A study of rotationally invariant and symmetric indices of diffusion anisotropy

Papadakis, N.; Xing, Da; Houston, Gavin C.; Smith, Justin M.; Smith, M. Paul; James, Michael F.; Parsons, Andrew A.; Huang, Christopher L.‐H.; Hall, Laurance D.; Carpenter, T. Adrian

doi:10.1016/s0730-725x(99)00029-6

Cited by 162 publications

(142 citation statements)

References 25 publications

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“…This improvement suggests that FA may be superior to RA for quantitative applications, though the advantage may diminish in less anisotropic structures. These results also corroborate the findings of previous simulation studies by others (19,20).…”

Section: Discussionsupporting

confidence: 93%

Analytical error propagation in diffusion anisotropy calculations

Poonawalla

Zhou

2004

Magnetic Resonance Imaging

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Purpose:To develop an analytical formalism describing how noise and selection of diffusion-weighting scheme propagate through the diffusion tensor imaging (DTI) computational chain into variances of the diffusion tensor elements, and errors in the relative anisotropy (RA) and fractional anisotropy (FA) indices. Materials and Methods:Singular-value decomposition (SVD) was used to determine the tensor variances, with diffusion-weighting scheme and measurement noise incorporated into the design matrix. Anisotropy errors were then derived using propagation of error. To illustrate the applications of the model, 12 data sets were acquired from each human subject, over a range of b-values (500 -2500 seconds/mm 2 ) and diffusion-weighting gradient directions (N ϭ 6 -55). The mean RA and FA values and their respective errors were calculated within a region of interest (ROI) in the splenium. The RA and FA errors as a function of b-value and N were evaluated, and a number of diffusion-weighting schemes were assessed based on a new metric, sum of diffusion tensor variances.Results: When the acquisition time was held constant, the sum of the diffusion tensor variances decreased as N increased. The same trend was also observed for several diffusion-weighting schemes with constant condition number when noise in the diffusion-weighted (DW) images was assumed unity. Errors in both FA and RA increased with b-value and decreased with N. The FA error in the splenium was approximately threefold smaller than RA error, irrespective of b-value or N. Conclusion:The condition number may not adequately characterize the noise sensitivity for a given diffusionweighting scheme. Signal averaging may not be as effective as increasing N, especially when N is small (e.g., N Ͻ 13). Due to its smaller error, FA is preferred over RA for quantitative DTI applications.

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Section: Discussionsupporting

confidence: 93%

Analytical error propagation in diffusion anisotropy calculations

Poonawalla

Zhou

2004

Magnetic Resonance Imaging

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“…The fractional anisotropy (FA) (Papadakis, et al 1999) and mean diffusivity (MD) values were computed for each subject. FA is a marker for diffusion anisotropy and has a range of zero, in the case of completely isotropic diffusion, to one, in the case of completely anisotropic diffusion, while MD is a directionally-averaged measure of water diffusion, reflecting tissue density.…”

Section: Methodsmentioning

confidence: 99%

Cognitive functions correlate with white matter architecture in a normal pediatric population: A diffusion tensor MRI study

Schmithorst¹,

Wilke²,

Dardzinski³

et al. 2005

Human Brain Mapping

364

233

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A possible relationship between cognitive abilities and white matter structure as assessed by magnetic resonance diffusion tensor imaging (DTI) was investigated in the pediatric population. DTI was performed on 47 normal children ages 5–18. Using a voxelwise analysis technique, the fractional anisotropy (FA) and mean diffusivity (MD) were tested for significant correlations with Wechsler full‐scale IQ scores, with subject age and gender used as covariates. Regions displaying significant positive correlations of IQ scores with FA were found bilaterally in white matter association areas, including frontal and occipito‐parietal areas. No regions were found exhibiting correlations of IQ with MD except for one frontal area significantly overlapping a region containing a significant correlation with FA. The positive direction of the correlation with FA is the same as that found previously with age, and indicates a positive relationship between fiber organization and/or density with cognitive function. The results are consistent with the hypothesis that regionally specific increased fiber organization is a mechanism responsible for the normal development of white matter tracts. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.

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“…The orientations were chosen according to the DTI acquisition scheme proposed by Papadakis et al (1999). The total of 24 diffusion-weighted measurements, each an average of four measurements, were divided into four blocks, each preceded by a non-diffusion-weighted acquisition.…”

Section: Diffusion Tensor Imagingmentioning

confidence: 99%

Basal forebrain integrity and cognitive memory profile in healthy aging

Düzel¹,

Münte²,

Lindenberger³

et al. 2010

Brain Research

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Age-related dysfunctions in cholinergic and dopaminergic neuromodulation are assumed to contribute to age-associated impairment of explicit memory. Both neurotransmitters also modulate attention, working memory, and processing speed. To date, in vivo evidence linking structural age-related changes in these neuromodulatory systems to dysfunction within or across these cognitive domains remains scarce. Using a factor analytical approach in a cross-sectional study including 86 healthy older (aged 55 to 83 years) and 24 young (aged 18 to 30 years) adults, we assessed the relationship between structural integrity-as measured by magnetization transfer ratio (MTR)-of the substantia nigra/ventral tegmental area (SN/VTA), main origin of dopaminergic projections, basal forebrain (major origin of cortical cholinergic projections), frontal white matter (FWM), and hippocampus to neuropsychological and psychosocial scores. Basal forebrain MTR and FWM changes correlated with a factor combining verbal learning and memory and working memory and, as indicated by measures of diffusion, were most likely due to vascular pathology. These findings suggest that frontal white matter integrity and cholinergic neuromodulation provide clues as to why age-related cognitive decline is often correlated across cognitive domains. IntroductionAge-related decline in learning and memory, often termed age-associated memory impairment (AAMI) (Crook et al., 1986), is a well-documented finding in healthy older adults (Balota et al., 2000;Cabeza et al., 2000;Craik, 1994;Salthouse, 2003), but the neurobiological correlates of this decline are still under debate. A consistent pattern of AAMI is a decrement in declarative memory (Tulving, 1985) most clearly apparent in impaired free recall and recollection (Buckner, 2004;Craik, 2006;Hedden and Gabrieli, 2004;Nilsson, 2003). Evidence from lesion studies in humans and animals indicates that

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A study of rotationally invariant and symmetric indices of diffusion anisotropy

Cited by 162 publications

References 25 publications

Analytical error propagation in diffusion anisotropy calculations

Analytical error propagation in diffusion anisotropy calculations

Cognitive functions correlate with white matter architecture in a normal pediatric population: A diffusion tensor MRI study

Basal forebrain integrity and cognitive memory profile in healthy aging

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