Comments on ‘Human magnetic resonance imaging at 8 T ’

7T vs. 4T: RF power, homogeneity, and signal‐to‐noise comparison in head images

“…The calibrated 90° flip angles in the center of the brain were 255 μsec and 369 μsec at 4T and 7T, respectively, for a 1 kW equivalent square pulse averaged over six studies. The calibrated 90° pulse for 4T compared well with previously reported values (16, 19). Thus, 2.1 times more power was needed at 7T compared to 4T to attain 90° in the center of the brain.…”

“…Each coil was driven in quadrature at four points, 45°, 135°, 225°, 315°, relative to 0° at the bottom of the coil (16, 18). Consistent with the literature (16, 18, 19), the 300 MHz coil had an unloaded Q to loaded Q ratio of 432/66 and the 170 MHz coil's Q ratio was 850/78. The B 1 gain, defined as the ratio of coil B 1 field strength to coil input signal, was 1 dB less at volume center for the 300 MHz coil compared to the 170 MHz coil.…”

Pacing in magnetic resonance imaging environment: Clinical and technical considerations on compatibility

“…The impact of magnetic resonance scanning at 0•5 Tesla with respect to heating should be less than that of 1•5 Tesla, since the power absorption of a linear antenna is proportional to the square of the frequency of the radiofrequency field [77] . Hence, the use of a 0•5 Tesla system reduces the power absorption considerably [78] . Likewise, magnetic resonance sequences with a low specific absorption rate (e.g.…”