Mid-Term Flashcards
What is an x-ray?
LIGHT; form of electromagnetic ionizing radiation; often called photons; has a wavelength much shorter than that of visible light; produced outside of the nucleus in the electron shells
What is another name for single x-ray in the beam?
photon
What determines the energy of the x-ray?
the amount of energy of each electron;
short wavelength= high frequency; long wavelength= low frequency
Do all of the x-rays in the beam have the same amount of energy?
no; different amounts of energy interacts with different matter
What is differential absorption?
difference between those x-rays that pass through tissue and those that don’t
What is radiographic density? How does a radiographically dense area appear on a radiograph?
mass per unit volume of black metallic silver; it’s a build up of blackness; it appears black metallic silver
How are radiographic density and anatomic density related?
inversely related
What is radiographic contrast?
degree of contrast between blacks and whites
How do we get contrast in an image? How does that happen?
differential absorption: differences in absorption that transmit the energy of the x-ray and absorption of the tissue
Is it really the x-ray that interacts with the film emulsion to produce the image?
No, it is the light from the rare earth screens
What would the film look like if all of the x-rays interacted with the emulsion and the film was then processed?
it will get black; when x-rays pass through the tissue, the energy will react with the film and produce blackness
What color of light do rare earth crystals typically emit?
green yellowish color
Define electromagnetic energy in terms of mass, charge, and velocity
no mass, no charge, travels at the speed of light
Define ionize
ability to totally remove an electron from it’s orbit around the nucleus
Which types of electromagnetic energies are able to ionize?
x-rays, gamma rays, some short UV rays
State the wave equation
velocity= frequency x wavelength
v) (f) (lambda
What is a gamma ray?
form of ionizing electromagnetic radiation; emitted from nucleus of a radioisotope and are usually associated with alpha or beta emission
What is the difference between x-rays and gamma rays?
origin; x-rays are located in the electron shells while gamma rays are from the nucleus
Why is a free electron a worry in human tissue?
Because they are highly reactive and believed to be involved in degenerative diseases and cancers.
- List other types of electromagnetic energies in order of their energies relative to x-ray
Tv, radio, microwaves, infrared light, ultraviolet light, x-rays, gamma rays
range of x-rays in matter
1 – 100 meters in air
0-30 cm in soft tissue
What makes an x-ray photon higher energy than a microwave
the difference in wave frequency
- HOW MUCH OF THE ELECTRIC AND KINETIC ENERGY OF THE PROJECTILE ELECTRONS IS CONVERTED TO HEAT? X-ray?
99%
<1%
Is heat production an excitation interaction or an ionization interaction?
excitation interaction
What 2 methods are x-rays produced by?
characteristic and Bremsstrahlung
- WHICH OF THESE METHODS PRODUCES X-RAYS WHEN ELECTRONS SHIFT ENERGY LEVELS / SHELLS WITHIN THE ATOM?
characteristic
Tungsten is used as a target material. It has electron shells from “__” (near the nucleus) to “__” (outermost shell).
K”, “P”
Which characteristic x-rays of tungsten are energetic enough to be useful?
K orbital
AT LEAST ______ kVp IS REQUIRED TO PRODUCE USEFUL ENERGY K-CHARACTERISTIC X-RAYS OF TUNGSTEN.
69.53 kVp
X-rays are converted from ___ energy to ___ energy.
kinetic, electromagnetic
Does an alpha particle or x-ray cause a double strand break in DNA?
alpha particle
What are the kVp values needed for each characteristic orbital?
K=69.53 L=12.1 M=2.82 N=.6 O=.08 P=not bound
The vast majority of x-rays are produced by which production process?
Bremsstrahlung
- THE CHARACTERISTIC X-RAY WITH THE MOST KeV OF ENERGY OCCURS WITH THIS ELECTRON TRANSITION : _____TO _____.
P to K
In Bremsstrahlung production process, what is the range of energy?
0-125 kVp
What is the highest energy x-ray in a beam dependent on?
kVp
Describe the Bremsstrahlung x-ray production process.
main way xrays are produced. b/c nucleus is + and electron is -, the electron travels close to nucleus and gets drawn to it and deflected from its original direction. this deflection causes a loss of energy and that loss is formed into an xray photon
Describe the characteristic x-ray production process.
interaction of the projectile electron with the k-shell target electron. the electon is kicked out of its shell. an electron from an outer shell then fills in where the electron left. the energy level drops causing a photon to be emitted.
WHAT IS THE AVERAGE ENERGY OF AN X-RAY BEAM PRODUCED AT 80 KVP?
1/3)*80 = 26.67 kVp
What is the purpose of the rectifier?
to let the electrical current flow in one direction, from cathode to anode, AC to DC, - to +
whatt type of current is required to produce x-rays?
DC
What does the power company provide for us?
AC, alternative current
What does kVp do inside the tube to produce x-rays?
it determines the quality of the x-ray beam
Which type of rectification produces the highest contrast radiograph?
Full Wave Rectification
Which type of rectification produces the highest energy x-rays, uses a 110 outlet, and reduces the patients exposure over 30%?
Hight Frequency rectification
What is MAS?
of x-rays being produced
What is kVp?
energy of x-rays
What is isotropic emission?
360degrees divergence of light
What is thermionic emission?
boiling off electrons
What is a cathode?
- negatively charged electrode
- contains small and large filament
- source of electrons for the production of x-rays
- where electrons “boil” off
What is a anode?
- positively charged electrode
- spinning disc
- acts as a coolant by distributing heat
What is the main function of the filter?
to reduce skin dose of radiation to the patient
What is the x-ray tube made of?
blown glass or metal ceramic
What is the advantage of the small filament?
produces a sharper image
What is the advantage of the large filament?
shorter exposure time
How is the filament/focal spot selected?
by selecting the mA
What photographic property does mAs control?
density
What electrical unit is set on the console to accelerate the electrons from cathode to anode?
kVp
What photographic quality does the kVp control?
contrast
What is contrast?
a photographic property that shows the degrees of difference between black, white and various shades of gray
The anode spins at ___rpm.
3,600rpm
How long should the anode spin after exposure is terminated to be sure there is no rotor bearing damage?
at least 90 seconds
What type of motor spins the anode?
electrical induction
What is the target area of the anode made of?
tungston
The focusing cup has a strong _____ charge to keep the electrons focused into a small focal spot area on the target of the anode.
positive
What is the tube housing lined with?
lead
What is the tube housing filled with?
oil to dissipate heat
What is the opening called that allows x-rays out of the housing tube?
port
Define ALARA
As low as reasonably achievable
Which rectification is most consistent with ALARA
Full Wave Rectification
Which of these types of rectifiers will extend the tube life?
High Frequency Rectification
Compare the cost of Full Wave Rectification to High Frequency Rectification.
HF is $3000 more
How much of a change in mAs if underexposed?
increase 100%
How much of a change in mAs if over exposed?
decrease 1/2
increase in kVp would be an ___ of KE, to an ____ of x-ray energy (______wave length)
increase, increase, shorter
the anode side of the tube can be located by:
negative label, positive label, listening for the spin, finding the wire for the AC current
Which side of a radiograph will exhibit the least radiographic density?
The anode
The high atomic # of the tungsten target absorbs low energy x-rays.
False
Where should the anode side of the tube be placed when performing a lateral thoracic spine radiograph?
down
Where should the anode side of the tube be placed when performing a lateral lumbar spine radiograph?
up
Where should the anode side of the tube be placed when performing an AP thoracic spine radiograph?
up
Where should the anode side of the tube be placed when performing a full spine radiograph on a 14 x 36” film?
up
Where should the anode side of the tube be placed when performing a lateral cervical spine radiograph?
It doesn’t matter on a 10x12” film at 40”
When the anode heel effect becomes important in terms of film size and source image distance (SID).
Large film sizes at short SID
How does placing the anode / cathode side in the proper place affect the radiograph’s overall density.
It produces uniform in density
Besides using the anode heel effect properly there are two other options that may help to produce a more uniform film density. They include:
Compensating Filters
Slow Speed where area is thin; faster speed where is thickest.
How should you have your tube installed? (Which side up?)
anode
Which side of the radiograph will be the sharpest?
anode
The ____ side of the x-ray tube emits x-rays that are relatively perpendicular to the film.
anode
State the unit that a physicist would use to describe ionizations in air in classical
nomenclature.
R
State the unit that a physicist would use to describe ionizations in air in Systems
International nomenclature.
Coulombs/kg
Coulombs/kg measure this type of radiation only:
X-ray and gamma
State the unit for occupational exposure in classical nomenclature.
REM
State the unit for occupational exposure in Systems International nomenclature.
Sievert
___ mRem = 1 Rem
1,000
State the formula for Rem. Rem = _____ x _____.
RAD x QF (quality factor)
20 mRad of x-ray exposure = ____ mRem
20
100 Rem = ______Sievert.
1
State the unit of absorbed dose in classical nomenclature.
RAD
State the unit of absorbed dose in Systems International nomenclature.
Gray
100 Rad = _____Gray
1
In x-ray: ____R = _____Rad = _____Rem
1,1,1
Comparing annual radiation exposure to the population in the U.S., most exposure comes from this source:
background: cosmic, terrestrial
List at least 3 consumer products that contribute to background exposure.
Tobacco, Television, Combustible Fuels
State the annual whole body MPD for occupationally exposed persons in Rem.
5 REM
State the average annual exposure that medical personnel receive.
< 100 mREM
