title: Variations in measured vessel diameters using coronary measurement system.
abstract: The Coronary Measurement System (CMS, MEDIS, Leiden, Netherlands) is a film-based QCA system that allows the user to vary the intensity of the light source which illuminates the film, thereby changing the brightness of the image viewed by the digitizing video camera. We found that significant variations in calibration factor (mm/pixel) and measured diameter can occur as a result of variations in either of these intensities. We calculated the variability of the measured diameters for a range of light intensities used for vessel measurement and for calibration. The root mean square deviations in estimated vessel diameter for simulated vessels having actual diameters of 2.03, 2.56, 3.03, and 3.55 mm were 0.13, 0.13, 0.13, and 0.11 mm, respectively, while the ranges (maximum-minimum estimates) were 0.47, 0.45, 0.47, and 0.36 mm, respectively. These results show that while mean errors due to changes in brightness are small, there is the potential for larger errors for certain combinations of light intensities.
authors.affiliation: Department of Medicine Biophysics, Sunnybrook Health Science Centre, University of Toronto, Ontario, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Robert
authors.forename: M J
authors.initials: MJ
authors.lastname: Yaffe
authors.forename: A
authors.initials: A
authors.lastname: Langer
mesh_terms: D017023:Coronary Angiography / Q000295:instrumentation* / Q000379:methods; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008962:Models, Theoretical; D012680:Sensitivity and Specificity