general
What are darker grays on images?
*ex: oxygen
keV
What is kilo Electron volts?
*electron binding energy measured in keV
*moderate energy photons (20-40 keV) involved in Compton scattering
mm Al/Eq
What is millimeters of Aluminum Equivalency?
*used to express x-ray filtration
According to this formula, as distance increases, exposure decreases with an inversely proportional relationship
What is Inverse Square Law (ISL)?
Scatter that reaches the IR
What is fog?
Wavelength and frequency have this type of relationship
What is inversely proportional?
*ex: increase in wavelength = decrease in frequency
Sv
What is Sievert?
*SI unit used to measure equivalent dose and effective dose for occupational exposure
*Traditional unit - Rem
mAs
What is milli-Ampere seconds?
*measure of radiation produced over a set amount of time
*controls x-ray quantity
This formula is used to calculate mAs
What is:
mAs = mA x s
mA = mAs / s
s = mAs / mA
Interaction most responsible for production of scatter, and therefore image fog and occupational exposure
What is Compton Scattering?
*involves middle and outer shell electrons
*involves moderate energy
*as kVp increases, so does Compton
Comprised of 2 protons and 2 neutrons; doesn't travel far, so causes ionization quickly
What are Alpha Particles?
*charge is +2
*mass number is 4; atomic number is 2
*most harmful particulate as an internal source (inhaled, swallowed, absorbed into bloodstream)
C/kg
What is Coloumb/kilogram?
*SI unit primarily used to measure patient exposure/ESE for fluoro exams
*measures Exposure (quantity of ionizations in air)
*Traditional unit - Roentgen (R)
kVp
What is kiloVoltage peak?
*used to measure electric potential
*increased kVp will increase Compton scattering
*controls x-ray quality
In this formula, the adjustment to kVp causes mAs to either be doubled or halved
What is the 15% Rule?
*ex: 80 kVp @ 20 mAs; REDUCE kVp by 15% and DOUBLE mAs = 68 kVp @ 40 mAs
*ex: 80 kVp @ 20 mAs; INCREASE kVp by 15% and HALVE mAs = 92 kVp @ 10 mAs
Total filtration includes the following
What are Inherent and Added Filtrations?
*typical amt of total filtration is 2.5 mm Al/Eq
The most common x-ray filtering material
What is Aluminum?
*lower atomic # absorbs low energy x-rays but allows higher energy x-rays to transmit through
MeV
What is Mega electron Volts?
*higher energy found in pair production (1.02 MeV) and photodisintegration (>10 MeV)
PBL
What is Positive Beam Limitation?
*restricts exposure field size to IR size
To convert between units (ex: kVp to V), the decimal will move this many places
What is 3 places?
*kilo base milli
--------> <------
This type of radiation has a low energy, originates within the patient, and cannot be completely eliminated
What is scatter radiation?
*does not accurately represent anatomy on images
*can cause fog and decrease image quality
Interaction in which the x-ray photon loses all of its energy and ionization occurs
What is Photoelectric Interaction?
*inner shell electron is ejected
*cascade effect occurs
Gy
What is Gray?
*SI unit used to measure absorbed dose for fluoro exams or if pregnant patient was exposed
*measures AirKERMA
*Traditional unit - Rad
GCF
What is Grid Conversion Factor?
*used to determine the mAs needed when grid use/nonuse or ratio changes
*aka Bucky Factor
Ratio of the height of lead strips to the distance between the lead strips
What is Grid Ratio?
*grid ratio = height/width of interspace
What is Angulation Error?
*beam divergence doesn't match angle of the lead strips
*results in grid cutoff across the entire image