Advanced Preclinical Cardiac MRI of Heart Diseases

Cardiovascular diseases remain a leading cause of morbidity and mortality, with more than three million people are estimated to suffer from heart disease worldwide [1]. Magnetic resonance imaging (MRI) has grown in importance as a non-invasive method of evaluating cardiac tissue. T1 and T2* mapping in MRI allows for the quantitative characterisation of tissue composition and function, which aids in the diagnosis and treatment of many cardiac diseases. The aim of this study was to develop and validate the alternative quantitative cardiac MRI techniques for non-invasive characterisation of myocardial tissue properties and oxygenation, as well as to examine their response to pharmacological stress with dobutamine. To accomplish this objective, the project was divided into four main parts. The first part focuses on evaluating and validating the variable flip angle (VFA) T1 sequence with different hardware settings using phantom and in vivo on the 9.4T Bruker MRI. Then, in the second part, the validated VFA T1 sequence was used with MRI contrast agent manganese, a calcium analogue, to evaluate its usability for assessing myocardial viability in normal, remote, and infarcted myocardium. In the third part, a ratiometric T2* sequence was developed with the aim of gaining insight into tissue oxygen dynamics and myocardial health. This sequence was then used to assess myocardial oxygenation with different gas mixtures in the hypertensive heart. The final section extends the research focus to introduce novel dobutamine-stress T1-Manganese Enhances MRI (T1-MEMRI) and ratiometric T2*-MRI to assess Ca2+ uptake and myocardial oxygenation, respectively. Collectively, this thesis highlights how novel quantitative MRI techniques can be utilised to generate detailed assessment of myocardial function, viability and oxygenation under a variety of normal and pathological conditions.