Wireless capsules

Chutkan R, Toubia N Effect of nonsteroidal anti-inflammatory drugs on the gastrointestinal tract Diagnosis by wireless capsule endoscopy. Gastrointest Endosc Clin N Am 2004 14 67-85. 

Ell, C., Remke, S., May, A., Helon, L., Henrich, R., Mayer, G. The first prospective controlled trial comparing wireless capsule endoscopy with push enteroscopy in chronic gastrointestinal bleeding. Endoscopy 2002 34 685 - 689... 

G. Iddan, G. Meron, A. Glukhovsky, and P. Swain, "Wireless capsule endoscopy," Nature,... 

M. T. Gettman and P. Swain, "Initial experimental evaluation of wireless capsule endoscopes in the bladder Implications for capsule cystoscopy," Eur. Urol., 55(5) 1207-1212,2009. 

Illustration of potential closed-loop system for real-time treatment of digestive diseases using mHealth technologies with a future novel wireless capsule endoscope with actuation mechanisms for therapeutic treatment. 

Endoscopes are important medical instruments that produce images of the interior surfaces of cavities in human bodies, for example the gastrointestinal (GI) tract including the esophagus, stomach, colon, and part of the small bowel joint spaces abdominal cavity thorax and other structures. In recent years, through technical improvements like wireless capsule endoscopy [32] and robotic surgery [33], minimally invasive surgery has become a common treatment. 

A. Moglia, A. Menciassi, M. O. Schurr, and P. Dario, "Wireless capsule endoscopy from diagnostic devices to multipurpose robotic systems," Biomedical Microdevices, vol. 9, pp. 235-243, Apr 2007. 

In this design example, a capacitive technique has been exploited to measure strong acidic and basic mediums. Such sensors can be integrated within the wireless capsule to measure pH of gastric acid. This technique provides higher sensitivity and low noise readout system while maintaining simple and low-cost fabrication process. 

Wireless capsule devices are used in the GI tract to measure physiological parameters. They can monitor motility of the GI tract as a pressure change and transmit the data using low frequencies [40,81]. A smmnary of previonsly reported wireless capsules is listed in Table 7.3. 

Figure 7.12 The block diagram of a wireless capsule system with biosensors, readout circuits, and transmitter.

The architecture of a wireless capsule system named the lab-in-a-pill (LIAP) is presented in Fig. 7.13 [113]. It consists of pH and temperature sensors and a custom-made application-specific integrated readout circuit. The pH sensor is a micro-fabricated ISFET with Ag/AgCl reference electrode. The temperature sensor is an n-channel silicon diode. The system consumes 15.5 mW. The circuit has a power saving feature to operate it for 42 h. 

A wireless capsule can provide an invasive method for the diagnosis of the GI tract. The sensor systems for a wireless capsule are composed of mechanical sensors for pressure and position measurement, chemical sensors for pH, conductivity, and dissolved oxygen measurement, and biosensors for bleeding and pathogens detection. In addition to the sensor systems, interface circuits for the sensors also play an important role for the development of low-noise and low-power sensor systems. As a result, wireless capsule requires the development of a reliable, miniaturized, and integrated sensor system with high sensitivity and resolution as well as a low noise, low cost, and a low-power interface circuit system. 

Figure 7.13 The architecture of a wireless capsule containing temperature and pH sensors at the front, followed by application-specific integrated circuit (ASIC) and batteries.

J.T. Farrar, C. Berkley, and V.K. Zworykin. Telemetering of intraenteric pressure in man by an externally energized wireless capsule. Science, 131(3416) 1814,1960. 

---