scholarly journals Low-field 1 H NMR spectroscopy: Factors impacting signal-to-noise ratio and experimental time in the context of mixed microstructure polyisoprenes

2020 ◽  
Author(s):  
Michael J. Minkler ◽  
Jung Min Kim ◽  
Vinita V. Shinde ◽  
Bryan S. Beckingham
Keyword(s):  
Nmr Spectroscopy ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Experimental Time ◽  
H Nmr ◽  
Low Field ◽  
Mixed Microstructure ◽  
Noise Ratio

Enhancing signal-to-noise ratio and resolution in low-field NMR relaxation measurements using post-acquisition digital filters

2018 ◽  
Vol 57 (9) ◽  
pp. 616-625 ◽  
Author(s):  
Tatiana Monaretto ◽  
Andre Souza ◽  
Tiago Bueno Moraes ◽  
Victor Bertucci-Neto ◽  
Corinne Rondeau-Mouro ◽  
...  
Keyword(s):  
Digital Filters ◽  
Signal To Noise Ratio ◽  
Nmr Relaxation ◽  
Signal To Noise ◽  
Low Field ◽  
Relaxation Measurements ◽  
Low Field Nmr ◽  
Noise Ratio

scholarly journals Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

2019 ◽  
Vol 9 (7) ◽  
pp. 1312 ◽  
Author(s):  
Tiago Bueno Moraes ◽  
Tatiana Monaretto ◽  
Luiz Colnago
Keyword(s):  
Time Domain ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Flip Angle ◽  
Time Interval ◽  
Single Shot ◽  
Free Precession ◽  
Signal To Noise ◽  
Low Field ◽  
Noise Ratio

This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval Tp shorter than the effective transverse relaxation time (T2*), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T1. Therefore, Tp should be as short as possible (limited by hardware). For Tp < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T1/T2; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T1 using a low flip angle (5°) or T2, using θ = 180°. For measuring T1 and T2 simultaneously in a single experiment, it is necessary to use θ = 90°, the values of T* and M0, and the magnitude of CWFP signal |Mss|. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T2. The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.

scholarly journals Development of signal to noise ratio of HTS-rf-SQUID for ultra-low field NMR / MRI by 77K LC resonant circuit

2012 ◽  
Vol 27 ◽  
pp. 348-351 ◽  
Author(s):  
Dan Zhang ◽  
Shohei Fukumoto ◽  
Shingo Tsunaki ◽  
Yoshimi Hatsukade ◽  
Saburo Tanaka
Keyword(s):  
Signal To Noise Ratio ◽  
Resonant Circuit ◽  
Signal To Noise ◽  
Low Field ◽  
Low Field Nmr ◽  
Noise Ratio ◽  
Rf Squid

scholarly journals In Vivo Magic Angle Magnetic Resonance Imaging for Cell Tracking in Equine Low-Field MRI

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Carolin Horstmeier ◽  
Annette B. Ahrberg ◽  
Dagmar Berner ◽  
Janina Burk ◽  
Claudia Gittel ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Signal To Noise Ratio ◽  
Superparamagnetic Iron Oxide ◽  
Magic Angle ◽  
Signal To Noise ◽  
Low Field ◽  
Superficial Digital Flexor Tendon ◽  
Low Field Mri ◽  
Noise Ratio

The magic angle effect increases the MRI signal of healthy tendon tissue and could be used for more detailed evaluation of tendon structure. Furthermore, it could support the discrimination of hypointense artefacts induced by contrast agents such as superparamagnetic iron oxide used for cell tracking. However, magic angle MRI of the equine superficial digital flexor tendon has not been accomplished in vivo in standing low-field MRI so far. The aim of this in vivo study was to evaluate the practicability of this magic angle technique and its benefit for tracking superparamagnetic iron oxide-labelled multipotent mesenchymal stromal cells. Six horses with induced tendinopathy in their forelimb superficial digital flexor tendons were injected locally either with superparamagnetic iron oxide-labelled multipotent mesenchymal stromal cells or serum. MRI included standard and magic angle image series in T1- and T2∗-weighted sequences performed at regular intervals. Image analysis comprised blinded evaluation and quantitative assessment of signal-to-noise ratio. The magic angle technique enhanced the tendon signal-to-noise ratio (P<0.001). Hypointense artefacts were observable in the cell-injected superficial digital flexor tendons over 24 weeks and artefact signal-to-noise ratio differed significantly from tendon signal-to-noise ratio in the magic angle images (P<0.001). Magic angle imaging of the equine superficial digital flexor tendon is feasible in standing low-field MRI. The current data demonstrate that the technique improves discrimination of superparamagnetic iron oxide-induced artefacts from the surrounding tendon tissue.

scholarly journals The use of high–sensitivity sapphire cells in high pressure NMR spectroscopy and its application to proteins

2004 ◽  
Vol 18 (2) ◽  
pp. 271-278 ◽  
Author(s):  
W. Kremer ◽  
M. R. Arnold ◽  
N. Kachel ◽  
H. R. Kalbitzer
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Prion Protein ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Chemical Shifts ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Human Prion Protein ◽  
Noise Ratio

The application of high pressure in bioscience and biotechnology has become an intriguing field in un/refolding and misfolding processes of proteins. NMR spectroscopy is the only generally applicable method to monitor pressure–induced structural changes at the atomic level in solution. Up to now the application of most of the multidimensional NMR experiments is impossible due to the restricted volume of the high pressure glass cells which causes a poor signal–to–noise ratio. Here we present high strength single crystal sapphire cells which double the signal–to–noise ratio. This increased signal–to–noise ratio is necessary to perform, for example, phophorus NMR spectroscopy under variable pressures. To understand the effect of pressure on proteins, we need to know the pressure dependence of1H chemical shifts in random coil model tetrapeptides. The results allow distinguishing structural changes from the pressure dependence of the chemical shifts. In addition, the influence of pressure on the buffer system was investigated. Since high pressure was shown to populate intermediate amyloidogenic states of proteins the investigation of pressure effects on proteins involved in protein conformational disorders like Alzheimer's Disease (AD) and Transmissible Spongiform Encephalopathies (TSE) is of keen interest.1H–15N–TROSY–spectra were acquired to study the effects of pressure and temperature on chemical shifts and signal volumes of the human prion protein. These measurements show identical pressure sensitivity ofhuPrP(23–230) andhuPrP(121–230). First results suggest a folding intermediate for the human prion protein which can be populated by high hydrostatic pressure.

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