title: Diffusion tensor MR microscopy of tissues with low diffusional anisotropy.
abstract: BACKGROUND
  Diffusion tensor imaging exploits preferential diffusional motion of water molecules residing within tissue compartments for assessment of tissue structural anisotropy. However, instrumentation and post-processing errors play an important role in determination of diffusion tensor elements. In the study, several experimental factors affecting accuracy of diffusion tensor determination were analyzed.
  
  
  METHODS
  Effects of signal-to-noise ratio and configuration of the applied diffusion-sensitizing gradients on fractional anisotropy bias were analyzed by means of numerical simulations. In addition, diffusion tensor magnetic resonance microscopy experiments were performed on a tap water phantom and bovine articular cartilage-on-bone samples to verify the simulation results.
  
  
  RESULTS
  In both, the simulations and the experiments, the multivariate linear regression of the diffusion-tensor analysis yielded overestimated fractional anisotropy with low SNRs and with low numbers of applied diffusion-sensitizing gradients.
  
  
  CONCLUSIONS
  An increase of the apparent fractional anisotropy due to unfavorable experimental conditions can be overcome by applying a larger number of diffusion sensitizing gradients with small values of the condition number of the transformation matrix. This is in particular relevant in magnetic resonance microscopy, where imaging gradients are high and the signal-to-noise ratio is low.
authors.forename: Franci
authors.initials: F
authors.lastname: Bajd
authors.affiliation: TU Ilmenau, Institute of Physics, Fachgebiet Technische Physik II, Ilmenau, Germany.
authors.forename: Carlos
authors.initials: C
authors.lastname: Mattea
authors.affiliation: TU Ilmenau, Institute of Physics, Fachgebiet Technische Physik II, Ilmenau, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Stapf
authors.affiliation: Jožef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Igor
authors.initials: I
authors.lastname: Sersa
keywords: anisotropy; cartilage; diffusion tensor imaging; microscopy; signal-to-noise ratio