Abstract #4911

An inhomogeneous magnetization transfer (ihMT) quantification method robust to B1 and T1 variations in magnetization prepared acquisitions

Gopal Varma¹, Fanny Munsch¹, Olivier M Girard², Guillaume Duhamel², and David C Alsop¹

¹Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, ²Aix Marseille Univ, CNRS, CRMBM, Marseille, France

Standard MT and ihMT ratio (ihMTR) measures can be sensitive to B₁and T₁, making them less specific to tissue microstructure. Using the inverse signal, i.e. one divided by the signal, and a high flip-angle reference image in calculation of an ihMTR metric has been proposed as a metric with improved insensitivity to T₁ and B₁ in steady-state gradient-echo sequences. We present a modified method for use in prepared sequences such as magnetization prepared rapid gradient echo (MPRAGE). The sensitivity of ihMT MPRAGE metrics to T₁ and B₁ was tested using simulations and acquisitions in brains of healthy volunteers.

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