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Radiology Physics

A cumulative run through physics in Radiology

QuestionAnswer
What are the three basic parts of the x-ray imaging system Operating Console, X-Ray Tube and High Voltage Generator
A line compensator ensures that what remains constantly delivered to the imaging system Voltage
What two separate circuits is the autotransformer used to supply power to High voltage and filament circuits
The process of heating the x-ray tube filament so that electrons can be boiled off is know as what thermionic Emission
Filaments normally operate at currents of how many amps 3 to 6
Examination tables are made of what strong, radiolucent material Carbon Fiber
The x-ray tube current is controlled by what circuit Filament
If an autotransformer moves from 1500 windings to 800 windings, what type of transformer is it Step-Down
What are the three basic parts of the high-voltage generator High Voltage Transformer, Filament Transformer and Rectifiers
Rectification is accomplished with the use of what Diodes
Does half-wave rectification require half the exposure time as full-wave rectification No
Is the x-ray tube a type of diode Yes
A three-phase twelve-pulse power has how much voltage ripple 4%
A three-phase, six-pulse power has how much voltage ripple 14%
A high-frequency generator has how much voltage ripple 1%
A single-phase power has how much voltage ripple 100%
What are the five types of exposure timers Manual, Mechanical, Synchronous, AEC and Electronic
Which exposure timer uses an ionization chamber to terminate exposure AEC
Name the parts of the x-ray tube Supporting wires, Focusing Cup, Filament, Window, Rotating Anode, Stater Coils, Target, Roter and Glass Envelope
What device is used to check exposure timers for accuracy Solid State Radiation Detector
Which exposure timer is based on the frequency of AC supplied to the imaging system Synchronous
Using a single-phase power, half-wave rectification results in how many x-ray pulses each second 60
Using single-phase power, full wave rectification results in how many x-ray pulses each second 120
Thermionic emission produces a cloud of electrons around the filament known as what Space Charge
The main advantage of a rotating anode over a stationary anode is what Better Heat Distribution
Once the filament current is high enough for thermionic emission, a small/large rise in filament current results in a small/large rise in tube current Small, Large
When imaging x-table lateral spines, one should use which focal spot Large
The anode serves three functions in an x-ray tube, what are they Electrical Conductor, Mechanical Support and Thermal Dissipator
X-ray tubes in mammography have targets made of either what two materials Rhodium and Molybdenum
The anode of a high-capacity tube rotates at how many RPM's 3400 and 10000 rpm
The rotating anode is powered by what Electromagnetic Induction Motor
What are the characteristics that make tungsten a good selection for target material High atomic number, Thermal conductivity and High melting point
Leakage radiation must be less than how many mR/hr at 1 meter 100
The protective housing may contain oil which serves two functions, what are they Insulator and Thermal Cushion
The x-ray tube enclosure may be made of what two materials Glass(Pyrex) or Metal
What is the melting point of tungsten 3410oC
What element is added to tungsten to increase the efficiency of the filament Thorium
The cathode is the negative side of the x-ray tube and contains what two primary parts Focusing Cup and Filament
X-rays emitted through the window are called what Useful or Primary Beam
The focusing cup sustains what type of charge Negative
The x-ray tube is: a vacuum tube, a type of transistor, or a diode A vacuum tube and a diode
Target angles may vary from what to what degrees 5 to 20
The heel effect results in less radiation on which side of the x-ray beam Anode
Should one use the maximum technique in order to warm a cold anode No
What are two causes of tube failure Too much technique on a cold tube(overheats) and arching effect due to vaporized tungsten
The line-focus principle results in which focal spot size much less than which focal spot size Effective focal spot/Actual Focal Spot
The smaller the anode angle, the heel effect becomes what Greater
What are the reasons that off-focus radiation is undesirable Extends the size of the focal spot, increases skin dose modestly and reduces image contrast
Most of the causes of x-ray tube failure are related to what Thermal Capacity
A magnetic field is created any time what type of particle is in motion A charge particle
What is the purpose of an electric generator To convert mechanical energy into electricity
What is the purpose of an electric motor To convert electricity into mechanical energy
A current carrying coil of wire is known as what Selenoid
Placing an iron core into a current carrying coil of wire would turn the device into what Electromagnet
An electric current is induced in a circuit if some part of that circuit is in what type of magnetic field Changing
What are the four factors of Faraday's law The velocity of the magnetic field to the conductor, the magnetic field strength, the angle of the conductor to the magnetic field and the number of turns in the coil.
The autotransformer operates on what principle Self-induction
A regular step-up or step-down transformer operates on what principle Mutual Induction
What are the three main causes of transformer inefficiency Resistance, Hysteresis and eddy-currents
Transformers require what type of voltage to operate, while the x-ray tubes must be supplied with this type of voltage AC/DC
Why is it important that the production of x-rays take place in a vacuum Air can cause electrons to scatter, reducing the efficiency of the beam production
What causes an "open filament" Over use of the filament causes vaporization of the tungsten
How much more area does a rotating anode provide to interact with the electron beam than a stationary anode 1000 times
Tube current is adjusted by controlling what circuit Filament
What are the SI units of magnetic field strength Tesla
List three types of transformers Closed-Core, Autotransformer and shell-type
A step-up transformer results in an increase in what Voltage
A step-down transformer results in an increase in what Current
Electron target interactions result in the conversion of electron kinetic energy into what two types of energy Thermal(Infared Radiation) and Electromagnetic (X-rays)
The production of heat in the anode increases directly with increasing x-ray tube what Voltage and Current
Using three-phase power is equivalent to a what percent increase in kVp over single phase equipment 12%
Using high-frequency power is equivalent to a what percent increase in kVp over single phase equipment 16%
What effect does added filtration have on the x-ray beam Removes low energy rays, and "hardens" the beam (increases quality while decreasing quantity)
Only what shell x-rays of tungsten are useful for imaging k-shell
The doubling of mAs causes a doubling of what striking the target, and consequently doubles the number of what emitted electrons/x-rays
The roentgen is a measure of the number of what produced in air by a quantity of x-rays Ion pairs
This is just a measure of the total number of electrons that travel from cathode to anode to produce x-rays CurrentxSeconds(mAs)
The four factors affecting quantity are what kVp, mAs, Filtration and Distance
X-ray quality is also known as what Penetration
Doubling the optical density on a radiograph using kVp alone requires an increase of what percent 15%
Two factors that affect x-ray quality are what kVp and filtration
Rectification The Conversion of AC power into DC power
Leakage Radiation The radiation that escapes from the tube housing
Off-Focus Radiation 3. Electrons that bounce off of the focal spot and strike other areas of the target causing x-rays to be produced outside of the focal spot.
Thermionic Emission The "boiling off" of electrons from the filament
Half-Value Layer The amount of absorbing material required to reduce the intensity of the beam by one half.
Proton A positively charged particle located inside the nucleus of an atom. It also defines the atomic number of an element.
Neutron A particle located inside the nucleus of an atom that has no charge.
Electron A small particle that usually orbits around the nucleus of an atom and has a negative charge
Atomic Number The total number of protons an element has, which consequently defines what the chemical element is.
Ionization The release of an electron by an orbiting shell
Rem "Radiation Equivalent Man" the radiation amount absorbed by a person through their occupation
Rad "Radiation absorbed dose" the absorbed amount of radiation by any object
Roentgen The amount of radiation that is traveling through the air
Radiation The transfer of energy by the ionization of atoms
Radioactivity the emission of particles or energy from an atom
Alpha particle Consists of two neutrons and two protons from the nucleus of an atom
Beta particle The emission of an electron from the nucleus that converts a neutron into a proton
Photon A packet of electromagnetic energy
Properties of a photon Frequency, wavelength, amplitude and velocity
Attenuation Reduction in intensity resulting from scattering and absorption
Coherent Scattering Results in a change in direction without a change in energy. AKA classical scattering and occurs below 10 keV
Compton Scattering The source of most occupational radiation exposure. An outer shell electron is struck and ejected (compton electron). The x-ray continues in a different direction with less energy, and it produces fog.
Photoelectric Effect An inner orbital electron is struck and ejected, ionizing the atom. The energy is completely absorbed. Responsible for characteristic diagnostic image.
Pair Production Creates two electrons, + and -. Energy is absorbed by the nucleus, but it must be at least 1.02 MeV
Photodisintegration Only occurs above 10MeV. Energy is absorbed by the nucleus which emits a nuclear fragmant
Insulator Any material that does not allow electron flow
Superconductor A material that exhibits no resistance below a critical temperature
Semiconductor A material that under some conditions behaves as an insulator, and in other conditions, behaves as a conductor
Conductor Any substance through which electrons flow easily
Resistance Anything that hinders or opposes the electric current flow of charge particles
Radiopaque A substance in which electromagnetic waves cannot travel through
Radiolucent A substance in which electromagnetic waves can travel through
Find the number of electrons in a shell 2n^2
Find frequency or wavelength C= (wavelength)x(frquency)
Inverse square law (I1)(D1)^2 = (I2)(D2)^2
What is the smallest particle that has all the properties of an element Atom
What is the maximum number of electrons that may be found in the outermost shell of any atom 8
A proton and neutron are how much larger than an electron 2000 times
Who discovered x-rays and when Wilhelm Roentgen, November 8th, 1895
What is the largest source of natural environmental radiation Radon
What is the largest source of man-made ionizing radiation Diagnostic
What are the fundamental building blocks of matter Atoms and Molecules
When x-rays were first discovered, what was their source Crooks Tube
What are the types of energy Potential, Kinetic, Chemical, Electrical, Thermal, Nuclear and Electromagnetic
What does ALARA stand for As Low As Reasonably Achievable
What did the Coolidge tube allow for the separation of Voltage and Current
What are three primary radiation protection devices Filtration, Shielding and Collimation
What are the two categories of ionizing radiation Electromagnetic (x and gamma) and Particulate (alpha and beta)
What is the smallest particle that has all the properties of a compound Molecule
What are two factors that decrease the affinity of an electron to its element? How do they effect it? The larger the atom the less the affinity and the further away an electron's orbit is, the less the affinity
At what speed does all electromagnetic radiation travel 3.0 x 10^8
What two natures does electromagnetic energy behave in Wave and Particle
Of these natures, which does it tend to behave more like Particle
How are frequency and wavelength related Inversely proportional
What is the smallest unit of negative electric charge Electron
If two negatively charged objects are brought near to each other will they be attracted or repelled Repelled
If an object gains an electron does it become positively or negatively electrified Negatively
Can protons move freely from one atom to another No
What are the three ways electrification can be created Induction, Friction and Contact
What is the electric charge of a coulomb 6.3 x 10^18
Do electric charges have potential energy Yes
What are the 3 main factors that characterize a simple circuit and their unit of measurement Voltage (Volts), Current (Amps) and Resistance (Ohms)
How is the volt meter connected to a circuit Parallel
How is an amp meter connected to a circuit In Series
What type of circuit does voltage remain constant Series
What are the four factors that influence the resistance of a conductor Cross sectional Area, Material Type, length and temperature
What are three devices that help protect against or minimize exposure to radiation Intensifying screens, filtration and lead shields
What is the difference between x-rays and gamma rays X-rays are emitted from the cloud of electrons, gamma rays are emitted from the nucleus.
Created by: John F Cairney II John F Cairney II on 2009-05-18



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