Israel-based Given Imaging and the researchers at the University of Buffalo in New York have developed a wireless type electronic device for biomedical measurement that can easily diagnose gastrointestinal system. What do you call this modern endoscopic monitoring system?
The microelectronic pill is a small capsule shaped electronic pill that can be comfortably swallowed by any normal patient. It consists of lens, antenna, transmitters, camera or sensors and battery. It can reach regions such as small intestine and provides the video wirelessly to the receiving device connected to the monitoring system outside the human body and kept at distance of 1 meter. The transmission of data takes place through the radio communication between electronic pill transmitter and external receiver.
Parameters such as temperature, pH and pressure of gastrointestinal tract can be measured, for the detection of diseases and disturbance in gastro intestinal system which prevents the entry of conventional endoscopic tube, thus a micro pill with single channel radio telemetric function is preferred. The invention of semiconductors provides ease in development of concise electronic pill capable to carry and transmit huge amount of data at a time without affecting the human body. The diagram below represents the wireless video transmission between transmitter and receiver:
A microelectronic pill construction requires narrow band transmission and has limited camera pixels. Given Imaging uses RF chip for wireless communication for real time video transmission based on Medical Implant Communication Service band. The channel bandwidth allowable for this band is limited to 300 kHz. The low frequency application provides high transmission efficiency through layers of skin. The fabrication of sensors of electronic pill are done on two silicon chips which are generally kept at the top of the capsule. The first chip encompasses diode, the pH ISFET sensor, temperature sensor and conductivity sensor. Another chip has thermometer and oxygen sensors.
All microelectronic pill is powered by a battery, in order to utilize the device in internal remote locations. There is also a scanning receiver which captures the wireless radio signal from pill through a coil antenna. A computer system is required for the control of data acquisition unit which acquires data in analog form from the scanning receiver. It provides recording of data on the computer. Stable transmission frequency must be constantly maintained. The transmission frequency is measured with the help of change in temperature. The change in frequency is measured with the help of scanning receiver, and the result obtained is used to evaluate the advantage of crystal stabilized unit.
The power consumption of microelectronic pill including transmitter and sensors connected is calculated to 12.1 milliwatt with current rating of 3.9 milliampere at 3.1 volt voltage supply, whereas free running radio transmitter consumes 6.8 milliwatt. Two silver oxide batteries SR44 are used to provide operating time of more than 40 hours. The pH measurement ranging from 1 to 13 can be carried out. The dissolved oxygen is up to 8.2 mg per liter. The temperature measurement is done from 0 ºC to 70 ºC. The pH ISFET sensor operated in constant current mode, with the drain voltage connected to the positive supply and the source voltage changes as per gate potential and gate potential is grounded. In control chip, the noise from application specific integrated circuit provides a constant level of 3Mega volt peak to peak, which provides single Least Significant Bit of Analog to Digital Converter; the second Least Significant Bit is used to provide an adequate noise margin, and here to have an effective resolution of 8 bits the 10-bit Analog to Digital Converter is used.
The components of capsule must be capable to protect itself from corrosive environment in gastrointestinal tract and it must be nontoxic to the human being but as the battery electrodes are toxic in nature, so extra care must be taken to prevent leakage of toxic fluids into the digestive system.