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. 2003 May;24(5):862–871.

Fig 3.

Fig 3.

CBF in patient 5, a 71-year-old man who had chronic right carotid occlusion.

A, Graph compares CBF values measured by MR imaging (MR CBF) with those measured by PET (PET CBF). CBF values measured by PET have been corrected for the finite permeability of water through the blood-brain barrier (see Methods). CBF values measured by MR imaging were calculated with AIFs from the proximal MCA, both ipsilateral to the occluded carotid artery (Ipsi AIF, open circles) and contralateral to the occluded carotid artery (Contra AIF, closed squares). The line of identity, with a slope of 1 and a y intercept of 0, is depicted by a solid line. The slopes of the regression line for the data from the ipsilateral AIF (dashed line) and for the data from the contralateral AIF (dotted line) are both close to 1 (Table 2). No statistically significant difference was observed in the slopes or y intercepts of the two regression lines (P > .05). The linear relationship between CBF values measured by MR imaging and those measured by PET is statistically significant for both the ipsilateral AIF (r = 0.88, P < .0001) and the contralateral AIF (r = 0.88, P < .0001). CBF values measured by PET in the subcortical white matter regions used in scaling the CBF values measured by MR imaging was 21.1 mL/100 mL/min, which is close to the assumed value of 22 mL/100 mL/min (see Methods).

B, Plots of the relaxivity ΔR2* versus time for the AIF in the M1 or M2 segment of the MCA ipsilateral to the carotid occlusion (open circles), and that contralateral to the occlusion (closed squares), show that they are almost identical. ΔR2* was determined as the negative log of susceptibility after baseline normalization. Because susceptibility is a relative measurement and not an absolute quantity, ΔR2* is expressed in arbitrary units. The amplitude of the observed change in ΔR2* is not quantitatively comparable between the ipsilateral and contralateral sides because of differences in factors such as vessel orientation and the extent of partial volume averaging of the blood vessel with surrounding tissue and/or CSF within the selected AIF pixels.