High-resolution multi-T -weighted contrast and T mapping with low 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 mapping with low transmitted bias field ( ) 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 mapping was compared with the one of the magnetization-prepared two rapid gradient echoes (MP2RAGE) sequence optimized for low 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 mapping references and 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 maps. The effect of on FLAWS T mapping was assessed using the Pearson correlation.

RESULTS

The FLAWS-hco images were characterized by a higher brain tissue CNR ( , , ) than the MP2RAGE-uni images ( , , ). The theoretical accuracy and precision of the FLAWS T mapping ( ) were in agreement with those provided by the MP2RAGE T mapping ( ). A good agreement was found between in vivo T values measured with the MP2RAGE and FLAWS sequences (r = 0.91). A weak correlation was found between the FLAWS T map and the map within cortical gray matter and white matter segmentations ( ; ).

CONCLUSION

The results from this study suggest that FLAWS is a good candidate for high-resolution T -weighted imaging and T mapping at the field strength of 7T.