From Diffusion MRI to Brain Connectomics - Modeling in Computational Biology and Biomedicine - page 217

6.7 Clinical Applications

Diffusion MRI has now proved to be extremely useful for studying the normal
and pathological human brain [ 11 , 27 ] and for improving diagnosis and therapy of
brain diseases. It has led to many applications in clinical diagnosis of neurological
diseases and disorders, neuroscience applications in assessing connectivity of
different brain regions and more recently, therapeutic applications, primarily in
neurosurgical planning. Indeed, the sensitivity of diffusion measures to changes in
the white matter have led to a wealth of clinical studies using second order diffusion
tensor imaging as an in vivo clinical marker and dMRI has opened up a landscape of
discoveries for neuroscience and medicine through research and clinical exploration
of fiber connectivity and CNS diseases.
The dMRI models and tools presented in this chapter are at the heart of what is
strongly needed to better recover, study and understand the anatomical connectivity
of the normal and pathological human CNS. These dMRI methodological develop-
ments have already been applied in many places to better describe, characterize and
quantify abnormalities within the CNS white matter and develop in vivo markers
for diseases in clinical neuroscience.
The first and most successful application of dMRI since the early 1990s has been
in acute brain ischemia, that emerged from the discovery of Moseley et al. that
water diffusion immediately drops after the onset of an ischemic event, when brain
cells undergo swelling through cytotoxic edema. This result was later confirmed by
different groups using animal models and human patients with stroke.
Since then, many important CNS diseases have attracted the interest of dMRI
researchers. Hence, DTI has appeared as a promising tool to look at brain maturation
and development, especially to monitor the myelination process, as well as changes
in connectivity in relation to functional disorders. Indeed, it has been shown by
many studies that the degree of diffusion anisotropy in white matter increases during
the myelination process, so that dMRI could be used to assess brain maturation
in children, newborns or premature babies, as well as to characterize white matter
disorders in children. DTI has now been used for more than 10 years to look, in vivo,
at the disorganization of white matter in schizophrenia, which is thought to come
from myelin abnormalities. Most neuroimaging studies of schizophrenia have used
second order DTI so far, as a means to quantify the integrity of the white matter.
Alzheimer's and Parkinson's diseases, two of the most important neurode-
generative diseases, as well as others like multiple sclerosis have characteristic
abnormalities in the microstructure of brain tissues that are not apparent and cannot
be revealed reliably by standard imaging techniques. Diffusion MRI can reveal these
co-lateral damages to the fibers of the CNS white matter that connect different brain
regions.
We in the Athena Project Team, Inria, France, are currently focusing on the
use of ultra high field MRI (3T and 7T) techniques for investigating the structural
disorders of the brain stem and of the central deep nuclei in the field of Parkinson's
syndrome. This work aims to identify the biomarkers of the pathology by benefitting