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. Author manuscript; available in PMC: 2012 Jul 16.
Published in final edited form as: J Magn Reson Imaging. 2009 May;29(5):1134–1139. doi: 10.1002/jmri.21721

Figure 2.

Figure 2

Mean coefficient of variation (CV) values were calculated for gray matter voxels for each perfusion case. Standard deviations (SD images) were calculated across perfusion time series to visually represent cases with large CV (magnitude) values. All SD images were normalized for comparison purposes. Three sample cases from which the ASL filter had no influence in the final CBF, completely recovered the perfusion signal, and recovered partial perfusion signal are shown in subfigure A, B, and C, respectively. It should be noted that CV can be used as one, but not an exclusive, factor to quantify the stability of a perfusion case. Although there was a trend that cases with high (magnitude) CV were less stable, exceptions may be made for patient with hypoperfusion. CV values were calculated for 185 cases out of 200. The remaining cases were excluded because the gray matter mask was either unavailable or visually inaccurate.