Abstract
Purpose
To characterize human gliomas using T~1~‐weighted dynamic contrast‐enhanced MRI (DCE‐MRI), and directly compare three pharmacokinetic analysis techniques: a conventional established technique and two novel techniques that aim to reduce erroneous overestimation of the volume transfer constant between plasma and the extravascular extracellular space (EES) (K^trans^) in areas of high blood volume.
Materials and Methods
Eighteen patients with high‐grade gliomas underwent DCE‐MRI. Three kinetic models were applied to estimate K^trans^ and fractional blood plasma volume (v~p~). We applied the Tofts and Kermode (TK) model without arterial input function (AIF) estimation, the TK model modified to include v~p~ and AIF estimation (mTK), and a “first pass” variant of the TK model (FP).
Results
K~TK~ values were considerably higher than K~mTK~ and K~FP~ values (P < 0.001). K~mTK~ and K~FP~ were more comparable and closely correlated (ρ = 0.744), with K~mTK~ generally higher than K~FP~ (P < 0.001). Estimates of v~p(mTK)~ and v~p(FP)~ also showed a significant difference (P < 0.001); however, these values were very closely correlated (ρ = 0.901). K~TK~ parameter maps showed “pseudopermeability” effects displaying numerous vessels. These were not visualized on K~mTK~ and K~FP~ maps but appeared on the corresponding v~p~ maps, indicating a failure of the TK model in commonly occurring vascular regions.
Conclusion
Both of the methods that incorporate a measured AIF and an estimate of v~p~ provide similar pathophysiological information and avoid erroneous overestimation of K^trans^ in areas of significant vessel density, and thus allow a more accurate estimation of endothelial permeability. J. Magn. Reson. Imaging 2004;20:748–757. © 2004 Wiley‐Liss, Inc.