In this work, we present a new method for predicting changes in tumor vascularity using only one flip angle in dynamic contrast-enhanced (DCE) imaging. The usual DCE approach finds the tissue initial T 1 value T 1 (0) prior to injection of a contrast agent. We propose finding changes in the tissue contrast agent uptake characteristics pre-and postdrug treatment by fixing T 1 (0). Using both simulations and imaging pre-and postadministration of caffeine, we find that the relative change (NR50) in the median of the cumulative distribution (R50) is almost independent of T 1 (0). Fixing T 1 (0) leads to a concentration curve c(t) more robust to the presence of noise than calculating T 1 (0). Consequently, the NR50 for the tumor remains roughly the same as the ideal NR50 when T 1 (0) is exactly known. Further, variations in eating habits are shown to create significant changes in the R50 response for both liver and muscle. In conclusion, analyzing data with fixed T 1 (0) leads to a more stable measure of changes in NR50 and does not require knowl- Dynamic contrast-enhanced MRI (DCE-MRI) is a method for imaging the physiology of the microcirculation. A series of recent clinical studies have shown that DCE-MRIbased measures correlate well with tumor angiogenesis. DCE-MRI is performed after the administration of an intravenous contrast agent, gadolinium-DTPA, to noninvasively assess tumor vascular characteristics. Recently, DCE-MRI has been used to assess antiangiogenic cancer drug effectiveness in Phase I pharmaceutical trials (1-3) by acquiring data before and after drug treatment. The contrast enhancement patterns on DCE-MRI are influenced by tumor angiogenesis, as reflected by elevated vascular endothelial growth factor (VEGF) expression. Therefore, they become valuable indicators for assessing tumor angiogenic activity (4,5) and tumor neovascularization in vivo in hepatocellular carcinoma patients (6,7). The use of DCE has been so important that one would be hesitant to continue testing a drug in the absence of any volume or vascular changes appearing in DCE-MRI unless the patients' survival increased (8).Despite its promise, there are problems in the acquisition and processing of DCE data. Repeatability has been a major problem (9 -11). Given the wide clinical use of DCE-MRI, this is an important issue that must be directly addressed. One approach is to improve the methodology itself with more rapid high-resolution respiratory free scanning methods (12). And this will happen with the advent of parallel imaging (13,14). The other is to better process existing data.From our review of many DCE-MRI experiments and projects at the MRI Research facility in the Department of Radiology at Wayne State University, we have found that the causes of most of the DCE errors are related to noise in the T 1 estimates and to physiologic changes in the blood flow (BF) from one day to the next. Normally, an estimate for the baseline T 1 (referred to here as T 1 (0)) is obtained from multiple flip angle (FA) images (15). Any inconsist...