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This study describes a method for imaging brain tumors that combines T1-weighted (T1W) and T2*-weighted (T2*W) dynamic contrast-enhanced acquisitions. Several technical improvements have been made to produce high-quality three-dimensional mapping of endothelial permeability surface area product (k) and leakage space (vl), based on T1W data. Tumor blood volume maps are obtained from T2*W images with a complete removal of residual relaxivity effects. The method was employed in 15 patients with brain tumors (5 gliomas, 5 meningioma, and 5 acoustic schwannoma). Mean values of vl were significantly greater in acoustic schwannomas (53% +/- 9%) than in meningiomas (34% +/- 7%) or gliomas (22% +/- 4%). Mean values of vl in meningioma were significantly greater than those of gliomas. Mean values of rCBV correlated closely with k. There was also a positive correlation between k and vl for pixels with low k values. This relationship was weaker in areas of high k. The highest mean ratios of k to vl (k(ep)) were seen in two patients with glioblastoma, one patient with transitional cell meningioma, and one patient with angioblastic meningioma. Pixel-by-pixel comparison showed a strong correlation between rCBV and k in 11 of 15 patients. However, decoupling between pixel-wise rCBV and k was found in four patients who had lesions with moderate k and vl elevation but no increase of rCBV. Results from this study suggest that in assessing the angiogenic activities in brain tumors it is advisable to monitor simultaneously changes in tumor blood volume, vessel permeability, and leakage space of tumor neovasculature., (Copyright 2000 Wiley-Liss, Inc.)

Dynamic susceptibility contrast-enhanced magnetic resonance (MR) imaging in tumors is restricted by relaxivity effects, which may obscure any abnormality of first-pass kinetics in the re-circulation phase. The purposes of this study were a) to document the magnitude of relaxivity effects with a variety of commonly used MR susceptibility imaging techniques; and b) to determine whether the re-circulation phase of the first-pass curve in tumors differs from that in normal tissue. We have confirmed that residual relaxivity effects can be eliminated from dynamic susceptibility contrast-enhanced data by several techniques. Application of these methods to enhancing vascular tumors allows detection of abnormalities in the re-circulation phase, which would otherwise be obscured. These abnormalities are independent of relative cerebral blood volume (rCBV) and presumably represent deviations from the predicted gamma variat flow pattern seen in normal tissues. We believe that the parameter rR described here provides an indicator of the chaotic nature of neovascular angiogenesis, which may be of benefit in diagnosis and management.