Questions Flashcards
frequency and wavelength are directly proportional eachother
true
in vacuum velocity of radio waves is equal to the infrared light
true
in vacuum they all travel at the speed of light.
visible light has a shorter wavelength than UV light
false
UV light is further up the spectrum and therefore has a shorter wavelength.
electromagnetic radiation includes beta particles
false
beta particles are emitted from the nucleus.
velocity of electromagnetic adiation increases as energy increases
False
The frequency increases as the energy increases, the velocity is constant.
Ionising radiation may require only to be shielded with Perspex
Beta radiation may require only Perspex shielding, optimal shielding is achieved with Perspex backed with lead.
Re secondary electron
They can interact with inner shell electron causing ionisation
False
They interact with outer shell electron
In radioactive decay
Emission of beta- particle reduces atomic no by 1
False
N–> p+ B-
Z +1
In radioactive decay
Positron emission reduces the number of protons by 1
True
P= n+ B+
Z-1
Re radioactivity
If stored long enough the radioactivity will drop to zero
True
Although decay is an exponential process, all of the atoms will eventually decay
Gamma rays are emitted at a single photon energy
False
More than one photon energy may be emitted
Direct emission from radioactive decay includes
Beta minus Characteristic x Ray Bremsstrahlung Alpha particle Positron emission
True True False True True
Radiation output from x Ray tube increases with:
Increasing cathode to anode distance
Addition of filter
Increasing kv
Increasing mA
A constant potential compared to a single phase waveform
False- no relation False- decreases total output True- output ~kv2* True- output~ mA True- kv is near its max for longer
In x Ray tube the anode angle is generally 20-30 degrees
False
The angle is generally 7-20
The spectrum of the x Ray beam
Is not affected by filtration
Varies with tube current
Has a max energy determined by peak tube potential kvp
Consists of bremsstrahlung and characteristic radiation if kvp exceeds the k edge energy of the anode
False. Filtration removes low energy photons hardening the beam and increasing the mean energy of the spectrum
False. Increasing mA increases no of photons. The shape of spectrum remains the same if kv is unchanged
True.
True. Bremsstrahlung is the continuous spectrum and characteristic radiation the peaks specific to anode material
Re x ray tube filament
It must have a high melting point and low resistance
False
High melting point and high resistance to generate heat for thermionic emission
The anode heel effect is more noticeable at the cathode end of tube
False
It’s anode heel effect
Increasing tube kv increases:
Patient entrance surface dose Scattered compared to primary radiation at the film Radio graphic contrast Film blackening Photoelectric compared to Compton
True
True. Higher kv x Rays are more penetrating
False. Contrast decreases as kv increases
True. Increased kv = increased exposure and increased film density
False. At higher kv Compton are favoured
Attenuation of x Rays
Increased tube filtration increases the HVL
True
Total beam hardening
HVL
Is a measure of penetrating power of x ray beam
For lead is greater than for Al
Is reduced as the photon energy of radiation decreases
Will produce exponential attenuation
True
False. The hvl decrease as the atomic number increases
True
True
The MAC is less for water than for ice
MAC measured incm2*/g
False
It is equal for water a ice as it is independent of physical density
LAC
it is the fractional reduction in intensity per unit thickness
It increases as the photon energy increases
It is measured in mm
True
False , it decreases as the photon energy increases
False, 1/mm
Re scattered radiation
More is measured in the Tyneside of patient.
During a Compton interaction a photoelectron is produced
At higher kv more photons are deflected through large angles
True- most interaction occurs at the entrance surface of patient and forward scattered are more attenuated than back scattered ones.
False. These are formed in photoelectric int.
False. There is slight increase in forward scatter as kv increases, therefore there are more small angle deflections.
Re photoelectric process
It may result in scattered radiation
False
There will be complete absorption
Re absorption edge
At photon energies just above the k shell binding energy of an element there is a sharp decrease in the probability of photoelectric interaction
False
There is a sharp increase in the probability is photoelectric interaction
Re absorption edge
An X-ray filter does not transmit photon well if they are of an energy equivalent to its own k absorption edge
False
It will be transparent
