Automatic Calibration Marker Detection for Radiography Images

In this paper we analyse the possibility of simple detection of circular radiography markers. To detect the marker, we utilised the Hough transform. Two approaches were analysed: with detecting image edges and without image edge detection where pixel gradient was used in Hough voting process, i.e. to increase the accumulator values. Approaches were evaluated on 13 clinical radiography images. It was shown that approach that detects image edges spatially matches the reference circles only 0.22 % less than manual annotation values, whereas approach that uses just the gradient magnitudes spatially matches the reference circles 3.2 % less than manual annotations.