Biomarkers.

Area of Science:

• Nuclear medicine
• Radiopharmaceutical imaging
• Biomarker quantification

Background:

• Increasing demand for amyloid positron emission tomography (Aβ PET) due to monoclonal antibody treatments.
• High costs and limited reimbursement drive interest in plasma biomarkers, which cannot quantify amyloid burden.
• Need for cost-effective and efficient diagnostic tools for Alzheimer's disease.

Purpose of the Study:

• To assess the impact of abbreviated 18F-NAV4694 (NAV) and 18F-Florbetapir (FBP) PET scan protocols on Centiloid amyloid quantification.
• To determine if shortened scan windows can maintain diagnostic accuracy while reducing costs and improving productivity.
• To evaluate the feasibility of reduced scan and uptake times for Aβ PET imaging.

Main Methods:

• Analysis of 38 dynamic NAV scans and 454 dynamic FBP scans using Centiloid quantification software.
• Comparison of standard 50-70 minute PET acquisition windows with abbreviated windows (50-60, 40-50, 30-40 minutes).
• Linear association modeling and Bland-Altman analysis to assess Centiloid error after linear correction of abbreviated scans.

Main Results:

• Strong correlations (R²>0.95) were observed between shortened and standard scan windows for both NAV and FBP.
• NAV scans acquired between 30-40 minutes showed a mean Centiloid error of 2.7 CL, allowing a 50% scan-time reduction.
• FBP scans acquired between 40-50 minutes demonstrated a mean error of 3.3 CL, enabling a 20% uptake-time reduction.

Conclusions:

• Abbreviated NAV (30-40 min) and FBP (40-50 min) PET protocols, with linear correction, are unlikely to alter clinical management decisions.
• Significant reductions in scan time (up to 50%) and uptake time (40% for NAV, 20% for FBP) are achievable.
• Accurate timing of acquisition windows is crucial as tracers may not reach steady-state in early acquisition periods.