Medical image processing techniques facilitate accurate diagnosis and treatment patients, using medical images for quantitative analysis and better visualization. The computer aided diagnosis (CAD) systems serve as a powerful tool for radiologists in the detection of disease. The magnetic resonance imaging (MRI) technique provides plentiful information about the soft tissue anatomy and helps to diagnose the abnormalities in brain. Nowadays, the brain tissue and tumor segmentation play an inevitable role in medical image processing. This book embodied to talks about the development of automatic methods for brain tissue and tumor segmentation in MRI head scans. The proposed methods can be formulated into three phases, namely, tissue segmentation, abnormality detection and tumor segmentation from MRI head scans. The last section of this book is about the development of an automated decision support system that helps in brain tissue and tumor segmentation techniques in MRI head scans. This system has the provision to assess all the developed methods for thresholding, tumor detection and tumor segmentation.