Rapid acquisition of NMR diffusion-diffraction q-space plots from erythrocytes with varying gradient orientation: Rapid acquisition of NMR diffusion-diffraction q-space plots fromerythrocytes with varying gradient orientation

The rapid-acquisition of q-space data from 1H2O undergoing restricted diffusion in suspensions of red blood cells (RBCs) is made possible using a recently implemented pulse sequence, where the phase cycling of the radio-frequency pulses is reduced by using unbalanced pairs of bipolar magnetic field-gradient pulses. The q-space plots obtained with this pulse sequence show a shift in the position of the first diffraction minimum when compared to data from classical pulsed field gradient stimulated echo experiments. Diffusion simulations were used to investigate the effect of the additional delay introduced by the bipolar gradient pulses on the form of the q-space plots. RBCs of normal discocyte shape align with an external magnetic field, and the angular dependence of q-space spectra from suspensions of RBCs was examined using a linear combination of gradients applied along the y- and z-axes. The resulting q-space plots showed a gradual disappearance of the first diffraction minimum as the angle at which the gradients were applied was changed from 0° (along the z-axis) to~40°, beyond which the q-space plots showed no diffraction features. These experimental results were also evident in Monte-Carlo random walk simulations of diffusion in RBCs with field-gradients applied at varying angles with respect to cells aligned with B0