OLD                        NEW

300 mA                _______mA

0.35 sec              0.10 sec

60 kVp               70 kVp

40" SID              50" SID

CALCULATIONS AND ANSWER BELOW

____________________________________________________________________________

Find mAs

Use 15% rule

direct square law (density maintenance or distance maintenance law)  new SID over old SID squared

Find new mA (mAs divided by the time)

300mA x 0.35sec =  105mAS

10 5mAs divided by 2 = 52.5 mAs (15% rule)

50/40 squared = 2500/1600 = 1.56 (multiply to the LATEST mAs)

52.5 mAs x 1.56 = 81.9.6 mAs

81.9 mAs divided by 0.1 sec = 819 mA (round down to 800 mA)

_____________________________________________________________________________________

OLD                        NEW

400 mA                300  mA

0.15 sec                _____ sec

80 kVp               70 kVp

72" SID              50" SID

CALCULATIONS AND ANSWER BELOW

____________________________________________________________________________

Find mAs

Use 15% rule

direct square law (density maintenance or distance maintenance law)  new SID over old SID squared

Find new mA (mAs divided by the time)

400 mA x 0.15 sec = 60 mAs

60 mAs x 2 = 120 mAs (15% rule)

50/72 = 2500/5184 =0 .48 (multiply to the LATEST mAs)

120mAs x  0.48 = 57.6 mAs

57.6 mAs divided by 300 mA = 0.19 sec