1. XR Production Flashcards
Describe nomenclature for elements
X: chemical symbol for atom
A: mass number (protons + neutrons)
Z: atomic number (protons)
How does atomic number influence binding energy?
increase Z, binding energy
what is binding energy?
energy required to free an electron from a shell
How does distance between nucleus and electron impact binding energy?
decreases binding energy
Describe elecromagnetic radiation?
wave of energy that can travel in vacuum, travels at 3 x 10 to the 8 m/s
Describe relationship of frequency and wavelength
inverse
Frequency
cycles/second
wavelength
distance between peaks
energy required to become ionizing radiation
15 ev
small wavelength = ? energy
high
gamma rays
emitted by nucleus; given during atom decay
x-ray
interactions between electrons/atoms
alpha particle and net charge
2 protons, 2 neutrons; net charge 2+, very attractive to electrons
beta particle
electron ejected from nucleus
isotopes
element with different number of neutrons and mass number A; same Z
maximum number of electrons that a shell can hold
2n to the second power
which shell has the higher binding force?
innermost shell, K > L > M
what is the kinetic energy of bound particles?
negative, most negative potential in the innermost shell
at what kinetic energy can the electron break free or reach binding energy?
0
synonym for binding energy
ionization potential; energy needed to remove electron from atom
what can increase/decrease binding energy?
increase: more protons
decrease: farther distance from nucleus
characteristic energy of an emitted x-ray/photo depends on?
atom involved and electron shell involved
Why is tungsten filament used ?
1) high melting temperature (>2000 degrees) so electrons can be “boiled off” thermionic emission;
2) high atomic number makes it a good the thermionic emitter
tungsten filament is anode or cathode?
cathode, negative end; slight positive charge so electrons go to anode
3 ways electrons lose kinetic energy
excitation, ionization, radiative losses (Bremsstrahlung)
electron cloud around the filament
space charge
Space Charge effect
space charge limits the emission of electrons
milliampere, mA
unit used to describe current; quantity of electrons moving from cathode to anode; electrons/sec moving from filament to target
effect of doubling mA
doubles the xrays
KvP affects quality or quantity?
both
mA affects quantity or quality?
quantity
goal of focusing cup?
keep electrons together as their negative charge will keep make them spread/separate
Why does the anode rotate?
to disperse heat over larger surface area as the xrays hit it; prevent anode from melting; it is usually connected to a molybdenum stem
what is the focal spot?
target zone for electrons from the cathode filament
apparent/effective focal spot vs actual focal spot
actual: where electrons land
apparenet: where x-rays land on patient (affects blur)
smaller anode has better/worse spatial resolution?
better
downside of small anode
can’t disperse heat, more prone to melt; can get around by angling anode or rotating anode
mammo focal spot
0.3-0.1 mm
xray focal spot
0.6-1.2 mm
portable x-ray device uses rotating vs stationary anode?
stationary
small focal spot results in ?
best resolution; lower heat tolerance
Line Focus Principal
angling target (anode) will keep actual focal spot large but effective focal spot small
small angle = ___ effective focal spot = ___ heel effect
small, greater (heel cut off)
Heel effect
loss of xray energy due to angling of target
smaller angle = ___ heel effect
worsening, loss of energy
highest intensity in heel effect is on the ____ side
cathode side (used in mammo); cathode is against the chest wall
vertical orientation with a CXR with cathode at lung bases/lower thoracic spine
larger focus to film distance, the _____ the heel effect
less
smaller film = ____ heel effect
less; central beam is most uniform
how does increasing Z impact Bremsstrahlung curve?
increase atomic number increases overall xrays produced; increases quantity; no change in characteristic peaks or quality
How does kVP influence quantity/quality?
increase, quantiy increases as a square of kvp
kvp define
maximum or peak energy of electron stream
what is the relationship between mA and quantity?
direct; increasing mA increase electrons
15% rule?
increasing kVP by 15%, decrease mA by 1/2 to maintain same xray intesnsity
decrease kVP 15%, double mA
single vs three phase generator for kVP?
triple phase is better at keeping kVP constant, but peak of curve is still not changed; triple phase has less ripple (more quantity/quality)
half value layer
amount of material attenuates x ay to half original output; depends on photon energy ; each consecutive HVL is greater than the last since the weaker photons are shifted out
HVL on quality and quantity
increases quality (filters out weaker photons) decreases quantity (filters out weaker photons)
what is the 10th HVL?
thickenes of material that can attenuate 90% of xrays, used for shielding calculations
