**1. Introduction**

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The organization of American Cancer Society reported that the total number of cancer related to GI track is about 149,530 in the United State only for 2010 (American Cancer Society, 2010). Timely detection and diagnoses are extremely important since the majority of the GI related cancers at early-stage are curable.

However, the particularity of the alimentary track restricts the utilization of the current available examine techniques. The upper gastrointestinal tract can be examined by Gastroscopy. The bottom 2 meters makes up the colon and rectum, and can be examined by Colonoscopy. In between, lays the rest of the digestive tract, which is the small intestine characterised by being very long (average 7 meters) and very convoluted. However, this part of the digestive tract lies beyond the reach of the two previously indicated techniques. To diagnose the small intestine diseases, the special imaging techniques like CT scan or MRI are less useful in this circumstance.

Therefore, the non-invasive technique Wireless Capsule Endoscopy (WCE) has been proposed to enable the visualisation of the whole GI track cable freely. The WCE is a sensor device that contains a colour video camera and wireless radiofrequency transmitter, and battery to take nearly 55,000 colour images during an 8-hour journey through the digestive tract.

The most popular WCEs, are developed and manufactured by Olympus (Olympus, 2010), IntroMedic (IntroMedic, 2010) and Given Imaging (Given Imaging, 2010). However, there are still several drawbacks limiting the application of WCE. Recently, there are two main directions to develop the WCE. One is for enlarging the advantages of current wireless capsule, for example they are trying to make the capsule smaller and smaller, to enhance the propagation efficiency of the antenna or to reduce the radiated effects on human body. While, others are working on minimizing the disadvantages of capsule endoscope, for instance, they use internal and external magnetic field to control the capsule and use technology to reduce the power consumption.

The role of the WCE embedded antenna is for sending out the detected signals; hence the signal transmission efficiency of the antenna will directly decide the quality of received realtime images and the rate of power consumption (proportional to battery life). The human body as a lossy dielectric material absorbs a number of waves and decreases the power of receiving signals, presenting strong negative effects on the microwave propagation. Therefore, the antenna elements should ideally possess these features: first, the ideal antenna for the wireless capsule endoscope should be less sensitive to human tissue influence; second, the antenna should have enough bandwidth to transmit high resolution images and huge number of data; third, the enhancement of the antenna efficiency would facilitate the battery power saving and high data rate transmission.

In this chapter the WCE system and antenna specifications is first introduced and described. Next, the special consideration of body characteristics for antenna design (in body) is summarized. State-of-the-art WCE transmitting and receiving antennas are also reviewed. Finally, concise statements with a conclusion will summarize the chapter.
