High‐resolution multi‐T 1 –weighted contrast and T 1 mapping with low B 1 >+ sensitivity using the fluid and white matter suppression (FLAWS) sequence at 7T

Purpose To demonstrate that fluid and white matter suppression (FLAWS) imaging can be used for high‐resolution T 1 mapping with low transmitted bias field ( B 1 + ) sensitivity at 7T. Methods The FLAWS sequence was optimized for 0.8‐mm isotropic resolution imaging. The theoretical accuracy and precision of the FLAWS T 1 mapping was compared with the one of the magnetization‐prepared two rapid gradient echoes (MP2RAGE) sequence optimized for low B 1 + sensitivity. FLAWS images were acquired at 7T on six healthy volunteers (21 to 48 years old; two women). MP2RAGE and saturation‐prepared with two rapid gradient echoes (SA2RAGE) datasets were also acquired to obtain T 1 mapping references and B 1 + maps. The contrast‐to‐noise ratio (CNR) between brain tissues was measured in the FLAWS‐hco and MP2RAGE‐uni images. The Pearson correlation was measured between the MP2RAGE and FLAWS T 1 maps. The effect of B 1 + on FLAWS T 1 mapping was assessed using the Pearson correlation. Results The FLAWS‐hco images were characterized by a higher brain tissue CNR ( CNR WM / GM = 5.5 ,CNR WM / CSF = 14.7 ,CNR GM / CSF = 10.3 ) than the MP2RAGE‐uni images ( CNR WM / GM = 4.9 ,CNR WM / CSF = 6.6 ,CNR GM / CSF = 3.7 ). The theoretical accuracy and precision of the FLAWS T 1 mapping ( acc = 91.9 % ; prec = 90.2 % ) were in agreement with those provided by the MP2RAGE T 1 mapping ( acc = 90.0 % ; prec = 86.8 % ). A good agreement was found between in vivo T 1 values measured with the MP2RAGE and FLAWS sequences ( r = 0.91). A weak correlation was found between the FLAWS T 1 map and the B 1 + map within cortical gray matter and white matter segmentations ( r WM = ‐ 0.026 ;r GM = 0.081 ). Conclusion The results from this study suggest that FLAWS is a good candidate for high‐resolution T 1 ‐weighted imaging and T 1 mapping at the field strength of 7T.