Fig 4.

Delay and dispersal of the AIF ipsilateral to the occluded carotid artery affects calculated CBF values measured by MR imaging (MR CBF). Conventions used are as described in the legend to Figure 3.

A, In a 65-year-old man with symptomatic left carotid occlusion (patient 7), CBF values measured by MR imaging systematically overestimated CBF values measured by PET (PET CBF). The linear regression between CBF values measured by MR imaging and those measured by PET has a slope of 1.65 for the ipsilateral AIF (Ipsi AIF, r = 0.79, P < .0001) and 2.14 for the contralateral AIF (Contra AIF, r = 0.81, P < .0001). This difference in slopes is statistically significant (P < .05). CBF value measured by PET in the subcortical white matter regions used in scaling the CBF values measured by MR imaging was 21.9 mL/100 mL/min, which is very close to the assumed value of 22 mL/100 mL/min.

B, AIFs in patient 7 show a delay in the peak of the ipsilateral AIF (open circles) and a broader peak of the ipsilateral AIF, compared with the contralateral AIF (closed squares).