Practical approach for comparative analysis of multilesion molecular imaging using a semiautomated program for PET/CT

Abstract

We propose a standardized approach to quantitative molecular imaging (MI) in cancer patients with multiple lesions. Methods: Twenty patients with castration-resistant prostate cancer underwent 18F-FDG and 18F-16β-fluoro-5-dihydrotestosterone ( 18FFDHT) PET/CT scans. Using a 5-point confidence scale, 2 readers interpreted coregistered scan sets on a workstation. Two hundred three sites per scan (specified in a lexicon) were reviewed. 18FFDG-positive lesion bookmarks were propagated onto 18F-FDHT studies and then manually accepted or rejected. Discordancepositive 18F-FDHT lesions were similarly bookmarked. Lesional SUV max was recorded. Tracer- and tissue-specific background correction factors were calculated via receiver-operating- characteristic analysis of 65 scan sets. Results: Readers agreed on more than 99% of 18F-FDG- and 18F-FDHT-negative sites. Positive- site agreement was 83% and 85%, respectively. Consensuslesion maximum standardized uptake value (SUV max) was highly reproducible (concordance correlation coefficient > 0.98). Receiver-operating- characteristic curves yielded 4 correction factors (SUV max 1.8-2.6). A novel scatterplot (Larson-Fox-Gonen plot) depicted tumor burden and change in SUVmax for response assessments. Conclusion: Multilesion molecular imaging is optimized with a 5-step approach incorporating a confidence scale, site lexicon, semiautomated PET software, background correction, and Larson-Fox-Gonen graphing. Copyright © 2011 by the Society of Nuclear Medicine, Inc.