Magn Reson Mater Phy DOI 10.1007/s10334-008-0104-8 RESEARCH ARTICLE Water proton T 1 measurements in brain tissue at 7, 3, and 1.5 T using IR-EPI, IR-TSE, and MPRAGE: results and optimization P. J. Wright · O. E. Mougin · J. J. Totman · A. M. Peters · M. J. Brookes · R. Coxon · P. E. Morris · M. Clemence · S. T. Francis · R. W. Bowtell · P. A. Gowland Received: 9 July 2007 / Revised: 17 December 2007 / Accepted: 7 January 2008 © ESMRMB 2008 Abstract Method This paper presents methods of measuring the lon- gitudinal 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. Results 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 ± 112 ms at 3 T, and 1,126 ± 97, and 1,939 ± 149 ms at 7T with the MPRAGE sequence. The T 1 of the putamen was found to be 1,084 ± 63 ms at 1.5 T, 1,332 ± 68 ms at 3 T, and 1,644 ± 167ms at 7T. The T 1 of the caudate head was found to be 1,109 ± 66 ms at 1.5 T, 1,395 ± 49 ms at 3 T, and 1,684 ± 76 ms at 7 T. Discussion 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 P. J. Wright · O. E. Mougin · A. M. Peters · M. J. Brookes · R. Coxon · P. E. Morris · S. T. Francis · R. W. Bowtell · P. A. Gowland (B ) Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK e-mail: Penny.gowland@nottingham.ac.uk J. J. Totman The Brain and Body Centre, University of Nottingham, Nottingham, UK M. Clemence Philips Medical Systems, Reigate Surrey, UK was found to have five readouts at TIs of 120, 260, 563, 1,221, 2,647, 5,736 ms 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 6,102 ms 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. Keywords High field · Relaxometry · Pulse sequences · Optimization Introduction Relaxation times provide a more reliable marker of tissue state than MRI signal intensities, which depend on the exact RF field, the sensitivity profile of the receiver coil, and other factors such as receiver gain and the competing effects of different relaxation times. If relaxation time measurements could be made with adequate sensitivity and accuracy, then they could provide an improved method for studying dis- ease progression and for characterizing normal tissue types, for instance in neurodevelopment [1, 2]. Furthermore, knowledge of the tissue relaxation times is important for opti- mizing sequences to provide maximum image contrast, opti- mizing contrast agent dose, and for optimizing quantitative sequences for measurements of other important parameters such as perfusion. It is expected that longitudinal relaxation times increase as the field strength is increased and that val- ues obtained from different tissues converge [3]. At present there are only a few reported in vivo measurements of longi- tudinal relaxation times in human brain at 7 T, although there has been one study considering the change in water proton relaxation times at fields from 0.2 to 7 T [4]. 123