REVISION

Question 1

fsd for machines using more than 60kv

Answer 1

200mm

Question 2

fsd

Answer 2

focal spot in x ray tubehead to patient skin

Question 3

name 4 effects/ artefacts that may be seen on dental radiographs

Answer 3

ghost images
double shadows
cervical burnout
mach band effect

Question 4

what interactions of radiation do x rays contain

Answer 4

continuous and characteristic radiation

Question 5

what names are given to the 2 interactions of radiation and patient tissues

Answer 5

compton effect
photoelectric effect

Question 6

breifly discuss these aspects of an x ray tubehead
- anode
- cathode
- glass envelope
- aluminium sheet
- spacer cone
- collimator

Answer 6

• anode (+ve) - tungsten target and copper heat dissipating block
• cathode (-ve) - tungsten filament and molybdenum focusing cup
• glass envelope - leaded glass to absorb excess photons
• aluminium sheet - absorbs low energy photons
• spacer cone - dictates fsd
• collimator - lead diaphragm to match beam to receptor

Question 7

what is the biologic effects of radiation dependent on (3)

Answer 7

• tissue type irradiated
• type of radiation
• amount of radiation (dose)
• time over which dose received

Question 8

what is tissue radiosensitivity dependent on

Answer 8

function of cells making up tissue
are the cells actively dividing

Question 9

what are the two types of radiation effects on tissues

Answer 9

1. deterministic - rare in radiology, only occur above a certain threshold e.g hair loss after radiotherapy
2. stochastic - no minimum threshold, increased dose means increased risk. either somatic (disease) or genetic impact

Question 10

what are the two types of digital receptor

Answer 10

phosphor plate
solid state

Question 11

solid state vs phosphor plate receptors

Answer 11

PP - lighter, flexible, thinner, cheaper
SS - more durable, no scanner needed, expensive

Question 12

what tool can be used to check radiograph image quality / contrast

Answer 12

step wedge (varying layers of lead foil)

Question 13

what are the 3 main aims of IRMER

Answer 13

• minimise unintended, excessive or incorrect exposure
• justify exposures (benefit>risk)
• optimise doses (ALARP)

Question 14

what does IRMER stand for

Answer 14

ionising radiation medical exposure regulations
in place to protect patients

Question 15

what does IRR stand for and who does it serve to protect

Answer 15

ionising radiation regulations
aims to minimise radiation exposure to staff and public

Question 16

What do IRR and IRMER detail

Answer 16

IRR - legal duties when using ionising radiation in workplace
IRMER - legal duties when exposing patients to ionising radiation

Question 17

radiation protection advisor

Answer 17

competent person to advice on radiation protection

Question 18

what bodies published guidance on safe use of x-ray equipment and simplifies info from IRR and IRMER17

Answer 18

dental public health england
faculty of general dental practice UK

Question 19

dose monitoring - max staff dose anually

Answer 19

1 miliesievert

Question 20

contingency plans

Answer 20

immediate actions should a reasonably forseeable accident occur
e.g emergency stop on panoramic mahcine if machine not rotating but patient being irradiated

Question 21

how often should digital radiograph receptors be checked using the 3 main checks

Answer 21

3 monthly

Question 22

3 main checks for digital radiograph receptors

Answer 22

1. visual condition of receptor
2. image uniformity - is image from unattenuated beam a uniform colour
3. image quality - radiograph of test object and compare to base line

Question 23

dental radiographic implications of pagets disease

Answer 23

hypercementosis
loss of lamino dura
migration due to bone enlargement

Question 24

potential radiographic finding in patients with hyperparathyroidism

Answer 24

brown tumours