Multiple small circular regions of interest (ROIs) of three voxels’ diameter

were positioned to sample the calculated T10, Et and Ct maps in white matter (84 ROIs), cortical gray matter (44 ROIs), deep gray matter (12 ROIs), CSF (10 ROIs) and major vessels (7 ROIs) on the pre-contrast 12° acquisition, using standard templates to ensure consistent sampling of brain regions blind to all other data including knowledge of post-contrast signal change. If necessary, the template ROI location was then adjusted slightly to avoid the recently ischemic lesion; however, ROIs were not adjusted to avoid white matter lesions. Measurements from all Forskolin ROIs were combined for each subject and tissue type to produce overall mean and standard deviation values for T10, Et and Ct. The mean

Et (Etave) and Ct (Ctave) were averaged over all post-contrast time points and along with T10 were averaged over all patients for each tissue type in each of the high- and low Fazekas-rated groups, to give overall mean and standard deviation values for each tissue in each group. A Student’s t test was performed Selleck GSK2118436 to look for significant differences in T10, Etave or Ctave between the low- and high Fazekas-rated groups in each tissue. The sensitivity of the FSPGR acquisition to scanner noise and drift was assessed using data acquired from volunteers and phantoms, processed in exactly the same way as the patient data. For the phantom data, ROIs were placed to cover the phantoms (cylindrical tubes of approximately 2 cm diameter and 10 cm length), and for volunteer data ROIs were placed as described above for the patient case. The contribution to the signal enhancement curves from scanner noise and drift was obtained by calculating the mean and standard deviation of Et for each tissue type (or phantom) over all time points and by analyzing the slope of

the signal enhancement profiles using standard linear regression analysis performed with the regression function in Microsoft Excel. These findings were then compared to the patient data. Errors in the estimation of intrinsic tissue parameters (T10, T20, r1 and r2) on the calculation of contrast agent concentration Thalidomide have been extensively studied by Schabel and Parker [19] who derived analytical expressions for the relative bias in the concentration measurement resulting from a biased estimate of the intrinsic tissue parameters. They demonstrated that T10 produces a negative concentration bias that has the greatest influence of all the tissue parameters, r1 also results in a negative concentration bias but to a lesser degree than T10, while r2 produces a fairly negligible positive concentration bias, only becoming significant at very high concentrations. The concentration estimation is independent of T20 in the fast exchange regime and so this parameter need not be considered further.