Test 2 Flashcards
T/F: energy does not vanish, it changes - transits from one state to another
TRUE
xrays are a type of _____ energy
electromagnetic energy
along with radiowaves, microwaves, UV, infrared
the imaging system creates electromagnetic energy by converting ______ to ______
electrical energy to xray photons
_____ is energy in transit
radiation
in the form of waves or particles
what intercepts/absorbs with radiation then the radiation is said to be exposed
matter
radiation when an electron is removed from its orbital
ionization
reduced with negative charge electron and positively charged atom
ion pair
what 3 rays/lights are capable ionizing matter
xray
gamma ray
UV light
what 6 waves/light are not capable of ionizing matter
microwave
radiowave
UV
radar
cell phone
ultrasound
radiation:
short freq vs long freq
short freq - greater energy
long freq - less energy
natural sources of radiation
radon and cosmic
man made radiation
medical imaging
____ rays are particulate radiation
cosmic
what is the largest natural radiation
radon gas
who created the xray and when did he do it
willhelm roentgen
Nov 8, 1895
x ray properties
no charge
penetrate most matter dependent on atomic number
ionization and biological effect
make compound fluoresce and emit light
travel at speed of light
what are the 3 major components of the imaging system
xray tube
operating console
high voltage generator
xrays are emitted ______ or in all directions
isotropically
negative end of the xray tube composed of heat resistant filament made of thoriated tungsten
cathode
______ : initially low electrical current heats the filament - when the temp becomes high enough the electrons boil off and are ejected from the filament - ______
filament current
thermionic emission
most electrons emitted by the cathode are driven back by repulsion of the cloud of electrons
space charge effect
cathodes filaments are embedded in _____, accelerates electron beam towards the anode target known as the focal spot
metal focusing cup
focusing cup is ____ charged
negatively
area of anode surface which receives the beam of electrons from the cathode
focal spot
all electrons accelerated from ___ to ___ are negatively chargd
cathode to anode
2 focal spots on anode corresponding to large or small filament of cathode
dual focus
_____mA or more is used for large body part
400
_____mA or less is used for smaller body parts
400
_____ is the positive charged end of the xray tube
anode
target for xray photons, rotates and dissipates heat during xray
anode function
small focal spot allows for greater resolution of image, small focal spots are unable to dissipate heat - if you angle focal spot 5-15* it will allow for larger area of heat dissipation whiole maintaining small focal spot
line focus principle
reduces potential heat damage to the tube by rotating and dissipating heat
anode
anode side must always face the thinner body part in order to maintain uniform tissue exposure
anode heel effect
electrons that have bounced off and landed outside the focal spot - may contribute to increase in patients dose
extrafocal or off focus radiation
will NOT reduce extrafocal radiation because it is not scatter radiation
grid
modifies incoming voltage and to provide xray tube with power needed to produce an xray beam - converts voltage to kilovoltage
xray generator
permits selection of technical factors and initiates the radiograph - allows you to select a given mA, kV, and time
control panel or operators console
modifies the voltage incoming alternating current electrical signals to increase or decrease voltage in a circuit
transformer
supplies the high voltage to xray tube - voltage increases and current decreases - creates higher voltage potential to ensure greater xray beam energry
step up transformer
supplies power to heat filament of the xray tube - voltage decreases and current increases - creates lower voltage with increased cathode filament current and greater heat - responsible for high number of electrons emitted from cathode
step down transformer
converts alternating current into direct current required by xray tube
rectifier
restricts current flow in xray tube to one direct from cathode to anode only - prevents damage to xray filament
rectifier
what are the two types of rectifiers
half wave
full wave
closed core transformer, autotransformer, shell type transformer
electromagnetic induction
converts alternating current to direct current to ensure sustained flow of electrons to minimize ripple and flunctuation in current
voltage rectification
provides constant potential voltage waveform, which doubles the radiation improving the image quality - also minimizes patient dose
high frequency power generator
special highly insulated cables - affects the average value of voltage and current across the xray tube - increase power delivered to xray tube
high tension voltage cables
beam restrictive lead lined device - used to reduce patients dose by restricting the xray beam
collimator
aluminum filters placed at the exit port of the xray tube - primary role is to harden the beam - also removes or absorbs the xrays of lower energy
filtration
aims at patient - helps identify the central ray position and bounded exposure area - cross hair of collimator light = central ray of xray beam - aimed at midpoint of anatomic area
collimator light
control panel which allows the operator to select appropriate factors such as mA, kvp, and time
operators console
adjustable and floatable - allows for better positioning
xray table
contains grid which removes scatter radiation and improves image quality - contains cassette holder with film and cassette
bucky system
composed of plastic exterior with inserted double sided intensifying screens
casettes
made of rare earth elements such as gadolinium oxysulfate - screens emit light photons when interacting with xrays in order to reduce the patients dose - minimizes the number of xray photons during film exposure
intensifying screens
composed of polyester and coated with emulsion containing silver halide crystals
radiographic film
when exposed to xrays the crystals turn into metallic silver which blackens the film in contrast to the white or unexposed areas corresponding to body parts that have absorbed xrays
silver halide crystals
image plate is used made up of photostimulable phosphor located inside cassette
computed radiography
NUHS used ______ radiography
computed
no cassettes requires - time efficient and lower radiation
digital radiography
_______ manual processing takes an hour to process
______ takes 3 min
______ processing takes less than a min
radiographic processor - hour
automatic processing - 3 min
computed tomography - 1min