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

THE PHYSICAL BRAIN

Imaging the Brain

Imaging the Brain

Modern medicine and neuroscience can see through

the skull to observe structures within the living brain.

However, imaging this soft and intricate organ has

required the invention of advanced technology.

MRI scanners

A magnetic resonance imaging (MRI)

machine gives the best general view

of the brain’s nervous tissue and is

most often deployed to search for

tumors. MRI does not expose the

brain to high-energy radiation, unlike

other scanning systems, which makes

it safe to use for long periods and

multiples times. Two refinements

of MRI, called fMRI and DTI, are

also useful for monitoring brain

activity (see p.43). Although ideal as

a tool for research and diagnosis, MRI

is expensive. With its liquid-helium

coolant system and superconducting

electromagnets, one machine also

uses the power of six family homes.

Protons unaligned

Before the MRI machine is

activated, the protons in the brain’s

molecules are unaligned—the axes

around which the particles are spinning

point in random directions.

How MRI works

MRI makes use of the way that protons in

hydrogen atoms align to magnetic fields.

Hydrogen is found in water and fats,

which are both common in the brain.

A scan takes about an hour, then the data

is processed to create detailed images.

Protons align to magnetic field

Activating the machine’s powerful magnetic

field forces all the protons to align with each other.

Approximately half face the field’s north pole, and

half face south. However, one pole will always have

slightly more protons facing it than the other.

1 2

THE ELECTROMAGNET

IN AN MRI SCANNER

CAN GENERATE A

MAGNETIC FIELD

40,000 TIMES AS

STRONG AS EARTH’S

Radiofrequency coil

emits and detects

radio waves

Liquid helium cools

electromagnet to

about –453°F (–270°C)

Layer of thermal

insulation keeps

liquid helium cold

Gradient magnets focus

magnetic field around area

to be scanned

Motorized

table moves

patient into

scanner

Patient lies inside body of

scanner during scanning

Superconducting

electromagnet generates

extremely strong magnetic field

LIQUID HELIUM

ACTIVE

ELECTROMAGNET

INACTIVE

ELECTROMAGNET

ACTIVE

ELECTROMAGNET

INACTIVE

ELECTROMAGNET

Protons

aligned

randomly

Magnetic

field line

Proton faces

south

Additional

south-facing

proton

Proton faces

north

ELECTROMAGNET

GRADIENT MAGNET

RADIOFREQUENCY COIL

MOTORIZED TABLE

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