of the following partial experiment. The amplitude-time integral, i.e. the duration and/or the amplitude of the additional spoiler slice gradient pulses is incremented and/or decremented from partial experiment to partial experiment of a given total experiment. Each spoiler amplitude may be repeated after a time of the order of T.sub.2.

Method for rapid acquisition of spin resonance data for a spatially

A method and an apparatus for a locally resolved investigation of a speci, wherein the specimen is exposed to a constant magnetic field and a variable combination of three gradient magnetic fields directed substantially perpendicularly to each other and to a sequence of high-frequency (RF) pulses which contains three successive pulses with flip angles not equal to .vertline.m Pi.vertline., and signals corresponding to a magnetic resonance of spin moments, in particular nuclear spin moments in said specimen are detected. The interval (tau) between the first and the second pulse is greater than T.sub.2eff and smaller than 5T.sub.2, and that the interval (T-tau) between the second and the third pulse is greater than T.sub.2eff and smaller than 5T.sub.1, wherein

Imaging magnetic spin resonance method and apparatus

A fast low angle shot ('FLASH') NMR method is described, which uses radio frequency excitation pulses having a flip angle substantially less than 90 degrees, and subsequent reading gradient reversal for producing a gradient echo signal. The small flip angle pulses create an equilibrium state between longitudinal and transverse magnetization, which allows to apply the radio frequency pulses repeatedly with high repetition rate to produce gradient echo signals of essentially equal strength, without any intervening delay for magnetization restoration or recovery.

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Goettingen, Germany

Jens Frahm