BACKGROUND AND PURPOSE: Voxel size/shape of diffusion tensor imaging (DTI) may directly affect the measurement of fractional anisotropy (FA) in regions where there are crossing fibers. The purpose of this article was to investigate the effect of voxel size/shape on measured FA by using isotropic and nonisotropic voxels. MATERIALS AND METHODS: Ten healthy adult volunteers had MR imaging by using a 1.5 T clinical imager. DTI was performed with 2 different voxel sizes: a 2-mm-section isotropic voxel (2 x 2 x 2 mm(3)) and a 6-mm-section nonisotropic voxel (2 x 2 x 6 mm(3)). Images were obtained by using a single-shot echo-planar imaging technique with motion-probing gradients in 15 orientations and a b-value of 1000 s/mm(2). FA and the apparent diffusion coefficient (ADC) were measured at different sites of the brain. RESULTS: When smaller isotropic voxels were used, the FA was greater in areas with crossing fibers, including the superior longitudinal fasciculus, the thalamus, and the red nucleus; the FA was not significantly different in areas without crossing fibers, such as the corpus callosum, the posterior limb of the internal capsule, and the corticospinal tract at the level of the centrum semiovale (P>.05). The ADC values were not affected by voxel size/shape at any of the areas of the brain that were measured. CONCLUSION: FA values that are measured in regions containing crossing fibers are underestimated when using nonisotropic DTI.
BACKGROUND AND PURPOSE: Voxel size/shape of diffusion tensor imaging (DTI) may directly affect the measurement of fractional anisotropy (FA) in regions where there are crossing fibers. The purpose of this article was to investigate the effect of voxel size/shape on measured FA by using isotropic and nonisotropic voxels. MATERIALS AND METHODS: Ten healthy adult volunteers had MR imaging by using a 1.5 T clinical imager. DTI was performed with 2 different voxel sizes: a 2-mm-section isotropic voxel (2 x 2 x 2 mm(3)) and a 6-mm-section nonisotropic voxel (2 x 2 x 6 mm(3)). Images were obtained by using a single-shot echo-planar imaging technique with motion-probing gradients in 15 orientations and a b-value of 1000 s/mm(2). FA and the apparent diffusion coefficient (ADC) were measured at different sites of the brain. RESULTS: When smaller isotropic voxels were used, the FA was greater in areas with crossing fibers, including the superior longitudinal fasciculus, the thalamus, and the red nucleus; the FA was not significantly different in areas without crossing fibers, such as the corpus callosum, the posterior limb of the internal capsule, and the corticospinal tract at the level of the centrum semiovale (P>.05). The ADC values were not affected by voxel size/shape at any of the areas of the brain that were measured. CONCLUSION: FA values that are measured in regions containing crossing fibers are underestimated when using nonisotropic DTI.
Authors: J S Shimony; R C McKinstry; E Akbudak; J A Aronovitz; A Z Snyder; N F Lori; T S Cull; T E Conturo Journal: Radiology Date: 1999-09 Impact factor: 11.105
Authors: M E Moseley; Y Cohen; J Kucharczyk; J Mintorovitch; H S Asgari; M F Wendland; J Tsuruda; D Norman Journal: Radiology Date: 1990-08 Impact factor: 11.105
Authors: Carola van Pul; Jan Buijs; Maurice J A Janssen; George F Roos; Marinus T Vlaardingerbroek; Pieter F F Wijn Journal: AJNR Am J Neuroradiol Date: 2005-03 Impact factor: 3.825
Authors: A G Sorensen; O Wu; W A Copen; T L Davis; R G Gonzalez; W J Koroshetz; T G Reese; B R Rosen; V J Wedeen; R M Weisskoff Journal: Radiology Date: 1999-09 Impact factor: 11.105
Authors: A G Sorensen; F S Buonanno; R G Gonzalez; L H Schwamm; M H Lev; F R Huang-Hellinger; T G Reese; R M Weisskoff; T L Davis; N Suwanwela; U Can; J A Moreira; W A Copen; R B Look; S P Finklestein; B R Rosen; W J Koroshetz Journal: Radiology Date: 1996-05 Impact factor: 11.105
Authors: Götz Thomalla; Volkmar Glauche; Martin A Koch; Christian Beaulieu; Cornelius Weiller; Joachim Röther Journal: Neuroimage Date: 2004-08 Impact factor: 6.556
Authors: R J Fox; K Sakaie; J-C Lee; J P Debbins; Y Liu; D L Arnold; E R Melhem; C H Smith; M D Philips; M Lowe; E Fisher Journal: AJNR Am J Neuroradiol Date: 2011-12-15 Impact factor: 3.825
Authors: Jungsu S Oh; Marek Kubicki; Gudrun Rosenberger; Sylvain Bouix; James J Levitt; Robert W McCarley; Carl-Fredrik Westin; Martha E Shenton Journal: Hum Brain Mapp Date: 2009-11 Impact factor: 5.038