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| How many centimeters are equal to 1 inch? | 2.5 cm
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| How many cm are in 40"? | 100 cm
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| How many cm are in 72"? | 180 cm
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| What does distance affect? | density, size distortion and sharpness
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| What does FFD mean? | focal film distance
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| What does TFD mean? | target film distance
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| If you increase SID what happens to magnification? | decreases
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| If you increase SID what happens to density? | decreases
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| If you increase SID what happens to sharpness of detail? | increases
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| What affect does SID contrast? | SID does NOT affect contrast
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| In order for image contrast to change, what has to happen? | The ratio between compton and photoelectric interactions has to change
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| If you have a large body part, do you have more or less penumbra? | more penumbra
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| Does penumbra increase or decrease when SID is decreasd? | increases
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| For magnification to change, what has to happen? | Umbra and penumbra have to grow at the same rate.
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| How does SID affect shape distortion? | SID NEVER affects Shape distortion
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| How do you prevent shape distortion? | beam/ part/ film alignment
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| How much change in SID do you need in order to get a visible change in density? | 20% or 10"
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| How much change in distance do you need to require an adjustment in technique? | 20% or 10"
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| The intensity of the radiation is inversely proportional to the square of the distance is what law? | Inverse Square Law
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| What does the inverse square law predict? | density
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| The change in technique should be equal to the square of the change in distance is what law? | Square Law
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| What is another name for the Square Law? | Density Maintainance Formula
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| mAs is directly related to the square of the distance is what law? | Square Law also called the density maintainance formula
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| What is the Air Gap Technique used for? | Combat image fog
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| How many inches of OID are used for the Air Gap Technique? | 6"-8"
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| If you increase OID, what happens to contrast? | Contrast increases
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| If you increase OID, what happens to density? | Density decreases
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| When OID is increased, what should you do to SID? | increase SID to decrease magnification
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| Does OID affect distortion? | yes, size distortion
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| What factor should be adjusted when you have large OID or long SID | mAs
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| what is the formula to determine magnification? | magnification= SID/ SOD
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| Which has a greater affect on magnification SID or OID? | OID
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| What does AEC mean? | Automatic Exposure Control
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| What are the two types of AEC? | Photo-multiplier and Ionization Chamber
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| What is the more connon type of AEC? | Ionization chamber
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| What year was AEC developed? | 1942
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| What are the advantages of AEC? | reduce inconsistancy, provides uniform density, radiologists are able to read uniform and consistant radiographs
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| What is the variable in AEC machines? | time mA and KVp are set
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| What does photomultiplier use to terminate the exposure? | Light
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| What does Ionization chamber use to terminate the exposure? | radiation
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| Is photomultiplier entrance type or exit type? | Exit
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| What tells where to center with AEC? | photo cells
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| Is Ionization chamber measured before or after the intesifying screens? | Before
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| Is ionization chamber entrance or wxit type? | entrance
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| Sufficient density is obtained when these fill and terminate the exposure. | Thyristor capacitator
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| What are modern ionization chambers formed from? | aluminum sheets
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| Why is higher KVP used in AEC? | the give a wider lattitude (which decreased the amount of repeats)
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| What is responsible for averaging out density? | photo cells
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| Where do you need to center for AEC? | must be centered over photo cells (choosing the proper cell is crucial)
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| The time it takes for the exposure to teminate is called? | reaction time
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| What is the typical minimum exposure time? | .002 seconds for new units .02 seconds for older units
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| What is it called when the AEC unit first detects radiation and then responds? | Minimun Response Time ( the shortest exposure time)
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| What is the longest amount of time an exposure can last before it is terminated? | Backup Time (patient protection)
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| How is the backup time determined? | Double the time used for an ideal radiograph (takes the reaction time and doubles it)
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| What is the most common error when using AEC? | Choosing the wrong IR (wall bucky vs. table)
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| What are the limitations of AEC? | selection of cell, can not use on extremities, can not use on table top exposures
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| What is AEC best for? | Trunk of body, femur, neck and cranium with the exception of the sinuses
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| Who is the biggest jerk in the class? | Joe
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| What are the 2 main factors of resolution? | Contrast and sharpness
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| What is resolution? | The ability to see 2 adjacent structures as separate structures within the image.
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| What are other terms that mean sharpness? | geometrical detail, recorded detail, sharpness of detail, definition
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| How are resolution and sharpness related? | directly proportional
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| How are distance and definition related? | They are inversely proportional
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| If you increase divergence, what happens to sharpness? | decreases
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| What are the visibilty factors? | density, contrast and noise
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| What are the recognizability factors? | Shape distortion (elongation and foreshortening) Size distortion (magnification) and Sharpness (detail)
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| How is FFD related to sharpness? | directly.. Increase FFD (also called SID) you increase sharpness
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| How is OFD related to sharpness? | indirectly.. Increase OFD (also called OID) you decrease sharpness
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| Do intensifying screens increase or decrease detail? | decrease
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| Do intensifying screens increase or decrease patient dose? | decrease
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| Is film sentitive to light or x-rays? | light
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| How does blur affect density? | NEVER affects density
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| What is the only thing focal spot size affects? | DETAIL (sharpness)
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| How do you know if you have motion of poor screen contact? | Motion would show all over the radiograph, poor screen contact shows as a localized blur that usually starts at the corners.
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| What are 4 types of motion? | Peristalsis, heart motion, breathing, and voluntary.. breathing can be voluntary or involuntary
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| What is the average respirations per minute for the average adult? | 16-18/ min
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| How do you minimize motion? | short exposure time, communication, and use of restraints
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| What affect does motion have on sharpness? | decreases it
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| How does slight motion show on the radiograph? | blur along the peripheral edges of the anatomy
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| How does severe motion show on the radiograph? | blur accross the whole image
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| What affect does motion have on contrast? | decreases contrast
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| Is motion considered a primary controller of image contrast? | No.. it is the only variable that reduces contrast without the affect of scatter
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| How does motion affect shape distortion? | gives a false image categorized as noise not shape distortion.
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| Does motion increase or decrease penumbra? | increase
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| What is the highest time you should use for a child? | 1/30th of a second
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| What type of patient is the most likely to cause motion? | pediatrics
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