TRADITIONAL POSTER - ismrm

Poster Sessions
inhomogeneity-related artifacts, acquired on the same subjects. Tensors derived from data with minimal artifacts were found to have higher primary
eigenvector coherence in white matter, compared to tensors derived from data contaminated with image artifacts. These results demonstrate that achieving
the most accurate spatial normalization of DTI data requires minimization of image artifacts.
1639. The Effect of Template Selection on Diffusion Tensor Imaging Voxel Based Analysis Results
Wim Van Hecke 1,2 , Caroline Sage 2 , Jan Sijbers 3 , Stefan Sunaert 2 , Paul M. Parizel 1
1 Department of Radiology, Antwerp University Hospital, Antwerp, Belgium; 2 Department of Radiology, Leuven University Hospital,
Leuven, Belgium; 3 VisionLab, University of Antwerp, Antwerp, Belgium
In this work, we examined the effect of the template or atlas selection on the voxel based analysis results of diffusion tensor images. To this end, simulated
data sets were used.
1640. Artificial Phantoms for Studies of Anisotropic Diffusion in the Brain
Ezequiel Alejandro Farrher 1 , Erasmo Batta 1 , Yuliya Kupriyanova 1 , Oleg Posnansky 1 , Farida Grinberg 1 , N
Jon Shah 1,2
1 Medical Imaging Physics, Institute of Neuroscience and Medicine 4 , Forschungszentrum Juelich GmbH, Juelich, Germany;
2 Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
Diffusion Tensor Imaging (DTI) provides access to fibre pathways and structural integrity in the white matter and finds important applications in the clinical
practice. Many advanced techniques have been recently suggested for the reconstruction of the diffusion orientation distribution function with an enhanced
angular resolution (HARDI). Examination of the sensitivity of the proposed diffusion indices to the underlying microstructure requires a development of the
model systems with deliberately tailored properties. The aim of this work was to construct artificial phantoms that are characteristic of sufficiently strong
diffusion anisotropy and are suitable for the validation of the analytical models.
1641. Evaluating the Uncertainty of DTI Parameters at 1.5, 3.0 and 7.0 Tesla
Daniel Louis Polders 1 , Alexander Leemans 2 , Johannes M. Hoogduin 1,3 , Jeroen Hendrikse 1 , Manus
Donahue 4 , Peter R. Luijten 1
1 Radiology, University Medical Center Utrecht, Utrecht, Netherlands; 2 Image Sciences Institute, University Medical Center Utrecht,
Utrecht, Netherlands; 3 Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Netherlands; 4 Department of
Clinical Neurology, University of Oxford, Oxford, United Kingdom
Diffusion Tensor Imaging data acquired at increased field strength shows increased Signal to Noise Ratio. This work compares the uncertainties of DTIbased
metrics when scanning at 1.5 3 and 7T. By scanning the same nine volunteers at each field strength, and applying a wild bootstrap method to calculate
the uncertainty of the fitted tensors, it is shown that with increasing SNR, the uncertainties for FA and the primary eigenvector decrease.
1642. Validation of Diffusion Tensor Imaging in the Presence of Metal Implants
Felix Schwab 1 , Bram Stieltjes 2 , Frederik Bernd Laun 3
1 Medical Physics in Radiology, Deutsches Krebsforschungszentrum , Heidelberg, Baden Württemberg, Germany; 2 Radiology,
Deutsches Krebsforschungszentrum, Heidelberg, Germany; 3 Medical Physics in Radiology, Deutsches Krebsforschungszentrum,
Heidelberg, Baden Württemberg, Germany
The diffusion weighted imaging of the spinal chord is often impeded by metal implants. A quantitative analysis of these effects is performed on a standard
titanium implant using phase maps acquired from FLASH sequences and ADC maps acquired from diffusion weighted EPI sequences. The shift δb/b is
calculated as a measure of the error. Artefacts caused by the separate parts of the implant are mostly benign and thus diffusion measurements should be
feasible if a small distance to the implant is observed.
1643. Within Subject Averaging of Diffusion Tensor MRI Data Sets: A Test-Retest Reproducibility
Evaluation
Nico Dario Papinutto 1 , Jorge Jovicich 1
1 Center for Mind/Brain Sciences, University of Trento, Mattarello, Trento, Italy
The accuracy and precision of a Diffusion tensor imaging (DTI) acquisition of in-vivo human brains depends on both the acquisition protocol and postprocessing
used for data analysis. In many cases multiple acquisitions from the same session are averaged to increase signal-to-noise ratio and reduce
sensitivity to motion during the acquisition. The complexity of DTI datasets allows for several processing paths to complete eddy current correction, coregistration,
averaging and tensor fitting. Here we assess the sensitivity of fractional anisotropy (FA) test-retest reproducibility to different methods for
merging multiple within-subject DTI acquisitions.
1644. The Signal Intensity MUST Be Modulated by the Determinant of the Jacobian When Correcting for
Eddy Currents in Diffusion MRI
Derek K. Jones 1
1 CUBRIC, Cardiff University , Cardiff, Wales, United Kingdom
Eddy currents plague diffusion MRI. When they produce a stretch / compression of the image along the phase encode direction, the resultant change in voxel
volume leads to a reduction/ increase in signal intensity. Many eddy current correction packages fail to account for this signal change. Here we show that the
consequences can be drastic for diffusion tensor MRI, with biases in fibre orientation being as big as 5 degrees in regions of low anisotropy. We conclude
that the signal intensity must be modulated by the volumetric change, in order to obtain meaningful and robust results from diffusion MRI.