Instrumentation for brain function X Ray equipment transmits high energy

electromagnetic waves and indicates relative tissue density on a photographic plate Eg Cerebral angiography, Cranial XRays, Brain

Scans, CT Scans Ultrasonic equipment transmits high

frequency sound waves and indicate tissue location by reflecting waves

Electrophysiological equipment detects low voltage, low freq bioelectric signals that are picked up by electrodes

Cerebral angiography X-Ray technique to display brain structure

and detailed images of blood vessels with the aid of a contrast medium

Radio opaque dyes that block X-Rays are injected in an artery and dispersed throughout the cerebrovascular tree

X-Ray images are taken at 1 sec intervals and can reveal blockages and tumors

Nuclear medicine Small amounts of short lived

radioactive isotopes are introduced into the cardiovascular system

The concentrated radioactivity is measured with a scintillation counter

Counter responds to impinging alpha, beta or gamma rays given off by the radioactive material

Cranial X-Rays 2 dimensional X-Ray exposures

taken of the cranium Used to indicate fractures in

cranial bones and blood clots or tumors

Positive diagnosis can be made only when the contrast is high

Brain scans Radiographs that are taken through

successive scanning Highly collimated X-Ray beams are

used Small contrast differences can be

seen Provide considerably more info than

simple cranial X-Ray exposures

Computed Tomography CT scanning – technique of

recording and processing a set of image projections that represent a reconstruction of the object scanned Scanning system Processing unit Viewing part Storage unit

Computed Tomography To identify structural abnormalities (such

as abscesses, tumors, and hydrocephalus) in the brain

To identify bleeding or evidence of strokes in the brain

To identify ruptured or herniated disks in the spine

To identify spinal fractures To monitor the effects of radiation

therapy on brain cancer or of antibiotics on a brain abscess

EEG The electroencephalogram (EEG) is

a recording of the electrical activity of the brain from the scalp.

The first recordings were made by Hans Berger in 1929 although similar studies had been carried out in animals as early as 1870.

Neuron Membrane potentials

Electroencephalography The EEG is recorded between electrodes

placed in standard positions on the scalp and has a typical amplitude of 2-100 microvolts and a frequency spectrum from 0.1 to 60 Hz.

Most activity occurs within the following frequency bands; delta (0.5 - 4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-22 Hz) and gamma (30-40 Hz).

EEG Frequency band <100uV <10uV <20uV

<2UuV

EEG EEG activity in particular frequency

bands is often correlated with particular cognitive states.

Signals in the alpha band, for example, are associated with relaxation. Thus, an electrode placed over the visual cortex that detects alpha band signals is detecting visual relaxation.

An electrode over the motor cortex picking up alpha band signals is detecting motor relaxation

EEG electrodes EEG electrodes transform ionic

currents from cerebral tissue into electrical currents. Electrodes used are Scalp Sphenoidal Nasopharyngeal Electrocorticographic Intracerebral

10-20 EEG electrode placement system

EEG Machine (8 channel)

EEG Telemetry system