Molecular imaging in the diagnosis of Alzheimer's disease: visual assessment of [11C]PIB and [18F]FDDNP PET images

Objective To evaluate visual assessment of [C-11]PIB and [F-18]FDDNP PET images as potential supportive diagnostic markers for Alzheimer's disease (AD). Methods Twenty-one AD patients and 20 controls were included. Parametric [C-11]PIB and [F-18]FDDNP global binding potential (BPND) images were visually rated as 'AD' or 'normal.' Data were compared with ratings of [F-18]FDG PET images and MRI-derived medial temporal lobe atrophy (MTA) scores. Inter-rater agreement and agreement with clinical diagnosis were assessed for all imaging modalities. In addition, cut-off values for quantitative global [C-11]PIB and [F-18]FDDNP BPND were determined. Visual ratings were compared with dichotomised quantitative values. Results Agreement between readers was excellent for [C-11]PIB, [(18) F]FDDNP and MTA (Cohen kappa kappa >= 0.85) and moderate for [F-18]FDG (kappa=0.56). The highest sensitivity was found for [C-11]PIB and [F-18]FDG (both 1.0). The highest specificity was found for MTA (0.90) and [C-11]PIB (0.85). [F-18]FDDNP had the lowest sensitivity and specificity (0.67 and 0.53, respectively). The cut-off for quantitative [C-11]PIB BPND was 0.54 (sensitivity and specificity both 0.95) and for [F-18]FDDNP BPND 0.07 (sensitivity 0.80, specificity 0.73). Agreement between quantitative analyses and visual ratings was excellent for [C-11]PIB (kappa=0.85) and fair for [F-18]FDDNP (kappa=0.40). Conclusion Visual assessment of [C-11]PIB images was straightforward and accurate, showing promise as a supportive diagnostic marker for AD. Moreover, [C-11]PIB showed the best combination of sensitivity and specificity. Visual assessment of [F-18]FDDNP images was insufficient. The quantitative analysis of [F-18]FDDNP data showed a considerably higher diagnostic value than the visual analysis.