The modulation transfer function (MTF) of a medical imaging display is typically determined by measuring its response to square
waves (bar patterns), white noise, and/or line stimuli. However, square waves and white noise methods involve capture and
analysis of multiple images and are thus quite tedious. Measurement of the line-spread function (LSF) offers a good alternative.
However, as previously reported, low-frequency response obtained from the LSF method is not as good as that obtained from
measurement of edge-spread function (ESF). In this paper, we present two methods for evaluating the MTF of a medical imaging
display from its ESF. High degree of accuracy in the higher frequency region (near the Nyquist frequency of the system) was
achieved by reducing the noise. In the first method, whichis a variant of the Gans' original method, the periodic raster noise
is reduced by subtracting a shifted ESF from the ESF. The second method employs a low-pass differentiator (LPD). A novel near
maximally flat LPD with the desired cut-off frequency was designed for this purpose. Noise reduction in both the methods was
alsoachieved by averaging over large portions of the image data to form the ESF. Experimental results show that the MTF obtained
by these methods is comparable to that obtained from the square wave response. Furthermore, the MTFs of rising and falling
edges of a cathode ray tube (CRT) were measured. The results show that the rising and falling vertical MTFs are practically
the same, whereas the rising horizontal MTF is poorer than the falling horizontal MTF in the midfrequency region.
Key Words Cathode ray tube (CRT) - liquid crystal display (LCD) - modulation transfer function (MTF) - edge-spread function (ESF) - line-spread function (LSF) - Gans' method - low-pass differentiator - image quality