VARIATIONS IN MEASURED VESSEL DIAMETERS USING CORONARY MEASUREMENT SYSTEM

The Coronary Measurement System (CMS, MEDIS, Leiden, Netherlands) is a film-based QCA system that allows the user to vary the intensity of t he light source which illuminates the film, thereby changing the brigh tness of the image viewed by the digitizing video camera, We found tha t significant variations in calibration factor (mm/pixel) and measured diameter can occur as a result of variations in either of these inten sities, We calculated the variability of the measured diameters for a range of light intensities used for vessel measurement and for calibra tion, 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 rang es (maximum-minimum estimates) were 0.47, 0.45, 0.47, and 0.36 mm, res pectively, These results show that while mean errors due to changes in brightness are small, there is the potential for larger errors for ce rtain combinations of light intensities. (C) 1996 Wiley-Lies, Inc.