x ray physics Flashcards
(3) parts of the cathode
lg filament
sm filament
focusing cup
what controls the quantity of electrons (mA) emitted from the filament
the temp of the filament
__ is the source of electrons in an X-ray machine
what is it made of?
filament, tungsten
the focusing cup is a part of the __
cathode
anode is positive electrons
the reason that an X-ray has a rotating target ?
dissipate the heat generated
the focal spot will be determined by the ___ of the filament
size
smaller filament = better detail
increase (mAs) will cause the image to look ___
darker (greater radiographic density)
more electrons produced = darker image
___: the overall blackening of the film
density
mAs and density are directly proportional
what is the primary method to control the blackening of the film?
changing mAs
___:the force applied to accelerate the electrons from the cathode to the anode at the time of exposure
kilovoltage (kVp)
Low kVp= __ penetration
high kVp= __ penetration
low kVp= weak penetration (black and white film)
high kVp= strong penetration = greater ability to penetrate the body = greater scatter
__ controls contrast
kVp
mAs controls density
to lower contrast: __ kVp and ___ mAs
lower contrast: (more grey)
incr kVp
dec mAs
to raise contrast: ___ kVp and __ mAs
to raise contrast:
decr kVp
incr mAs
15% Rule: a ___ in kVp by 15% will double the overall density. A 15% __ in kVp will cut the density by 1/2
an increase in kVp by 15% will double the overall density
A 15% decrease in kVp will cut the density by 1/2
Anode heel effect: the intensity of the X-ray is greater at the __ side
cathode
intensity and density on the anode side of the film decrease
What type of body part should be placed not eh anode side of the film? (anode heel effect)
anode: toes, thin body areas
cathode: heel, thicker body areas
give 4 differences between the anode and cathode side of the X-ray machine
anode:
1. less X-rays
2. smaller focal spot
3. more detail
4. thinner body part
cathode: 1 more X-rays 2. lg focal spot 3. less detail 4. thicker body part
__: the length of space from the focal spot (tube) to the recording medium (film)
focal film distance (FFD)/ source image distance (SID)
intensifying screens are made of __
fluorescent crystals
fluorescent salts change xray photons into visible light photons
___: the blurry halo parts of the image
penumbra
4 causes of penumbra
- tube to close to the film (short FFD)
- pt to far fro the film (long OFD)
- to big of a filament on the cathode
- focal spot to big
name the 2 types of distortion
size and magnification
name 4 methods to decrease scatter radiation
- grids
- air gap technique
- collimator
- filter
fun of the grid?
improve in exposure factors to maintain density
grid ratio is the ___ of the lead strips to the ___
height of the strips to the distance between them
grid ratio is 12: 1
___: limits the size of the beam to the size of the body part needed to be captured on the film
collimation
what is the best way to reduce scatter radiation to the pt
collimate
___: removal of low NRG photons
what is it made of?
filtration
made of aluminum
___ REMs/ RADs is the safe limit per year
5 REMs
____: the number of REMs a person can get in a lifetime without getting radiation poisoning
Maximum Permissible Dose (MPD = 5)
___: is a type of radiation. It is the majority of useful beams. Interacts with eh target nucleus
Bremsstrahlung aka Braking Radiation
___: moderate NRG Xray knocks out n outer shell e- . This causes loss of NRG (primary source of scatter)
compton scatter (incr patient radiation)
__: Low NRG X-ray that changes direction with no NRG loss. Contributes to film fog
classical scatter (aka: Thompson Scatter, coherent scatter)
___: caused by fluctuation of the number of photons absorbed by the intensifying screen to form the image on the film
quantum mottle (aka: radiographic noise)
faster screen = more mottle
developer exposes the ___ crystals to bring out the image
silver halide
look at pg 6 X-ray physics in Irene gold for see the types of developers
.
__: changes AC to DC
rectifier
__: changes the NRG from one form to another
transducer
___: beam of radiation loses NRG as it passes thru matter
attenuation
