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Abstract #1845

Optimisation of Flip-Angle Schedules for MR Fingerprinting with inhomogeneous Transmit Fields

Felix Horger1,2,3, Sarah McElroy1,4, Shaihan Malik1,2,3, and Jo Hajnal1,2,3
1Imaging Physics and Engineering Research Department, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 2London Collaborative Ultra high field System (LoCUS), London, United Kingdom, 3Early Life Imaging Research Department, School of Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, 4MR Research Collaborations, Siemens Healthineers, Camberley, United Kingdom

Synopsis

Keywords: MR Fingerprinting, MR Fingerprinting

Motivation: Unlocking SNR benefits of ultra-high field for high-resolution quantitative MRI is hindered by transmit-field (B1+) inhomogeneities because optimal flip-angles are not realised throughout the field-of-view.

Goal(s): We investigate how flip-angle schedules for MR Fingerprinting can be adjusted to enhance robustness towards B1+ inhomogeneity.

Approach: We incorporate B1+ into Cramer-Rao bound optimisation, demonstrate that predicted errors are reduced compared with a conventionally optimised flip-angle schedule, and show this in invivo experiments.

Results: B1+ informed CRB optimisation reduces predicted peak T2-error by a factor of three, which removes artefacts in invivo experiments. B1+ corrections successfully removed shading in T1-maps.

Impact: This work addresses one of the problems of quantitative imaging at ultra-high field to make its benefit more accessible. The larger aim is to achieve high resolution parameter maps which can be useful for diagnosis and research of neurodegenerative diseases.

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