Amyotrophic lateral sclerosis is characterized by degeneration of upper and lower motor neurons. Diffusion tensor imaging (DTI) indexes obtained along the corticospinal tracts distinguish ALS patients and control subjects. Diffusion tensor imaging can be estimated from at least 6 diffusion-weighted images; however an acquisition scheme with a higher number of diffusion directions allows a more robust estimation of DTI indexes.
The aim of the study was to establish if a higher number of diffusion encoding gradients increases the diagnostic accuracy of DTI in ALS.
We studied 18 patients and 16 control subjects acquiring 2 DTI data sets with 6 and 31 gradient orientations. The mean diffusivity and fractional anisotropy values were measured along the corticospinal tract.
Mean diffusivity in ALS was significantly increased (P = 0.026) with respect to control subjects in acquisition scheme with 31 but not (P = 0.214) with 6 diffusion-weighting directions. Fractional anisotropy was significantly lower in patients both with 6 (P = 0.0036) and with 31 (P = 0.0004) diffusion-weighting directions (0.538 vs 0.588 and 0.530 vs 0.594). Fractional anisotropy receiver operating characteristic curve analysis showed a higher diagnostic accuracy by using 31 diffusion-weighting direction (85.76%) with respect to 6 directions (79.86%).
Diffusion tensor imaging confirms its potentials in diagnosing ALS with a good accuracy; the acquisition scheme with a higher diffusion-weighting directions seems to better discriminate between ALS patients and control subjects.
From the *Department of Neuroscience, University of Pisa; Units of †Neuroradiology and ‡Medical Physics, S. Chiara Hospital, §Department ofRadiology, University of Pisa, Pisa, Italy.
Received for publication February 1, 2010; accepted April 12, 2010.
Reprints: Mirco Cosottini, MD, Department of Neuroscience, University of Pisa, Via Roma 67, Pisa 56100, Italy (e-mail: firstname.lastname@example.org).
There is no actual or potential conflict of interest in relation to this article.
No funding was received for research from any of the following organizations: National Institutes of Health, Wellcome Trust, or the Howard Hughes Medical Institute.