This is particularly important for tissues with high blood volume as this can make a particularly large contribution to the estimated concentration. In practice, pharmacokinetic modeling is used to relate the contrast agent concentration in the different compartments to underlying physiological

parameters. While such models have been applied to DCE-MRI data of tumors and multiple sclerosis [6], none has modeled exchange to and from the CSF, which may be necessary in more subtle disorders [14]. Statistical modeling has also been employed, but great care is required to ensure that parameters are adequately modeled between tissues. Further work is required to establish whether these complex models can be supported by the data generated from DCE-MRI studies of subtle BBB disorders. It may be that other contrast agents need to be investigated MAPK Inhibitor Library cell line with the aim of increasing the signal enhancement compared to that from gadodiamide, or scanner electronics and gain setting improved to increase the dynamic range of signal capture and reduce the influence of noise and signal discretization error. However, if the ultimate goal is to establish whether differences in concentration profiles are truly reflective of endothelial permeability in subtle disorders, then a quantitative assessment is required and these problems need to be overcome. ABT-199 mw DCE-MRI was performed on a group of mild stroke patients classified

into two groups using the Fazekas

white matter rating scale. No significant differences were found between patients with a high or low white matter rating, although there was a trend towards greater enhancement in patients with a higher degree of white matter abnormality. The effect of noise, scanner drift, intrinsic tissue parameters and imaging sequence parameters on the interpretation of the signal enhancement profiles was assessed. Background noise was found to be comparable in magnitude to the observed differences, while scanner drift had less influence except in the CSF where a progressive rise in signal was observed. Calculation of contrast agent concentration, correcting for systematic differences in intrinsic tissue parameters, noticeably altered the relationship between Ergoloid tissues when compared to signal enhancement measurements, although differences between patient groups remained insignificant. These results suggest that it may be inappropriate to draw conclusions about the amount of contrast agent present in a tissue, and hence it is likely BBB impairment, from signal enhancement data. Therefore, studies of subtle BBB abnormalities should establish the influence of noise, drift and intrinsic tissue parameters on their data before conclusions are drawn. If this is not done, systematic errors introduced by drift and intrinsic tissue parameters may be erroneously perceived as BBB differences between patients.