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Brain Imaging

The brain is composed of soft tissue, displaying without much structure on x-ray images. Radiologists used to drain the brain of cerebrospinal fluid before taking x-rays to attain some contrast up until the late 1980s, but it was an unhealthy procedure. Holes were drilled in the skull, after which the tapping of cerebrospinal fluid caused vomiting and motor dysfunction, with patient recovery times stretching to months. Today, we visualize brains using scanning techniques such as positron emission tomography (PET), computed tomography (CT), functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and magnetoencephalography (MEG).

Computed Tomography

CT provides a two- or three-dimensional image of the brain, with a maximum spatial resolution of about half a cubic millimeter. It is used for diagnosis and reveals medical complications.

How It Works

A contrast agent is often injected into the bloodstream, and then a rotating x-ray source circles the brain in the same plane. The rays are detected by sensors surrounding the head, and the data are used to reconstruct a two-dimensional brain slice. Multiple slices can be merged into a three-dimensional image. The word “tomography” comes from tomos (slice) and graphia (write), so the word means “slice writing.”

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