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Final-10
| Question | Answer |
|---|---|
| How the 90 second rapid processing (1965)became possible? | Developing of new chemistry and emulsions. Faster drying thanks to the polyester of film base. |
| What is the approximate time for automatic and manual developing? | Automatic: 22 seconds Manual: 5 Minutes |
| What are the reducing agents in the developer? | Phenidone and hydroquinone. |
| What is the trace of passage way in the processor? | Transport (moves film through developer, fixer, wash, and dryer) |
| What is acetic acid, where can we find it and why we use it for? | Is used as the activator in the fixer. maintaining an acidic PH of 4.0 - 4.5 to enhance the function of the clearing agent. Also reduces agents from continuing to function when film is immerse in film. |
| Three subsystems of Transport system | Transport racks, crossover networks, drive system. |
| Replenishment system | Replaces chemicals that are depleted through the chemical reactions of processing, oxidation and evaporation. |
| What controls speed of transport system? | Is control by the speed of the motor and gear reduction system used. Drive system turns the rollers in the processor. controls the time each chemical is immersed in each chemical solution. |
| What are the critical time periods is a processor. | the most critical time period is the Developer: 20-25 sec. (Fixer: 20 sec. Wash: 20 sec. dry: 25-30 sec.) |
| Developer temperature | 92 to 96 F (33 to 35 C) |
| Temperature control system | Developer, washer and dryer required precise temperature. developer (most critical) wash water is maintain at 3C (5F) or lower. |
| Silver halides | have a negative exteriors (where bromide and iodine are located) and positive interiors (where silver ions are located. |
| Chemical Fog | The effect of a film when unexposed silver halides are reduced. |
| Black metallics | When a silver ion obtains en extra electron, it is converted to a stable black metallic silver atom. |
| Silver halides thats have fewer than ____ silver atoms on their sensitivity speck are unable to open a gate and remain undeveloped. | 3 |
| What are the 2 major chemicals for development. | Phenidone and Hydroquinone |
| Phenidone | Reducing agent, rapidly produces fine detail shades of gray. |
| Hydroquinone | Reducing agent, slowly produces heavy densities. (black tone) |
| Contamination of developer | only 0.1 % of fixer in the developer tank will destroy the ability of the reducing agents. a film will appear extremely gray. |
| Why should the lid of the processor should be propped open whenever the processor is not in use? | Because when processor is shut down, excessive condensation can occur as it cools. |
| PH of solutions | Developer-Reducing agents 10.0 to 10.5. Fixer-Activator (4.0 to 4.5) Concentrating solution containing hydroquinone has a PH of 12.0 |
| What happens if fixer is not washed off? | can result in silver stains or a yellowing of the emulsion after a few years. |
| Volume replenishment system | is used for high volume units. |
| Flood replenishment system | is used for low volume units. |
| How is the replenishment system activated? | when the film enters the processor, the entrance rollers activate a microswitch or an infrared sensor. |
| Layers of the screen | 1. Base 2. Reflective layer 3. phosphor 4.protective coating |
| Deficiency of screens to produce light | As screens age, their phosphors decrease in activity. |
| What is luminescence? | Is the ability of a material to emit light in response to excitation. |
| What is fluorescence? | type of luminescence, is the instantaneous emission of light. Light is emitted within the time it takes an electron to complete one orbit. |
| What is phosphorescence? | type of luminescence.Is delayed emission of the light. phosphorus continues to emit light after the incident x-ray photon energy has dissipated. |
| screen lag or afterglow | delayed phosphorescent emission, common in older intensifying screens. |
| Normal life of intensifying screen phosphors is? | 5 to 7 years |
| Intensifying screen characteristics | Resolution, speed, contrast and latitude. |
| Resolution and speed are affected by? | concentration of the crystals , phosphor crystal size, layer thickness, |
| What is Isotropic emission? | refers to radiation emitted with equal intensity in all directions. |
| Reflective Layer | Layer of material used in an intensifying screen to reflect light towards the film. |
| what does Wire mesh test tool checks for? | Is used to check good screen- film contact. Areas of poor screen will appear blurry and cloudy. |
| Construction of various layers of screen | 1. Base: Polyester plastic 1mm thick. 2. Reflective layer: magnesium oxide or titanium oxide 25um thick. 3. phosphor layer: 150 to 300 um. 4. Protective coat: plastic 25 um thick. |
| Atomic number for phosphors | High atomic number is desirable to increase the probability of an incident x-ray photon interactions. |
| Spectral emission | is an indication of precise wavelength of light emitted by the phosphors. |
| High resolution | small crystal size and thin emulsion |
| Low resolution | large crystal size and thick emulsion. |
| Why are rare earth screens preferred? | because they have greater absorption abilities, intensification factors, and conversion efficiency. Rare earth screens use phosphors with z# of 57-71. difficult to isolate. |
| How cassettes should be store? | on end. |
| Sensitometer | equipment design to expose a reproducible uniform, optical wedge onto a film. has controlled intensity light source. |
| Penetrometer | aka step wedge. a series of increasingly thick uniform absorbers. |
| Densitometer | instrument that provides a readout of the amount of blackening (density) of the film. |
| Base plus fog | is the density at no exposure or density that is inherent in the film. |
| Straight line portion | between toe and shoulder.Useful range of densities. |
| Sensitometric curve | radiographic relationship between amount of exposure and resultant density on the film (D log E curve, characteristic curve, Hurter and Driffield curve) |
| Dmax | the maximum density the film is capable of recording. |
| Resolution | ability to accurately image an object. unit line pair per millimeter lp/mm. Small crystals=darken small area of film. Large crystals= darken large areas. |
| Speed | The amount of density a film produces for a given amount of exposure in the film speed. |
| Speed is controlled by what? | activity of phenidone because affects the toe of the D log E curve. |
| Film speed and crystal size are _____ proportional | directly |
| speed and number of sensitivity specks are____ proportional | directly |
| film speed and thickness layer are ______ related. | directly |
| Latitude | is the range of exposures that will produce densities within the diagnostic range. |
| Latitude and contrast are _____ related | inversely. as contrast increases, latitude tends to decrease. |
| Density | one of the two photographic properties that comprises visibility to detail. Overall balckening from the black metallic silver deposited in the emulsion. |
| Controlling factor of density | mAs |
| The minimum change necessary to cause a visible change in density must be? | 30 % of mAs or other influencing factor that would equal this change. |
| an increase in Kvp will ___ density | increase |
| an increase in mAs will _____ density | increase |
| an increase in kvp will ______ contrast | decrease |
| increasing mAs will _____ contrast | no change |
| High contrast | Fewer shades of gray, increased contrast, low kvp, short scale of contrast. |
| Low Contrast | Many shades of gray, decreased contrast, high kvp, long scale contrast. |
| increasing SID will _____ IR exposure | decrease |
| Decreasing SID will _____ IR exposure | increase |
| Umbra | : is the distinctly sharp area of a shadow or the region of complete shadow. The umbra receives essentially no photons. |
| Penumbra | : Is the imperfect, unsharp shadow surrounding the umbra. Receives more photons at the outer edges w/ progressively fewer photons toward the umbral area. |
| Factors that affect recorded detail are | SID, OID and focal spot size, image receptor and motion. |
| Distortion | is the 2nd of the two geometric properties affecting radiographic image quality. Is misrepresentation of size or shape. |
| Magnification size distortion is controlled by | positioning the body part and tube to maximized SID while minimizing OID. |
| Foreshortening occurs when | the part is improperly aligned. Changes in the tube angle cause elongation, never foreshortening. |
| Guide shoe mark | improper positioning or springing of guide shoe in turnaround assembly |
| Pi line: | dirt or chemical stains on rollers |
| Sharp increase or decrease in OID | dirty or warped rollers, leaves sludge deposit on film Gray fog: improper processing chemistry |
| Curtain effect | improper squeezing of processing chemicals of film |
| improper squeezing of processing chemicals of film | pressure caused by irregular or dirty rollers |
| Yellow-brown drops on film | oxidized developer |
| Milky appearance | : underreplenished fixer |
| Greasy appearance | inadequate washing |
| Brittle appearance | improper dryer temperature or hardener in the fixer |
| AEC | : the function of aec is to eliminate the need for the radiographer to set an exposure time |
| Configuration | determining the location of the AEC chambers is important. If plastic inserts are not provide to determined the location of aec’s a tech must take an image without a body part , exposed at very low Kvp for maximum contrast. |
| AEC cells, when more than one cell is used | the signals from the cells are sent to a special operational amplifier which sums the voltages received from each cell. Divides by the # of cell that have been activated, and then terminates the exposure. |
| Backup time | should be set at 150% of the anticipated manual exposure time |
| U.S. public law requires | that generators automatically terminate AEC exposures at 600 mAs nor 60 kilowatt seconds above 50 kVp and 2000 mAs below 50 kvp. |
| Current | the quantity or # of electrons flowing. |
| Resistance | the amount of opposition to the current in the circuit |
| The length of a conductor has ____ proportional relationship to resistance | directly |
| The movement of electrons is facilitated by | material that allow electrons to flow easily. This materials are known as conductors. |
| Non-conducting materials are called | insulators. |
| Rectification | : process by which alternating current is change into pulsating direct current |
| Generator | : device that converts mechanical energy into electrical energy |
| Overhead support system | is the most flexible and costly |
| Exposure switch | remote control device that permits current flow through the circuit. initiates exposure. |
| Thermionic cloud | is produced by the cathode. Conduction of high voltage to the gap |
| Melting of the anode occurs due to | rotor-bearing failure. Also when temperatures exceed the melting point of tungsten melting will occur. (long used at high temperatures) |
| Characteristic interaction | an incident electron interacts with an inner-shell electron, knocking out the inner shell electron and continuing in a slightly different direction, which creates a hole in the inner-shell, making the shell unstable. |
| Characteristic cascade | : the reaction of electrons dropping into holes created during a characteristic interaction until there is only a hole in the outer-shell. |
| Bremstrahlung interaction | an incident electron reacts with the force field of the nucleus, causing the electron to slow down, diverting the electron’s course; the electron loses energy and changes direction; the energy lost is the “braking”. |
| Filtration: | is the process of eliminating low energy photons by the use of aluminum. Reduces patient dose . |
| Half Value Layer | is the amount of absorbing material that will reduce the intensity of the primary beam to one-half its original value |
| Types of filtration | Inherent (inside the tube), Added (outside tube), Compound (2 or more materials, placing high z# closest to the tube and lowest Z# closest to the pt), compensating (wedge and trough). |
| Quality of photons | kvp |
| Quantity of photons | mAs |
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