Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Exposure I
MCC Exposure Mid Term
| Question | Answer |
|---|---|
| What is the Bohr atom | Atom arranged like a mini solar system - electrons revolve around a nucleus in orbits or energy levels |
| Significant parts of Bohr atom | Protons, neutrons and electrons |
| What does the periodic table show | All known elements arranged in periods and groups. Elements in the same group will react chemically similarly and have similar physical properties. |
| What is the valence number of an element | Number of electrons in the outermost shell |
| Define ionization | Physical process of turning an atom into an ion by adding or removing electrons |
| Name six types of ionization | 1) Exposure of matter to x-rays or gamma rays 2) Exposure of matter to a stream of electrons 3) Spontaneous decay of radionuclides 4) Exposure of certain elements to light 5) Chemical ionization 6) Thermionic emission (in x-ray tube) |
| Who devised the Theory of Relativity | Albert Einstein in early 20th c. |
| What does Theory of Relativity mean | Describes motion of particles traveling close to the speed of light |
| Name the three types of energy produced in the x-ray tube | Heat (thermal), kinetic and electromagnetic |
| Identify the four conditions needed for the production of x-rays | 1) Source of electrons (thermionic emission off filament) 2) Acceleration of electrons (application of kVp) 3) Focusing of electrons (focusing cup direct electrons toward target) 4) Sudden deceleration of electrons (converts kinetic energy into radiation |
| X-ray quantity | Output intensity of x-ray imaging system; # of photons produced (in roentgens - R) |
| X-ray quality | Penetrability of an x-ray beam (effective energy) |
| What is an emission spectrum | Graph that shows range of energies of x-rays emitted; continuous for bremsstrahlung, line for characteristic (specific, K x-rays) |
| Three things that effect the x-ray emission spectrum | 1) Current (mA & mAs)incr amplitude2) Voltage (kVp)incr amplitude & position 3) Added filtration (ampltd at lower energies) |
| Name seven properties of x-rays | 1) penetrating & invisible2) electrically & magnetically neutral3) have different energies (polyenergetic)4) travel in straight lines and diverge from source5) travel at the speed of light6) capable of ionizing gases in air7) produce chemical & biological |
| How much of projectile electron's kinetic energy is converted to x-ray energy | 1% |
| Name two types of x-ray | Characteristic & Bremsstrahlung |
| Most of x-rays produced are which type | Bremsstrahlung |
| Why is term discrete spectrum used for characteristic radiation | Discrete = apart or detached from others; separate. B/C characteristic x-rays have precisely fixed energy values. |
| Two physical characteristics of x-rays | Quantity and quality |
| Primary x-ray beam | Radiation produced in the target |
| Hardened beam | Filtered; lower energy, lesser quality electrons have been removed |
| Heat Unit formula for single phase | kVp x mA x S |
| Heat Unit formula for three phase | kVp x mA x S x 1.35 |
| Heat Unit formula for three phase 12 pulse | kVp x mA x S x 1.41 |
| How can you extend tube life | 1) "Prime" tube (warm up per mfg instr) 2) don't hold rotor switch unnecessarily 3) use lower mA's when possible 4) use lower speed rotors when possible 5) don't make repeat exposures when near tube loading limits 6) don't rotate tube housing rapidly from |
| What does increased mAs do to filament | Heats it hotter |
| Do's to preserve tube | 1) Understand limitations (charts) 2) prime tube with warmup procedure |
| Dont's to preserve tube | 1) Avoid high mA settings 2) avoid prolonged use of rotor 3) don't ignore focal spot size - if on line for small, use large |
| Name the four main parts of an x-ray tube | Cathode, anode, housing (tube shield) and vacuum tube |
| What is the main function of the cathode | Releases electrons; negatively charged side of tube |
| What is the main function of the anode | Positively charged target for electrons |
| What is the focal spot | Region of the target from which x-rays are emitted |
| What is the focal track | Ring around rotating anode that gets heated by electrons hitting it; produces more x-rays from increased heat production |
| What is the useful beam | Part of primary radiation that passes through the window of x-ray machine & produces the image |
| What is the actual focus | Area on the anode target that is exposed to electrons from the tube current |
| What is the effective focus | Area projected onto the patient and the image receptor |
| Diode tube means what | Tube has two electrodes - anode (pos) and cathode (neg) |
| Explain how tube operates using the law of electrostatics | Force of attraction between unlike charges - positively charged surface of anode target attracts the negatively charged electrons burned off filament; high speed electrons smash into the target and produce photons of x-rays |
| Why use tungsten in x-ray tube | High atomic # so there are a lot of electrons available to be burned off; has high melting point so it can withstand large amounts of heat |
| rotor | rotating part of electromagnetic induction motor (spins target) |
| stator | part of electromagnetic induction motor that lies outside glass tube but inside housing; has stationary coil windings that generate pulses sequentially which turns rotor |
| anode face | spinning disc that the target is mounted on |
| filament | part of the cathode that emits electrons when heated "thermionic emission", resulting in a tube current |
| focusing cup | neg charged metal shroud that surrounds the filament, directs the electrons towards target |
| tungsten disc target | actual disc made of tungsten that the electrons strike |
| x-ray window | thin section of glass envelope through which the useful beam emerges |
| pyrex glass envelope | glass enclosure of tube components that encloses the vacuum chamber & can withstand high levels of heat |
| anode | positively charged side of x-ray tube that contains target |
| cathode | negatively charged side of x-ray tube that contains filament(s) & focusing cup |
| leakage radiation | x-ray which penetrates the metal housing |
| space charge | electron cloud around heated filament |
| thermionic emission | process of boiling electrons off filament |
| line focus principle | principle by which the target angle is used to increase recorded detail without losing heat load capacity of the anode |
| baking | process of evacuating gas from the tube |
| effective focus | size of focal spot projected toward the film |
| actual focus | area of target electrons strike |
| rotating anode tube | modern x-ray tube where heat to anode is spread out |
| Explain the line focus principle on the production of a radiograph | image size is controlled by the angle of the target - steeper angle will produce a radiograph that is smaller with better definition |
| Explain the anode heel effect on the production of a radiograph | the cathode side of an x-ray beam produced from a beveled edge will be more intense than the anode side; this can be used to your benefit when making an image of a part that has different thickness, i.e. thoracic spine. Point cathode side towards thicker |
| What amount of leakage does housing have to maintain by law | 100 mR/hr at 1 meter |
| arcover | electrons attracted to ash from burned filament that coats inside of glass tube; can crack tube |
| gassy tube | when tube cracks and vacuum compromised; exposures inconsistent - light/dark because electrons now interace with air and not just target; decreases output |
| What does copper hub do | directs heat out of the tube |
| Characteristics of an acceptable radiograph | adequate density; penetration; contrast; positioning; detail/visibility; correct legal details (markers, id's etc) |
| X-Ray Quantity | # of photons in the useful (primary) beam |
| Technical factors controlling density | Primarily mAs (# of photons produced in tube); kVp (speed of photons); SID; filtration |
| Radiographic density | degree of blackening of a film (mAs primary control) |
| Density defined | Log light output / light transmitted |
| attenuation | weakening of x-ray beam; reduction in radiation intensity that results from absorption and scattering |
| primary radiation | all radiation produced directly from the target in an x-ray tube |
| scattered radiation | radiation whose direction has been altered; major source of image degradation |
| secondary radiation | emitted from the interaction of X-rays with body tissues or other matter; generally lower in energy |
| remnant radiation | x-rays that pass through the patient and interact with the image receptor to create image (about 5% of x-rays) |
| absorption | transfer of energy from an electromagnetic field to matter; removal of x-rays from a beam via the photoelectric effect |
| x-ray wavelength | 10-10 – 10-11 m |
| differential absorption | different degrees of absorption in different tissues that result in image contrast and formation of the x-ray image |
| Classical or Coherent Scattering | Low KeV. No ionization. Incident photon interacts with atom and changes direction with no change in energy. |
| Photoelectric Effect | Moderate KeV, more at low kVp. Incident photon totally absorbed & loses all energy interacting with an inner shell electron, ejecting it from orbit; outer shell electrons move in to fill void & produce photons of secondary radiation. Greatest negative eff |
| Compton Effect | Moderate KeV, more at high kVp. Enemy #1 - most danger of exposure to RT. Incident photon interacts with outer shell electron, loses energy and continues in different direction; ionizes atom. |
| Pair Production | Interaction of high energy (min 1.02 MeV) photon with electrostatic field around nucleus. Photon disappears, energy converts into two particles of matter: electron & positron, which are ejected from atom. |
| Photodisintegration | High energy (over 10MeV) photon interaction with nucleus; nucleus is raised to an excited state and ejects a nuclear fragment; can cause chain reaction |
| Which x-ray photon interactions are significant in production of diagnostic x-ray images | photoelectric effect and Compton effect |
| What is unit used to measure x-ray quantity | Roentgen (R) or milliroentgen (mR) |
| Which technical factor is primary control of density | mAs |
| What is density | degree of blackening of a radiograph |
| Name four main factors that control density on a radiograph | 1) voltage (kVP) 2) current (mA) 3) exposure time (s) 4) source-to-image receptor distance (SID) |
| What device measures density on a radiograph | densitometer |
| Name 6 factors that will affect radiographic density (and how effects with increase) | 1) mAs (increase density) 2) kVp (increase density 3) SID (decrease density) 4) thickness of part (decrease density) 5) development time (increase density) 6) IR speed (increase density) |
| define x-ray quantity (AKA exposure, output and intensity) | number of x-ray photons in the useful beam, measured in R or mR |
| increase in quantity will | increase density |
| useful range of densities | .25 to 2.50 |
| quantity of photons in x-ray beam primarily determined by | mA |
| intensity fo the x-ray beam measured in | milliroentgen |
| rate of flow of electrons across the x-ray tube, or tube current, is | milliamperage |
| which factor does not directly affect density on a film | positioning |
| overall darkness of a radiographic film describes | density |
| if filtration is increased the effect on radiographic image will be | decreased density |
| an overly dense radiograph is one that is | too dark |
| as x-ray beam intensity increases the density on a radiograph will | increase |
| which of the following will produce the lease amt of density on a radiograph: 25, 50, 100 or 400 mA | 25 mA |
| Central Ray (CR) | center of the beam of x-rays coming from an x-ray tube |
| Focal Spot (FS) | small spot on the target of an x-ray tube which receives the impact of electron stream from the cathode, from which x-rays are emitted in all directions |
| electric current | flow of electrons |
| amperes | Amp, A, unit of current. 1 ampere = 1 coulomb/ 1 second. |
| volt | V, the SI unit for electric potential and potential difference |
| kilovoltage peak | kVp, the maximum possible energy a photon exiting the x-ray tube can reach |
| milliampere | mA, radiographic exposure factor that regulates the intensity of radiation emitted by the x-ray tube; directly influences density; 1/1000 of an ampere of electrical current |
| watt | W, The SI unit for electric power, may be mathematically expressed as amps times volts |
| milliampere seconds | mAs, the product of milliamperes and seconds of time; important exposure factor in the regulation of the amount of silver deposit in the x-ray image |
| kilovoltage | kV, 1000 volts; exposure factor used in radiography to influence radiographic contrast, penetration of tissues; directly influences radiographic film quality |
| time of exposure | in seconds (S), duration which exposure lasts |
| contrast | differences in radiographic density that enables image details to become visible; product of film contrast and subject contrast |
| film contrast | characteristic of film and developing process |
| subject contrast | result of the differences in absorption of the radiation by recorded detail of the part under examination |
| recorded detail | visible quality that depends first upon sharpness (detail), then by radiographic contrast |
| good definition | when the boundaries of various anatomic structures are sharp and clearly delineated and when density differences between the structures (contrast) are sufficient for the eye to distinguish one from another easily |
| darkroom safelight | light used in a photographic darkroom, designed to provide illumination without that part of the light spectrum to which the material in use is sensitive |
| CR | computed radiography with CR cassette and digital display |
| DR | direct radiography (no film or plate) |
| HIS | hospital information system |
| RIS | radiology information system |
| PACS | picture archiving communication system |
| Landscape | cassette layout orientation (long side horizontal) |
| Portrait | cassette layout orientation (short side horizontal) |
| image detector | captures and converts image, changes light photons into an electrical signal |
| CR Plate ID System | identifies image/projection, etc. |
| CR Latent image | 10/10 rule - 10% image degradation every 10 minutes |
| CR plate reader | processes the captured image into a digitized image |
| density index /"S" value | acceptable raange of exposure in terms of quality and dose |
| MPM | medical profile matrix; exposure "software adjustment" that "tweaks" exposure to produce a diagnostic image |
| Law of Conservation | matter cannot be created or destroyed; energy cannot be created or destroyed |
| Bremsstrahlung radiation | slowed-down or braking radiation; results from stopping of projectile electrons by target/nucleus |
| Characteristic radiation | x-ray emitted when an outer shell electron fills an inner shell void |
| thermal energy | energy of molecular motion; heat; infrared radiation |
| incandescence | emission of visible light from a substance or object as a result of heating it to a high temperature |
| dual focus | focal spot size controlled by heating either small or large filament |
| alloy | substance composed of two or more metals or a metal(s) with non-metal |
| bombardment | subjecting a body or substance to the impact of high-energy particles (i.e. electrons) |
Created by:
RoPray