Comparison of amyloid burden in the brain using Florbetapir F 18 and 11C-PIB PET data

Objectives 11C-PIB and Florbetapir F 18 PET imaging have been used to study amyloid burden in living patients. Alzheimer’s Disease Neuroimaging Initiative (ADNI), an ongoing study, allows for the comparison of 11C PIB to Florbetapir F 18 PET in the same patient.

Methods Florbetapir F 18 imaging results, qualitative visual read (Aβ+/Aβ-) and SUVr were compared to the most recent 11C-PIB imaging results in 16 subjects (12 MCI and 5 cognitively normal controls) with data available for both ligands in the ADNI database. Volumes of interest created on the standard template were automatically applied to the PET data. Amyloid burden was quantified by computing standard uptake value ratio (SUVr) of target to reference region. The target region is composed of six cortical grey matter regions including Frontal, Precuneus, Posterior cingulate, Anterior cingulate, Parietal and Temporal with the reference region composing the entire cerebellum (both grey and white matter). Correlations between SUVr values of PIB and Florbetapir F 18 were calculated in MCI, healthy controls and the entire patient population.

Results Mean time between Florbetapir-PET scan and the most recent 11C-PIB scan was 1 year. Qualitative visual reads of the Florbetapir F 18 and 11C-PIB scans done to date (n=16) yielded identical results. There is a strong correlation between Florbetapir F 18 and 11C-PIB SUVr values in the 16 subjects who had both studies (r=0.97, p<0.0001). The Florbetapir to PIB correlation in MCI subjects (n=11) was r=0.97 (p=0.0001) and the correlation in normal subjects (n=5) was r=0.98 (p=0.0040) Moreover the strength of the correlation of Florbetapir to PIB results is similar to the correlation between two consecutive 11C PIB scans in the same subjects (n=8; r=0.94).

Conclusions Data thus far indicates excellent correlation between SUVr values for Florbetapir F 18 and 11C-PIB