Neuroimaging

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Neuroimaging techniques

The aim of neuroimaging methods is to produce images of the brain. The two major fields are structural and functional imaging. Many different methods are used for this purpose, including

• Electroencephalography (EEG)
• Magnetoencephalography (MEG)
• Positron emission tomography (PET)
• Magnetic resonance imaging (MRI)

Functional neuroimaging

Functional neuroimaging is used to image metabolic activity in neural tissue.

Positron emission tomography

Radioactive labels are injected into the human body. In their decay they emit gamma-rays. These are measured and the source is localized by tomographic reconstruction.

Functional MRI (fMRI)

ACtive regions in neural tissue need a high oxygen supply. When a region gets the body provides it with more oxygenated blood. Because of the different magnetic susceptibility of oxygenated and deoxygenated blood this can be made visible by MRI methods. This technique is called blood-oxygen level dependent (BOLD) fMRI. It is often used in research to measure the reaction of the brain to certain stimuli or actions.

Data processing issues

Data provenance

To be useful as data resource in scientific collaborations, the history of images has to be tracked. This is called "provenance" (also "lineage" or "pedigree"). Provenance consists of the data part and the process part. The data provenance contains information about the origin of raw images, while the process provenance documents the way those images have been manipulated.

Measuring the Brain structure

Diffusion-tensor MRI

By applying a gradient to the magnetic field the diffusion of water can be imaged. To get 3D diffusion information a series of measurements with different gradient directions has to be performed.