Early Phase PIB-PET as a Surrogate for Global and Regional Cerebral Blood Flow Measures

Background and purpose: To explore the potential for simplified measures of [¹¹ C]PIB uptake to serve as a surrogate for cerebral blood flow (CBF) measures, thereby, providing both pathological and functional information in the same scan.

Methods: Participants (N = 24, 16 M, 8 F, 57-87 years) underwent quantitative [¹⁵ O]water imaging and dynamic [¹¹ C]PIB imaging. Time-activity curves were created for each participant's regional [¹¹ C]PIB data scaled in standardized uptake values (SUVs). The frame in which maximal uptake occurred was defined for each subject (ie, "peak"). The concentration (SUV) for each region at the individual's peak, during the 3.5-4 minute time interval and for the initial 6 minute sum, was determined. R1 (ie, relative delivery using cerebellum as reference tissue) from the simplified reference tissue model 2 was determined for each region. PIB SUVs were compared to the absolute CBF global and regional values (in mL/minute/100 mL) and the R1 values were compared to the cerebellar-normalized rCBF.

Results: Significant linear relationships were found for all SUV measures with measures of absolute global and regional CBF that were comparable to the relationship between normalized CBF and R1. The individual SUV_peak exhibited the strongest relationship both regionally and globally. All individuals and all regions had highly significant regression slopes. Age, gender, or amyloid burden did not influence the relationship.

Conclusion: Early PIB uptake has the potential to effectively serve as a surrogate for global and regional CBF measures. The simple and readily obtainable individual's SUV_peak value was the strongest predictor regionally and globally of CBF.