Scan-time Corrections for 80-100 Minute Standardized Uptake Volume Ratios to Measure the 18F-AV-1451 Tracer for Tau Imaging

• Published in: IEEE transactions on medical imaging Vol. 38; no. 3; pp. 697 - 709
• Main Authors: He, Mark, Baker, Suzanne L., Shah, Vyoma D., Lockhart, Samuel N., Jagust, William J.
• Format: Journal Article
• Language: English
• Published: 17.09.2018
• ISSN: 0278-0062; 1558-254X
• DOI: 10.1109/TMI.2018.2870441

The 18 F-AV-1451 PET tracer binds to tau, an Alzheimer’s Disease (AD) biomarker. The standardized uptake value ratio (SUVR) 80–100 min window is widely used to quantify tau binding, although 18 F-AV-1451 continues increasing relative to a reference region in regions with tau deposition. Left uncorrected, acquisition time inaccuracies can lead to errors from −4% to 6% in 20-min SUVR measurements in subjects with Alzheimer’s Disease. In 40 subjects with scans from 75–115 min following 18 F-AV-1451 injection, we created 20-min reconstructions (4×5 min) of start-times ranging from 75­85 min, as proxies of offset scans and calculated the mean in regions of interest (ROIs). We developed a Segmented Least Squares (SLS) method to obtain error-minimizing weighting coefficients for 18 F-AV-1451 ROIs that best predict SUVR 80–100 from weighted means of SUVRs from offset start-times. We compared residual errors of our SLS method to those in (1) uncorrected offset 20-min-SUVRs, (2) the mean of 5-min frames within the 80–100 window, and (3) a least-squares interpolation method. We evaluated errors induced by start-time offset on SUVRs for each method. SLS, which corrected using least-squares coefficients of 5-min components, consistently reduced errors across all offset start-times. Effect size analysis for simulated clinical longitudinal 18 F-AV-1451 drug trials showed that uncorrected 20-min offset SUVRs would require up to 20% more participants to detect treatment effects compared to using SLS. Correction of SUVR scan­time errors by SLS minimizes errors compared to other correction methods and may be extended to other scanners and tracers.