title: Use of Carr-Purcell pulse sequence with low refocusing flip angle to measure T₁ and T₂ in a single experiment.
abstract: The Carr-Purcell pulse sequence, with low refocusing flip angle, produces echoes midway between refocusing pulses that decay to a minimum value dependent on T(2). When the refocusing flip angle was π/2 (CP(90)) and τ>T(2), the signal after the minimum value, increased to reach a steady-state free precession regime (SSFP), composed of a free induction decay signal after each pulse and an echo, before the next pulse. When τ<T(2), the signal increased from the minimum value to the steady-state regime with a time constant (T)=2T(1)T(2)/(T(1)+T(2))(,) identical to the time constant observed in the SSFP sequence, known as the continuous wave free precession (CWFP). The steady-state amplitude obtained with M(CP90)=M(0)T(2)/(T(1)+T(2)) was identical to CWFP. Therefore, this sequence was named CP-CWFP because it is a Carr-Purcell sequence that produces results similar to the CWFP. However, CP-CWFP is a better sequence for measuring the longitudinal and transverse relaxation times in single scan, when the sample exhibits T(1)∼T(2). Therefore, this sequence can be a useful method in time domain NMR and can be widely used in the agriculture, food and petrochemical industries because those samples tend to have similar relaxation times in low magnetic fields.
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-carlense 400, São Carlos, SP 13560-970, Brazil. fabianadiuk@yahoo.com.br
authors.forename: Fabiana Diuk
authors.initials: FD
authors.lastname: De Andrade
authors.forename: Antonio
authors.initials: A
authors.lastname: Marchi Netto
authors.forename: Luiz Alberto
authors.initials: LA
authors.lastname: Colnago
mesh_terms: D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D012815:Signal Processing, Computer-Assisted