Rad Tech: Technique and Exposure
How much do you increase by to double?
100%
How much of a change do you need to see a visible difference in density?
30%
How much do you decrease by to half something?
50%
What controls density? Resulting in how much of a change in density?
AEC (...-2, -1, N, +1, +2..), 25%
Positive side of the xray tube is called?
Anode
Negative side of the xray tube is called?
Cathode
What is black on an image called?
Density
What is mAs related to?
Density
What is the most common cause for repeat radiographs?
Exposure Error
How does exposure time (mAs) affects recorded detail?
Exposure time (mAs) doesn't affect recorded detail
Reciprocity Law
as long as the product remains the same the mA and time can be altered and can create the same total exposure ex: 2mA x 1s = 2mAs 1 mA x 2s = 2 mAs
Where are the AEC photons located?
between the patient and image receptor
Exposure time does not affect what but can be a contributing factor?
does not directly affect patient's motion (and thus recorded detail) and however is considered a contributing factor
To see a darker image you do what?
double mAs
What does electrons do as they flow through the filament circuit?
electrons will boil off at the filament
Exposure Time (s)
expressed in seconds
To see a lighter image you do what?
half mAs
Wide Exposure Latitude
high kvp with long scale of contrast
mAs is the primary controller of what?
image density
Quantum Mottle
insufficient mAs when you use a very low mass; you will have a very low quantity of xrays, which results in a grainy appearance on image.
mAs and time is what to each other when what is maintained?
is indirectly proportional to each other when the total exposure density is maintained.
What is Exposure Time?
is the amount of time which the xray beam is activated and exposure occurs
What is mAs?
is the total exposure or the total quantities produced after the exposure
What happens when AEC receives the right amount of exposure?
it terminates
When you hear exposure latitude you should think of?
kvp
The higher the _________ the wider the ________.
kvp, latitude
The lower the ______ the smaller the ________.
kvp, window
Narrow Exposure Latitude
low kvp with short scale of contrast
higher the _________ the higher the __________.
mA, current
increase in the ________ increases the _______ where electrons boil off at the filament.
mA, quantity
Things that affect density.
mA, time, mAs
mA x s =
mAs
How does mAs affect contrast?
mAs is directly proportional to density. You can change density but have the same contrast ratio. mAs is not a variable that affects contrast.
Optimal mA
maximum mA setting for a given focal spot size
Kilovoltage Peak (kvp)
measure of electrical force in the xray tube
Motion
one way that you can create an blur on an image
Thermionic Emission
the boiling off of electrons of the filament
Milliamperage (mA)
the flow rate of electrons from the xray tube
What is directly proportional to mA?
the intensity of the xray beam
Where are the current of the electrons going to flow to?
they going to flow to the positive side of the xray tube. (anode)
Density on a film is directly proportional to what?
to the total exposure (mAs)
Space Charge or Electronic Cloud
where electrons are in the focusing cup and they stay together as they boil off
