title: Longitudinal monitoring of reconstructed activity concentration on a clinical time-of-flight PET/CT scanner.
abstract: Positron emission tomography (PET) images are potential quantitative biomarkers. Understanding long-term (months/years) biomarker variability is important for establishing confidence intervals on studies using such biomarkers over these time frames. PET biomarkers are derived from activity concentration ([Formula: see text]) extracted from PET images. Over 30 months, we measured the stability of decay-normalized counts ([Formula: see text]) and [Formula: see text] by scanning the same 4.5-cm-diameter Ge-68 cylinder weekly, the same Na-22 point source daily, and a refilled 20-cm F-18 cylinder phantom monthly on a clinical TOF-PET/CT scanner. Longitudinal and adjacent-measurement variability was characterized. We found no drift in [Formula: see text] or [Formula: see text] for properly calibrated images over 24 months. During this time, [Formula: see text] ranged [Formula: see text] to 6% for count-matched Ge-68 and F-18 images, with coefficient of variation (COV) across time of 2.3% (Ge-68, 81 scans) and 3.2% (F-18, 24 scans). At typical patient image count levels the Ge-68 [Formula: see text] ([Formula: see text]) COV across time was 6.9% (9.6%). Changes in [Formula: see text] between adjacent F-18 scans ([Formula: see text]) ranged between [Formula: see text], with corresponding date-matched changes in Ge-68 [Formula: see text] ranging [Formula: see text]. We recommend (1) tracking trends in [Formula: see text] with image [Formula: see text] as a check of quantitative data corrections/calibrations and (2) tracking both mean and COV of [Formula: see text] (single time point measures) to hundredths precision using standardized uptake values.
authors.affiliation: University of Washington , Radiology Department, 1715 Northeast Columbia Road, Box 357987, Seattle, Washington 98195-7987, United States.
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: MacDonald
authors.affiliation: Philips Healthcare , 595 Miner Road, Highland Heights, Ohio 44143, United States.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Perkins
authors.affiliation: Philips Healthcare , 595 Miner Road, Highland Heights, Ohio 44143, United States.
authors.forename: Chi-Hua
authors.initials: CH
authors.lastname: Tung
keywords: PET/CT; SUV variance; quality control procedure; quantitative imaging biomarker; quantitative imaging biomarker alliance