On resonance phase alternated CWFP sequences for rapid and simultaneous measurement of relaxation times

Autor(es)

Monaretto, Tatiana ^{[1, 2]} ; Andrade, Fabiana Diuk ^[2] ; Moraes, Tiago Bueno ^[3] ; Souza, Andre Alves ^[4] ; deAzevedo, Eduardo Ribeiro ^[3] ; Colnago, Luiz Alberto ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[2] Embrapa Instrumentacao, BR-13560970 Sao Carlos, SP - Brazil

^[3] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[4] Schlumberger Brazil Res & Geoengn Ctr, BR-21941907 Rio De Janeiro, RJ - Brazil

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF MAGNETIC RESONANCE; v. 259, p. 174-178, OCT 2015.
• Citações Web of Science: 6

Resumo

T-1 and T-2 relaxation times have been frequently used as probes for physical-chemical properties in several time-domain NMR applications (TD-NMR) such as food, polymers and petroleum industries. T2 measurements are usually achieved using the traditional Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence because it is a fast and robust method. On the other hand, the traditional methods for determining T-1 i.e., inversion and saturation recovery, are time-consuming, driving several authors to develop rapid 1D and 2D methods to obtain T-1 and T-2 or T-1/T-2 ratio. However, these methods usually require sophisticated processing and/or high signal to noise ratio (SNR). This led us to develop simple methods for rapid and simultaneous determination of T-1 and T-2 using Continuous Wave Free Precession (CWFP) and Carr-Purcell Continuous Wave Free Precession (CP-CWFP) pulse sequences. Nevertheless, a drawback of these sequences is that they require specific adjustment of the frequency offset or the time interval between pulses (T-p). in this paper we present an alternative form of these sequences, named CWFPx-x, CP-CWFPx-x, where a train of pi/2 pulses with phases alternated by pi enable performing the experiments on-resonance and independently of T-p when T-p < T-2{*}. Moreover, a CPMG type sequence with pi/2 refocusing pulses shows similar results to CP-CWFP when the pulses are alternated between y and y axis, CPMG(90y-y). In these approaches, the relaxation times are determined using the magnitude of the signals after the first pulse vertical bar M-0 vertical bar and in the steady-state vertical bar M-ss vertical bar, as well as the exponential time constant T{*} to reach the steady-state regime, as in conventional CWFP. CP-CWFP, shows the highest dynamic range to measure T{*} among CWFP sequences and, therefore, is the best technique to measure T-1 and T2 since it is less susceptible to SNR and can be performed for any T-1/T-2 ratio. (C) 2015 Elsevier Inc. All rights reserved. (AU)

• Processo FAPESP: 13/03770-1 - Desenvolvimento e aplicações de sequências com pulsos com alternância de fases em RMN no domínio do tempo
• Beneficiário: Tatiana Monaretto
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 11/11160-3 - Desenvolvimento de técnicas de precessão livre no estado estacionário (SSFP) com alternância de fase para aquisição rápida de espectros de RMN em alta resolução
• Beneficiário: Tiago Bueno de Moraes
• Modalidade de apoio: Bolsas no Brasil - Doutorado