finals Flashcards
Unit for effective dose
Sv & REM
Unit for absorbed dose
Gy & RAD
Becquerel is a unit of
radioactivity
Coulombs/kg is a unit of
exposure
equation for inverse square law
I1/I2 = (D2)^2/ (D1)^2
equation for grid ratio
h/d
equation for GCF (nongrid –> grid)
mAs (grid)/ mAs (w.o grid)
Higher grid ratio means ___ (2)
better scatter clean up
better contrast
equation for GCF (grid –> another)
mAs1/mAs2 = GCF1/GCF2
equation for wavelength
w = c/f
equation for frequency
f = c/ w
ionization radiation = ___ wavelength = _____ frequency
short, high
unit for frequency
hertz (Hz)
rank longest to shortest wavelength
radiowave
microwave
infrared light
visible light
UV light
xray
gamma rays
cosmic rays
5 characteristics of Xray
- highly penetrating (short wave, high frequency)
- cannot be reflected or focused
- neutrally charge
- no mass
- travels in straight line
high penetrating, low ionization is ___
gamma
low penetrating, high ionization
alpha
which radiation produced at the anode
primary
beams with different energy is called ___ (aka ___ radition)
heterogenous - primary
What are considered primary radiation
Brems & characteristics
Brems produced ____ xray spectrum
continuous
Characteristics produced ___ xray spectrum
discrete
primary beam photons have keV energy of ___
30-40% kVp
What are considered secondary radiation
scatter & leakage
what is produced by the energy of primary beam redirected after interacting with matter
scatter
scatter radiation does not produce __
quantum mottle
scatter radiation effect on images (3)
produce noise
reduce contrast resolution
makes image less visible
how do we reduce scatter (4)
- decrease volume of tissue
- decrease kVp
- increase collimation
- increase atomic #
decrease kVp = ___ scatter
reduce
increase atomic # = ___ scatter
decrease
what devices are used to reduce scatter (3)
collimator
beam-restring devices
grid
which beam-restring devices is the simplest? and which is the most effective in scatter cleanup
simplest: aperture diaphragm
effective: cone
which of the following is not beam-restricting devices:
a. aperture diaphragm
b. grid
c. collimator
d. cones
e. all of the above are beam-restring devices
B
what is the purpose of grid
reduce scatter radiation that reached IR
what is beam restrictors and grid have in common
reduce scatter
reduction in total # of xray photons remaining in beam after passing thru given thickness of material is ___
a. HVL
b. attenuation
B
thickness of absorbing material required to reduce x-ray intensity to half of its original value is ___
a. HVL
B. attenuation
A
what does HVL measures?
a. quantity
b. quality
A
2 ways to remove low-energy photons
filteration
hardening of beam
remove low-energy photons = ___ patient dose
decrease
High-voltage generator is ___ circuit
secondary
Components of primary circuit (5)
- power supply
- autotransformer
- kVp meter
- timer
- step-up transformer
what controlled autotransformer?
a. kVp selector
b. mA adjusment
A
What operate autotransformer
self-induction
what component of the circuit directly determine V
autotransformer
AEC timer utilized ____ for exposure control
ionization chamber
cons of AEC backup timer
too short = underexposed image
AEC measures ___ of radiation reached IR
a. quantity
b. quality
A
mA selector controls ___ in the circuit
amperage
Rectifiers are located in ___ circuit
secondary
which component transform AC to DC
rectifiers
Rectifiers is ___ diode
solid state semiconductor
half wave have ____ diodies
full wave have __ diodes
0,1,2
4
ionization chamber is radio___
radiolucent
what does rectifier require to operate
voltage rectification
what does high-voltage transformer require to operate
AC
Which component increase voltage from autotransformer by a fixed amount
step-up transformer
what does filament circuit control
degree & saturation the filaments are heated
what activate step-down transformer
a. kVp seelctor
b. mA adjustment
B
3 parts of high-voltage generators
step-up transformer
filament transformer
rectifiers
increase amperage = increase in __
of e- boiled off
the filaments are at which side of the tube
cathode
Tube housing can reduce ____
leakage radiation
Tube housing can prevent ___
electric shock
what is used in the tube housing as an insulator & thermal cushion
OIL
why glass is used for tube envelope
withstand heat
tube window for useful beam to exit is located in ___
glass envelope
TUbe current related to ___
mAs
what components are on the cathode side?
filament coil
focusing cup
function of filament coil
emits electrons when heated
function of focusing cup
confines electron beam to a small area of anode
what components are on the anode side
target
rotor
stator
functions of anode (3)
- electrical conductor
- mechanical support for target
- thermal dissipater
Xray emission source is at __
a. effective focal spot
b. actual focal spot
B
why tungsten is chosen as material for target (3)
- high atomic #
- high thermal conductivity
- high melting point
____ effective focal spot
____ actual focal spot
small
large
a sharper image will have ___ focal spot
small effective
pros & cons of small effective focal spot
pros: better spatial resolution
cons: more heat concentration
xray emission source is at ___
actual focal spot
xray are produced at ___
actual focal spot
Bremsstrahlung radiation interacts with
The nuclear field
Characteristic radiation interacts with
inner shell electrons
Characteristic radiation produced at ___ kVp
above 70
The xray primary beam most often consists of
Brems radiation
The energy of the beam can be changed through adjustments in
a. kvp
b. mas
c. quantity
d. distance
kVp
Off-foused radiation happend at the ___
anode
Target is on ___ side
anode
off focused radiation produced
ghosting effect
what helps reduce the amount of off-focused radiation
upper shutter of collimator
rotor is made up of ___
copper shaft & soft iron
stator consists of ___
electromagnet
Incident e- in photoelectric interacts with
inner shell e-
incident e- in compton interacts with
outer shell e-
what are ejected from photoelectric
photoelectron
what are ejected from compton
electron with ionizing capability
what happened when xray strike matter
- absorbed (photoelectrically)
- scatter
- direct transmission
reduction in intensity results from ____
absorption & scattering
increase kVp = __ PE = ___ Compton
decrease / increase
decreased patient dose = ___ PE = ___ Compton
decrease/ increase
Which of the following is not required for xray production
a. accelerating of e-
b. slowing of e-
c. rotating target
d. source of free e-
c. rotating target
Compton scatter most likely occurs with
a. An xray interacting with an outer shell electron
b. projectile electron interacting with outer shell e-
A
The anode heel effect causes
a. An x ray field with lower intensity on the anode side
b. xray with lower contrast
c. xray with higher quality on anode side
An x ray field with lower intensity on the anode side
thicker body part is placed on which side of xray tube
cathode
increase anode heel effect = ____ angle
small
increased anode heel effect = ___ SID
decreased
The line focus principle explains the relationship between:____
a. The actual focal spot and the effective focal spot
b. The large focal spot and small focal spot
c. The large focal spot and actual focal spot
A. The actual focal spot and the effective focal spot
Line focus principle results in greater ____ & ____
heat capacity
image sharpness
For line focus principle, what needed to be angled for heating while maintaining small focal spot
TARGET
Quantity aka ____ (3)
xray output
intensity
exposure
quantity is affected by ____ (4)
kvp
mas
distance
filtration
quantity is measured by _____
milliroentgens
Quantity is also known as all of the following except :____
a. xray output
b. exposure
c. energy
d. intensity
C
IR exposure is measured by ___
numeric exposure value
Quality aka ___
penetrability
HIGH penetration in material of ____ atomic #
LOW
quality is affected by ____ (2)
kvp
filtration
increase mAs = ____ quantity
increase
increase kVp = ____ quantity
increased 4x
increase distance = ___ quantity
decrease
increase filtration = ____ quantity
decrease
intensity is _____
a. quantity
b. quality
A
increase kVp = ____ speed + energy of photons
increase
what can remove low-energy photons
increase filtration
increase filtration = ___ resolution
increase
Beam quality is a measurement of
a. Half-value layer
b. beam divergence
c. amount of radioactivity
d. amount of xray in primary beam
A
What are the prime factors
kvp
mas
distance
what material is used for filtration
aluminum
thicker filters = ___ atomic # = ____ reduction of output
high
high
purpose of filtration
remove low-energy xray photons
filtration ____ intensity of beam AND ____ photon energy
decrease
increase