High b-value diffusion tractography: Abnormal axonal network organization associated with medication-refractory epilepsy

Gleichgerrcht, Ezequiel; Keller, Simon; Bryant, Lorna; Moss, Hunter G.; Kellermann, Tanja S.; Biswas, Shubhabrata; Marson, Anthony G; Wilmskoetter, Janina; Jensen, Jens Højgaard; Bonilha, Leonardo

doi:10.1016/j.neuroimage.2021.118866

Cited by 5 publications

(3 citation statements)

References 46 publications

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“…DTI cannot discern between intra- and extra-axonal water because it relies on signals stemming from a mixture of both. DTI is based on an orientation distribution function, which reflects the preferred direction of water diffusion 63 , 64 . Consequently, DTI may underestimate the number fibers and may not be able to resolve fiber crossings 65 .…”

Section: Discussionmentioning

confidence: 99%

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Wilmskoetter

Busby

et al. 2023

Commun Biol

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Brain structure deteriorates with aging and predisposes an individual to more severe language impairments (aphasia) after a stroke. However, the underlying mechanisms of this relation are not well understood. Here we use an approach to model brain network properties outside the stroke lesion, network controllability, to investigate relations among individualized structural brain connections, brain age, and aphasia severity in 93 participants with chronic post-stroke aphasia. Controlling for the stroke lesion size, we observe that lower average controllability of the posterior superior temporal gyrus (STG) mediates the relation between advanced brain aging and aphasia severity. Lower controllability of the left posterior STG signifies that activity in the left posterior STG is less likely to yield a response in other brain regions due to the topological properties of the structural brain networks. These results indicate that advanced brain aging among individuals with post-stroke aphasia is associated with disruption of dynamic properties of a critical language-related area, the STG, which contributes to worse aphasic symptoms. Because brain aging is variable among individuals with aphasia, our results provide further insight into the mechanisms underlying the variance in clinical trajectories in post-stroke aphasia.

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Section: Discussionmentioning

confidence: 99%

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Wilmskoetter

Busby

et al. 2023

Commun Biol

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“…However, the clearer biological meaning of the fODF makes FBI preferable for some applications, such as fiber tractography and microstructural modeling. 10,[15][16][17][18][19] Several other dMRI methods also generate fODFs, with constrained spherical deconvolution (CSD) being among the most popular. [20][21][22] FBI is distinguished from many of these in avoiding complicated numeric fitting and obviating the need for an empirically determined response function.…”

Section: Introductionmentioning

confidence: 99%

“…An advantage of QBI is that it does not, unlike FBI, rely on assumptions regarding the details of white matter microstructure. However, the clearer biological meaning of the fODF makes FBI preferable for some applications, such as fiber tractography and microstructural modeling 10,15–19 …”

Section: Introductionmentioning

confidence: 99%

Impact of intra‐axonal kurtosis on fiber orientation density functions estimated with fiber ball imaging

Jensen

2022

Magnetic Resonance in Med

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To determine the impact of an intra-axonal kurtosis on estimates of the fiber orientation density function (fODF) obtained with fiber ball imaging (FBI).Theory and Methods: Standard FBI assumes Gaussian diffusion within individual axons and estimates the fODF by applying an inverse generalized Funk transform to diffusion MRI data for b-values of 4000 s/mm 2 or higher. However, recent work based on numeric simulations shows that diffusion inside axons is non-Gaussian with an intra-axonal kurtosis of ∼ 0.4. Here, the theory underlying FBI is extended to incorporate an intra-axonal kurtosis. This is done to first order in the intra-axonal kurtosis without making assumptions about the details of the diffusion dynamics and to all orders for a specific model based on a gamma distribution of diffusivities. The first order approximation is used to assess the effect of an intra-axonal kurtosis on FBI estimates for the fODF and axonal water fraction. The gamma distribution model is used to test the validity of the approximation. Results:The first order approximation indicates the estimated fODF is altered by a few percent for an intra-axonal kurtosis of 0.4 in comparison to predictions of standard FBI. If one neglects the intra-axonal kurtosis, the angular resolution of the point spread function for the fODF is changed by <1 • , whereas the axonal water fraction is overestimated by ∼ 5%. The gamma distribution model shows that the first order approximation is accurate to within a few percent. Conclusion:The intra-axonal kurtosis has a small impact on fODFs estimated with FBI.

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Neurocysticercosis-related seizures: Imaging biomarkers

Ratcliffe¹,

Adan²,

Marson³

et al. 2023

Seizure: European Journal of Epilepsy

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High b-value diffusion tractography: Abnormal axonal network organization associated with medication-refractory epilepsy

Cited by 5 publications

References 46 publications

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Dynamic network properties of the superior temporal gyrus mediate the impact of brain age gap on chronic aphasia severity

Impact of intra‐axonal kurtosis on fiber orientation density functions estimated with fiber ball imaging

Neurocysticercosis-related seizures: Imaging biomarkers

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