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

Monaretto, Tatiana; Souza, Ademária Aparecida de; Moraes, Tiago Bueno; Bertucci-Neto, Victor; Rondeau-Mouro, Corinne; Colnago, Luiz Alberto

doi:10.1002/mrc.4806

Cited by 24 publications

(8 citation statements)

References 44 publications

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“…Although the SNR of CWFP-T1 is much lower than obtained with IR, the T1 values were similar. We demonstrated that several post-acquisition digital filters (low pass, linear and logarithm compression, Savitzky-Golay, and Wavelet filters) can be used to enhance SNR in CWFP-T1 signals without significant deviation of the T1 values [39]. Figure 11 shows a SNR enhancement of one order of magnitude on CWFP-T1 signal using second-order, a 41-points window, and a Savistiky-Golay (SG) filter.…”

Section: Fast and Simultaneous T 1 And T 2 Measurementsmentioning

confidence: 96%

“…Therefore, samples with higher fat contents show a large 100 ms peak. The ratio of the area of these two peaks has been used to measure fat content in beef with higher precision than standard CWFP sequences [39].…”

Section: Agri-food Productsmentioning

confidence: 99%

“…The multivariate analyses of CWFP have been used to classify beef samples based on animal sex or breed [26,40], to predict water loss during beef cooking, and fat and moisture contents [41]. More recently, we showed that CWFP-T 1 can be a simple method to measure fat content in beef [39]. Figure 12 shows the relaxation profile of two beef samples with 20% and 62% fat contents.…”

Section: Agri-food Productsmentioning

confidence: 99%

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

2019

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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 T p shorter than the effective transverse relaxation time (T 2 *), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T 1 . Therefore, T p should be as short as possible (limited by hardware). For T p < 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 T 1 /T 2 ; 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 T 1 using a low flip angle (5 • ) or T 2 , using θ = 180 • . For measuring T 1 and T 2 simultaneously in a single experiment, it is necessary to use θ = 90 • , the values of T* and M 0 , and the magnitude of CWFP signal |M ss |. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T 2 . 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.to suppress these anomalies using a small variation of T p that cancels the echo component. In the same year, Schwenk [4] proposed the Quadriga Fourier Transform (QFT) to suppress these anomalies. The QFT method was based on a small variation in frequency offset. Although these procedures minimize these anomalies, SSFP sequences were not routinely used in high resolution NMR.We revised these methods and suggested some modifications to increase the applications of SSFP in high-resolution NMR using the Traff apodization function [5] to minimize the truncation problem, or processing the SSFP time domain signal with a parametric method based on Krylov Basis Diagonalization Method (KBDM) [6]. KBDM solves the truncation and phase anomalies but not the amplitude problem. Therefore, SSFP sequences cannot be used to efficiently enhance signal to noise ratio (SNR) in high-resolution NMR. SSFP sequences have been successfully used in magnetic resonance imaging [7,8] and in low-field, time-domain NMR [9][10][11]. The use of a SSFP sequence in low field time domain (TD-NMR) started in year 2000 [12,13]. The applications of SSFP sequences in TD-NMR can be performed under the drastic condition where T p < 1 ms. Under this condition, a truly continuous wave free precession (CWFP) regime is obtained [13]. Normally, CWFP sequences use T p < 0.5 ms, as T p has to be shorter than T 2 *, which is in the order of 1 ms in most TD-NMR spectrometers.In the CWFP regime, F...

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Section: Fast and Simultaneous T 1 And T 2 Measurementsmentioning

confidence: 96%

Section: Agri-food Productsmentioning

confidence: 99%

Section: Agri-food Productsmentioning

confidence: 99%

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

2019

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“…The low SNR in the CWFP–T 1 signal is due to the small flip angles in the pulse sequence. However, the SNR of the CWFP–T 1 signals can be enhanced using post-acquisition digital filters, such as Savistky–Golay or wavelet filters [ 36 ]. Figure 10 shows that the CWFP–T 1 signal has similar results to those obtained with the standard IR method; however, in a shorter measuring time [ 14 ].…”

Section: One-dimensional (1d) Pulse Sequencesmentioning

confidence: 99%

Recent 1D and 2D TD–NMR Pulse Sequences for Plant Science

Monaretto

Moraes

Colnago

2021

Plants

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Time domain nuclear magnetic resonance (TD–NMR) has been widely applied in plant science in the last four decades. Several TD–NMR instruments and methods have been developed for laboratory, green-house, and field studies. This mini-review focuses on the recent TD–NMR pulse sequences applied in plant science. One of the sequences measures the transverse relaxation time (T2) with minimal sample heating, using a lower refocusing flip angle and consequently lower specific absorption rate than that of conventional CPMG. Other sequences are based on a continuous wave free precession (CWFP) regime used to enhance the signal-to-noise ratio, to measure longitudinal (T1) and transverse relaxation time in a single shot experiment, and as alternative 2D pulse sequences to obtain T1–T2 and diffusion-T1 correlation maps. This review also presents some applications of these sequences in plant science.

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“…Fonte: figura adaptada da referência71 .Com permissão de John Wiley and Sons. Contudo, após a aquisição os sinais obtidos com as sequências de pulsos CPMG e Discussão utilizando uma solução contendo o complexo [Mn(H 2 O) 6 ] 2+ 0,02 mM, cujo T 2 = 680 ms (Figura 29 (a) -sinal vermelho -escala de tempo superior).…”

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Desenvolvimento e aplicação de sequências de pulsos CWFP uni e bidimensionais para RMN no domínio do tempo

Monaretto¹

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DEDICATÓRIA Aos meus pais, Aparício e Terezinha, pelo apoio incondicional em todos os momentos da minha vida. Ao meu irmão Adriano, por acreditar em meu potencial e sempre me incentivar a superar os meus limites. Aos meus sobrinhos Ana Clara e Arthur, meus maiores presentes. Ao Lucas, pelo amor, paciência, companheirismo incondicional e apoio durante a realização deste trabalho. AGRADECIMENTOS Ao Dr. Luiz Alberto Colnago, pela amizade, orientação sempre muito dedicada, confiança e incentivo no desenvolvimento desse trabalho. Ao Dr. Elton Tadeu Montrazi, pela sua ajuda no processamento dos dados e pelas valiosas discussões que auxiliaram no desenvolvimento deste trabalho. Ao Me. Rodrigo Henrique dos Santos Garcia, pela sua ajuda na implementação das sequências de pulsos e pelas valiosas discussões que auxiliaram no desenvolvimento deste trabalho. Ao Dr. Victor Bertucci Neto, pelas valiosas discussões sobre os métodos de filtragem. Ao Dr. André, pela colaboração no desenvolvimento deste trabalho. À Cirlei e à Fernanda, pelo seu incentivo, carinho, amizade e companheirismo durante o desenvolvimento deste trabalho. Aos amigos do grupo de RMN da Embrapa Instrumentação: pela amizade, convivência e ajuda mútua. Aos todos os amigos que fiz em São Carlos. À Embrapa Instrumentação, pela infraestrutura e por todas as suas facilidades oferecidas. Ao Instituto de Química de São Carlos (IQSC) -USP, por todo o suporte acadêmico. À Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), pelo suporte financeiro por meio do processo de financiamento 1541262.A todos que contribuíram de forma direta ou indireta para realização deste trabalho. EPÍLOGO"A vida começa no final da sua zona de conforto. "

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

Cited by 24 publications

References 44 publications

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

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

Recent 1D and 2D TD–NMR Pulse Sequences for Plant Science

Desenvolvimento e aplicação de sequências de pulsos CWFP uni e bidimensionais para RMN no domínio do tempo

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