Image processing in medical has been progressing far than it ever did when it's one of the main techniques used in the biomedical imaging system and computer aided diagnosis systems. Few of the well-known medical imaging modalities are Magnetic Resonance Imaging (MRI), Computed Tomography (CT) Scan, X-Ray and Ultrasound. The output from these imaging modalities would later be reviewed by expert for an accurate result. Computer aided diagnosis not only save time as it can process thousand images just in a few minutes, it can also be used as tool to aid the expert as a second opinion, which in turn could save more lives. Thorax consist of several organs which include heart, lungs, thymus gland, muscles and other various internal structures such as diaphragm. Thorax disease refer to diseases that affect the chest and the most common symptom is the chest pain. Some of the common thoracic disease are atelectasis, pneumothorax, pneumonia, nodule, mass, infiltration, effusion and cardiomegaly. Figure 1 shows the thorax diseases observed in chest X-ray [1]. Correct diagnosis and disease treatment are important especially during the early stage, which is the most difficult part of the process due to similarity in appearance.