An Improved 3D Stack-of-Spirals Sequence for Simultaneous Brain and Skull Thermometry in Clinical Transcranial MRgFUS Surgery

Motivation: Monitoring off-target heating of the skull and soft tissue during transcranial MRgFUS surgery is necessary. However, both T1- and PRF-based thermometry with the previously proposed sequence may be biased in clinical settings. Goal(s): To improve the accuracy of both T1 mapping in cortical bone and PRF temperature measurement in soft tissue. Approach: An improved 3D stack-of-spirals sequence was implemented featuring fat suppression, variable UTE, and a retraced spiral-in-and-out readout with fixed later TE. The sequence was tested in both phantom and human studies in a clinical setting. Results: Improved accuracy of T1 and temperature maps were demonstrated. Impact: The proposed sequence that features fat suppression, variable UTE, and a retraced-spiral-in-and-out trajectory should improve accuracy in simultaneous brain (PRF-based) and skull (T1-based) thermometry in a clinical setting and is promising in monitoring unintended heating during clinical transcranial MRgFUS surgery.