DCE Overview

What is DCE imaging and how does it differ from DSC imaging?  
Dynamic Contrast Enhanced (DCE) imaging measures T1 changes in tissues over time after bolus administration of gadolinium. It differs from Dynamic Susceptibility Contrast (DSC) imaging in that the latter measures T2 and T2* changes.
Immediately after injection, gadolinium contrast agents reside in plasma and are circulated to organs in proportion to blood flow.  The relatively small molecular size of these agents (500−1000 Da) allows them to pass through the vascular endothelium via passive diffusion into the extracellular space of most tissues. The only exceptions are the brain and spinal cord, where specialized tight endothelial junctions create a blood-brain barrier (BBB) that precludes this process. If the BBB is disrupted by tumor, infection, or other disease, however, gadolinium will then accumulate, producing T1-shortening and contrast enhancement.
glioma contrast
Breakdown of BBB in a glioma
Observing and quantifying the time course of this contrast enhancement is the major goal of DCE imaging. As a general principle, the degree of contrast enhancement depends on regional blood flow (F), the size and number of blood vessels quantified by their surface area per unit mass of tissue (S), and their leakiness or permeability (P).

Although it may not be possible to separate F, P, and S components individually, by mathematical modeling we can measure their combined effect reflected in the so-called transfer constant (Ktrans) . Ktrans is an index characterizing the diffusive influx of gadolinium contrast across the vascular endothelium. DCE-derived indices like Ktrans have become increasingly important in the evaluation of tumor response to therapy, especially for non-cytotoxic agents that target tumor vascularity. Ktrans has also been used to assess inflammatory processes in the the lung, joints, and other organs.

In addition to Ktrans, additional tissue specific parameters may be estimated by DCE including: the volume fraction of the extravascular extracellular space (ve) in tissue, the volume fraction of plasma in tissue (vp), and the rate constant for efflux of gadolinium contrast back into plasma from the tissue extracellular space (kep).

The meaning, significance, and calculation of these various DCE parameters will be elucidated in the next several Q&A's.

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References
     Jahng G-H, Li K-L, Østergaard l, Calamante F. Perfusion magnetic resonance imaging: a comprehensive update on principles and techniques. Korean J Radiol 2014; 15:554-577. (good recent review).
     Tofts PS. T1-weighted DCE imaging concepts: modelling, acquisition and analysis. MAGNETOM Flash 2010; 3:30-35.
Related Questions
     What are the differences between DSC, DCE and ASL perfusion methods used in MRI? 
     How do you evaluate the information obtained from a DCE imaging study? 
     What quantitative parameters can be extracted from the DCE data?