RAD03-2006 How do you limit the dose to patients and yourselves?

Question 1

What are the aims of radiation protection?

Answer 1

Prevent detrimental deterministic effects

Limit the probability of stochastic effects to acceptable levels

Question 2

What is the only way to eliminate the risk?

Answer 2

Not use X-rays at all

Question 3

What are the three principles of the International Commission on Radiological Protection ?

Answer 3

Justification: No practice should be adopted unless there is a net positive benefit
Optimisation: All exposures shall be kept as low as reasonably practicable
Limitation: The equivalent dose to individuals does not exceed the limit set by the commission

Question 4

How is the dose limited to patients with regards to equipment?

Answer 4

70kV
1.5mm aluminium filtration
Adjustable kV, mA and time
DC- constant potential
Long Fsd
Rectangular collimation
 (40mm x 50mm)

Question 5

How does 70kV reduce the dose?

Answer 5

Higher voltage so more high energy photons so less photons stop in the patient

Question 6

How does 1.5mm aluminium filtration reduce dose?

Answer 6

Removes lowest energy photons from beam

Question 7

How does adjustable kV, mA and time reduce dose?

Answer 7

Allows short exposure times

Question 8

How does DC reduce dose?

Answer 8

Ensures X-ray exposure is shorter

Question 9

How does long FSD reduce dose?

Answer 9

reduces size of the beam

Question 10

How does rectangular collimation reduce dose?

Answer 10

Reduces size of the beam

Question 11

How is the dose reduced in image receptors?

Answer 11

Fast film (E/F speed)
Rare earth intensifying screens
Digital detector system (solid state or phosphor plate)

Question 12

How does a faster film reduce the dose?

Answer 12

Short exposure film required

Question 13

How does rare earth intensifying screens reduce dose?

Answer 13

Fewer photons required to emit green light

Question 14

How does a digital detector system reduce dose?

Answer 14

Increased sensitivity so shorter exposure times

Question 15

What is the selection criteria for different caries risk level?

Answer 15

High caries risk: every 6 months
Medium caries risk: every year
Low caries risk: every 2 years

Question 16

What radiographic techniques can reduce dose?

Answer 16

Use image receptor holders with beam aiming devices to produce geometrically accurate images
Take minimum number of images
Avoid retakes
Use lead apron

Question 17

How can risk to staff be reduced?

Answer 17

Always stay at least 2m away from X-ray machine and patient or behind a protective screen
Never stand in line with the main beam
Always stand outside the controlled area
never hold the X-ray film packet in the patient’s mouth
Never hold X-ray tube head during an exposure

Question 18

How is dental staff members radiation exposure measured?

Answer 18

Thermoluminescent dose meter film badge

Electronic personal dosemeter