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Physics Test #1
Ch 1, 2, 3
| Question | Answer |
|---|---|
| List 7 Characteristics of X-rays: | * Invisible * Electrically neutral * No mass * Cannot be optically focused * Travel @ speed of light in vaccum * Form a polyenergetic beam * Can be produced in a range of energies * Can cause some substances to fluoresce |
| List 7 more Characteristics of X-rays | * Travel in a straight line * Can cause some substances to fluoresce * Cause chemical changes in radiographic & photographic film * Can penetrate body * Can be absorbed or scattered in the body * Can produce secondary radiation * Can dam |
| What is the medically useful diagnostic range of x-ray energies? | 30 to 150 kVp |
| In what year were x-rays discovered? | 1895 |
| What is the speed of light? | 3 x 10 to the eighth or 186,000 mph. |
| In what year were some of the biologically damaging effects of x-rays discovered? | 1898 |
| X-rays were discovered in experiments dealing with: | the conduction of high-voltage electricity through low-vacuum tubes |
| X-rays were discovered when they caused a barium platinocyanide-coated plate to: | fluoresce |
| X-radiation is part of which spectrum? | electromagnetic |
| X-rays have a dual nature, which means that they behave like both: | waves and particles |
| How are the wavelength and frequency of x-rays related? | inversely |
| Who won the 1st Nobel prize in physics in 1901? | Wilhelm Conrad Roentgen |
| How fast does a rotating anode spin? | 3,000 to 10,000 rpm |
| What is the atomic number of tungsten? | 74 |
| What is a mammography target made of? | Molybdenum - atomic #42 |
| Where to the majority of heat come from in x-ray production? | the anode |
| What percent of the primary beam reaches the image receptor? | 5% |
| The physical area of the target that is bombarded by electrons during x-ray production? | Focal spot |
| The actual focal spot and effective focal spot are related: | Directly |
| What is the advantage of a rotating anode verses a stationary anode? | Rotating anode dissipates heat better |
| What is the acceptable leakage radiation? | 100 mR per hr no more than 1 meter from the source |
| What is the Source-to-skin distance requirements? | Shall not be less than 12 inches and should not be less than 15 inches |
| What percentage of interactions above 70kVp are Bremsstrahlung? | 85% |
| What percentage of interactions below 70kVp are Bremsstrahlung? | 100% |
| Produced when a projectile electron interacts with an electron from the inner shell (K-shell) of the tungsten atom | Characteristic interactions |
| A German word meaning "braking" or "slowing down" | Bremmstrahlung |
| True or False: There is no difference between a Bremsstrahlung interaction and a Characteristic interaction at the same energy level. | True |
| What determines the speed at which the electrons in the tube current move? | kVp |
| What is the unit used to measure the tube current? | milliampere (mA) |
| Coiled tungsten wire that is the source of electrons during x-ray production | filament |
| What is made up of nickel & nearly surrounds the filament? | focusing cup |
| Allows electrons to flow freely across the tube from the cathode to the anode | focusing cup |
| positively charged electrode | anode |
| a metal that abruptly decelerates & stops electrons coming from the tube current, thereby allowing the production of x-rays | target |
| What is the target of rotating anode tubes made of? | Tungsten |
| Atomic # of tungsten | 74 |
| What is the melting point of tungsten? | 3370 C |
| In mammography, what is the target made of? | Molybdenum |
| Atomic # of molybdenum | 42 |
| What has a high melting point, but produces a much lower x-ray beam? | Molybdenum |
| Number of waves passing a given point per given unit of time. | Frequency |
| What is the difference between Bremstrahlung & Characteristic x-rays at the same energy level? | There is no difference, they are just different processes. |
| What turns the rotor at a very high speed? | stator |
| What rotates rapidly during x-ray production? | rotor |
| The physical area of the target that is bombarded by electrons during x-ray production. | focal spot |
| Any x-rays other than the primary beam that escape the tube housing. | leakage radiation |
| In what direction do electrons travel? | cathode to anode |
| How fast do electrons travel? | half the speed of light |
| What 2 interactions produce x-ray photons? | Bremsstrahlung & Characteristic |
| German word that means "breaking" or "slowing down" | Bremsstrahlung |
| Focal spot size as measured directly under anode target | Effective focal spot size |
| True or False: The amount of anode angle determines the size of the focal spot. | True |
| Describes how x-ray intensity is greater on cathode side, with the intensity diminishing | Anode heel effect |
| How is mAs calculated? | mA x s milliamperage x seconds |
| Doesn't allow any more electrons to be boiled off the filament. | space charge effect |
| What is the ejected electron in Compton effect called? | compton electron or recoil electron |
| single-phase factor | 1.0 |
| The amount of heat produced from an exposure is expressed by the... | heat unit |
| What factors do radiographers select to produce a quality image? | * kilovoltage (kVp) * milliampere (mA) * exposure time |
| How is mAs calculated? | mA x s milliamperage x seconds |
| Doesn't allow any more electrons to be boiled off the filament. | space charge effect |
| What is the ejected electron in Compton effect called? | compton electron or recoil electron |
| single-phase factor | 1.0 |
| The amount of heat produced from an exposure is expressed by the... | heat unit |
| What factors do radiographers select to produce a quality image? | * kilovoltage (kVp) * milliampere (mA) * exposure time |
| Allows imaging movement of internal structures. | fluoroscopy |
| invisible until processed | latent image |
| visible image | manifest image |
| positively charged electrode | anode |
| How are the quantity of electrons that flow from cathode to anode & the quantity of x-rays produced related to exposure time? | they are directly proportional |
| The most important part of the x-ray machine because it is where x-rays are produced. | x-ray tube |
| Describes how x-ray intensity is greater on cathode side, with the intensity diminishing toward the anode side. | Anode heel effect |
| x-rays are also called | photons |
| A radiographic image is created by passing an x-ray beam through the patient & interacting with the | image receptor |
| True or False: At higher kilovoltages, fewer photon interactions occur, resulting in more x-ray transmissions. | True |
| What percentage of electrons in the tube current is converted to heat? | 99% |
| What kind of paper was Roentgen using when he discovered x-rays? | barium platinocyanide |
| Absorption is similar to what interaction? | Characteristic |
| negatively charged electrode | cathode |
| focuses electrons | electrostatic lenses |
| Flow of electrons from cathode to anode | tube current |
| Process where some of the x-ray beam is absorbed in the tissue & some passes through the body | Differential absorption |
| True or False: The more mA, the more x-rays produced | True - they are directly related |
| How are wavelength and frequency related? | inversely |
| Three types of x-ray generators: | * Single-phase * Three-phase 6 pulse * Three-phase 12 pulse * High frequency |
| Type of double-wedge filter used for AP projection of the thorax | trough filter |
| How fast is the speed of light? | 3 * 10^8 meters per second 186,000 miles per second |
| X-ray tubes operating above 70 kVp must have a minimum total filtration of ______ or its equivalent | 2.5 mm of aluminum |
| What percentage of electrons in the tube current are converted to x-rays? | 1% |
| Type of double-wedge filter used for AP projection of the thorax | trough filter |
| How fast is the speed of light? | 3 * 10^8 meters per second 186,000 miles per second |
| X-ray tubes operating above 70 kVp must have a minimum total filtration of ______ or its equivalent | 2.5 mm of aluminum |
| What percentage of electrons in the tube current are converted to x-rays? | 1% |
| Incoming x-ray photon passes through the anatomic part without interactions | transmission |
| What kind of relationship does the speed of electrons traveling from cathode to anode have with kilovoltage? | direct relationship; speed of electrons increase as kilovoltage increases |
| Heat unit equation | HU = mA * time * kVp * gen. factor |
| Boiling off of electrons from the filament | thermiotic emission |
| What is made of nickel & nearly surrounds the filament? | focusing cup |
| Coiled tungsten wire that is the source of electrons during x-ray production | filament |
| Occurs with low energy x-rays; photon interacts with atom & excites it; the atom DOES NOT lose energy, but it does change direction | Coherent scattering |
| cloud that forms around filament after thermiotic emission | space charge |
| Three-phase 6 pulse factor | 1.35 |
| Three-phase 12 pulse | 1.41 |
| Filtration added to the port of the x-ray tube | Added filtration |
| Most common type of compensating filter - thicker portion is lined up with thinner portion of body | wedge filter |
| When the attenuated x-ray beam leaves the patient, the beam is called | exit radiation |
| During this interaction, projectile electrons interacts with k-shell electron & produces a "cascading" effect which produces x-ray photons | Characteristic interaction |
| What heats the tungsten filament? | filament current |
| filtration permanently in the path of the x-ray | inherent filtration |
| the amount of filtration that reduces the intensity of the x-ray to 1/2 its original value | half-value layer |
| radiation that has both electrical & magnetic properties | electromagnetic radiation |
| creates brighter image | output phosphor |
| any x-rays other than the primary beam that escape the tube housing | leakage radiation |
| tube current is measured in | mA |
| Incoming photons are not absorbed, but they lose energy during interaction in the body | scattering |
| When does complete absorption occur? | when incoming x-ray photon has enough energy to remove the inner shell electron |
| Components that contribute to inherent filtration: | * glass envelope * oil that surrounds tube * mirror inside collimator |
| can be added to the primary beam to alter intensity | compensating filters |
| What is used to determine whether a particular exposure will be safe to make? | instantaneous load tube rating chart |
| Bremsstrahlung Interaction | electron avoids orbital electrons & get close to nucleus & changes directions |
| polyenergetic beam that consists of a wide range of energies | x-ray emission spectrum |
| focal spot size as measured directly under anode target | effective focal spot size |
| interactions that can occur within all diagnostic x-ray energies | Compton interactions |
| allows electrons to flow freely across the tube from the cathode to the anode | focusing cup |
| What exposure factors allow the x-ray beam to be altered? | * quality * quantity |
| What do low energy photons do? | Contribute to patient dose. They do NOT contribute to image formation. |
| radiation measuring device | dosimeter |
| distance between two successive crests or troughs | wavelength |
| The ejected electron resulting from total absorption of the photon during the photoelectric effect interaction. | photoelectron |
| the ability of an x-ray photon to remove an electron | ionization |
| In what year did they discover that x-rays could cause biological damage? | 1898 |
| converts light to electrons | photocathode |
| What converts exit radiation photons to visible light in the image intensifier? | input phosphor |
| Interaction where energy scatters and changes direction | Compton effect |
| Process in which exit radiation from the area of interest interacts with light emitting material | image intensification |
| What is x-ray energy measured in? | kiloelectron volts (kev) |
| density on the x-ray is equal for any combination of mA & time as long as the product is equal | mAs reciprocity |
| High frequency generator factor | 1.45 |
| Product of both flux/minification gain | Brightness gain |
| When ionization occurs in the diagnostic range | Photoelectric effect |
| What is exit radiation composed of? | * transmitted radiation * scattered radiation |
| Added filtration and inherent filtration | total filtration |
| What kind of tubes was Roentgen working with when he discovered x-rays? | Crookes tubes |
| Reduction in the energy of the primary beam | attenuation |
| refers to the instantaneous production of light resulting from the interaction of some type of energy & some element/compound | fluorescence |
| What determines the length of time that the x-ray tube produces x-rays? | exposure time |
| size of the area on the anode target that is exposed to electrons from the tube current | actual focal spot |
| the relationship between the actual focal spot & the effective focal spot | Line-focus principle |
| What relationship does kVp and penetrability have? | Direct relationship: as kVp increases, penetrability increases |
| What is the device that receives the radiation that exits the patient to create the radiographic image? | image receptor |
| What are some factors that affect the beam interaction? | * quantity of primary beam * quality of primary beam * composition of the anatomic tissues |
| The process of image formation is a result of: | differential absorption |
| What is the process whereby some of the x-ray beam is absorbed in the tissue and some passes through the anatomic part? | differential absorption |
| What does the word "differential" mean? | varying |
| Does differential absorption increase or decrease as kVp is reduced? | increase |
| What are the processes that occur during beam attenuation? | * absorption * scattering * transmission |
| The variations between _______ and __________ of the exiting x-ray beam will structurally represent the anatomic area of interest. | absorption and transmission |
| The reduction in the energy of the primary beam is known as: | attenuation |
| When absorption takes place, what is the ejected electron called? | photoelectron |
| A total x-ray absorption interaction | Photoelectric Effect or Photoelectric Interaction |
| Photoelectric interaction results in areas in the radiograph that are ____. This means that the resulting image will possess ______ density. | light low |
| Probability of total photon absorption is dependent on: | * the energy of the incoming x-ray photon * the composition of the anatomic tissue |
| What is the ability of an x-ray photon to remove an electron? | ionization |
| The photoelectric effect if responsible for total ________ of the incoming x-ray photon. | absorption |
| The energy of the incoming x-ray photon must be at least _____ to the binding energy of inner shell electrons. | equal |
| True or False: The overall energy of the primary beam increases as it passes through the anatomic part. | False |
| The process of ________ means that the photons lose energy and are not absorbed during interaction; instead, the photon changes direction. | Compton scattering |
| _____ is an outer shell electron interaction. | Compton effect |
| The electron that is ejected during the compton effect is called a | compton electron or recoil electron |
| During the process of Compton scattering, the incident photon continues on an altered path, scattered, with less energy and a _____ wavelength than before the collision. | longer |
| True or False: Scattered radiation contributes to radiation dose to the patient and provides useful information about the anatomic area of interest. | False |
| The percentage of Photoelectric interactions _______ at a higher kilovoltage. | decrease |
| The percentage of Compton interactions _______ at higher kilovoltage. | increase |
| If the incoming x-ray photon passes through the anatomic part without any interaction with the same atomic structures, it is called: | transmission |
| Transmission is more likely to occur with ________ kVp. | high |
| The incoming x-ray photons that are transmitted create the _______ areas on the radiograph and the resulting image will produce _______ density. | dark / high |
| True or False: The quality of the image created is compromised if the scattered x-ray photon strikes the image receptor. | True |
| Radiation that leaves the patient is called: | exit radiation |
| Exit radiation consists of ________ and ________ radiation. | transmitted and scattered |
| Scatter radiation creates unwanted density on the image called: | fog |
| What percentage of the primary x-ray beam actually reaches the image receptor? | less than 5% |
| The x-ray beam that reaches the image receptor creates the ______ or invisible image. | latent |
| Developing and processing an exposed film produces the _______ image. | manifest |
| Anatomic tissues that vary in absorption and transmission create the ___________ on the image. | range of densities |
| Imaging the movement of internal structures is known as: | fluoroscopy |
| What is the process in which the exit radiation form the anatomic area of interest interacts with a light emitting material for conversion to visible light? | image intensification |
| The light emitting material is called | input phosphor |
| Which image intensifier component converts the visible light intensities from the input phosphor to electrons? | photocathode |
| What is the purpose of electrostatic focusing lenses? | to focus electrons into a narrow stream toward the output phosphor |
| The image light intensities from the output phosphor are converted to an __________ and sent to a TV monitor for viewing. | electronic video signal |
| What are the 2 types of digital radiography that is commonly used today? | CR - Computed radiography DR - Direct digital radiography |
| True or False: Regardless of whether the imaging is CR or DR, the computer can manipulate radiographic image in a variety of ways. | True |
| In digital imaging, the latent image is stored as ________ and must be processed by computer for viewing. | digital data |
| True or False: The process of differential absorption is different on each type of image receptor. | False |
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