| Magnetic Resonance Imaging (MRI) has been established as a primary imaging module in clinical practices. The usefulness of MR contrast agents to improve visualization of MR imaging is firmly established. Extracellular gadolinium(Gd)-based contrast agents are the most widely used MR contrast media. The Gd-based contrast agent is intravenously injected, follows the pathway of blood circulation, enters into extravascular space, and then diffuses back into the vasculature, thereby acting as a probe to visualize microcirculatory properties.;Functional dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) uses T1-weighted acquisition to observe the uptake of contrast agents. The use of DCE-MRI has become increasingly widespread for quantifying and visualizing microvascular characteristics such as microvessel density and vascular permeability. Pharmacokinetic analysis of DCE-MRI can assess pathophysiological permeability changes in cancerous tissues with abnormal angiogenesis. Different kinetic models of DCE-MRI were used, including a modified two-compartment pharmacokinetic model based on more realistic model assumptions. Using all of these pharmacokinetic models to investigate the predictors of imaging biomarkers were performed at 1.5T, 3T and 7T MRI systems.;Total 45 patients with metastasis thyroid carcinomas were enrolled in a clinical trial study using a RAF/VEGF-R inhibitor drug. DCE-MRI was performed in a baseline scan and followup scans after every eight weeks during therapy. DCE-MRI pharmacokinetic results were correlated with biomarkers, such as serum calcitonin and RESICT measurement. The study showed DCE-MRI appeared to be a valuable diagnostic adjunct for monitoring the microvascular properties of malignant tumors during anti-angiogenic therapy. Therapy monitoring using DCE-MRI provides the capability for evaluating the biologic therapeutic responses by a clinically readily available approach. This also indicates that this approach appears feasible for clinical drug development and validation as an imaging biomarker in 1.5T and 3T clinical MR systems.;Ultra-high field MR imaging can provide higher signal to noise ratio (SNR), superior temple and special resolution. In this dissertation, a pre-clinical MR contrast agents comparison study using DCE-MRI was demonstrated in the ultra-high field 7T scanner using a pre-clinical beagle dog model. The study compared three Gd-based contrast agents and standardized the clinical MR contrast agent injection protocol for DCE-MRI under ultra-high field 7T system. |
