%0 Generic
%A Müller, Lars
%C Heidelberg, Deutschland
%D 2017
%F heidok:23226
%K microspic anisotropy  fraktionelle Anisotropie  fractional anisotropy  concomitant fields  Intravoxel incoherent motion  doppelte Diffusionswichtung  double diffusion encoding  Flusskompensation  flow-compensation
%R 10.11588/heidok.00023226
%T Improved Estimation of Microscopic Tissue Parameters by Double Diffusion Encoding and Flow-Compensated Single Diffusion Encoding Magnetic Resonance Imaging
%U https://archiv.ub.uni-heidelberg.de/volltextserver/23226/
%X Diffusion weighted magnetic resonance imaging (MRI) can be used to gain information on the microstructure of the examined tissue on length scales below the actual image resolution. The large gradient amplitudes required for diffusion measurements can lead to artifacts due to eddy currents and concomitant fields. Another source of image artifacts, is the presence of directed motion such as blood flow or pulsation. In a first MRI sequence, a common approach for eddy current compensation, the twice-refocused spin echo was adjusted for a double diffusion encoding (DDE) sequence. In measurements of healthy volunteers, this approach reduced the falsely elevated microscopic fractional anisotropy (uFA) in the gray matter on average from 0.57 +- 0.19 to 0.50 +- 0.19 and in the ventricles on average from 0.54 +- 0.19 to 0.28 +- 0:27.  A second sequence, with a single diffusion encoding, was compensated for any combination of the three artifact sources flow, concomitant fields and eddy currents. For most in vivo measurements, it proved to be sufficient to compensate for flow and concomitant fields. An additional eddy current compensation led only in the brain measurements to a higher reproducibility. The developed sequence was also used to measure the incoherent intravoxel motion (IVIM) effect in the abdomen as well as the prostate of healthy volunteers, where a difference between flow-compensated and non-flow-compensated measurements was observed. This difference could not be seen in patients with prostate carcinoma.