Water proton T 1 measurements in brain tissue at 7, 3, and 1.5T using IR-EPI, IR-TSE, and MPRAGE: results and optimization
- 1.8k Downloads
This paper presents methods of measuring the longitudinal relaxation time using inversion recovery turbo spin echo (IR-TSE) and magnetization-prepared rapid gradient echo (MPRAGE) sequences, comparing and optimizing these sequences, reporting T 1 values for water protons measured from brain tissue at 1.5, 3, and 7T. T 1 was measured in cortical grey matter and white matter using the IR-TSE, MPRAGE, and inversion recovery echo planar imaging (IR-EPI) pulse sequences.
In four subjects the T 1 of white and grey matter were found to be 646±32 and 1,197±134ms at 1.5T, 838±50 and 1,607±112ms at 3T, and 1,126±97, and 1,939±149ms at 7T with the MPRAGE sequence. The T 1 of the putamen was found to be 1,084±63ms at 1.5T, 1,332±68ms at 3T, and 1,644±167ms at 7T. The T 1 of the caudate head was found to be 1,109± 66ms at 1.5T, 1,395±49ms at 3T, and 1,684±76ms at 7T.
There was a trend for the IR-TSE sequence to underestimate T 1 in vivo. The sequence parameters for the IR-TSE and MPRAGE sequences were also optimized in terms of the signal-to-noise ratio (SNR) in the fitted T 1. The optimal sequence for IR-TSE in terms of SNR in the fitted T 1 was found to have five readouts at TIs of 120, 260, 563, 1,221, 2,647, 5,736ms and TR of 7 s. The optimal pulse sequence for MPRAGE with readout flip angle = 8° was found to have five readouts at TIs of 160, 398, 988, 2,455, and 6,102ms and a TR of 9 s. Further optimization including the readout flip angle suggests that the flip angle should be increased, beyond levels that are acceptable in terms of power deposition and point-spread function.
KeywordsHigh field Relaxometry Pulse sequences Optimization
- 6.Kiefer B (1998) Turbo spin echo imaging. In: Schmitt F, Stehling MK, Turner R(eds) Echo planar imaging. Theory, technique and applications. Springer, Berlin, pp 583–604Google Scholar
- 8.Weiss GH, Gupta RK, Ferretti JA et al (1980) Choice of optimal parameters for measurement of spin-lattice relaxation-times. 1. Math Formul 37: 369–379Google Scholar
- 10.Zaitsev M, Steinhoff S, Shah NJ (2003) Error reduction and parameter optimization of the TAPIR method for fast T-1 mapping 49: 1121–1132Google Scholar
- 11.Lin MS, Fletcher JW, Donati RM (1986) 2-Point T1 measurement—wide-coverage optimizations by stochastic simulations 3: 518–533Google Scholar
- 15.Press WH, Teukolsky SA, Vettering WT et al (1995) Numerical recipies in C, 2nd edn. Cambridge University Press, LondonGoogle Scholar
- 19.Meara SJP, Barker GJ (2007) The impact of magnetization transfer effects on inversion recovery sequences using a fast spin echo readout. International Society of Magnetic Resonance in Medicine, p 1818Google Scholar
- 20.Mitchell C, Truong T, Ibrahim T et al (2003) Accurate T1 measurements at 8Tesla despite radiofrequency inhomogeneity. Proc Int Soc Mag Reson Med, Toronto, p 1089Google Scholar
- 21.Ikonomidou V, Gelderen Pv, Zwart JD et al (2006) T1 measurements at 7T with application to tissue specific imaging. Proc Int Soc Mag Reson Med, Seattle, p 921Google Scholar
- 22.Li T, Deoni C (2006) Fast T1 mapping of the brain at 7T with RF calibration using three point DESPOT1 method. Proc Int Soc Mag Reson Med, Seattle, p 2643Google Scholar