Will the following pulse sequence adhere to the USFDA SAR guidelines for the head?
Sequence = multi-slice, spin echo
TR = 500 ms
TE = 25 ms
Thk = 5 mm
Number of slices = 10
Energy per 90o pulse = 5 J
Width of 90o pulse = 50 ms
Signal acquisition time = 10 ms
Patient weight = 72 kg

SAR = Joules/second/killogram

The number of joules deposited per second by the sequence is
(5J)(number of equivalent 90o pulses per SE slice) (Number of slices per TR)
J/s = (5J)(3 90o pulse equivalents per SE slice)(10 slices per TR) / (500 ms per TR)
J/s = (5J)(3)(10) / (0.500 s) = 300 J/s
SAR = J/s/kg = 4.17 W/kg

Since the 2003 FDA SAR limit for the head is 3 W/kg, this imaging sequence exceeds the limit.