Final Exam Week 1 Radiologic Imaging
The quantity of the beam is controlled by
mAs (Milliamperage + seconds)
What 3 things comprise of inherent filtration?
Glass Envelope, Glass Window and Insulating Oil
Inherent Filtration + _________ = total filtration
Added filtration (Aluminum)
What does Bremsstrahlung translate to in German?
Braking radiation or slowing down
For the best patient protection use...
high kV and Low mAs
What amount of aluminum is required on all x ray machines that operate over 70kV?
2.5 mm/al eq
What measures beam quality?
Half Value Layer (HVL)
At 90 kV, what % of the x ray is formed by an interaction with the K shell of a Tungsten atom?
With increasing filtration, beam quality _________and beam quantity
What percentage of kV increase is needed to double the quantity of x rays on an image?
Name the three parts of the Anode.
Stator, rotor and target
Name 4 properties of x rays:
Travel at the speed of light
They are Invisible
Have no charge, are neutral
What is the mathematical formula for the speed of light?
3x10^8 mps ( 3 X 10 to the 8th power in meters per second)
What does RAD stand for?
Its new form is?
Radiation Absorbed Dose
What does REM stand for?
Its new form is?
Radiation Equivalent Man
What is potential energy?
What is kinetic energy?
energy in motion or being expanded.
What material is the focusing cup made from?
- surrounds the filament
- electrostatic repulsion : a greater negative charge than the electrons which keeps the beam of electrons from spreading apart
- pushes and focuses the stream of electrons toward the target whrn voltage is applied
What percent of electrons hitting the target are converted to heat?
What happens at the cathode in the "prep" portion of an exposure?
As the target angle decreases, the effective focal spot...
Frequency is expressed as what units?
As wavelength increases, frequency...
As wavelength decreases, frequency...
decreases, less damaging but less detail in x ray
increases, more damaging but more detail in x ray
The diagnostic medical range of energies that x rays can be produced is from is
30 to 150 kV
name 3 fundamental particles are:
Electrons - negative charge
Neutrons - neutral charge
Protons - Positive charge
The Nucleus is central in the atom and is made of protons and neutrons.
The atomic number of an atom refers to?
The number of protons in the nucleus
The closer the the electron to the nucleus
the stronger the binding energy
The K shell is closest to
The K shell has a characteristic interaction
Characteristic cascade is
for any kV above 70 it is at 85% brems and 15% characteristic, 70kV or below is brems at 100% and 0% characteristic.
When one outer shell incident electron drops into the open position and causes an energy difference
These x rays have such a long wavelength and low frequency that they are stopped at the filter and will not make it to the patient.
At the end of the characterstic cascade, the ______ shell is missing an electron.
X rays are characterized as?
Both: electromagnetic waves of short wavelength and electromagnetic waves with high frequencies
During a characteristic interaction, the kinetic energy of the incident electron must be _______the electron it knocks from orbit.
Greater than that of
Electrons traveling from the cathode filament to the anode are called?
What is energy exerted on electrons by the nucleus of the atom?
What is the difference between xray and gamma rays?
Xray is man made, gamma is naturally occuring
The quantity or intensity of the beam
The quality or value of the beam
indicates the number of photons in the primary beam
indicates its penetrating power
Kv, distance and filtration affects
(Filtration removes low energy photons form the beam)
Output or Quantity - Changing the kV has a great effecton the beam quantity (15% rule, doubles the kv by adding 15%)
(distance affects quantity by) Inverse Square Law
Quantity decreases, quality increases
Quantity increases, quality decreases
Doubling your distance from the source reduces your dose to 1/4 (divide by 4) in other words, How much radiation are you getting?
Or: the intensity quadruples if the distance is reduced to one half of its original value (multiply by 4)
HVL, Half Value Layer
measures beam quality and filters reduce the intensity to half the original value and increases the quality of the beam. 2.5 mm/al eq is minimum.
Factors affecting beam quantity
As mAs increases, quantity increases
As kV decreases, quantity decreases
AS distance decreases, quantity increases
As filtration increases, quantity decreases
Kv controls Quality
As kV increases, quality increases
As filtration increases, quality increases
Filtration affects quality (quality goes up removing low energy protons and reducing patient dose.
Middle of Crosshairs on Goniometer
Central Ray (CR)
Beam lighting Device that controls the shape of the x ray field; length and width
To 'collimate' means to decrease the size of the field, to make smaller
Collimation/beam limitation/field size
As low as reasonably achievable
Part of the cardinal principles of Time - Distance + and shielding.+
Must be used on children and all adults of reproductive age
Has an atomic # of 82 due to being made of lead (Z)
3 main types:
- 1. flat contact,
- 2. shaped contact and
- 3. shadow shield
Any worker that is likely to receive more than 1/10th of the recommended dose should be monitored.
Students should wear an OSL dosimeter, you are not allowed to hold a patient down!!
it is unaffected by heat, moisture and pressure and "M" = below the minimum measurable quantity.
Dose Limit Recommendations
- Occupational exposure: Me - Annual 5 REM (Radiation equivalent man)
- Cumulative exposure is 1 rem x age. (Entire life span)
- Public/patient exposure: Frequent exposure 0.1 rem (every 6 months) e.g. bone testing
- Infrequent exposure: 0.5 rem (annually)
Law of Bergonie and Tribondeau
- Cells are most sensitive to radiation during division (mitosis) : skin, cells in small intestines, germ cells.
- Some cells are more resistant to radiation because they do not undergo repeated division: ex. nerve, muscle and brain.
- Ancel and Vitemberger modified the theory and say that all cells are sensitive to radiation; dividing cells demonstrate injury sooner.
Effects on radiation exposure
- Prodromal stage, (nausea, vomiting and diarrhea)
- Latent period (organs feel fine but the body is undergoing changes
- Manifest stage leads to either recovery or death.
- Somatic effects -develop in the exposed individual as cataracts and cancer
- Genetic effects - occur in future generations from germ cell damage as mutations.
Which x ray tube component serves as a source of electrons for x ray production?
Electron interact with the ________ to produce x rays and heat
Which primary exposure factor influences both quantity and quality of x ray photons?
The unit used to express tube current is ____________.
mA (How many x rays)
According to the line focus principle, as the target angle decreases, the ______
effective focal spot size decreases
Increasing the kVp results in
X rays with higher energy and more x rays
Which of the following is not necessary for x rays to be produced?
A source of protons
The primary components of the x ray tube are
Anode and the Cathode
- Anode is a positive charge
- cathode is a negative charge
- anodes can be stationery or rotating at 3,400 to 10,000 per minute
- Cathode is made up of the filament and the focusing cup and the filament is a wire made of tunsten with 1-2% thorium, is the source of electrons.
The component that controls the size and shape of the x ray exposure field is the
The target base of the x ray tube is made from
Molybdenum with a coating of tungsten, Rhenium is added sometimes.
- the target is part of the anode.
- tungsten is used for the target because it has a high atomic # of 74 and a high melting point of 3400 degrees C
Line Focus principle
- The actual focal spot size depends on the filament size selected at the mA station.
- Effective focal spot size refers to the size measured under the anode target.
- The target is angled to help x rays exit the tube at the window
- rotating targets typically have an angle between 7 and 18 degrees, ( most common is 12)
Anode Heel effect
- This occurs because of the angle of the target
- A portion of the beam is absorbed by the heel of the anode causing the beam to be stronger at the cathode side of the tube.