title: Repeatability of Quantitative 18F-NaF PET: A Multicenter Study.
abstract: 18F-NaF, a PET radiotracer of bone turnover, has shown potential as an imaging biomarker for assessing the response of bone metastases to therapy. This study aimed to evaluate the repeatability of18F-NaF PET-derived SUV imaging metrics in individual bone lesions from patients in a multicenter study.
  
  
  METHODS
  Thirty-five castration-resistant prostate cancer patients with multiple metastases underwent 2 whole-body (test-retest)18F-NaF PET/CT scans 3 ± 2 d apart from 1 of 3 imaging sites. A total of 411 bone lesions larger than 1.5 cm3were automatically segmented using an SUV threshold of 15 g/mL. Two levels of analysis were performed: lesion-level, in which measures were extracted from individual-lesion regions of interest (ROI), and patient-level, in which all lesions within a patient were grouped into a patient ROI for analysis. Uptake was quantified with SUVmax, SUVmean, and SUVtotalTest-retest repeatability was assessed using Bland-Altman analysis, intraclass correlation coefficient (ICC), coefficient of variation, critical percentage difference, and repeatability coefficient. The 95% limit of agreement (LOA) of the ratio between test and retest measurements was calculated.
  
  
  RESULTS
  At the lesion level, the coefficient of variation for SUVmax, SUVmean, and SUVtotalwas 14.1%, 6.6%, and 25.5%, respectively. At the patient level, it was slightly smaller: 12.0%, 5.3%, and 18.5%, respectively. ICC was excellent (>0.95) for all SUV metrics. Lesion-level 95% LOA for SUVmax,SUVmean, and SUVtotalwas (0.76, 1.32), (0.88, 1.14), and (0.63, 1.71), respectively. Patient-level 95% LOA was 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.
  
  
  CONCLUSIONS
  The repeatability of SUVmax, SUVmean, and SUVtotalfor18F-NaF PET/CT was similar between lesion- and patient-level ROIs. We found significant differences in lesion-level and patient-level distributions between sites. These results can be used to establish18F-NaF PET-based criteria for assessing treatment response at the lesion and patient levels.18F-NaF PET demonstrates repeatability levels useful for clinically quantifying the response of bone lesions to therapy.
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.
authors.forename: Christie
authors.initials: C
authors.lastname: Lin
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin.
authors.forename: Tyler
authors.initials: T
authors.lastname: Bradshaw
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.
authors.forename: Timothy
authors.initials: T
authors.lastname: Perk
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Harmon
authors.affiliation: Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, Wisconsin.
authors.forename: Jens
authors.initials: J
authors.lastname: Eickhoff
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia.
authors.forename: Ngoneh
authors.initials: N
authors.lastname: Jallow
authors.affiliation: Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.affiliation: Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: William L
authors.initials: WL
authors.lastname: Dahut
authors.affiliation: Molecular Imaging and Therapy Service, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Steven
authors.initials: S
authors.lastname: Larson
authors.affiliation: Molecular Imaging and Therapy Service, Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: John Laurence
authors.initials: JL
authors.lastname: Humm
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, Wisconsin.|University of Wisconsin Carbone Cancer Center, Madison, Wisconsin; and.
authors.forename: Scott
authors.initials: S
authors.lastname: Perlman
authors.affiliation: Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Apolo
authors.affiliation: Department of Medical Oncology, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Morris
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin.|University of Wisconsin Carbone Cancer Center, Madison, Wisconsin; and.
authors.forename: Glenn
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, Wisconsin rjeraj@wisc.edu.|University of Wisconsin Carbone Cancer Center, Madison, Wisconsin; and.
authors.forename: Robert
authors.initials: R
authors.lastname: Jeraj
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000556:secondary; D005462:Fluorine Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography; D064129:Prostatic Neoplasms, Castration-Resistant / Q000473:pathology; D015203:Reproducibility of Results; D012969:Sodium Fluoride / Q000378:metabolism; D051598:Whole Body Imaging
chemical_list: D005462:Fluorine Radioisotopes; D012969:Sodium Fluoride
keywords: PET; metastatic prostate cancer; multicenter clinical trial; repeatability; sodium fluoride