title: Stability of FDG-PET Radiomics features: an integrated analysis of test-retest and inter-observer variability.
abstract: OBJECTIVE
  Besides basic measurements as maximum standardized uptake value (SUV)max or SUVmean derived from 18F-FDG positron emission tomography (PET) scans, more advanced quantitative imaging features (i.e. "Radiomics" features) are increasingly investigated for treatment monitoring, outcome prediction, or as potential biomarkers. With these prospected applications of Radiomics features, it is a requisite that they provide robust and reliable measurements. The aim of our study was therefore to perform an integrated stability analysis of a large number of PET-derived features in non-small cell lung carcinoma (NSCLC), based on both a test-retest and an inter-observer setup.
  
  
  METHODS
  Eleven NSCLC patients were included in the test-retest cohort. Patients underwent repeated PET imaging within a one day interval, before any treatment was delivered. Lesions were delineated by applying a threshold of 50% of the maximum uptake value within the tumor. Twenty-three NSCLC patients were included in the inter-observer cohort. Patients underwent a diagnostic whole body PET-computed tomography (CT). Lesions were manually delineated based on fused PET-CT, using a standardized clinical delineation protocol. Delineation was performed independently by five observers, blinded to each other. Fifteen first order statistics, 39 descriptors of intensity volume histograms, eight geometric features and 44 textural features were extracted. For every feature, test-retest and inter-observer stability was assessed with the intra-class correlation coefficient (ICC) and the coefficient of variability, normalized to mean and range. Similarity between test-retest and inter-observer stability rankings of features was assessed with Spearman's rank correlation coefficient.
  
  
  RESULTS
  Results showed that the majority of assessed features had both a high test-retest (71%) and inter-observer (91%) stability in terms of their ICC. Overall, features more stable in repeated PET imaging were also found to be more robust against inter-observer variability.
  
  
  CONCLUSIONS
  Results suggest that further research of quantitative imaging features is warranted with respect to more advanced applications of PET imaging as being used for treatment monitoring, outcome prediction or imaging biomarkers.
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center (MUMC+) , Maastricht , The Netherlands.
authors.forename: Ralph T H
authors.initials: RT
authors.lastname: Leijenaar
authors.forename: Sara
authors.initials: S
authors.lastname: Carvalho
authors.forename: Emmanuel Rios
authors.initials: ER
authors.lastname: Velazquez
authors.forename: Wouter J C
authors.initials: WJ
authors.lastname: van Elmpt
authors.forename: Chintan
authors.initials: C
authors.lastname: Parmar
authors.forename: Otto S
authors.initials: OS
authors.lastname: Hoekstra
authors.forename: Corneline J
authors.initials: CJ
authors.lastname: Hoekstra
authors.forename: Ronald
authors.initials: R
authors.lastname: Boellaard
authors.forename: André L A J
authors.initials: AL
authors.lastname: Dekker
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gillies
authors.forename: Hugo J W L
authors.initials: HJ
authors.lastname: Aerts
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D015588:Observer Variation; D049268:Positron-Emission Tomography; D011379:Prognosis; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
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