Purpose: To compare blood T1 estimation approaches used for quantifying cerebral blood flow (CBF) with arterial spin labeled (ASL) perfusion MRI in a developmental cohort of chronic kidney disease (CKD) patients with anemia and a control group. Methods: 61 patients with CKD and 47 age-matched control subjects were studied. Blood T1 approaches included: (1) a fixed value, (2) estimation based on measured hematocrit (Hct), and (3) estimation based on Age + Sex using a published formula. Resulting T1 and CBF values were compared along with group, age and sex effects. Results: Highly significant group differences in CBF using fixed blood T1 were reduced when Hct-corrected blood T1 was used, and were eliminated entirely when using the Age + Sex estimated approach. In the control cohort, fixed T1 method showed the strongest correlations of CBF with age and sex. Hct-corrected T1 preserved a significant correlation between CBF and age and sex, while Age + Sex estimated T1 produced a poor fit of CBF with age and sex. Conclusions: Blood T1 estimation method can confound the interpretation of CBF changes measured using ASL MRI in patients with CKD. Blood T1 should ideally be corrected for hematocrit effects in clinical populations with anemia.
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