Functional Imaging Technique Measures Brain Resting State

A new study suggests that functional magnetic resonance imaging (fMRI) could be a cost-effective alternative for estimating relative levels of activity in a cerebral metabolic map.

Researchers at Western University (WU; London, Canada) and the University Hospital of Liège (Belgium) conducted a study to gauge the possibility of using fMRI instead of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) for generating the metabolic maps that are used to asses changes in brain activity in clinical applications, such as during the study of severe brain injury and disorders of consciousness.

To do so, the researchers first extracted resting state fMRI functional connectivity maps using independent component analysis, and combined only components of neuronal origin. They then compared the generated maps with the FDG-PET maps in 16 healthy controls, 11 vegetative state/unresponsive wakefulness syndrome patients, and in four locked-in patients.

The results showed a significant similarity for healthy controls and for vegetative state/unresponsive wakefulness syndrome patients between the FDG-PET and the fMRI based maps, with conjunction analysis showing decreased frontoparietal and medial regions in vegetative patients with respect to controls. Subsequent analysis in locked-in syndrome patients, which are known to be conscious, also produced consistent neuronal maps with healthy controls. The study was published on December 29, 2015, in Brain and Behavior.

“Many hospitals in developing countries have access to functional MRI technology or FDG-PET, but not both. By developing new fMRI techniques, hospitals that already have the expensive scanning equipment or wish to purchase a unit effectively get 'more bang for their buck’,” said lead author Andrea Soddu, PhD, of the WU department of physics and astronomy. “If no metabolic absolute measures can be extracted, our approach may still be of clinical use in centers without access to FDG-PET.”

PET scans are widely used to diagnose and track a variety of diseases, including cancer, because they show how organs and tissues function in the body, in contrast to MRI or CT scans, which mostly show anatomy. Using radioactive tracers that produce a signal from within the body, PET scanners produce a 3D image that is constructed by computers using sophisticated mathematical techniques.

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Western University
University Hospital of Liège