Fig 1.
Three different RF pulses applied in the power amplifier (left column) and the actual signal generated by the RF coil (right column).
(a) A square pulse and (b) its actual signal on the RF coil, (c) a square pulse with a post-pulse-damping lobe and (d) its actual signal on the RF coil, and (e) a square pulse with both pre-emphasis and a damping pulse and (f) its actual signal on the RF coil.
Fig 2.
Example of the sinc pulse (N0 = 3, i = 1, NS = 13).
Fig 3.
Input RF pulses (left column) and the signal generated by the RF coil (right column) for sinc pulse (top row), calculated pulses with NS = 13 (second row), NS = 25 (third row), NS = 37 (bottom row).
Fig 4.
Three different methods for measuring Q-factor.
(a) Diagram using two decoupled sniffer loops and (b) example insertion loss between two sniffer loops. (c) Diagram to measure return loss of the RF coil and (d) example return loss of the RF coil. (e) Diagram to measure ring-down time and (f) example waveform of the applied RF pulse.
Fig 5.
(a) Schematic diagram of an open, table-top, MRI system with photos of (b) the RF solenoid coil and (c) the magnet.
Fig 6.
A spin-echo sequence with pre-polarization.
Table 1.
NMR signal acquisition parameters used in this study.
Fig 7.
Measured actual pulses of (a) square pulse input and (b) compensated square pulse input.
Vertical solid lines indicate the input pulse ends.
Fig 8.
Sinc pulses (top row) and calculated input pulses for compensation calculated with different NS (13 (second row), 25 (third row), and 37 (bottom row)) for different bandwidth (30 kHz (left column), 90 kHz (middle column), and 150 kHz (right column)).
Fig 9.
Measured actual pulses (output pulses, vertical dashed lines indicate the input pulse ends).
And frequency spectrums of the sinc pulses (top row) and compensated sinc pulses calculated with NS values of 13 (second row), 25 (third row), and 37 (bottom row) and bandwidths of 30 kHz (left column), 90 kHz (middle column), and 150 kHz (right column). The y-axis shows normalized values (from -1 to 1 for waveforms, from 0 to 1 for frequency spectrums).
Table 2.
Relative errors of the signal magnitude of the frequency spectrum.
Fig 10.
1H 25th, 50th, 75th, 100th, and 125th echoes from a train of 1000 echoes, of water obtained using square pulse (top row), compensated square pulse (second row), sinc pulse with 90 kHz bandwidth (third row), and compensated sinc pulse, 90 kHz bandwidth, n = 37 (bottom row).
Table 3.
SNR values measured by using uncompensated and compensated pulses (square and sinc pulses).