Review ArticleThe Utility of Diffusion Tensor Imaging in Neuromodulation: Moving Beyond Conventional Magnetic Resonance Imaging
Section snippets
INTRODUCTION
Neuromodulation is an emerging therapy for a vast number of medically refractory neurological and psychiatric disorders. This treatment modality has been guided primarily by advances in imaging and neurophysiology, which have led to new strategies for better targeting, identification of optimal stimulation sites, and understanding of its therapeutic mechanisms. Among the brain stimulation therapies, deep brain stimulation (DBS) is a well-established treatment that involves surgically implanting
DTI
DTI is a neuroimaging technique that measures the three-dimensional movement of water molecules in biological tissue to characterize white matter microstructure (28). The diffusion of water in three dimensions is calculated by fitting a tensor to every voxel in the brain of a diffusion-weighted MR scan. This tensor may be represented as an ellipsoid shaped mathematical model, defined by three orthogonal eigenvectors and corresponding eigenvalues (λ1, λ2, λ3). The shape of the tensor depends on
BETTER GUIDING NEUROMODULATION TARGETS BASED ON DTI
DTI has the potential to enhance surgical targeting by allowing detailed visualization of white matter tracts and their connections, given that precision and accuracy are one of the main goals of neuromodulation targeting. This approach is especially important when the putative target location cannot be reliably seen by conventional targeting methods. Along with the success of DBS for movement disorders, tractography-guided neuromodulation targeting has primarily been explored for DBS in
FINDING NEW OR OPTIMAL NEUROMODULATION TARGETS BASED ON DTI
Beyond enhancing brain stimulation targeting, DTI can also be used to find new or optimal targets. The advent of the human connectome project has enabled the opportunity to explore the full landscape of structural and functional connections of the human brain in a large-scale manner (75). Using diffusion MRI tractography, an approach for mapping the white matter connections of the entire human brain and its resulting network has been proposed (43). Connectivity and network analyses can be used
TRACTOGRAPHY-BASED TARGETING IN MRgFUS
The benefits of tractography for enhanced target identification may also be extended to noninvasive neuromodulation technologies such as MRgFUS. This method allows deep brain regions to be targeted through an intact skull. In ablative therapies, acoustic energy from an array of ultrasound transducers is concentrated to generate thermal lesions on a desired focal point (Fig. 5). Clinically, the most common application of MRgFUS is thalamotomy for ET. Using the tractography-based VIM targeting
LIMITATIONS
With any tractography method, there is the inherent drawback of the estimated white matter pathways not being wholly representative of actual tissue microstructure or anatomical connectivity. For one, the diameter of individual axons is much smaller (~1.0 μm) than a typical DTI voxel (resolutions in the range of 1–3 mm). In addition, many areas of the brain contain multiple population(s) of fibers or fibers that cross each other. The single-tensor model is particularly susceptible to the
CONCLUSIONS
In conclusion, there is increasing evidence that DTI is superior to the historically used CT and MRI scans with respect to improving brain stimulation therapies. In an era of precision medicine, it is time we move beyond conventional MRI and embrace the integration of these advanced neuroimaging modalities in neuromodulation targeting platforms. In particular, DTI has the ability to better define anatomical targets by allowing detailed visualization of white matter tracts and localizing targets
Acknowledgements
S. Tohyama is a recipient of a Canadian Institutes of Health Research Doctoral Research Award.
Authorship Statements
Sarasa Tohyama and Mojgan Hodaie conceived of the manuscript. Sarasa Tohyama, Matthew Walker, and Mojgan Hodaie prepared the manuscript draft with important intellectual input from all authors. All authors approved the final manuscript.
REFERENCES (111)
- et al.
Probing and regulating dysfunctional circuits using deep brain stimulation
Neuron
(2013) - et al.
Deep brain stimulation of the ventral capsule/ventral striatum for treatment-resistant depression
Biol Psychiatry
(2009) Transcranial magnetic stimulation: a primer
Neuron
(2007)- et al.
Transcranial direct current stimulation: State of the art 2008
Brain Stimul
(2008) - et al.
Rapid-rate transcranial magnetic stimulation of left dorsolateral prefrontal cortex in drug-resistant depression
Lancet
(1996) - et al.
Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: A multisite randomized controlled trial
Biol Psychiatry
(2007) - et al.
Treatment of major depressive disorder via magnetic resonance-guided focused ultrasound surgery
Biol Psychiatry
(2018) - et al.
Transcranial pulsed ultrasound stimulates intact brain circuits
Neuron
(2010) - et al.
A review of low-intensity focused ultrasound pulsation
Brain Stimul
(2011) - et al.
Diffusion tensor imaging of the brain
Neurotherapeutics
(2007)
An unexpectedly high rate of revisions and removals in deep brain stimulation surgery: Analysis of multiple databases
Parkinsonism Relat Disord
Revision surgery of deep brain stimulation leads
Neuromodulation
Diffusion-based tractography in neurological disorders: Concepts, applications, and future developments
Lancet Neurol
Abnormal trigeminal nerve microstructure and brain white matter in idiopathic trigeminal neuralgia
Pain
Diffusion tensor imaging detects and differentiates axon and myelin degeneration in mouse optic nerve after retinal ischemia
Neuroimage
Demyelination increases radial diffusivity in corpus callosum of mouse brain
Neuroimage
Dysmyelination revealed through MRI as increased radial (but unchanged axial) diffusion of water
Neuroimage
Clinical applications of diffusion tensor imaging
World Neurosurg
Robust determination of the fibre orientation distribution in diffusion MRI: Non-negativity constrained super-resolved spherical deconvolution
Neuroimage
Probabilistic diffusion tractography with multiple fibre orientations: What can we gain?
Neuroimage
Resolving crossings in the corticospinal tract by two-tensor streamline tractography: Method and clinical assessment using fMRI
Neuroimage
Toward defining deep brain stimulation targets in MNI space: A subcortical atlas based on multimodal MRI, histology and structural connectivity
Neuroimage
Connectivity profile predictive of effective deep brain stimulation in obsessive-compulsive disorder
Biol Psychiatry
Individualized parcellation of the subthalamic nucleus in patients with Parkinson’s disease with 7T MRI
Neuroimage
Individualized tractography-based parcellation of the globus pallidus pars interna using 7T MRI in movement disorder patients prior to DBS surgery
Neuroimage
Diffusion tensor imaging and neuromodulation: DTI as key technology for deep brain stimulation
Int Rev Neurobiol
Deep brain stimulation of the Dentato-Rubro-thalamic tract: Outcomes of direct targeting for tremor
Neuromodulation
Comparison of posterior subthalamic area deep brain stimulation for tremor using conventional landmarks versus directly targeting the dentatorubrothalamic tract with tractography
Clin Neurol Neurosurg
Rapid effects of deep brain stimulation for treatment-resistant major depression
Biol Psychiatry
Deep brain stimulation of the medial forebrain bundle: Distinctive responses in resistant depression
J Affect Disord
Tractography-assisted deep brain stimulation of the superolateral branch of the medial forebrain bundle (slMFB DBS) in major depression
Neuroimage Clin
Deep brain stimulation to the medial forebrain bundle for depression- long-term outcomes and a novel data analysis strategy
Brain Stimul
Subcallosal cingulate gyrus deep brain stimulation for treatment-resistant depression
Biol Psychiatry
Deep brain stimulation for treatment-resistant depression
Neuron
Subcallosal cingulate deep brain stimulation for treatment-resistant depression: A multisite, randomised, sham-controlled trial
Lancet Psychiatry
Nucleus accumbens deep brain stimulation decreases ratings of depression and anxiety in treatment-resistant depression
Biol Psychiatry
A tractography analysis of two deep brain stimulation white matter targets for depression
Biol Psychiatry
Defining critical white matter pathways mediating successful subcallosal cingulate deep brain stimulation for treatment-resistant depression
Biol Psychiatry
StimVision software: Examples and applications in subcallosal cingulate deep brain stimulation for depression
Neuromodulation
Diffusion MRI tractography for improved transcranial MRI-guided focused ultrasound thalamotomy targeting for essential tremor
Neuroimage Clin
Deep brain stimulation
Annu Rev Neurosci
Bilateral deep brain stimulation vs best medical therapy for patients with advanced Parkinson disease: A randomized controlled trial
JAMA
Deep brain stimulation for Parkinson disease: An expert consensus and review of key issues
Arch Neurol
Subthalamic nucleus deep brain stimulation: Summary and meta-analysis of outcomes
Mov Disord
Deep brain stimulation for essential tremor: A systematic review
Mov Disord
Deep brain stimulation for primary generalized dystonia: Long-term outcomes
Arch Neurol
A multicenter pilot study of subcallosal cingulate area deep brain stimulation for treatment-resistant depression
J Neurosurg
Deep brain stimulation of the ventral internal capsule/ventral striatum for obsessive-compulsive disorder: Worldwide experience
Mol Psychiatry
Deep brain stimulation for chronic pain: Results of two multicenter trials and a structured review
Pain Med
Deep brain stimulation for pain in the modern era: A systematic review
Neurosurgery
Cited by (8)
Research and application progress of magnetic resonance‑guided focused ultrasound in mental disorders
2023, Chinese Journal of PsychiatryDiffusion Tractography in Neurosurgical Planning: Overview of Advanced Clinical Applications
2023, Functional Neuroradiology: Principles and Clinical ApplicationsFunctional Neuronavigation
2022, Medical RadiologyA narrative review of multimodal imaging of white matter lesions in type-2 diabetes mellitus
2021, Annals of Palliative Medicine
Source(s) of financial support: Sarasa Tohyama is a recipient of a Canadian Institutes of Health Research Doctoral Research Award.
For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http://www.wiley.com/WileyCDA/Section/id-301854.html