Abstract #2701

Extrapolated-B1-corrected Variable Flip Angle T1 Mapping in Cortical Bone with a Phase-Sensitive Method

Sheng Chen¹, Yekaterina K. Gilbo², Helen L. Sporkin¹, Samuel W. Fielden³, Steven P. Allen⁴, John P. Mugler III⁵, G. Wilson Miller⁵, and Craig H. Meyer^1,5

¹Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²Netflix, Los Gatos, CA, United States, ³U.S. Food and Drug Administration, Silver Spring, MD, United States, ⁴Electrical & Computer Engineering, Brigham Young University, Provo, UT, United States, ⁵Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, United States

Synopsis

Keywords: MR-Guided Focused Ultrasound, Bone, Skull, UTE, B1, T1, VFA

Motivation: Unintended heating of the skull and nearby soft tissue during transcranial MR-guided Focused Ultrasound surgery needs to be monitored. However, T1-based thermometry in cortical bone may be biased with variable flip angles.

Goal(s): Our goal was to correct flip angles to improve the T1 mapping accuracy in cortical bone.

Approach: In phantom and human studies, B1 maps of soft tissue were measured with a phase-sensitive method, extrapolating from which B1 maps of bone were generated and were used to correct flip angles for T1 mapping.

Results: Improved accuracy and homogeneity of T1 maps were demonstrated as validation.

Impact: Extrapolated-B1 correction with a phase-sensitive method should improve accuracy and homogeneity of T1 maps in cortical bone and is promising in monitoring unintended heating in the skull and nearby brain tissue during transcranial MR-guided Focused Ultrasound surgery.

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