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What is sensitometry
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What is accomplished by exposing and processing film and then measuring and evaluating the resulting densities
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film sensitometry
chapter 21
| Question | Answer |
|---|---|
| What is sensitometry | the measurement of the characteristic responses of film to exposure and processing |
| What is accomplished by exposing and processing film and then measuring and evaluating the resulting densities | sensitometry |
| *What method is useful in establishing, evaluating, and maintaining technical exposure factor charts and systems | *sensitometric methods |
| *Who can only perform the duties of the sensitometric methods | *qualified radiographer |
| A penetrometer, sensitometer, and a densitometer are what type of equipment | equipment for sensitometric procedures |
| What is an increasingly thick uniform absorbers made of aluminum steps, sometimes use tissue equivalent plactic | penetrometer |
| What is another name for a penetrometer | step wedge because of its shape |
| How does the penetrometer create a step wedge on radiographic film | by exposure to x-ray |
| Why is the penetrometer is a excellent method for monitoring both x-ray equipment and film/intensifying screen combinations | it reproduces the variables associated witha clinical situation |
| What is designed to expose a reproducible uniform, optical step wedge onto a film | sensitometer |
| The sensitometer contains________ (a pulse stroboscopiclight is best) and a piece of film with astandardized _________(a step tablet) | controlled intensity light source,optical step wedge image |
| *What reproduces the same amount of light each time it is triggered | *cotrolled light source |
| *What are controlled by circuits that supply an exact quanity of to a capacitor that discharges to astroboscopic light when triggered | *volume fluctuations |
| What absorbs a calibrated amount of controlled light | optical step wedge |
| The optical step wedge leaves a uniform and reproducible _________ to expose any film placed in the _________ over the optcal ste wedge | light penetrometer, sensitometer |
| What should not be touched because hands leaves a film of oil that interfers with the light intensity | optical step wedge |
| What usually increase density 100 percent by a factor of 2 per step | 11 step wedge |
| What increases density up to 41 percent by a faactor of 1.41 times | 21 step wedge |
| *What wedge is perfect for processor quality control monitoring | *sensitometer produced step wedge |
| *When the film is processed, what is carried backward on the emulsion as it is driven through the rollers of an automatic processor | *exhausted reducing agents and bromide ions |
| *how is the sensitometric strips fed into the automatic processor | *with either the long axis of the step wedge parallel to the entrance rollers or with the light edge entering the processor first |
| What instrument provide a readout of the amount of blackening on the film | densitometer |
| What do the densimeter consist of | calibrated uniform light source, stage, light aperture, sensor arm, readout display, and calibration control |
| *What must be calibrated before each reading by recording the amount of light the light source is emitting | *densitomter |
| *The calibrating of the densitometer is done by pushing the __________ so that the sensor is in contact with the light source | *sensor arm |
| *What is used to set the readout display of the densitometer to zero | *calibration control |
| *What can calculate the difference between the calibration intensity and the intensity of light the film is transmitting | *densitometer |
| *What do some densitometers include to to negate the blue tint in the film base | *filter |
| *because films are sensitive to a wide range of exposures, their _______ are best visualized if the range is compressed into a logarithmic scale | *densities |
| When using a logarithmic scale with a base of _____ and increment of 0.3 represents a ____________ of exposure | 10, doubling |
| What are the numbers displayed by the densitometer | optical density numbers |
| What is the density range for radiographic film | OD 0.0 to 0.4 |
| *What is the ability of a film to stop light | *opacity |
| What is normally shown as a graphic relationship between the amount of exposure and the resultant density on the film | sensitometry |
| Which axis is composed in a logarithmic scale | horizontal exposure axis (x axis) |
| Which axis is shown as a linear scale | vertical density axis (y axis) |
| The curves of the axis is known as | density log exposure or D log or E curves |
| Characteristic, sensitometric, and Hunter and Driffield curves are also known as what | D log or E curves |
| What are the important elements of a typical D log E curve | the base plus fog, toe, straight line gamma , shoulder, and maximum density Dmax |
| What represents the density at no exposure or the density that are inherent | base + fog |
| What includes the density of the film base, its tints and dyes, plus any fog the film experiences | base + fog |
| What is the ranges for the radiographic film density | OD 0.05-0.10 |
| True or False: the total base fog is seldom below OD 0.10 but should not exceed OD 0.22 | true |
| What usually adds about OD 0.05-0.10 in _______ | processing the film, fog density |
| What is the measurement of the diagnostic quality of the information on a radiograph | OD 0.5 to 1.25 |
| Why is the straight line portion of the curve fairly straight | the film is reacting in a linear fashion to exposure |
| What is primarily caused by the high temperature at which automatic processors operate | the hyperactivity of the developer solution |
| What is the reducing agent that controls the subtle gray tones early in the development process | phenidone |
| What is the region of the curve predominately controlled by the phenidone | toe |
| What is the portion of the curve that is between the toe and the shoulder | straight line portion |
| What is the range of the diagnostic densities | from the low of OD 0.25-0.50 to a high of OD 2.0 to 3.0 |
| What is the reducing agent that controls the heavy black tone later in the developer | hydroquinone |
| What is the name of the curve that is controlled by the hydroquinone | shoulder |
| What is the maximum density the film is capable of recording | Dmax |
| Dmax is what point on the D log or E cure | highest |
| *What represents the points where all sulver halides have a full complement of silver atoms andcannot accept more | *the highest point on the D log or E curve |
| *What is the result of the exposure beyond Dmax | *less density |
| *why would there be less density beyond Dmax | *silver atoms attached to the sensitivity specks will be ionized again, reversing their charge and causes them to repell from the speck |
| *what is the process of reducing the intensity of the latent image, producing less density | *reversal or solarization |
| *what is the shape of the true D log E curve | *bell shaped |
| what is the name of the film that is preexposed to Dmax | duplication film |
| What will cause a reversed duplicated image instead of a negative one | additional exposure |
| *What will cause a reversed duplicated image instead of a negative one | *additional exposure |
| What will cause a reversed duplicated image instead of a negative one | *additional exposure |
| What are the classification of the primary characteristic of film | resolution, speed, contrast, and latitude |
| What permit the analysis of speed, contrast, and latitude within the normal exposure ranges of the film | sensitometry |
| *What can causr reciprocity failure | *extremely high or long intensity exposure |
| *What can happen to silver halide crystals, when they are exposed to extremely long or high intensity levels | *they can overload |
| What is the ability to accurately image an object | resolution |
| What is another name for detail, sharpness, definition, and resolving power | resolution |
| How is resolution measured | by the ability to see pairs of lines |
| What is the unit of resolution | lp/mm ( line pairs per millimeter) |
| How is film resolution determined | by the size of the silver halide crystals |
| *Smaller crystals will darken what area of film | *small area |
| What cannot be visualized if it is smaller than a silver halide crystal | information |
| What kind of relationship exist between film resolution and crystal size | inverse |
| The smaller the crystal the _________ the resoluti on | higher |
| The _________ the crystal, the lower the resolution | larger |
| *What is grains another term for | *silver halide crystals |
| What does poor resolution called | graininess |
| Although film graininess can be seen, what controls the radiographic film/screen system resolution | intensifying screen phosphers |
| *True or False: The radiographic film/screen system resolution is controled by the size of the silver halide crystals | *false |
| What is the amount of density a film produces for a given amount of exposure | film speed |
| What is controlled by the activity of the phenidone | speed |
| How is film sensitivity determined | size of the silver halide crystals |
| What else have an effect on the film sensitivity | number of sensitivity specks and the thickness of the elmulsion |
| True or False: the film speed and the crystal size are directly related | true |
| The _______ the crystal, the ________ the film speed | larger, faster |
| True or false: the film speed and the number of sensitivity specks are directly related | true |
| True or false: the thicker the emulsion layer, there are more crystals | true |
| What will pprduce more film density | same number of photons |
| True or False: the film speed and thickness of emulsion are directly related | true |
| The _______ the emulsion the _________ the film speed | thicker, faster |
| The thinner the emulsion the _______ the film speed | slower |
| What is the point on the D log E curve where a density of OD 1.o + b+f is achieved | speed point |
| What is the log exposure that will produce the speed point for a given film | exposure point |
| What can determined by using the reciprocal of the exposure required to produce a given density | relative film/screen speed |
| What does ______1______ exposure in R needed to produce speed point density (OD 1.0+b+f) | relative speed |
| What does emmersion time, solution, temperature, amd chemical activity affects | film speed |
| What will cause a visible change in film density | 0.5 degrees |
| What is the difference between adjacent densities | contrast |
| What of the D log E curve determines contrast | shoulder |
| True or False: steeper the slope the higher the contrast | true |
| What is controlled by the level of activity of the hydroquinone | contrast |
| What is simply a measure of the solpe of the straight line portion of the curve at the speed point (OD 1.0) | Gamma |
| What defines the overall radiographic film contrast | average gradient |
| What does this formula __D__ represent E | average gradient |
| What are the most radiographic film average gradient | between 2.5 and 3.5 |
| In radiography, what is the doubling the exposure with double the density | common misnomer |
| What is the range of exposures that will produce densities within the diagnostic range | latitude |
| Latitude can be recorded as the _____ of the range of exposures that will produce diagnostic range densities | width |
| True or false: latitude and contrast is inversely related | true |
| As contrast ________ latitude tends to _______ | increase, decrease |
Created by:
rachel43