High‐resolution multi‐T1–weighted contrast and T1 mapping with low B1>+ sensitivity using the fluid and white matter suppression (FLAWS) sequence at 7T

다국어 초록 (Multilingual Abstract)

To demonstrate that fluid and white matter suppression (FLAWS) imaging can be used for high‐resolution T1 mapping with low transmitted bias field (B1+) sensitivity at 7T.
The FLAWS sequence was optimized for 0.8‐mm isotropic resolution imaging. The theoretical accuracy and precision of the FLAWS T1 mapping was compared with the one of the magnetization‐prepared two rapid gradient echoes (MP2RAGE) sequence optimized for low B1+ 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 T1 mapping references and B1+ 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 T1 maps. The effect of B1+ on FLAWS T1 mapping was assessed using the Pearson correlation.
The FLAWS‐hco images were characterized by a higher brain tissue CNR (CNRWM/GM=5.5, CNRWM/CSF=14.7, CNRGM/CSF=10.3) than the MP2RAGE‐uni images (CNRWM/GM=4.9, CNRWM/CSF=6.6, CNRGM/CSF=3.7). The theoretical accuracy and precision of the FLAWS T1 mapping (acc=91.9%;prec=90.2%) were in agreement with those provided by the MP2RAGE T1 mapping (acc=90.0%;prec=86.8%). A good agreement was found between in vivo T1 values measured with the MP2RAGE and FLAWS sequences (r = 0.91). A weak correlation was found between the FLAWS T1 map and the B1+ map within cortical gray matter and white matter segmentations (rWM=‐0.026; rGM=0.081).
The results from this study suggest that FLAWS is a good candidate for high‐resolution T1‐weighted imaging and T1 mapping at the field strength of 7T.