title: Application of gray level mapping in computed tomographic colonography: a pilot study to compare with traditional surface rendering method for identification and differentiation of endoluminal lesions.
abstract: OBJECTIVE
  In traditional surface rendering (SR) computed tomographic endoscopy, only the shape of endoluminal lesion is depicted without gray-level information unless the volume rendering technique is used. However, volume rendering technique is relatively slow and complex in terms of computation time and parameter setting. We use computed tomographic colonography (CTC) images as examples and report a new visualization technique by three-dimensional gray level mapping (GM) to better identify and differentiate endoluminal lesions.
  
  
  METHODS
  There are 33 various endoluminal cases from 30 patients evaluated in this clinical study. These cases were segmented using gray-level threshold. The marching cube algorithm was used to detect isosurfaces in volumetric data sets. GM is applied using the surface gray level of CTC. Radiologists conducted the clinical evaluation of the SR and GM images. The Wilcoxon signed-rank test was used for data analysis.
  
  
  RESULTS
  Clinical evaluation confirms GM is significantly superior to SR in terms of gray-level pattern and spatial shape presentation of endoluminal cases (p < 0.01) and improves the confidence of identification and clinical classification of endoluminal lesions significantly (p < 0.01). The specificity and diagnostic accuracy of GM is significantly better than those of SR in diagnostic performance evaluation (p < 0.01).
  
  
  CONCLUSIONS
  GM can reduce confusion in three-dimensional CTC and well correlate CTC with sectional images by the location as well as gray-level value. Hence, GM increases identification and differentiation of endoluminal lesions, and facilitates diagnostic process. Advances in knowledge: GM significantly improves the traditional SR method by providing reliable gray-level information for the surface points and is helpful in identification and differentiation of endoluminal lesions according to their shape and density.
authors.affiliation: 3 School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan, ROC.|4 Department of Medical Imaging, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan, ROC.
authors.forename: Lih-Shyang
authors.initials: LS
authors.lastname: Chen
authors.affiliation: 2 Department of General Surgery, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan, ROC.|3 School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Ta-Wen
authors.initials: TW
authors.lastname: Hsu
authors.affiliation: 3 School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan, ROC.|4 Department of Medical Imaging, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan, ROC.
authors.forename: Shao-Jer
authors.initials: SJ
authors.lastname: Chen
authors.affiliation: 1 Department of Electric Engineering, National Cheng Kung University, Tainan, Taiwan, ROC.
authors.forename: Shu-Han
authors.initials: SH
authors.lastname: Chang
authors.affiliation: 3 School of Medicine, Buddhist Tzu Chi University, Hualien, Taiwan, ROC.|4 Department of Medical Imaging, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan, ROC.
authors.forename: Chih-Wen
authors.initials: CW
authors.lastname: Lin
authors.affiliation: 4 Department of Medical Imaging, Buddhist Dalin Tzu Chi General Hospital, Chia-Yi, Taiwan, ROC.
authors.forename: Yu-Ruei
authors.initials: YR
authors.lastname: Chen
authors.affiliation: 5 Department of Radiology, National Cheng Kung University Hospital, Tainan, Taiwan, ROC.
authors.forename: Chin-Chiang
authors.initials: CC
authors.lastname: Hsieh
authors.affiliation: 6 Department of Radiology, Tainan Municipal Hospital, Tainan, Taiwan, ROC.
authors.forename: Shu-Chen
authors.initials: SC
authors.lastname: Han
authors.affiliation: 7 Department of Computer Science and Information Engineering, Da-Yeh University, Changhua, Taiwan, ROC.
authors.forename: Ku-Yaw
authors.initials: KY
authors.lastname: Chang
authors.affiliation: 8 Department of Electrical Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan, ROC.
authors.forename: Chun-Ju
authors.initials: CJ
authors.lastname: Hou
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003106:Colon / Q000000981:diagnostic imaging; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007414:Intestinal Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012189:Retrospective Studies; D012680:Sensitivity and Specificity