MR-based skull parametric modeling for blood-brain barrier opening in non-human primates

Focused ultrasound (FUS) transcranial procedures require of simulation planning using the computed tomography (CT) of the skull, leading to ionizing radiation. Zero echo time (ZTE) magnetic resonance imaging (MRI) is a safe alternative for blood-brain barrier opening (BBBO) planning in non-human primates (NHP), with good contrast for bone imaging. In this study, we applied a classical coordinate-to-coordinate linear-regression method to obtain the ZTE-to-CT relationship for six NHP skulls. First, we compared ZTE-based (pseudo-CT/pCT) and CT-based simulations ex-vivo, with differences of [Formula: see text], [Formula: see text], [Formula: see text] mm and [Formula: see text] mm for the focal volume, attenuation, axial and lateral shifts, respectively. The differences between pCT simulations and experiments were [Formula: see text], [Formula: see text] mm and [Formula: see text] mm for the focal attenuation, axial and lateral shifts, respectively. Finally, pCT-based and CT-based simulations for in-vivo planning resulted in differences of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] mm and [Formula: see text] for the focal volume, attenuation, in-focus BBBO volume, sonicated skull thickness, and Skull Density Ratio, respectively, where pCT and CT predicted a [Formula: see text] and [Formula: see text] of BBBO volume, respectively. These results demonstrate for the first time the feasibility of a ZTE-to-CT skull modeling method for BBBO planning in NHPs, defining a fully non-ionizing planning technique for transcranial FUS applications.