chapter 6 image enhancement - 医学影像处理实验室mipl.ppt

Chapter 6Image Enhancement Chuan-Yu Chang (張傳育)Ph.D. Dept. of Electronic Engineering National Yunlin University of Science Technology chuanyu@yuntech.edu.tw Office: ES709 Tel: 05-5342601 Ext. 4337 Image Enhancement The purpose of image enhancement methods is to process and acquired image for better contrast and visibility of features of interest for visual examination and subsequent computer-aided analysis and diagnosis. Different medical imaging modalities provide specific characteristic information about internal organs or biological tissues. Image contrast and visibility of the features of interest depend on the imaging modality and the anatomical regions. There is no unique general theory or method for processing all kinds of medical images for feature enhancement. Specific medical imaging applications present different challenges in image processing for feature enhancement. Image Enhancement (cont.) Medical images from specific modalities need to be processed using a method that is suitable to enhance the features of interest. Chest X-ray radiographic image Required to improve the visibility of hard bony structure. X-ray mammogram Required to enhance visibility of microcalcification. A single image-enhancement method may not serve both of these applications. Image enhancement tasks and methods are very much application dependent. Image Enhancement (cont.) Image enhancement tasks are usually characterized in two categories: Spatial domain methods Manipulate image pixel values in the spatial domain based on the distribution statistics of the entire image or local regions. Histogram transformation, spatial filtering, region growing, morphological image processing and model-based image estimation… Frequency domain methods Manipulate information in the frequency domain based on the frequency characteristics of the image. Frequency filtering, homomorphic filtering and wavelet processing methods… Model-based techniques are also used to extract specific features fo