Ankündigung des Promotionsvortrags von Herrn Gregor Körzdörfer;
Magnetic resonance imaging (MRI) is largely limited to producing qualitative contrast images instead of quantitative maps of tissue characteristics. A novel framework for quantitative MRI termed Magnetic Resonance Fingerprinting (MRF) to map tissue parameters such as the relaxation times T1 and T2 has recently been introduced. In MRF, tissue signals are generated by applying a pseudo-randomly varying MRI acquisition, acquired using highly undersampled trajectories and matched to a database of simulated tissue signals.
MRF was investigated regarding its susceptibility to undersampling artifacts and magnetic field inhomogeneities. Results show that the originally proposed temporal order yields artifacts of similar frequencies as the signal responses from tissues, which leads to spatially dependent misestimations of parameters. An optimized temporal order was developed in simulations and proven in in-vivo experiments. Different local amplitudes of the radio frequency (RF) field B1+ can lead to misestimations of parameters, which can be resolved by measuring a B1+ map. Similarly, the static magnetic field B0 can have an impact on MRF. The dependency was analyzed and a technique to mitigate the dependency by additionally dephasing spins before RF pulses was developed. MRFF (Magnetic Resonance Field Fingerprinting) is presented, which exploits the freedom in sequence design to explicitly add B0 and B1+ dependent signal information. MRFF enables the robust and fast simultaneous generation of T1, T2, B0, B1+ and intravoxel phase dispersion maps. The in-vivo reproducibility of MRF with the newly developed improvements was evaluated by scanning ten volunteers on ten scanners showing high precision.
(Vortrag auf Englisch)
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