Many cardiac disease processes are characterized by remodeling of myocardial tissue. For example, in hypertensive heart disease, the heart muscle hypertrophies to cope with the increased after-load pressure. Although this response may be benign initially, in the chronic stage, it leads to increased levels of connective tissue in the interstitial space between the cardiomyocytes, and an expansion of the extra-cellular space. In effect, the heart muscle becomes stiffer, thereby impeding its relaxation of the muscle during diastolic filling of the ventricle. Ultimately, such pathological changes can lead to heart failure, though the role of changes at the tissue level on the development of heart failure are not well understood.
We have developed new methods for quantifying changes of the extracellular space using MR T1 relaxography, i.e., mapping myocardial T1 relaxation before and after administering a gadolinium contrast agent, and thereby determining the extra-cellular volume (ECV) fraction. Although during the last few years, this field has experienced a steep rise in applications, many aspects remain to be investigated and are the subject of our current research: the physiological causes of ECV expansion and what they represent; the physical conditions necessary for making T1 measurements an accurate representation of ECV expansion; and, technical advances for making these measurements faster and more convenient.
