TY - JOUR T1 - Repeatability of Quantitative <sup>18</sup>F-NaF PET: A Multicenter Study JF - Journal of Nuclear Medicine JO - J Nucl Med DO - 10.2967/jnumed.116.177295 SP - jnumed.116.177295 AU - Christie Lin AU - Tyler J Bradshaw AU - Timothy G Perk AU - Stephanie Harmon AU - Jens Eickhoff AU - Ngoneh Jallow AU - Peter Choyke AU - William Dahut AU - Steven M. Larson AU - John Laurence Humm AU - Scott Perlman AU - Andrea B. Apolo AU - Michael J. Morris AU - Glenn X Liu AU - Robert Jeraj Y1 - 2016/07/01 UR - http://jnm.snmjournals.org/content/early/2016/07/21/jnumed.116.177295.abstract N2 - Purpose: 18F-NaF, a positron emission tomography (PET) radiotracer of bone turnover, has shown potential as an imaging biomarker for assessing therapeutic response of bone metastases. This study aims to evaluate the repeatability of 18F-NaF PET-derived SUV metrics in individual bone lesions from patients in a multicenter study. Methods: Thirty-five metastatic castrate-resistant prostate cancer patients with multiple metastases received two whole-body (test-retest) 18F-NaF PET/computed tomography (CT) scans 3±2 days apart from one of three imaging sites. A total of 411 bone lesions larger than 1.5 cm3 were automatically segmented using standardized uptake value (SUV) &gt; 15 g/mL threshold. Two levels of analysis were performed: lesion-level, where measures were extracted from individual lesion regions of interest (ROI), and patient-level, where all lesions within a patient were grouped into a single ROI for analysis. Uptake was quantified with the maximum (SUVmax), average (SUVmean), and total (SUVtotal) SUV. Test-retest repeatability was assessed using Bland-Altman analysis, intraclass correlation coefficient (ICC), coefficient of variation (CV), critical percent difference, and repeatability coefficient. The 95% limits of agreement (LOA95%) of the ratio between test-retest measurements were calculated. Results: At the lesion-level, CV for SUVmax, SUVmean, and SUVtotal were 14.1%, 6.6%, and 25.5%, respectively. At the patient-level, CV was slightly smaller: 12.0%, 5.3%, and 16.5%, respectively. ICC was excellent (ICC&gt;0.95) for all imaging metrics. Lesion-level LOA95% for SUVmax, SUVmean, and SUVtotal were (0.76, 1.32), (0.88, 1.14), and (0.63, 1.71), respectively. Patient-level LOA95% were slightly narrower at (0.79, 1.26), (0.89, 1.10), and (0.70, 1.44), respectively. We observed significant differences in the variance and sample mean of lesion-level and patient-level measurements between imaging sites. Conclusion: Repeatability of 18F-NaF PET/CT of SUVmax, SUVmean, and SUVtotal were similar between lesion- and patient-level regions of interest. We found significant differences in lesion-level and patient-level difference distributions between sites. These results can be used to establish 18F-NaF PET-based treatment response assessment criteria at the lesion- and patient-levels. 18F-NaF PET demonstrates repeatability levels useful for clinical quantification of bone lesion response to therapy. ER -