title: Assessment of tumor heterogeneity by CT texture analysis: can the largest cross-sectional area be used as an alternative to whole tumor analysis?
abstract: OBJECTIVE
  To determine if there is a difference between contrast enhanced CT texture features from the largest cross-sectional area versus the whole tumor, and its effect on clinical outcome prediction.
  
  
  METHODS
  Entropy (E) and uniformity (U) were derived for different filter values (1.0-2.5: fine to coarse textures) for the largest primary tumor cross-sectional area and the whole tumor of the staging contrast enhanced CT in 55 patients with primary colorectal cancer. Parameters were compared using non-parametric Wilcoxon test. Kaplan-Meier analysis was performed to determine the relationship between CT texture and 5-year overall survival.
  
  
  RESULTS
  E was higher and U lower for the whole tumor indicating greater heterogeneity at all filter levels (1.0-2.5): median (range) for E and U for whole tumor versus largest cross-sectional area of 7.89 (7.43-8.31) versus 7.62 (6.94-8.08) and 0.005 (0.004-0.01) versus 0.006 (0.005-0.01) for filter 1.0; 7.88 (7.22-8.48) versus 7.54 (6.86-8.1) and 0.005 (0.003-0.01) versus 0.007 (0.004-0.01) for filter 1.5; 7.88 (7.17-8.54) versus 7.48 (5.84-8.25) and 0.005 (0.003-0.01) versus 0.007 (0.004-0.02) for filter 2.0; and 7.83 (7.03-8.57) versus 7.42 (5.19-8.26) and 0.005 (0.003-0.01) versus 0.006 (0.004-0.03) for filter 2.5 respectively (p ≤ 0.001). Kaplan-Meier analysis demonstrated better separation of E and U for whole tumor analysis for 5-year overall survival.
  
  
  CONCLUSIONS
  Whole tumor analysis appears more representative of tumor heterogeneity.
authors.affiliation: Paul Strickland Scanner Centre, Mount Vernon Hospital, Northwood, Middlesex, UK. kher_shing_ng@yahoo.co.uk
authors.forename: Francesca
authors.initials: F
authors.lastname: Ng
authors.forename: Robert
authors.initials: R
authors.lastname: Kozarski
authors.forename: Balaji
authors.initials: B
authors.lastname: Ganeshan
authors.forename: Vicky
authors.initials: V
authors.lastname: Goh
mesh_terms: D000328:Adult; D000465:Algorithms; D019412:Anatomy, Cross-Sectional / Q000379:methods / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality*; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D016016:Proportional Hazards Models; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D015996:Survival Rate; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000706:statistics & numerical data*; D006113:United Kingdom / Q000453:epidemiology