Microcalcifications Detection in Digitized Mammographic Images

A method has been developed to detect and analyse microcalcifications in digitized mammographic images. The algorithms presented in this work combine an image preprocessing to denoise the digital image and image treatment techniques to localize and characterize the features of the microcalcifications. Two image denoising methods have been applied to the mammographies, the first one is an adaptive noise removal Wiener filter and the second one is a wavelet filter based on the wavelet coefficients shrinkage. After denoisig, the microcalcification location is carried out by applying digital image processing techniques as image local thresholding to detect objects of interest, a regional growing method based on determining the maximum of the slope function for different space directions of a wavelet smoothed version of the mammographic image, and the morphological operator application to fix the microcalcifications shape and size. Once the microcalcifications are characterized in the image, a big quantity of data about its characteristics can be obtained as location, size, eccentricity, bright level in relation to the background, signal to noise ratio, etc. This information about the mammography microcalcifications, that due to its small size and lowly contrast can be obtained very difficultly by direct observation, can be used to define an image quality index (IQI) which characterizes the quality image in an objective way. The image quality index is defined as the smallest microcalcification diameter calculated as the average at the major and minor axes of the microcalcification. This way of determining the image quality is similar to the system used by the radiologist, with the difference that the presented computer assisted method is more objective and independent of the radiologist who analyses the image. The IQI serve to compare images obtained at different mammographic centers and also, to study the temporal evolution of the image quality produced by determined mammographic equipment.