RAD03-2006 How do you limit the dose to patients and yourselves? Flashcards
What are the aims of radiation protection?
Prevent detrimental deterministic effects
Limit the probability of stochastic effects to acceptable levels
What is the only way to eliminate the risk?
Not use X-rays at all
What are the three principles of the International Commission on Radiological Protection ?
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
How is the dose limited to patients with regards to equipment?
70kV 1.5mm aluminium filtration Adjustable kV, mA and time DC- constant potential Long Fsd Rectangular collimation (40mm x 50mm)
How does 70kV reduce the dose?
Higher voltage so more high energy photons so less photons stop in the patient
How does 1.5mm aluminium filtration reduce dose?
Removes lowest energy photons from beam
How does adjustable kV, mA and time reduce dose?
Allows short exposure times
How does DC reduce dose?
Ensures X-ray exposure is shorter
How does long FSD reduce dose?
reduces size of the beam
How does rectangular collimation reduce dose?
Reduces size of the beam
How is the dose reduced in image receptors?
Fast film (E/F speed) Rare earth intensifying screens Digital detector system (solid state or phosphor plate)
How does a faster film reduce the dose?
Short exposure film required
How does rare earth intensifying screens reduce dose?
Fewer photons required to emit green light
How does a digital detector system reduce dose?
Increased sensitivity so shorter exposure times
What is the selection criteria for different caries risk level?
High caries risk: every 6 months
Medium caries risk: every year
Low caries risk: every 2 years
What radiographic techniques can reduce dose?
Use image receptor holders with beam aiming devices to produce geometrically accurate images
Take minimum number of images
Avoid retakes
Use lead apron
How can risk to staff be reduced?
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
How is dental staff members radiation exposure measured?
Thermoluminescent dose meter film badge
Electronic personal dosemeter
