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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
Created by: 570419180