Edge enhancement applied in endoscopic systems

Activity: Talk or presentationOral presentationAcademic


Introduction. Flexible endoscopes are essential for diagnostics. Digital endoscopes are connected to a video processor that can perform various operations with the aim of improving the image. One of those operations is edge enhancement. Edge enhancement has a major impact on the perception of image quality by medical professionals. However, the algorithm and parameters that the processors apply are unknown, the name varies per video processor and the units that express the strength are arbitrary. These unknowns make it difficult to compare the image quality. We solved this by measuring the level of edge enhancement with test images. We also measured the effect on sharpness and noise. Method. Edge enhancement has been studied in four types of flexible digital ENT endoscopes by taking pictures of the Rez checker target. This test card has a horizontal and vertical slanted edge and a number of gray areas. The step response was measured on the slanted edges. Based on these step responses, the level of edge enhancement was measured by subtracting the zero step response from the step responses measured with the other levels of edge enhancement. This difference gives a wave whose peak-to-peak value is measured, which is then normalized by dividing it by the step size. Sharpness was measured by calculating the Modulation Transfer Function (MTF) with the step response and determining at which frequency the MTF curve equals 50%. Finally, the noise was measured on the gray areas and calculated as the sum of the variation of the luminance and two chrominance channels. Result. The measured levels of edge enhancement are consistent with the strength set on the video processor. Both sharpness and noise increase with the strength of edge enhancement. Conclusion. The described method overcomes the problem of manufacturers expressing the level of edge enhancement differently in arbitrary units. This makes it possible to compare the effect of edge enhancement between the different types. Now we can investigate the relationship between these effects and the influence on the perception of medical professionals and perhaps determine a substantiated optimum. Full article available at Journal of Biomedical Optics. https://doi.org/10.1117/1.JBO.27.10.106001
Period14 Oct 2022
Event titleNVKF Conference 2022 (Dutch Society for Clinical Physics)
Event typeConference
LocationWoudschoten, NetherlandsShow on map
Degree of RecognitionNational