Physics Chapter 6 Test Flashcards
Know the 2 ways filament electrons interact with target atoms to produce x-rays?
Characteristic interaction and bremsstrahlung interactions
How do characteristic photons get their name?
Their energy is “characteristic” or dependent on the difference in binding energy between the shells involved
Know why medical imaging generally focuses on the K shell
It has the highest energy and the most useful for imaging purposes
Know how you remove orbital electrons during characteristic interactions
the filament electron must have kinetic energy equal to or greater than the binding energy of the electron with which it interacts
Describe what happens during a bremsstrahlung interaction
A filament electron is attracted to the nucleus causing it to slow down and change direction. The energy loss is emitted as a bremsstrahlung photon
Know what the strength of the interaction depends on with a brems interaction
How close the filament electron passes to the nucleus
Know how to find the energy of a brems photon
Subtracting the energy that filament electron leaves the atom with from the energy it had upon entering
Know the 4 technical factors that affect beam quantity
mAs
KVP
Distance
Filtration
Know what you should always associate beam quantity with
Radiation dose
Know what is directionally proportional with beam quantity?
mAs
Know what is considered the primary controlling factor for beam quantity
mAs
Know how beam quantity varies
Square of the ratio of the change in kVp
Know what a 15% increase in kVp is equivalent to
Doubling the mAs
Be able to work a problem using the Inverse Square Law
I1/I2= D2^2/D1^2
Know how filtration affects beam quantity
Decreases
Know what it looks like on an image when photons reach the IR
dark shades of the image
Know what image looks like when no photons reach the IR
light or clear areas of the image
Know what affects beam quality
kVp and filtration
Know what the purpose filtration serves
To remove the lower-energy photons, making the average energy (quality) higher
Know how beam quality is measured
half value layer
Know how to find half value layer
First measuring the intensity of the beam with a radiation detector, then placing aluminum filters of known thickness between the tube and detector until the intensity reading is reduced to half the original value
Know the normal HVL range for general diagnostic beams
3-5 mmAC
Know how the characteristic photons are named (2)
for the shell being filled
Know why a brems photons energy depends on the strength of attraction
Because brems photons are the result of the filament electrons attraction to the nucleus
Know what the most common range of energy of a brems photon is
just above zero to max kVp
Know what shape a brems photon graph represents
bell shape
Know what the left and right side of the curve represents for a brems photon graph
left just above zero, right-touches the x axis at the kVp selected
know what the peak of a brems photon graph represents
one third of the kVp selected
On the emission spectrum changes in the following indicate:
a. y axis
b. X axis
Y Axis- changes in quantity
X axis- changes in quality
Know what the five factors are that change the appearance of the xray emission spectrum
mA, kVp, tube filtration, generator type, and target material
Know what changes in mA affect (include discrete line)
Affect beam quantity but has no affect on quality and does not change the position of the discrete line
Know what changes in kVp affect ( include the discrete line)
Affect beam quality and quantity but does not change the position of the discrete line
Know what tube filtration affects when all other factors remain the same
Decrease in Quantity
Increase in quality
Know what the changes in generator type can affect
Change the xray production efficiency
Know why high frequency generator units are used over single phase units
more efficient in producing xray than single phase units
Know what happens when a generator operates more efficiently
More filament electrons have the energy to produce xrays, increasing quantity (amplitude of curve)
Know what happens as the atomic number of the target material goes up
As it goes up, so does the average energy, quantity of photons, and the position of the discrete line of the spectrum.
