Researchers at Given Imaging (Yoqneam, Israel) incorporated a digital camera, battery, radio transmitter, and light source into a pill-sized package that can be swallowed by patients to enable nonsurgical imaging of the gastrointestinal tract (Figure 1).
Figure 1. A wireless endoscopy system in a capsule provides real-color images of the GI tract after the patient swallows the device.
The torpedo-shaped capsule can provide more than five hours of real-color images. The patient need not be in a hospital or clinic during this time. The disposable capsule, which is 30 mm long and 11 mm in diameter, is propelled by peristalsis through the gastrointestinal tract. The images are transmitted from the capsule using UHF signals to an antenna array attached to the patient (much like an ECG test). The aerials also record position information. The received images are stored in a recorder worn on a belt around the waist.
The data is later downloaded to a computer workstation and processed to produce a 20-minute video clip of the images transmitted by the capsule. The data also indicates where in the abdomen the capsule was at the time; this is important for locating diseased tissue should surgery be necessary.
The company is targeting the need for imaging the small intestine, which is difficult to adequately image using other methods. Arkady Glukhovsky, vice president of R&D at Given Imaging, said there is no real alternative for imaging parts of the small intestine:
Endoscopy provides very good images, but it can only be used to view the first third of the small intestine, requires sedating the patient, and is uncomfortable and includes the risk of perforation. Radiology, using a contrast agent such as barium, can show inflammation or large abnormalities in the intestine, but it is uncomfortable and includes exposure to x rays. Ultrasound is noninvasive, but does not produce clear images of organs that may be filled with gas. CT scan is an x-ray technique that produces an image showing a detailed cross-section of tissue. Although it is used to diagnose conditions throughout the body, including abnormalities a normal x ray would not pick up, both the exposure to x rays and the cost to the patient are higher. In contrast, the cost of Given's system is comparable to that of endoscopy and it is more comfortable for the patient.
Figure 2. The capsule incorporates the imaging system at one end, the UHF telemetry system at the other, and batteries in between.
The company's system incorporates several technological breakthroughs that have only recently come to market. For this application, small size and power efficiency are important. Glukhovsky cites three vital technologies that made the tiny imaging system possible: improvement of the signal-to-noise ratio (SNR) in CMOS detectors, development of white LEDs, and development of application-specific integrated circuits (ASICs).
"CMOS detectors have active pixel resolutions that provide comparable performance to CCDs, while drawing less power than CCDs," Glukhovsky said. The SNR of CMOS detectors has improved because each pixel is now equipped with a buffer amplifier, and there is room for these components because the element size was reduced. The device is a camera on a chip.
Figure 3. Image of the inside of the small intestine produced by Given Image's capsule-size camera.
The silver oxide batteries in the capsule power the CMOS detector, as well as the LEDs and transmitter. Glukhovsky said the white-light LEDs are important because pathologists distinguish diseased tissue by color.
The developers provided a novel optical design that uses a wide-angle lens over the imager, and manages to integrate both the LEDs and imager under one dome while handling stray light and reflections.
Recent advances in ASIC design allowed the integration of a video transmitter of sufficient power output, efficiency, and bandwidth of very small size into the capsule. Synchronous switching of the LEDs, the CMOS sensor, and the ASIC transmitter minimizes power consumption.
The earliest telemetry-providing pills gave temperature and pH measurements. These or similar sensors could be integrated with the capsule in the future. But for the near future, Given Imaging has completed animal studies and is conducting human studies of the system in preparation for a 510(k) filing with the Food and Drug Administration later this year.
Yvonne Carts-Powell Yvonne Carts-Powell, based in Boston, writes about optoelectronics and the Internet.