title: Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve.
abstract: OBJECTIVE
  To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves.
  
  
  METHODS
  We used vascular models (actual attenuation value of the wall: 87HU) with wall thicknesses of 1.5, 1.0, or 0.5mm, filled with contrast material of 250, 348, or 436HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI.
  
  
  RESULTS
  Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103HU.
  
  
  CONCLUSIONS
  The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0mm thickness are difficult.
authors.affiliation: Department of Radiology, Saitama Red Cross Hospital, 8-3-33 Kamiochiai, Chuo-ku, Saitama, 338-8553, Japan. shig.suz@gmail.com
authors.forename: Shigeru
authors.initials: S
authors.lastname: Suzuki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kidouchi
authors.forename: Sadatoshi
authors.initials: S
authors.lastname: Kuwahara
authors.forename: Mani
authors.initials: M
authors.lastname: Vembar
authors.forename: Ryoji
authors.initials: R
authors.lastname: Takei
authors.forename: Asako
authors.initials: A
authors.lastname: Yamamoto
mesh_terms: D000465:Algorithms; D000792:Angiography / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D010363:Pattern Recognition, Automated / Q000379:methods*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*