Synopsis
Both task-based and resting-state fMRI have been widely used
to understand the functional organization of the brain. Both techniques have
also been applied in patients for guiding neurosurgery, distinguishing disease
phenotypes, supporting clinical management, and evaluating treatment response. Nonetheless,
several technical and pathophysiological issues will need to be considered for clinical
fMRI.
Functional MRI (fMRI) has been widely used for mapping
neural areas and their activity engaged in sensory, motor, or cognitive
functions by measuring the blood oxygenation level dependent (BOLD) signal that
correlates with the task performance. Resting-state fMRI provides another way
for brain mapping by measuring the spontaneous synchronous oscillation of the
BOLD signal to derive the functional connectivity without the need to perform a
task. Both techniques provide complementary information for understanding the
functional segregation and integration of the brain. They have been applied to
understand motor function, perception, attention, learning, memory, language, emotion,
pain, consciousness, etc.
Besides being research tools for
understand the normal brain, both task-based and resting-state fMRI have been
applied to patients in the following areas [1,2]:
•
fMRI-guided neurosurgery for locating functional
area for brain tumor resection safety, for targeted ablation/resection in
epilepsy, or for guiding brain stimulation loci.
•
Understand disease mechanisms, phenotypes, or polymorphism.
•
Clinical management, including diagnosis, risk
assessment, monitoring disease progress, treatment response or relapse.
•
Treatment development, such as for differentiating
responders, measuring drug pharmacokinetic and pharmacodynamics, and treatment
response.
Among these clinical applications,
task-based fMRI has been established for the assessment of eloquent cortex (especially
for motor, language and memory) before and after surgery for intracranial tumor
and epilepsy. Its sensitivity and specificity have been evaluated using the intraoperative
electrocortical mapping [3,4]. Clinical guidelines have
been provided by the American College of Radiology (ACR) and current procedural
terminology (CPT) codes have been established by Centers for Medicare and
Medicaid Services (CMS) for conducting neurofunctional assessment using
task-based fMRI in patients. Compared to task fMRI, resting-state fMRI has some
advantages for imaging young children, patients with altered mental status,
sedated patients, and those who are paretic or aphasic. However, its
specificity is lower and clinical practice has yet to be established.
Several technical and
pathophysiological issues need to be considered in the study design and
interpretation for clinical fMRI [5,6]. Head motion is a particular
concern especially when the task involves moving the impaired body part. The
need to map activity robustly at individual level rather than group level also
poses technical challenges. Inferring neural activity from BOLD signal relies
on proper neurovascular coupling. However, this assumption may not hold true in
diseases that alter cerebrovasculature, such as high-grade glioma, arteriovenous
malformations or stroke.
Acknowledgements
No acknowledgement found.References
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doi:10.1007/978-3-662-45123-6_12