Visual interpretation compared with caliper and computerized measurements in experimental vessel stenosis.

To explain visual interpretation errors on angiograms, visual interpretation, caliper measurement, and computerized measurement of cine film were compared using each of 10 graphic models and 10 acrylic models with "stenotic vessels". Stenosis > 40% was overestimated and stenosis < 40% underestimated by visual interpretation. In caliper measurement, stenosis > 40% at exposure of 90 kV was greatly overestimated by a degree similar to the estimation by visual interpretation, and stenosis > 40% at exposures of 74 kV and 58 kV was slightly overestimated. In computerized measurement, the estimation was consistent with the actual degree of stenosis. Therefore, visual interpretation was not reliable for estimation, and computerized measurement was indispensable for estimation of vessel stenosis. Moreover, we consider the most common cause of error in visual interpretation to be optical illusions.