Abstract: For improving Kirsch operator, this paper presents an edge detection algorithm
with multi-threshold selection and edge connection, which is used to detect the edge of images,
especially medical images. The method first denoises the original image by Gaussian filter and
calculates the gradient with the traditional Kirsch operator, then sets a lower threshold and
adaptive thresholds to protect the weak edge and pick up the true edge, and finally detects the
disconnected edge of the image by use of the modified edge connection algorithm. The
experiment results show the efficiency of this method.

Key words: edge detection, Kirsch operator, multi-threshold selection, edge connection