[Investigations on the conditions of scanning on cell images by means of a microscope-TV-system (author's transl)]

Abstract

One common method for determining the spatial resolution of a TV-microscope scanning system is to measure a sharp edge, differentiate the digitized response and calculate the Modulation Transfer Function (MTF) using the Fourier transformation. The MTF provides a measure of the information content of a digitized picture as well as the resolving power of the whole system. Knowledge of this measure is prerequisite for understanding the capabilities and limitations of computer aided techniques for analyzing cellular structures as observed in the light microscope. The information content of a digitized image depends on the MTF of the whole measurement system. Results from this study show that the information content increases almost linearly up to a sampling rate of approximately 20 pixel/micrometer and saturates at 30--35 pixel/micrometer. The MTF and the signal/noise ratio is effected by averaged multiscans. The aliasing error is presented as a function of the sampling rate for the described system. The need for this resolving power of the cell image analysis system is demonstrated by an example in the haematology. Small granules with a diameter of 0.2 to 1.0 micrometer must be registered with a high sampling rate up to 30 pixel/micrometer. The analysis of the small granules is basic for automated detection and differentiation of many leukemic conditions.