Fig. 6: Synthetic NMR spectra reconstructed for four uncoupled sites with relative intensities 1:0.4:0.1:0.7 positioned at 3.5, 1.6, 1.0 and -4.05 kHz, assumed subject to PI-SSFP experiments with different flip-angles α. | Nature Communications

Fig. 6: Synthetic NMR spectra reconstructed for four uncoupled sites with relative intensities 1:0.4:0.1:0.7 positioned at 3.5, 1.6, 1.0 and -4.05 kHz, assumed subject to PI-SSFP experiments with different flip-angles α.

From: Maximizing spectral sensitivity without compromising resolution in phase-incremented, steady-state solution NMR

Fig. 6

Additional common parameters of all “experiments” included TR = 20 ms, M = 40 phase increments, 13.5 kHz sampling rates, 2 Hz digital resolutions, instantaneous (δ) pulses, identical relaxation times T1 = 5 s, T2 = 2 s, and a constant (α-independent) noise level created by a random number generator with an RMS amplitude amounting to 25 % of the maximum single-site longitudinal magnetization (the peak at 3,5 kHz). Notice the slight SNR drop that data “acquired” for increasing α shows when processed based on the β-coefficients, despite the increase signals emitted as flip-angles increase (Fig. 1). We ascribe this to a broadening of the β-derived filter functions, which is absent in the regularized version that keeps all peaks at similar half widths regardless of the flip angle used in the PI-SSFP acquisition. No such penalty affects the regularized reconstruction introduced in this work.

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