Reported September 2006

BACKGROUND: Engineers at Purdue University in West Lafayette, Indiana, are creating a wireless device the size of a rice grain that could be implanted into tumors to tell doctors the precise dose of radiation received and locate the exact position of tumors during treatment. Doctors could use the wireless technology to precisely track a tumor by using electrical coils placed around the body to pinpoint the location of the electronic device inside the body. The prototype device has been tested with a radioactive material called cesium.

HOW IT WORKS: The device is called a "passive wireless transponder," and works much like a small tuning circuit in a radio. It has no batteries, can be activated with electrical coils placed next to the body, and will be sealed airtight so it can stay in the body indefinitely. Along with the wireless tracking technology, the device contains a miniature version of the dosimeters worn by people who work in jobs involving radioactivity to monitor their exposure. The technology operates on the same principle as the electric microphones commonly found in consumer electronics. The microphones contain a membrane that vibrates in response to sound waves. Between the membrane and a metal plate is an air gap that stores electricity. As the membrane vibrates, the size of the air gap increases and decreases. This changes its capacity to store energy, altering the flow of electric current through the circuit. This, in turn, creates a signal that transmits the information stored in the dosimeter to a receiver.

THE PROBLEM: There is currently no way to determine the exact dose of radiation that reaches a tumor. Also, most organs shift inside the body depending on whether a person is sitting or lying down, which causes the tumor to shift also. Imaging systems are used to get a 3-D fix on a tumor's shifting position, but such methods are difficult to use during radiation therapy, are expensive, and may require X-rays, which can damage surrounding tissue over repeated uses.

WHAT ARE MEMS? Micro-Electro-Mechanical Systems (MEMS) are tiny functional machine systems in which various components -- microscale gears, pumps, sensors, pipes and actuators -- are integrated onto a single chip. Examples of MEMS include ink-jet printers, accelerometers in cars, pressure sensors, high-precision optics, and microfluidics. The most common application of the latter is in "lab on a chip" technology, devices that can process tiny chemical or DNA samples for medical diagnoses.

The Institute of Electrical and Electronics Engineers, Inc., contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Babak Ziaie, Ph.D.
Electrical & Computer Engineer
Purdue University
(765) 494-0725
bziaie@purdue.edu

Institute of Electrical and Electronics Engineers, Inc.
Washington, D.C. 20036-5104
(202) 785-0017
ieeeusa@ieee.org
http://www.ieee.org

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See a picture of the transmitter