Speaker: Nate Pack

Title: DCE MRI Myocardial Perfusion Studies

Abstract:

In dynamic contrast enhanced MRI myocardial perfusion studies, blood and tissue enhancement data are simultaneously acquired to estimate the time-dependent regional concentration of an injected tracer (ie. Gd-DTPA) in the left ventricle of the heart. The resulting blood and tissue enhancement curves are discretely deconvolved to estimate the impulse response function, h(t), which relates the blood (input) and tissue (output) signals of the biological system. In theory, h(t) should be related to a physiologically relevant metric such as regional blood flow and the distribution volume of the tracer in the heart tissue.

In this presentation, I will discuss two seminal papers (see below) that provide unique theoretical frameworks for relating h(t) to regional fluid flow in the tissue of interest. Both frameworks begin from the expression of a tracer mass balance using the Fick principle and result in estimates of fluid flow within the system. Kety et al. pioneered use of compartmental models in the 1940s, while Zierler et al. established the setting for a model-independent approach with the central volume principle to quantitate blood flow in 1962.

Compartmental modeling and the central volume principle are both used in practice today to quantify blood flow to the heart in MRI studies. As part of the presentation, I will highlight differences and similarities of the frameworks and interactively discuss with the audience the pros and cons of each, with the hopes of unifying the frameworks or better employing one/both to my own research of quantitative myocardial perfusion.

Papers for discussion:

1) Kety SS. The theory and applications of the exchange of inert gas at the lungs and tissues. Pharmacol Rev 1951; 3:1-41.

2) Zierler KL. Theoretical basis of indicator-dilution methods for measuring flow and volume. Circ Res 1962; 10:393-407.