Diagnostic imaging

Question 1

CR

Answer 1

• computed radiography

- used to show moving images

Question 2

CT

Answer 2

• computed x-ray tomography

- makes images of sections through body

Question 3

scintigraphy

Answer 3

uses gamma rays which are injected to show metabolism

Question 4

MRI

Answer 4

• magnetic resonance imaging

- uses radiowaves to image things like the brain or spinal cord

Question 5

ultrasound

Answer 5

shows echogenicity of tissues

Question 6

2 types of x-ray image

Answer 6

positive and negative

Question 7

bone colour of positive x-ray images

Answer 7

dark

Question 8

bone colour of negative x-ray images

Answer 8

white

Question 9

how x-rays are made

Answer 9

by electrons colliding into a heavy metal (e.g. tungsten)

Question 10

where are x-rays produced

Answer 10

x-ray tube

Question 11

components of an x-ray tube

Answer 11

glass or metal envelope, -ve cup shape behind the filament, +ve tungsten target with copper behind it.

Question 12

how are x-rays produced in x-ray tube

Answer 12

electorns are fired of by filament and aimed by -ve cup shape at the tungsten target. x-rays are angled down towards patient by angle of tungsten target

Question 13

function of copper behind tungsten target in x-ray tube

Answer 13

conducts heat away from tungsten target

Question 14

colimator (radiography)

Answer 14

found under the x-ray tube it shapes the x-ray beam

Question 15

x-ray absorption depends on

Answer 15

density and thickness of tissue and the atomic number of element sin the tissue

Question 16

5 types of tissue seen radiographically in order of absorption

Answer 16

air, fat, soft tissue, bone and metal

Question 17

what colour does air show up on radiograph

Answer 17

lucent/black

Question 18

colour of bone on radiograph

Answer 18

white/opaque

Question 19

2 types of contrast medium in radiograph

Answer 19

positive and negative

Question 20

positive contrast medium colour on radiograph

Answer 20

radiopaque (white) as it absorbs lots of x-rays

Question 21

example of positive contrast mediums radiograph

Answer 21

iodine, or barium sulphate (GIT)

Question 22

negative contrast medium colour radiograph

Answer 22

radiolucent (black) as absords no x-rays

Question 23

example positive contrast medium radiograph

Answer 23

gasses (air)

Question 24

radiograph mAs

Answer 24

• milliamperes per second

- number of electrons passing accross the x-ray tube

Question 25

increasing mAs

Answer 25

increases number of x-rays produced so more will get through and you can decrease exposure time and so reduce motion blur

Question 26

kVp radiograph

Answer 26

- kilovoltage peak | - peak voltage applied accross the x-ray tube

Question 27

increaseing kVp radiograph

Answer 27

increases the energy of the beams so more get through

Question 28

values low kVp

Answer 28

45-60

Question 29

value middle kVp

Answer 29

65-75

Question 30

values high kVp

Answer 30

over 80

Question 31

x-ray machine button

Answer 31

- has 2 stages - 1st stage prepares machine - 2nd stage sends the beam

Question 32

x-ray sunburn

Answer 32

caused by low energy x-rays

Question 33

preventing x-ray sunburn

Answer 33

aluminium sheet filters out low energy x-rays

Question 34

effects of scattered radiation on the image

Answer 34

makes image grey, fuzzy and indistinct

Question 35

4 things that reduce radiation scattering

Answer 35

- use colimator to reduce volume of tissue being irradiated - put a layer of lead between table and cassette - increase kVp to make beams go through patient better - use an x-ray grid to reduce scattered radiation getting to cassette

Question 36

what needs to be done to compensate for use of x-ray grid

Answer 36

increase mAs by the grid factor

Question 37

appearance of x-ray grid

Answer 37

thin lead strips parallell to 1* beam. about 24 per cm

Question 38

roentgen

Answer 38

- ability of radiation to ionise the air | - measured in couloms per kg of air (C/kg)

Question 39

becquerel

Answer 39

- Bq - rate of radioactive decay - measured as disintegration per second

Question 40

gray

Answer 40

- Gy - absorbed dose of radiation - measured in joules per kg of tissue (joule/kg)

Question 41

sievert

Answer 41

- Sv - dose equivalent radiation - measures the effect of radiation - = gray x quality factor

Question 42

max dose of radiation for people at work

Answer 42

20 mSv per year

Question 43

Sv measured by

Answer 43

film badge or thermoluminescent detector (TLD)

Question 44

ALARA (radiation)

Answer 44

- as low as reasonably possible | - radiation wise it should be ALARA

Question 45

you can achive ALARA radiation in 5 ways

Answer 45

- wear lead aprons and gloves - keep as far away from the source as possible - use lead mobile barriers or walls - do things at arms length - have a long line for the exposure button

Question 46

controlled area of radiation

Answer 46

- is the area immediately around the 1* beam in which the radiation dose exceeds permissible limit - usually 2 metre radius around 1* beam - needs warning signs around it

Question 47

radiation protection adviser

Answer 47

- person who inspects radiography facilities in an area and writes reports on improvements - also sets local practice rules

Question 48

radiation protection supervisor

Answer 48

- person in practice - responsible for notifying health and safety executive theat radiography is performed at the practice - responsible for following local rules - looks after dosimeter readings - reports radiography problems