Abstract #4280

Optimisation of Post-processing Correction of Transmit Field Inhomogeneity in R1 Maps by Relaxometry Modelling

Martina F Callaghan¹, Frederic Dick², Patrick Grabher³, Tim Keller⁴, Patrick Freund^1,3,5, and Nikolaus Weiskopf^1,5

¹Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, United Kingdom, ²Birkbeck/UCL Centre for Neuroimaging, London, United Kingdom, ³Spinal Cord Injury Center Balgrist, University Hospital Zurich, Zurich, Switzerland, ⁴Department of Psychology, Carnegie Mellon University, Pittsburgh, PA, United States, ⁵Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Unified segmentation based correction of R₁ brain maps for RF transmit field inhomogeneities (UNICORT) has previously been shown to reduce bias in R₁ maps caused by inhomogeneity in the RF transmit field (B₁⁺). This approach simultaneously estimates the B₁⁺ inhomogeneities and R₁ values from the uncorrected R₁ maps without the need for additional B₁⁺ calibration data. It employs a probabilistic framework that incorporates a physically informed generative model of smooth transmit field inhomogeneities and their multiplicative effect on R₁ estimates. However, different systems may require different priors, depending on the particular transmit coil used. Here we show that these parameters can be estimated using a linear relaxometry model framework, without the need to acquire B₁⁺ mapping data.

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