I. Introduction
Endoscopy is a commonly used technique in which the gastrointestinal (GI) tract of human is examined. The conventional endoscope cannot reach the small intestine which prevents diagnosing many diseases that appear there, such as Chron's disease, celiac disease, irritable bowel syndrome or different types of cancer [1]. Because of this, the first wireless capsule endoscope (WEC) was developed in 2001. It is a small, capsule-shaped device that is swallowed by the patient. It travels through the whole GI tract due to gravitation and natural peristalsis and takes thousands of pictures during its way. These pictures are transmitted to a recording device outside the body and can be visualized on a computer screen. [2]