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ShareSeptember 1, 2006 — Radiologists could soon measure the amount of radiation exposure experienced by different tissues using an implantable capsule. The device contains a small dosimeter and sends radiation exposure data back wirelessly. The method is safer and cheaper than imaging the organs during therapy using X-rays. The current prototype is the size of a dime, but electrical and computer engineers hope to bring that down to the size of a grain of rice.
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WEST LAFAYETTE, Ind. -- Ready, set, radiate! Seems simple enough, but doctors say there's a lot of guesswork that goes into delivering radiation to cancer patients. They can't always pinpoint a tumor's exact spot and know exactly how much radiation hits it.
"If the tumor doesn't get enough to control it -- doesn't get enough radiation to control it -- you'll have treatment failure," says Wallace Morrison, a cancer specialist at Purdue University in West Lafayette, Indiana.
Electrical and computer engineer Purdue Babak Ziaie is working to change that. "This is our first prototype. It's about the size of a dime," he says. His goal is a prototype as small as a grain of rice that solves two big problems.
"Our target right now is to combine the two capabilities in a single device -- tracking and measurement of the dose in a single device -- to give a lot more information, really, and a lot better treatment planning," Ziaie tells DBIS.
Doctors will implant the capsule into a tumor and activated with electrical coils placed next to the body. It contains a miniature version of a dosimeter, which tells how much radiation the tumor receives. They could also implant the device into healthy tissue so doctors know how much damage there is to surrounding organs.
Other radiation systems can track tumors, but Ziaie says they are often very costly and rely on Z-rays that increase the amount of radiation exposure patients have.
Patients are excited about what better treatment could mean for them.
"I just hope I get a little time, you know," says radiation patient Josephine Diener. "I don't want to go in six months, that's for sure."
Radiation patient Jack Eiler says, "...Grow old. Be happy. Pretty much have a successful life..."
BACKGROUND: Engineers at Purdue University 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 and 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 3D 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 which 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.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
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