Anmerkungen:
Kumulative Dissertation, enthält Zeitschriftenaufsätze
Tag der Verteidigung: 16.01.2024
Zusammenfassungen in deutscher und englischer Sprache
Beschreibung:
4D-flow velocity mapping is a technique in magnetic resonance imaging (MRI) to quantify blood flow velocity in 3D space and over time. To increase accuracy, novel sequences have been developed to overcome its technical limitations, including the low signal-to-noise ratio (SNR), low velocity-to-noise ratio (VNR), background velocity fluctuations due to concomitant fields, and flow-related intra-voxel dephasing. However, for a long time, this field was almost untouched in preclinical imaging until Krämer et al. (2017) developed the self-gated ultra-short-echo 4D-flow (UTE-4D-flow) technique. Although UTE-4D-flow showed superior SNR and VNR compared to the conventional prospectively-gated Cartesian-4D-flow method, its total scan time was too long to be applied in routine practice, especially in bigger animals than mice. To shorten the total scan time and preserve SNR and VNR, we combined the concepts of UTE-4D-flow and Cartesian-4D-flow techniques, which resulted in a Stack-of-Stars 4D-flow (SoS-4D-flow) sequence. The in-vitro evaluations of the sequence proved that it benefited from an improved SNR, VNR, and background velocity bias compared to the Cartesian counterpart. Thereafter, we applied the sequence on rats by integrating it into a prospective-gating system. The initial results prompted us to quantify the pulmonary and vena-cava venous blood flow in addition to arterial hemodynamics. The later study resulted in a novel diagnostic marker – “the pulmonary arteriovenous pressure gradient” – to diagnose pulmonary arterial hypertension non-invasively by MRI. Finally, by refining the sequence and replacing the prospective-gating system with a retrospective k0-navigator and compressed sensing (CS) reconstruction, we could shorten the scan time to almost half the measurement time in the UTE-4D-flow sequence. Finally, we tested the sequence on phantoms and mice, and could confirm the expected advantages which the previous study on rats revealed.