Dynamic Contrast EnhancedMRI

DCE-MRI generally refers to a rapidly acquired Tl-weighted volume acquisition before, during, and after the administration of a gadolinium chelate. This is distinct from the T2*-weighted dynamic sequences described previously. These sequences require a rapid injection of contrast and ultrafast imaging, and are complete within a minute of injection after the first pass. Tl-weighted, dynamic contrast-enhanced images are 3D volume acquisitions obtained every 2 to 10 seconds for a period of minutes and the kinetics reflect perfusion and permeability as well as vascular volume. The kinetics of the time-signal curve can be fit to a pharmacokinetic model from which parameters can be derived which relate to vessel permeability and relative vascular volume (Fig. 7). The theory of these models is covered in another chapter in this book. Since most MRI studies performed in oncology utilize gadolinium chelates, this functional test adds little total time to the imaging (29).

Applications of DCE-MRI include attempting to distinguish radiation necrosis from recurrent disease. Tumors tend to have rapid enhancement and relatively rapid washout while necrosis enhances less intensely and more slowly, and therefore washes out more slowly. DCE-MRI has also been used to monitor therapies, particularly those directed against angiogenesis, because changes on DCE-MRI directly relate to changes in vascular permeability (30).

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