Repeatability of B inhomogeneity correction of volumetric (3D) glutamate CEST via High-permittivity dielectric padding at 7T.
Paul S Jacobs, Blake Benyard, Abigail Cember, Ravi Prakash Reddy Nanga, Quy Cao, M Dylan Tisdall, Neil Wilson, Sandhitsu Das, Kathryn A Davis, John Detre, David Roalf, Ravinder Reddy
Author Information
Paul S Jacobs: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. ORCID
Blake Benyard: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. ORCID
Abigail Cember: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Ravi Prakash Reddy Nanga: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. ORCID
Quy Cao: Penn Statistics in Imaging and Visualization Center, Department of Biostatistics, Epidemiology, and Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
M Dylan Tisdall: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. ORCID
Neil Wilson: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Sandhitsu Das: Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Kathryn A Davis: Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
John Detre: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
David Roalf: Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Ravinder Reddy: Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
PURPOSE: Ultra-high field MR imaging lacks B inhomogeneity due to shorter RF wavelengths used at higher field strengths compared to human anatomy. CEST techniques tend to be highly susceptible to B inhomogeneities due to a high and uniform B field being necessary to create the endogenous contrast. High-permittivity dielectric pads have seen increasing usage in MR imaging due to their ability to tailor the spatial distribution of the B field produced. The purpose of this work is to demonstrate that dielectric materials can be used to improve glutamate weighted CEST (gluCEST) at 7T. THEORY AND METHODS: GluCEST images were acquired on a 7T system on six healthy volunteers. Aqueous calciumtitanate pads, with a permittivity of approximately 110, were placed on either side in the subject's head near the temporal lobes. A post-processing correction algorithm was implemented in combination with dielectric padding to compare contrast improvement. Tissue segmentation was performed to assess the effect of dielectric pads on gray and white matter separately. RESULTS: GluCEST images demonstrated contrast enhancement in the lateral temporal lobe regions with dielectric pad placement. Tissue segmentation analysis showed an increase in correction effectiveness within the gray matter tissue compared to white matter tissue. Statistical testing suggested a significant difference in gluCEST contrast when pads were used and showed a difference in the gray matter tissue segment. CONCLUSION: The use of dielectric pads improved the B field homogeneity and enhanced gluCEST contrast for all subjects when compared to data that did not incorporate padding.
