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

Abstract

Objective To evaluate visual assessment of [11C]PIB and [18F]FDDNP PET images as potential supportive diagnostic markers for Alzheimer's disease (AD).

Methods Twenty-one AD patients and 20 controls were included. Parametric [11C]PIB and [18F]FDDNP global binding potential (BPND) images were visually rated as ‘AD’ or ‘normal.’ Data were compared with ratings of [18F]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 [11C]PIB and [18F]FDDNP BPND were determined. Visual ratings were compared with dichotomised quantitative values.

Results Agreement between readers was excellent for [11C]PIB, [18F]FDDNP and MTA (Cohen kappa κ≥0.85) and moderate for [18F]FDG (κ=0.56). The highest sensitivity was found for [11C]PIB and [18F]FDG (both 1.0). The highest specificity was found for MTA (0.90) and [11C]PIB (0.85). [18F]FDDNP had the lowest sensitivity and specificity (0.67 and 0.53, respectively). The cut-off for quantitative [11C]PIB BPND was 0.54 (sensitivity and specificity both 0.95) and for [18F]FDDNP BPND 0.07 (sensitivity 0.80, specificity 0.73). Agreement between quantitative analyses and visual ratings was excellent for [11C]PIB (κ=0.85) and fair for [18F]FDDNP (κ=0.40).

Conclusion Visual assessment of [11C]PIB images was straightforward and accurate, showing promise as a supportive diagnostic marker for AD. Moreover, [11C]PIB showed the best combination of sensitivity and specificity. Visual assessment of [18F]FDDNP images was insufficient. The quantitative analysis of [18F]FDDNP data showed a considerably higher diagnostic value than the visual analysis.

  • Alzheimer's disease
  • PET, ligand studies
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