Firstly, a representative Et value was obtained for each tissue by calculating the mean post-contrast Et (Etave) across the entire 30-min

imaging period from the group of patients with low overall Fazekas rating (<1.5). For each tissue, mean enhancement Etave was converted into contrast agent concentration Ctave, with T10 taken as the mean pre-contrast value in each tissue measured from all low Fazekas-rated patients and r1 (r2) assumed to be 4.3 (5.2) s−1 mM−1 in all tissues [30]. The variation in T10 or r1 required to produce the Etdiff observed between the low- and high Fazekas-rated patients in each tissue (see Table 1) was then calculated, Target Selective Inhibitor Library assuming the concentration Ctave remained fixed in each tissue. This procedure estimates the Selleckchem AZD4547 T10 or r1 change that would be required to cause the mean enhancement difference observed in subtle BBB breakdown due to white matter abnormalities, assuming that there is no difference in the contrast agent concentration between the two patient groups. A more generic analysis of the effects of T10, r1 and r2 on measurements of contrast agent concentration can be found in Schabel and Parker [19]. This error analysis also enables calculation of the relative uncertainty in the estimation of contrast agent concentration ɛrel when

varying experimental parameters such as SNR, flip angle αb and the number of baseline images Nb. The effect of varying these parameters was investigated for the relevant concentration range associated with subtle BBB disorders. The relationship was explored for T10 and T20⁎

parameters representative of blood, gray matter, white matter and CSF, while the effect of varying flip angle αb, number of post contrast measurements N and number of baseline measurements Nb was explored for white matter. Fig. 1 illustrates the average temporal evolution of Et triclocarban and Ct obtained from the 60 stroke patients (mean±S.D. age: 67±12 years; time from stroke onset: 68±36 days), 32 with low Fazekas rating and 28 with high rating, and Table 1 summarizes Etave and Ctave measurements for each tissue. As expected, the blood signal enhances the most with Etave≈1.5, which is approximately 20 times greater than either cortical gray matter (Etave≈0.08) or deep gray matter (Etave≈0.07). White matter enhances the least with Etave≈0.02, and CSF enhances by about double that of gray matter with Etave≈0.15. The relationship between tissues is noticeably altered when contrast agent concentration is considered. In this case, blood signal again has the highest estimated concentration with Ctave≈0.8 mM, which is roughly 40 times greater than cortical or deep gray matter which both have Ctave≈0.