How the Brain Works The Facts Visually Explained by DK (z-lib.org)

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THE PHYSICAL BRAIN

Imaging the Brain 40 41

A pulse of radio waves

With the magnetic field on, the MRI

machine’s radiofrequency coil sends a pulse

of radio waves through the brain. This input

of extra energy makes the spare protons

flip out of alignment.

Radio signal emitted

Once the pulse is switched off, the

unaligned protons flip back into alignment with

the magnetic field. This causes them to release

energy as a radio signal, which is detected by

the machine.

3 4

Receiver creates image

All the signal data is then processed by

computer to create two-dimensional “slices”

of the brain. Protons in different body tissues

produce different signals, so scans can show

the tissues distinctly and in great detail.

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PET (positron

emission

tomography)

DOI (diffuse

optical imaging)

Cranial

ultrasound

TYPE OF SCAN TECHNOLOGY AND USES

Used in order to image the blood flow through the brain and highlight

active regions. PET scans track the location of radioactive tracers

injected into the blood.

An array of newer techniques that works by detecting how bright

light or infrared rays penetrate into the brain. DOI provides a way

of monitoring blood flow and brain activity.

A safe imaging technique that is based on the way ultrasonic waves

bounce off structures in the brain. Cranial ultrasound is mostly used

on infants. It is used less often in adults because the images lack detail.

LIQUID HELIUM

RADIOFREQUENCY COIL RADIOFREQUENCY COIL

RADIOFREQUENCY COIL RADIOFREQUENCY COIL

Radio-wave pulse

Additional proton flips into

different orientation

Radio signal

emitted

Flipped proton

realigns

Radiofrequency coil

detects signal and passes

it to computer

MONITOR

COMPUTER

Computer

processes

signal data

Image shows

tissues in

cross section

ELECTROMAGNET

GRADIENT MAGNET

RADIOFREQUENCY COIL

MRI SCANNER

Imaging certain brain features require particular scanning techniques,

which may also be used if MRI or CT are dangerous or unsuitable.

X-ray source

Person being

scanned

X-ray

CT scans detectors

Computer tomography (CT), or

computerized axial tomography

(CAT), takes a series of X-ray images

through the brain from different

angles. A computer then compares

the images to create a single cross

section of the brain. CT scans are

quicker than MRI and are best for

detecting strokes, skull fractures,

and brain hemorrhages.

Rotating X-ray

The X-ray source shines through the

brain, arcing around the patient to vary

the angle of each image.

OTHER TYPES OF SCANNING TECHNOLOGY

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