title: Identification of low variability textural features for heterogeneity quantification of18F-FDG PET/CT imaging.
abstract: OBJECTIVE
  To identify those textural features that are insensitive to both technical and biological factors in order to standardise heterogeneity studies on18F-FDG PET imaging.
  
  
  METHODS
  Two different studies were performed. First, nineteen series from a cylindrical phantom filled with different18F-FDG activity concentration were acquired and reconstructed using three different protocols. Seventy-two texture features were calculated inside a circular region of interest. The variability of each feature was obtained. Second, the data for 15 patients showing non-pathological liver were acquired. Anatomical and physiological features such as patient's weight, height, body mass index, metabolic active volume, blood glucose level, SUV and SUV standard deviation were also recorded. A liver covering region of interest was delineated and low variability textural features calculated in each patient. Finally, a multivariate Spearman's correlation analysis between biological factors and texture features was performed.
  
  
  RESULTS
  Only eight texture features analysed show small variability (<5%) with activity concentration and reconstruction protocol making them suitable for heterogeneity quantification. On the other hand, there is a high statistically significant correlation between MAV and entropy (P<0.05). Entropy feature is, indeed, correlated (P<0.05) with all patient parameters, except body mass index.
  
  
  CONCLUSIONS
  The textural features that are correlated with neither technical nor biological factors are run percentage, short-zone emphasis and intensity, making them suitable for quantifying functional changes or classifying patients. Other textural features are correlated with technical and biological factors and are, therefore, a source of errors if used for this purpose.
authors.affiliation: Servicio de Física Médica y Protección Radiológica. Hospital Universitario Araba - Sede Txagorritxu, C/ Jose Atxotegui, s/n, 01009 Vitoria-Gasteiz, Spain. Electronic address: jesus.cortesrodicio@osakidetza.eus.
authors.forename: J
authors.initials: J
authors.lastname: Cortes-Rodicio
authors.affiliation: Servicio de Física Médica y Protección Radiológica. Hospital Universitario Araba - Sede Txagorritxu, C/ Jose Atxotegui, s/n, 01009 Vitoria-Gasteiz, Spain.
authors.forename: G
authors.initials: G
authors.lastname: Sanchez-Merino
authors.affiliation: Servicio de Física Médica y Protección Radiológica. Hospital Universitario Araba - Sede Txagorritxu, C/ Jose Atxotegui, s/n, 01009 Vitoria-Gasteiz, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Garcia-Fidalgo
authors.affiliation: Servicio de Medicina Nuclear, Hospital Universitario Araba - Sede Santiago, C/ Olaguibel, 29, 01004 Vitoria-Gasteiz, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Tobalina-Larrea
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Heterogeneidad; Heterogeneity; PET/CT; PET/TC; Radiomics; Radiónica; Textura; Texture