ISMRM Weekend course – 5th of May 2012 Measuring Diffusion Properties in Tissue:

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ISMRM Weekend course – 5th of May 2012 Measuring Diffusion Properties in Tissue:

Tang, John, News Editor has reference to this Academic Journal, PHwiki organized this Journal ISMRM Weekend course – 5th of May 2012 Measuring Diffusion Properties in Tissue: The Diffusion Tensor & Derived Indices Gwenaëlle Douaud FMRIB, University of Ox as long as d Historical description of the diffusion tensor ISMRM Weekend course – 5th of May 2012 Formalised by Peter Basser in addition to colleagues (1994a; 1994b) In an isotropic, unconstrained environment: D = scalar In an anisotropic, constrained environment: D = 33 definite symmetric positive D = “diffusion tensor” ISMRM Weekend course – 5th of May 2012 Historical description of the diffusion tensor In an anisotropic, constrained environment: D = 33 definite symmetric positive D = “diffusion tensor” with i {1,2,3}

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First clinical application: brain ischemia (Moseley et al., 1990; Warach et al., 1992) Diffusion tensor indices: Mean Diffusivity Formalised by Peter Basser in addition to Carlo Pierpaoli (1995; 1996) Magnitude of diffusion ISMRM Weekend course – 5th of May 2012 Bammer, 2003 Warach et al., 1995 Visible only 3 hours after onset of stroke Formalised by Peter Basser in addition to Carlo Pierpaoli (1995; 1996) RA = “Relative Anisotropy” Anisotropy of diffusion ISMRM Weekend course – 5th of May 2012 Bammer, 2003 Diffusion tensor indices: diffusion anisotropy ISMRM Weekend course – 5th of May 2012 Diffusion tensor indices: diffusion anisotropy Formal comparison of three anisotropy indices (Papadakis et al., 1999) FA: mapped diffusion anisotropy with the greatest detail in addition to SNR VR: provided the strongest CNR, but with noise contamination, resolution RA: intermediate between FA in addition to VR

ISMRM Weekend course – 5th of May 2012 Diffusion tensor indices: diffusion anisotropy Further comparison between FA in addition to RA (Hasan et al., 2004) ISMRM Weekend course – 5th of May 2012 Developmental study: anatomical in addition to tractography-defined ROI (Lebel et al., 2008) Fractional Anisotropy in addition to Mean Diffusivity: ROI in addition to voxel-based/TBSS analysis Fractional Anisotropy in addition to Mean Diffusivity: ROI in addition to voxel-based/TBSS analysis ISMRM Weekend course – 5th of May 2012 Developmental study: comparison between ROI in addition to VBD (Snook et al., 2007) The discrepancies related to: – ROI approach inherently limited – issues with the spatial normalisation as long as VBD analysis – masking localised changes by averaging all the voxels within a ROI

ISMRM Weekend course – 5th of May 2012 Fractional Anisotropy in addition to Mean Diffusivity: ROI in addition to voxel-based/TBSS analysis Increasing sensitivity in addition to interpretability of results compared with voxel-based approaches based purely on non-linear registration: TBSS (Smith et al., 2006) TBSS VBD Mean Control Mean Patient ISMRM Weekend course – 5th of May 2012 Fractional Anisotropy in addition to Mean Diffusivity: ROI in addition to voxel-based/TBSS analysis Large developmental in addition to ageing study using TBSS (Westlye et al., 2010) ISMRM Weekend course – 5th of May 2012 Fractional Anisotropy in addition to Mean Diffusivity: first applications Cognitive per as long as mance (review in Moseley et al., 2002) Development (review in Beaulieu et al., 1999) Psychiatric diseases (review in Lim in addition to Helpern, 2002): schizophrenia (Buchsbaum et al., 1998), alcoholism (Pfefferbaum et al., 2000) , depression etc. Ageing (review in Moseley, 2002) White matter diseases (review in Horsfield in addition to Jones, 2002): multiple sclerosis (Horsfield et al., 1998), Alzheimer’s disease (Hanyu et al., 1998), ALS, CJD etc.

ISMRM Weekend course – 5th of May 2012 Fractional Anisotropy in addition to Mean Diffusivity: Two complementary measures An intriguing finding in multiple sclerosis (Ciccarelli et al., 2001) Patient Control White matter basal ganglia Increased FA in the basal ganglia in MS: selective Wallerian degeneration, with the intact connections showing an increase of their coherence ISMRM Weekend course – 5th of May 2012 Fractional Anisotropy in addition to Mean Diffusivity: Two complementary measures Same findings seen in the basal ganglia in Huntington’s disease (Douaud et al., 2009) ISMRM Weekend course – 5th of May 2012 Using the in as long as mation from the PDD (Schwartzmann et al., 2005) Douaud et al., 2009

ISMRM Weekend course – 5th of May 2012 Decrease of the dispersion of the PDD in Huntington’s disease (Douaud et al., 2009) ISMRM Weekend course – 5th of May 2012 No difference in the white matter of mild cognitive impairment (MCI) patients using MD or FA (Douaud et al., 2011) Mode of anisotropy (MO): 3rd moment of the tensor, introduced by Basser (1997), as long as malised by Ennis in addition to Kindlamnn (2006). -1 Planar, disc-like 1~ 2: e.g., areas of crossing fibres +1 Linear, cigar-like 2~ 3: e.g., areas of one predominating fibre population Beyond Fractional Anisotropy in addition to Mean Diffusivity: the Mode of anisotropy ISMRM Weekend course – 5th of May 2012 Significant difference in the white matter of MCI patients, with an increase of MO MCI>CON AD>CON AD>CON Douaud et al., 2011 Beyond Fractional Anisotropy in addition to Mean Diffusivity: the Mode of anisotropy

ISMRM Weekend course – 5th of May 2012 Significant increase of MO in MCI in addition to AD also related to selective degeneration in crossing fibres region (here, centrum semiovale) Douaud et al., 2011 Beyond Fractional Anisotropy in addition to Mean Diffusivity: the Mode of anisotropy Validated in animal models by Song in addition to colleagues (2002; 2005) = 1 Parallel diffusivity or axial diffusivity: assessing axonal injury ISMRM Weekend course – 5th of May 2012 Perpendicular diffusivity or radial diffusivity: assessing myelin injury Beyond Fractional Anisotropy in addition to Mean Diffusivity: Parallel in addition to Perpendicular Diffusivity ISMRM Weekend course – 5th of May 2012 Beyond Fractional Anisotropy in addition to Mean Diffusivity: Parallel in addition to Perpendicular Diffusivity Validated in humans using the model of callosotomy (Concha et al., 2006) Axonal degradation Myelin degradation

ISMRM Weekend course – 5th of May 2012 Diffusion tensor indices: in vivo models in addition to histological validation Basis of diffusion anisotropy in the brain: comprehensive review by Beaulieu (2002) Anisotropy due to membrane, not myelin Myelin modulates anisotropy Axonal cytoskeleton does not contribute to anisotropy ISMRM Weekend course – 5th of May 2012 Diffusion tensor indices: in vivo models in addition to histological validation Combined in vivo diffusion/histological study: animal model (van Camp et al., 2012) ISMRM Weekend course – 5th of May 2012 Diffusion tensor indices: in vivo models in addition to histological validation Combined in vivo diffusion/histological study: epilepsy (Concha et al., 2010)

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ISMRM Weekend course – 5th of May 2012 The depressing slide Sensitivity to noise increases with higher order moments: noise(MD) < noise(FA) < noise (MO) Crossing-fibres: effects can be averaged out Groeschel et al., ISMRM 2011 ISMRM Weekend course – 5th of May 2012 Sensitivity to noise increases with higher order moments: noise(MD) < noise(FA) < noise (MO) Crossing-fibres: effects can be averaged out Crossing-fibres: problematic interpretation of in addition to The depressing slide ISMRM Weekend course – 5th of May 2012 Sensitivity to noise increases with higher order moments: noise(MD) < noise(FA) < noise (MO) Crossing-fibres: effects can be averaged out Crossing-fibres: problematic interpretation of in addition to Crossing-fibres: not only influence on FA, but also MD (Vos et al., 2012) The depressing slide Vos et al., ISMRM 2011 ISMRM Weekend course – 5th of May 2012 Sensitivity to noise increases with higher order moments: noise(MD) < noise(FA) < noise (MO) Crossing-fibres: effects can be averaged out Crossing-fibres: problematic interpretation of in addition to Crossing-fibres: not only influence on FA, but also MD Effect of partial volume effect on FA, MD etc. (Jones, ISMRM 2011) Correction as long as CSF contamination (Metzler-Baddeley et al., 2012) Choice of sequence: anisotropic voxels (Vos et al., ISMRM 2011) The depressing slide Choice of sequence: 12 orientations, 5 b-values: more sensitive to using MD 30 orientations, 2 b-values: more sensitive to using FA ISMRM Weekend course – 5th of May 2012 Take home message FA in addition to MD complementary to interpret results: higher FA is not necessarily better Do not as long as get about PVE, noise in addition to crossing fibres to help interpret results in addition to give additional in as long as mation (e.g., Salat et al., 2010) Vos et al., ISMRM 2011 Choice of sequence: isotropic voxels, optimised as long as specific question If ambiguous interpretation: MO, dispersion of PDD, Westin indices (Westin et al., 1997) ISMRM Weekend course – 5th of May 2012 Take home message FA in addition to MD complementary to interpret results: higher FA is not necessarily better Do not as long as get about PVE, noise in addition to crossing fibres to help interpret results Choice of sequence: isotropic voxels, optimised as long as specific question If ambiguous interpretation: MO, dispersion of PDD, Westin indices (Westin et al., 1997) in addition to give additional in as long as mation (e.g., Salat et al., 2010) Crossing fibres helps detect subtle differences (Tuch et al., 2005; Douaud et al., 2011) Tuch et al., 2005 FMRIB, University of Ox as long as d - Karla Miller - Stamatios Sotiropoulos - Timothy Behrens Steve Smith Peter Jezzard Saad Jbabdi THANK YOU Special thanks to: SHFJ, CEA, Orsay Cyril Poupon - Yann Cointepas - Denis Riviere - Jean-Francois Mangin ISMRM Weekend course – 5th of May 2012 ISMRM Weekend course – 5th of May 2012 Other diffusion tensor-derived measures “Westin” indices describing the tensor shape: sphericity, linearity in addition to planarity (Westin et al., 1997) Inter-voxel measures: lattice index (Pierpaoli) Fourth moment: kurtosis (Assaf)

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