Optimal temporal convolution smoothing for the perception of the recurrent display of a dynamic image series

The visual perception of temporal changes in a dynamic series of images, e.g. a recurrent movie display of an equilibrium gated angiography, depends strongly on the frequency of the changes in activity of the images. The human eye is three times as sensitive for frequencies at about ten hertz, as for frequencies lower than three hertz. This causes a low sensitivity for the relevant activity changes in the information of the series and a much higher sensitivity for activity changes due to noise. Linear combination of subsequent images allows to filter the frequency content of the series at about ten hertz. This does not affect the information of the series as this contains typically frequencies lower than three hertz (about the third harmonic in a typical angiography). For a filter which creates a new series of images by adding three subsequent images with factors a,b and a respectively, the optimal ratio A=a/b to reduce frequencies at ten hertz depends on the speed of projection of the dynamic series. A projection at 16 images per second leads to A=1.6. The effect of the filter is both objective on the static images (convolution smoothing) and subjective (psychophysical) on the dynamic series. Itmore » allows the reduction of the fast disturbing changes in the images due to noise and does not affect the diagnostic information in the images.« less