Researchers from the Massachusetts Institute of Technology (MIT) and Massachusetts General Hospital in the United States have developed a wireless ‘in-body GPS’ system that can track tumours and pinpoint the location of ingestible implants inside the body. In tests conducted on animals, the system called ‘ReMix’ was found to be able to easily track the implants with centimetre-level accuracy. Similar implants could be used to deliver drugs to specific regions in the body.
1. To test ReMix, the researchers first implanted a small marker in animal tissues. To track its movement, the researchers used a wireless device that reflects radio signals off the patient.
2. The marker inside the body does not need to transmit any wireless signal, as it reflects the signal transmitted by the wireless device outside the body. Therefore, it does not need a battery or any other external source of energy.
3. This was based on a wireless technology that the researchers previously demonstrated to detect heart rate, breathing and movement. A special algorithm then uses that signal to pinpoint the exact location of the marker.
The scientists found that a key challenge in using wireless signals in this way was the many competing reflections that bounce off a person’s body. In fact, the signals that reflect off a person’s skin are actually 100 million times more powerful than the signals of the metal marker itself. The researchers did this using a small semiconductor device called a ‘diode,’ which mixes signals together so the team can then filter out the skin-related signals. Hence, for example, if the skin reflects at frequencies of F1 and F2, the diode creates new combinations of those frequencies, such as F1-F2 and F1+F2.