Connecting CMR and Physiology : Expanding the capabilities of cardiovascular magnetic resonance in quantifying physiology

Abstract: The assessment of cardiovascular physiology is crucial to facilitate clinical diagnostics, treatment, and research. Physiology and anatomy can be assessed noninvasively using cardiovascular magnetic resonance (CMR), a versatile and reliable medical imaging modality free from ionizing radiation. CMR is capable of providing a vast amount of information such as displacement, velocity, flow, length, area, volume, and tissue properties. Considered the gold standard for noninvasive quantification of cardiac function and morphology, CMR is increasingly envisioned as a future one-stop-shop imaging examination for cardiovascular disease. However, quantification of important physiological aspects such as valvular motion, pressure, and force are still not accessible or readily available when using CMR. The general aim of this thesis was therefore to expand the current capabilities of CMR to include new reliable methods and tools for quantification of the atrioventricular plane displacement, transmitral flow, pressure, and ventricular force-length loops, hence allowing a more complete assessment of subject-specific cardiovascular physiology that could potentially be achieved in a single noninvasive examination.In this thesis, the current capabilities of CMR were expanded by developing and validating four new methods for quantification of physiology. In Study I, an imaging processing algorithm for feature-tracking of the atrioventricular plane displacement was proposed. The combination of this algorithm and a phase contrast CMR sequence was proposed in Study II to improve measurements of transvalvular flow, which are challenging due to the significant movement of the atrioventricular valves over the cardiac cycle. In Study III, CMR imaging, a noninvasive brachial pressure, and mathematical modelling was combined to enable a noninvasive quantification of left ventricular pressure-volume loops. Study IV used the atrioventricular plane displacement algorithm and the noninvasive pressure-volume loop technique to propose a novel method for evaluation of ventricular force-length loops, which was used to describe the energetics of longitudinal and radial pumping mechanics.The proposed methods in Study I, II, and IV require only brachial pressure and images which are typically acquired during standard clinical CMR scanning. Addition of the sequence in Study II would prolong a CMR protocol by a few minutes, suggesting that the capabilities of CMR to evaluate cardiovascular physiology during a single noninvasive examination have been expanded, thus getting closer to the one-stop-shop vision for CMR.