IR Exposure Flashcards
What is needed to produce a decent image
IR needs to absorb the same exposure
Back then if an image was dark what did that indicate
Too much exposure
Back then if the image was bright, what did that indicate
That the image had too little exposure
What do we use today to determine proper IR exposure
By the exposure number, exposure indicator, deviation index
Does IR exposure effect technique
No
What is the number for an ideal exposure
0
If DI is more than +3 what does that mean
Exposure too high
Need ti repeat
What does it mean if DI is -3
Not enough exposure
Need to repeat
How are Deviation index and exposure related
Directly
If you double your exposure what happens to DI
Goes up by 3
If you cut your exposure in half what happens to DI
Goes down -3
How do you find DI after image is in pack
Hit “H”
Where is exposure indicator calculated at
The region of interest (ROI)
Of exam selected
What are the 2 controlling factors for IR exposure
mAs and kVp
As mAs and kVp increases IR exposure…
Increases (diretly proportional relationship)
Exposure indicator depends on what
Dose
mAs is the product of what
mA and time
To increase mAs what has to happen
mA or time is increased
What is the reciprocity law
When mA and time are adjusted to maintain same mAs
if one goes up/ the other goes down
What’s the 50% rule
The double / half rule
A double or half in mAs is needed to make a significant change
If we double the mAs what will the DI be
+3
increase by 3
If I divide my mAs by half, what will the DI be
-3
decrease by 3
A smaller change in kVp has what kind of effect of IR exposure
Large effect
What’s the 15% rule
Increasing or decreasing kVp by 15% will increase or decrease your IR exposure
A change of 15% in kVp is equal to what
Double/ half in mAs
An increase of 15% in kVp will make DI what
+3
A decrease of 15% in kVp will make DI what
-3
As kVp goes up mAs goes down to maintains what
IR exposure
15/50 rule
Which rule do you use if DI is out of range
50 % rule for mAs
Or
15% rule for kVp
Which rule do you use if DI was in range
15/50 rule
Adjust mAs and kVp to keep pt dose low
DI and exposure have what kind of relationship
direct
