Abstract
The topic of this work is on reliable resolving of J-coupled resonances in spectral envelopes from proton nuclear magnetic resonance (NMR) spectroscopy. These resonances appear as multiplets that none of the conventional nonderivative shape estimators can disentangle. However, the recently formulated nonconventional shape estimator, the derivative fast Padé transform (dFPT), has a chance to meet this challenge. In the preceding article with a polyethylene phantom, using the time signals encoded with water suppressed, the nonparametric dFPT was shown to be able to split apart the compound resonances that contain the known J-coupled multiplets. In the present work, we address the same proton NMR theme, but with sharply different initial conditions from encodings. The goal within the nonparametric dFPT is again to accurately resolve the J-coupled resonances with the same polyethylene phantom, but using raw time signals encoded without water suppression. The parallel work on the same problem employing two startlingly unequal time signals, encoded with and without water suppression in the preceding and the current articles, respectively, can offer an answer to a question of utmost practical significance. How much does water suppression during encoding time signals actually perturb the resonances near and farther away from the dominant water peak? This is why it is important to apply the same dFPT estimator to the time signals encoded without water suppression to complement the findings with water suppression. A notable practical side of this inquiry is in challenging the common wisdom, which invariably takes for granted that it is absolutely necessary to subtract water from the encoded time signals in order to extract meaningful information by way of NMR spectroscopy.
Highlights
In the accompanying article [1], we laid the ground for the specific problem under study by focusing on resolving J-coupled resonances in spectral envelopes corresponding to a polyethylene phantom [2, 3]
In customary magnetic resonance spectroscopy (MRS), spectra are never acquired, i.e. encoded or measured. They are reconstructed from the encoded time signals or free induction decay (FID)
This is to be distinguished from the nomenclature of the dawn of nuclear magnetic resonance (NMR), when in the 1940s and 1950s spectra were recorded directly on oscilloscopes by slowly sweeping across the preassigned intervals of the external magnetic field strength B0
Summary
In the accompanying article [1], we laid the ground for the specific problem under study by focusing on resolving J-coupled resonances in spectral envelopes corresponding to a polyethylene phantom [2, 3]. As a prelude to this particular problem, we went beyond its immediate framework, by revisiting the background of chemical shift as one of key milestones in nuclear magnetic resonance (NMR) spectroscopy from a historical perspective This and some other related aspects of the NMR problem under study need not be reiterated in the present article. Such an opportunity leaves the space for concentrating here on the new information from reconstructions with time signals encoded without water suppression. Such time signals are not merely an alternative set of the acquired data. They raise a fundamental question which requires a proper answer: how much can the reconstructed information be impacted by partially removing the giant water peak in the process of encoding time signals?
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