This syllabus focuses on the quantification of myocardial perfusion using rapid dynamic imaging during the first pass of contrast bolus through the heart. This remains by far the most widely used technique for cardiac perfusion imaging, though initial results with arterial spin labeling at 3 Tesla and higher field strengths suggest that this latter technique could become a viable alternative that does not require injection of a contrast agent.

The approaches which can be used for quantifying myocardial blood flow from the observed contrast enhancement can be broadly divided into two categories, which we refer to as model-based and model-independent. For model-based approaches one specifies the functional spaces in myocardial tissue, how tracer moves through these spaces, and how it traverses permeable barriers between the spaces. A considerable degree of simplification is necessary to arrive at models that can be used for numerical calculations and simulations. As commonly used MR contrast agents such as Gd-DTPA are excluded from the intracellular space one can consider a simplified models comprising only the vascular and interstitial spaces.

Model-independent analysis means that one foregoes specifying a model of the tissue structure. Model-independent analysis is based on the central volume principle introduced by Ken Zierler in the the 1960’s. For its derivation one can start with the observation that the rate at which a substance accumulates in a tissue region of interest is given by the difference of concentrations of tracer substance flowing into and leaving a myocardial region of interest, multiplied by the flow rate (F). The Central Volume Principle allows one to quantify myocardial blood flow (F) through a region of interest, if one measures the contrast residue in the myocardial region of interest and and the arterial input to that region. For both quantities one needs to make approximations which will be discussed in detail in the presentation. For example, for the arterial input one generally takes as surrogate the contrast enhancement measured in the cavity of the left ventricle.