RS 240 FALL 2013

mAs / kVp EXERCISE

1. 300 mA @ 1/10(s) @ 80 kVp600 mA @ 1/20 (s) @ 80 kVp

DO this to get rid of motion Law of reciprocity

2. 50 mA @ 3.0(s) @ 65 kVp400 mA @ .375 (s) @ 65 kVp

50 mA= 1/50 Use 3 seconds to use self motion to visualize structures (lateral t-spine to blur out

lungs and vascular organs)

3. 200 mA @ 30 ms @ 75 kVp800 mA @ 7.5 ms @ 75 kVp

mA doubled twice so you cut ms in half twice

4. 325 mA @ .19 (s) @ 75 kVp250 mA @ 0.25(s) @ 75 kVp

250*.25= 62 so you do 325/62 which is = to .19 You need a 25% to see a change in kVp to see a difference

5. 400 mA @ 0.35(s) @ 75 kVp400 mA @ .175 (s) @ 86 kVp

15% rule- 15% change in kVp is the same as doubling total mAs, if you subtract then you halve it

Do this to try to cut dose to patient in half but the second image might be grayer than the first image because more penetrated through

More kVp= less contrast 75*.15= 11 that is the change in kVp

6. 200 mA @ 0.15(s) @ 70 kVp100 mA @ 0.075(s) @ 92 kVp

200*.15= 30 kVp changed by +2 or 30% change in kVp -1 change in seconds because it is half So you only minus 1 so the 2 changes equal zero

7. 1000 mA @ 50 ms @ 65 kVp500 mA @ 200 ms @ 55 kVp

15% change in kVp= -1 mA= -1 so you have to make it = 0 so you add 2 200 ms because you have to make it +2 so you multiply

8. 100 mA @ ¾(s) @ 70 kVp200 mA @ 3/8(s) @ 70 kVp

mA= +1 s= -1 So you keep kVp at 70

9. 1000 mA @ 0.16 (s) @ 130 kVp250 mA @ .512 (s) @ 80 kVp

You do 15% of each change 15% of 130= 110 15% of 110= 95 15% of 93.5= 80 mA= -2 kVp= -3 0.16*5= .512

1= you halved it once so 200 is 100 ½ 2= you halved it twice so 1000 is ½ =500 then ½ of 500 =250