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MR-Acquisition and Processing in Preclinical Research and Material Science

Three-dimensional  ultra-short  TE  imaging.  Like  the  two-dimensional UTE introduced with PV5.0, UTE3D acquires the k-space radially during the rising  ramp  of  the  readout  gradient. The 3-dimensional  sampling  eliminates  the need of slice selection and allows a significant reduction of the echo time. It is possible to achieve TE values as short as 10 microseconds. The reconstruction is based on the k-space gridding with automatically measured trajectories and produces artefact-free images without manual trimming of the sequence.

Three-dimensional radial sampling using a hard RF pulse applied during the readout gradient. Due to the absence of a delay between the excitation and the k-space centre, the effective "echo time" of the sequence is zero. ZTE can be used for materials of extremely short T2* and in the presence of high susceptibility gradients. The acquisition dead time occurring in this kind of techniques is handled by a special algebraic reconstruction step.

A variant of Echo-Planar Imaging in which a train of images is acquired in a single inversion-recovery experiment allowing a snapshot acquisition of T1 maps  using  the  principle  of  the    Look-Locker  sequence. The method  uses  k-space segmentation and cyclic slice permutations to achieve required time resolution in multi-slice experiments.

A multi-echo variant of EPI providing a train of images with different radient echo times in a single shot. The method is useful for fast T2* mapping and for quantitative fMRI experiments.

A multi-echo variant of EPI based on the CPMG sequence for fast T2
mapping.

A pulsed arterial spin marking method for perfusion imaging based on  the  FAIR  preparation  and  a  fast  RARE  readout.  The  advantage  of  this method compared to the existing FAIR_EPI is the lack of distortions and signal voids caused by magnetic susceptibility at high fields.

Voxel  spectroscopy with  a  localisation  based  on  a  cycle  of  selective inversion pulses. Since no echoes are generated, the method  is advantageous for  short T2  signals,  e.g. of quadrupolar nuclei.    It can also be useful  for 1H experiments with surface transmit coils due to the B1-insensitivity of adiabatic inversion pulses.

A new reconstruction option has been added to FLASH that enhances the contrast of veins and other elements of distinct magnetic susceptibility. It consists of including the phase information, which is discarded in the standard magnitude reconstruction, in the calculation of image intensity. The user is given a range of possibilities to treat the phase component in order to optimize the protocol for a given imaging target.

The methods FAIR EPI and FAIR RARE offer a new interleaving mode for acquisition of images with global and selective inversion in direct succession, a user editable TI spacing, the new time saving constant recovery mode and are provided with a macro for the computation of perfusion maps.