6.5

Question 1

Compton scattering

Answer 1

Effect where an X-ray deflected by interaction with an orbital electron has a longer wavelength than its initial wavelength. The electron is ejected from the atom at high speed.

Question 2

Attenuation

Answer 2

Gradual increase in intensity

Question 3

Attenuation coefficient

Answer 3

Constant used to calculate how the intensity of X-rays decreases as they pass through a material

Question 4

X-ray images

Answer 4

X-rays can be transmitted, absorbed or reflected when passing through a material. Dark areas on an x-ray image show where x-rays are transmitted with no reflection or absorption

Question 5

Computerised Axial Tomogrpahy

Answer 5

Process using multiple X-ray scans to produce images of ‘slices’ through the body in one plane, to produce a 3D image

Question 6

Tracer

Answer 6

Radioactive substance either ingested by or injected unto a patient. It emits gamma photons to be detected by a gamma camera

Question 7

Gamma camera

Answer 7

Detects gamma photons emitted from a patient given a radioactive tracer. This is used to produce real time images of the path of the tracer through the body

Question 8

Collimator

Answer 8

A device for producing a parallel-sided beam of electromagnetic radiation

Question 9

Scintillator

Answer 9

Material that produces many photons of visible light when struck by a high energy photon

Question 10

Photo-multiplier tube

Answer 10

Device used to give a pulse of electrons for each incident photon

Question 11

Positron Emission Tomography

Answer 11

use of gamma photons produced when positrons annihilate with electrons inside the body to map out biologically active area within the body

Question 12

PET scan tracers

Answer 12

Radioactive material (often Fluorine-18) attached to a biologically active molecule. This molecule will go predominantly to areas in the body that use it specifically or in large amounts and so are highlighted when scanned

Question 13

Ultrasound

Answer 13

Longitudinal waves above the audible range of sounds

Question 14

Transducer

Answer 14

A device which translates non-electrical signal into an electrical signal and vise versa

Question 15

Piezoelectric effect

Answer 15

Change in volume of a material when a p.d. is applied across its opposite faces. Alternatively it is the production of an induced e.m.f. when certain crystals are placed under stress

Question 16

Acoustic Impedance

Answer 16

Defined by the equation Z=pc (density of material * speed of sound in material). It is the amount a material affects the speed of sound through it.

Question 17

Impedance matching

Answer 17

Reduction in intensity of reflected ultrasound at the boundary between two substances, achieved when the two substances have similar or identical acoustic impedances