Multi-Directional Phase-Contrast Flow MRI in Real Time
Jost M. Kollmeier
Doctoral thesis
Date of Examination:
2020-08-31
Date of issue:
2021-01-28
Advisor:
Frahm, Jens Prof. Dr.
Referee:
Frahm, Jens Prof. Dr.
Referee:
Enderlein, Jörg Prof. Dr.
Referee:
Scheffler, Klaus Prof. Dr.
Persistent Address: http://hdl.handle.net/21.11130/00-1735-0000-0005-155C-D
Files in this item
Name:
2020_KollmeierJ_diss.pdf
Size:
20,0 MB
Format:
PDF
Abstract
English
This work describes the development of a phase-contrast MRI technique that achieves multi-directional velocity quantification in real time, i.e. at high spatio-temporal resolution and without any physiological gating or data sorting. The technique exploits highly undersampled radial acquisitions with time-efficient flow encoding, a correction strategy for concomitant fields applicable to radial imaging, and an iterative solution for the non-linear image reconstruction problem. MRI is a potent and versatile imaging technique that allows to measure flow velocities, e.g. of blood flow. Unfortunately, MRI is intrinsically slow. Recent advances in real-time MRI based on radial FLASH and non-linear inversion offer high spatio-temporal resolutions and the realization of cross-sectional MRI movies. This real-time approach had been combined with uni-directional phase-contrast flow MRI that quantifies velocities only perpendicular to the imaging plane. In this work, the imaging technique is extended to more velocity dimensions. Opening with a brief overview on the basic principles of phase-contrast and real-time MRI (Chapter 2), this thesis presents the uni-directional flow technique in Chapter 3 followed by proposals for further improvements. Chapter 4 describes the development of a multi-directional extension and its optimization towards high spatio-temporal resolutions, while Chapter 5 proposes further methodological refinements. Chapter 6 addresses the technical accuracy and presents a correction strategy to eliminate background phase errors by concomitant magnetic fields applicable to radial imaging. Preliminary in vivo results demonstrated in Chapter 7 include cardiac flow imaging with velocity quantification in all three directions at less than 2 x 2 mm² pixel-size and more than 60 frames per second. The novel MRI technique developed in this thesis increases the potential of MRI based cross-sectional velocimetry.
Keywords: real-time MRI; phase-contrast MRI; radial MRI; model-based reconstruction; radial Maxwell correction; multi-directional flow; 4D flow; velocimetry; Karman vortex shedding; blood flow; CSF flow; 3D flow
This item appears in the following Collection(s)
-
GGNB - Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften [899]
GGNB - Göttingen Graduate School for Neurosciences, Biophysics and Molecular Biosciences