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Radiology Physics
A cumulative run through physics in Radiology
| Question | Answer |
|---|---|
| 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. |
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