S2 L3 Flashcards
Bremsstrahlung
E- interact with nucleus of target atoms and give up energy
Characteristic radiation
E- interact with e- in shell of target atoms
Overcome bound e- binding energy
Vacancy filled by e- from another shell
Alpha vs beta characteristic radiation
Beta = m-k shell
Alpha = l-k shell
X-ray beam quality
Hard is more penetrative
Soft is more absorbed
What is the threshold for Characteristic radiation
70kVp
What is kV / tube voltage
Potential difference between anode and cathode
What is mA / tube current
Current flowing between anode and cathode
What is ms / pulse duration
Time which current flows
What is mAs
Current x time
What is X-ray beam intensity
Number of photons per unit area
What is X-ray beam energy
Energy of the photons
How many photons have each energy
How does Increasing kV affect X-ray
Increase beam intensity, average energy and max energy
Not linear
Characteristic X-ray made
How does increasing mA affect X-ray
Increase beam intensity linear
Doesn’t change average energy, maximum or minimum energy
How Does filtration thickness affect X-ray
Increase average energy
Decrease intensity
Lower energy photons more likely to be absorbed
What is entrance surface dose/air kerma
Radiation concentration delivered to a point
Measure amount of radiation energy in J deposited or absorbed in a unit mass of air
Why is air Kerma an estimate of patient dose
Energy deposited in air similar to water which we are mostly made of
Don’t use to indicate risk
What is inverse square law
As distance increases X-ray beam diverges
Intensity decreases by square of distance
E.g distance double intensity quarters
