title: Observer performance in the assessment of contract enhanced CT: effects of contrast medium and grey scale window on detection of defects in a simulated peripheral rim border.
abstract: The image contrast of X-ray CT systems depends on the properties of the imaging system, the number of grey scales used in the digital sampling process, and the addition or otherwise of a contrast medium. The effect of contrast medium is often emphasized in the peripheral rim of pathologic masses. In this study, a special hexagonal test object made of acrylic phosphate and a cylindrical container were employed. When the contrast medium IOPAMIRON 300 was used to fill the space between the test object and its cylindrical container, a contrast-enhanced peripheral rim with or without signal of defect was observed. Visual perceptibility was examined from the signals resulting from varying contrast by use of contrast medium and adjusting the grey scale by image processing. Threshold contrast influenced by window width was recorded in each image contrast, different ranges of window width was recorded in each instance using statistical analyses. While window width was inversely proportional to image contrast, different ranges of window width and image contrast provided better visual perceptibility for each concentration of the contrast medium. The range of window width for obtaining the best visual perceptibility was determined for a contrast-enhanced image.
authors.affiliation: Department of Oral and Maxillofacial Radiology, Tokyo Dental College, Chiba, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Wakoh
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Kuroyanagi
mesh_terms: D015502:Absorptiometry, Photon; D000704:Analysis of Variance; D003287:Contrast Media; D015350:Contrast Sensitivity; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging; D015588:Observer Variation; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care; D011856:Radiographic Image Enhancement; D012044:Regression Analysis; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards*
chemical_list: D003287:Contrast Media