title: Respiration-Averaged CT for Attenuation Correction of PET Images - Impact on PET Texture Features in Non-Small Cell Lung Cancer Patients.
abstract: OBJECTIVE
  We compared attenuation correction of PET images with helical CT (PET/HCT) and respiration-averaged CT (PET/ACT) in patients with non-small-cell lung cancer (NSCLC) with the goal of investigating the impact of respiration-averaged CT on 18F FDG PET texture parameters.
  
  
  METHODS
  A total of 56 patients were enrolled. Tumors were segmented on pretreatment PET images using the adaptive threshold. Twelve different texture parameters were computed: standard uptake value (SUV) entropy, uniformity, entropy, dissimilarity, homogeneity, coarseness, busyness, contrast, complexity, grey-level nonuniformity, zone-size nonuniformity, and high grey-level large zone emphasis. Comparisons of PET/HCT and PET/ACT were performed using Wilcoxon signed-rank tests, intraclass correlation coefficients, and Bland-Altman analysis. Receiver operating characteristic (ROC) curves as well as univariate and multivariate Cox regression analyses were used to identify the parameters significantly associated with disease-specific survival (DSS). A fixed threshold at 45% of the maximum SUV (T45) was used for validation.
  
  
  RESULTS
  SUV maximum and total lesion glycolysis (TLG) were significantly higher in PET/ACT. However, texture parameters obtained with PET/ACT and PET/HCT showed a high degree of agreement. The lowest levels of variation between the two modalities were observed for SUV entropy (9.7%) and entropy (9.8%). SUV entropy, entropy, and coarseness from both PET/ACT and PET/HCT were significantly associated with DSS. Validation analyses using T45 confirmed the usefulness of SUV entropy and entropy in both PET/HCT and PET/ACT for the prediction of DSS, but only coarseness from PET/ACT achieved the statistical significance threshold.
  
  
  CONCLUSIONS
  Our results indicate that 1) texture parameters from PET/ACT are clinically useful in the prediction of survival in NSCLC patients and 2) SUV entropy and entropy are robust to attenuation correction methods.
authors.affiliation: Departments of Nuclear Medicine, Chang Gung Memorial Hospita, Linkou, Chang Gung University College of Medicine, Taoyuan City 33305, Taiwan.|Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu City, 30071, Taiwan.
authors.forename: Nai-Ming
authors.initials: NM
authors.lastname: Cheng
authors.affiliation: Department of Biomedical Engineering, National Cheng Kung University, Tainan City, 70101, Taiwan.
authors.forename: Yu-Hua Dean
authors.initials: YH
authors.lastname: Fang
authors.affiliation: Department of Radiation Oncology, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan City 33305, Taiwan.
authors.forename: Din-Li
authors.initials: DL
authors.lastname: Tsan
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu City, 30071, Taiwan.
authors.forename: Ching-Han
authors.initials: CH
authors.lastname: Hsu
authors.affiliation: Departments of Nuclear Medicine, Chang Gung Memorial Hospita, Linkou, Chang Gung University College of Medicine, Taoyuan City 33305, Taiwan.
authors.forename: Tzu-Chen
authors.initials: TC
authors.lastname: Yen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000401:mortality; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D016016:Proportional Hazards Models; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed / Q000379:methods