title: Utility of the iodine overlay technique and virtual nonenhanced images for the preoperative T staging of colorectal cancer by dual-energy CT with tin filter technology.
abstract: OBJECTIVE
  To evaluate the diagnostic accuracy and the potential radiation dose reduction of dual-energy CT (DECT) for tumor (T) staging of colorectal cancer (CRC) using iodine overlay (IO) and virtual nonenhanced (VNE) images.
  
  
  METHODS
  This retrospective study included 103 consecutive patients who underwent nonenhanced CT and enhanced DECT for preoperative CRC staging. Enhanced weighted-average (WA), IO and VNE images were reconstructed from enhanced 80 kVp and Sn140 kVp scans. Two radiologists assessed image qualities of the true nonenhanced (TNE) and VNE images. For T-staging, another two radiologists independently interpreted all scans in two separate reading sessions: in the first session, only images derived from the single phase DECT acquisition (IO and VNE images) were read. In the second reading session after 30 to 50 (average:42) days, the same assessment was again performed with the TNE and enhanced WA images thereby simulating conventional dual-phase single-energy CT. The tumor node metastasis (TNM) system was used for staging with histopathologic reports as gold standard. Analysis of variance was used for statistical analysis.
  
  
  RESULTS
  The signal-to-noise ratios (SNRs) of the tumors and normal reference tissues showed significant correlation between the TNE and VNE images (P<0.01). The mean iodine overlay value (48.4 HU±12.2) and enhancement (49.4 HU±11.8) value of CRCs had no significant difference (P = 0.52).The mean image noise on TNE (5.0±1.1) and VNE (5.3±1.1) images were similar (P = 0.07). The quantitative qualities of the VNE images were mildly inferior to the TNE images. Overall accuracy of T-stage CRC when using single-phase acquisition was slightly better than the dual-phase acquisition (90.3% vs 87.4%) (P = 0.51). The mean dose of the single-phase DECT acquisition was 6.2 mSv comparing with 14.3 mSv of dual-phase.
  
  
  CONCLUSIONS
  Single-phase DECT using IO and VNE images yields a high accuracy in T-staging of CRCs. Thereby, the radiation exposure of the patients can be reduced.
authors.affiliation: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Chiao-Yun
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Jui-Sheng
authors.initials: JS
authors.lastname: Hsu
authors.affiliation: Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Twei-Shiun
authors.initials: TS
authors.lastname: Jaw
authors.affiliation: Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan; Department of Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Deng-Chyang
authors.initials: DC
authors.lastname: Wu
authors.affiliation: Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan.
authors.forename: Ming-Chen Paul
authors.initials: MC
authors.lastname: Shih
authors.affiliation: Department of Public Health, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chien-Hung
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Department of Medicine, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Chao-Hung
authors.initials: CH
authors.lastname: Kuo
authors.affiliation: Department of Pathology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Chen
authors.affiliation: Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Ming-Lai
authors.initials: ML
authors.lastname: Lai
authors.affiliation: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Radiology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Gin-Chung
authors.initials: GC
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D023881:Colonography, Computed Tomographic / Q000379:methods*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007455:Iodine; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D057234:Preoperative Period; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D014131:Trace Elements
chemical_list: D014131:Trace Elements; D007455:Iodine