Early detection of the brain tumor in the brain magnetic resonance imaging is important because physician needs to quantification and classify of the tumor and its area. The computer and image processing techniques can provide great help in analyzing the tumor area and its type by classification. On the other side, computer-aided detection (CAD) has been developing fast in the last two decades. The main idea of CAD is to assist radiologists in interpreting medical images by using dedicated computer systems to provide 'Accurate System'. Studies on CAD systems and technology show that CAD can help to improve diagnostic accuracy of radiologists, lighten the burden of increasing workload, reduce cancer missed due to fatigue, overlooked or data overloaded and improve inter- and intra-reader variability. The final medical decision is made by the radiologists. Consequently, radiologists expect that CAD systems can improve their diagnostic abilities based on synergistic effects between the radiologist and the computer with medical image analysis and machine learning techniques.