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August 20, 2018

Body GPS provides pinpoint locations for better radiotherapy in cancer treatment

By Priya Kantaria

“The ability to continuously sense inside the human body has largely been a distant dream,” said Romit Roy Choudhury, professor of electrical engineering and computer science at the University of Illinois. Now MIT researchers have developed an “in-body GPS” called ReMix that pinpoints the location of ingested implants inside the body using wireless signals.

Similar implants could be used to deliver drugs to specific regions in the body and ReMix could be used in proton therapy, a cancer treatment that hits tumours with beams of magnet-controlled protons, radiation.

In-body GPS improve radiotherapy

With a detectable marker inside the body, doctors could more accurately determine the location of the tumour, which is prone to moving around, and apply higher doses of radiation.

The treatment will become more precise, which would open it up for use against a wider range of cancers.

The current risk of proton therapy is that the tumour could move during the radiation process, which would cause exposure of healthy areas of the body to the radiation.

The hope is that ReMix will become accurate to within a few millimetres and could then be used in clinical settings.

At the moment the marker can be detected to centimetre-level accuracy.

Professor Dina Katabi leads the team, which includes PhD student Deepak Vasisht, who said: “If we want to use this technology on actual cancer patients one day, it will have to come from better modelling a person’s physical structure.”

He said that one reason proton therapy is currently so expensive is because of the cost of installing the necessary hardware, and if ReMix systems can encourage more applications of the technology, there will be more demand, which will mean more therapy centres, and lower prices.

There are currently only 100 proton therapy centres worldwide.

Wireless system avoids cutting a patient open or swallowing huge tubes

ReMix works using a wireless device that transmits radio signals at the patient from outside.

These are reflected by the ingestible implant inside the body, which acts as a marker, and using a special algorithm pinpoints the marker’s location.

One of the main challenges in using wireless signals like this was in separating the signals from the marker from the signals reflecting off the patient’s skin, which are in fact 100 million times more powerful.

The CSAIL team solved the problem by using a diode, a small semiconductor, which mixes signals to help filter the ones they are interested in.

For example, if the skin reflects frequencies F1 and F2, the diode can create frequencies like F1-F2 and F1+F2, and when all the signals are reflected the system only picks out the combined frequencies.

The plan now is to combine the wireless data with medical information such as MRI scans to improve the system’s accuracy.