Jan Willem van der Veen1 and Jun Shen1
1Magnetic Resonance Spectroscopy Core, NIH, NIMH, Bethesda, MD, United States
1Magnetic Resonance Spectroscopy Core, NIH, NIMH, Bethesda, MD, United States
Phase modulation of adiabatic pulses with a modulated selection gradient may exceed Nyquist limits when a spatial offset is applied.
Figure 2. Simulated voxel profiles a) pulse 1 and b) pulse 2. Spatial
offsets range from 0, 2, .., 12 cm. The vertical dotted lines show
the Nyquist frequencies.
Figure 1. Point to point phase increments of two popular
GOIA-WURST(16-4) adiabatic pulses, number of points, sample interval,
bandwidth range, B1 max level, and gradient amplitude modulation
factor: a) pulse1: 175, 20 us, -10 kHz … 10 kHz, 817 Hz, 0.90 from
(3), and b) pulse2: 450, 10 us, 5 kHz … 5 kHz, 640 Hz, 0.85) from
(1). The Nyquist limit at 180 degrees is shown as the dotted line.
The number at the left in the plot indicate the spatial shift of the
pulse in cm.