In-body ‘GPS’ developed by MIT could track tumours and deliver pills internally
The system, ReMix, consists of an ingestible sensor, an external source of radio waves, and a special algorithm designed by researchers at MIT’s Computer Science and Artificial Intelligence Laboratory that captures the right signal and eliminates noises.
It can be used to obtain high resolution images and even deliver medication to precise locations inside the body, since the system can track the sensors with centimetre-level accuracy, researchers said at the SIGCOMM 2018 conference in Budapest, Hungary over the weekend.
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The study was conducted by MIT researchers Zhang Guo, Deepak Vasisht and Dina Katabi, professor Omid Abari at the University of Waterloo, physicist Hsiao-Ming Lu and technical director Jacob Flanz at the Massachusetts General Hospital.
SIGCOMM is an annual conference focused on the applications, technologies, architectures, and protocols for computer communication.
The sensor is made up of a microchip the size of a grain of rice that can be put into a capsule and swallowed by patients. It needs no battery since the sensor merely reflects the radio waves generated by an external device, reducing the size of the tracker and prolonging its function time, the study said.
While the technology of radio wave identification is no longer new to scientists, the MIT team cracked the challenge of achieving centimetre-level accuracy by adding a secret spice – the algorithm that picks up the exact signal from the tracker and filters noises from other parts of human body.
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That makes it possible for the system to read signals reflected, or back-scattered, by the swallowable tracker, which is 100 million times weaker than the signal reflected by the human skin, the study said.
“Back-scatter requires zero transmission power, making it a compelling technology for in-body communication and localisation,” the team, supervised by MIT computer scientist Dina Katabi, wrote.
“But the fact that signals no longer travel along straight lines inside the human body destroys the geometric principles underlying many localisation algorithms.”
The microchip tracker can also be injected, researchers said.
In tests using animal tissues, the team put a small marker in a fake tumour and showed that the system could pinpoint the tumour’s marker with an accuracy of 1.4cm.
The high level of accuracy suggests that the in-body “GPS” could improve the success rate of proton therapy, a type of cancer treatment.
The therapy – which involves bombarding tumours with beams of magnet-controlled protons – relies on the premise that a tumour stays where it is during the radiation process.
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However, if tumours move during the process, they will escape the bombarding while healthy areas are exposed to radiation. The tracking system could help doctors to aim for the tumour in real time treatment, researchers said.
MIT’s Katabi said that, to qualify for clinical use, the system should achieve a margin of error closer to a couple of millimetres.
ReMix will also help doctors obtain high resolution images and videos inside the body without actually cutting the patient open or make them swallow long tubes with built-in cameras, the study said.
The accuracy can be improved by tweaking ReMix’s design and customising the algorithm’s parameters for each patient, researchers said.
“The ability to continuously sense inside the human body has largely been a distant dream,” said Romit Roy Choudhury, an electrical engineering professor at the University of Illinois in the US, who was not involved in the study.
“ReMix makes a leap in this direction by showing that the wireless component of implantable devices may no longer be the bottleneck.”