Is Weisskoff Model Valid For The Correction Of Contrast Agent Extravasation With Combined T-1 And T-2* Effects In Dynamic Susceptibility Contrast Mri?

Purpose: The Weisskoff model has been widely applied for correcting the T-1 effect of the contrast agent leakage in the measured dynamic susceptibility contrast (DSC)-MRI signals. This study aimed to modify the Weisskoff model for the inclusion of both T-1 and T-2 effects of the contrast agent extravasation.Methods: A two-compartment model was proposed and implemented into the original Weisskoff model to describe the combined T-1 and T-2 effects from the contrast agent leakage in the measured DSC-MRI signals. A computer simulation was performed to evaluate the dependence of T-1 versus T-2 dominance on imaging parameter, field strength, baseline T-1, and severity of the leakage. The modified Weisskoff model was employed to correct the relative cerebral blood volume (rCBV) maps in three patients with brain tumors to demonstrate its use.Results: The resultant equation had the same mathematical form as the original model, but with a different expression for the fitting constant K-2. This new parameter can be of either a positive or a negative value. Results of the computer simulation showed more probable T-2 dominance with longer TE, higher field strength, shorter baseline T-1, and greater extraction of the contrast agent. Clinical data were well fitted by the model, with a positive K-2 indicating T-1 dominance and underestimated rCBV and a negative K-2 indicating T-2 dominance and overestimated rCBV. The K-2 values of normal-appearing brain tissues were distributed in a much smaller range than the K-2 values of enhancing tumors. The ratios of corrected over uncorrected normalized CBV (nCBV) for gray matter (GM) were in the range between 1.04 and 1.05, meaning that the nCBV remained rather stable before and after correction. The ratios for the tumors were 0.65, 0.42, and 2.81, either much smaller or greater than the ratios for GM.Conclusions: This study proposed a modified Weisskoff model that was able to explain both T-1 and T-2 dominant effects of the contrast agent extravasation in DSC-MRI. Further development is needed to make the K-2 parameter a quantitative indicator of the vessel permeability. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3534197]