The advent of nanorobots capable of autonomous movement within the human body, tasked with drug delivery, conducting tissue measurements, or executing minor surgeries, marks a significant leap in medical technology. While scientists have developed magnetically driven prototypes capable of traversing through muscle tissue, the vitreous humor of the eye, or the vascular system, the real-time monitoring and control of these robots deep within the body remains a challenge. Conventional imaging methods fall short: MRI's temporal resolution is too low, CT scans carry the risk of radiation exposure, and ultrasound's effectiveness is diminished by strong scattering of sound waves. Scientists have now developed a signaling method based on an oscillating magnet that can significantly improve such medical applications.

A team of scientists at the German Cancer Research Center (DKFZ, Heidelberg, Germany) has developed a tiny device based on a magnetic oscillator—essentially a magnet that vibrates mechanically within a millimeter-sized housing, set into motion by an external magnetic field. This signal can be recorded using magnetic sensors when the oscillation subsides again, based on the same principle applied to nuclear magnetic resonance in MRI. This technique, dubbed "Small-Scale Magneto-Oscillatory Localization" (SMOL), boasts the capability to accurately determine the position and orientation of the small device from a considerable distance (beyond 10 cm), with outstanding precision (under 1 mm), and in real-time.

As compared to conventional static magnet-based tracking methodologies, SMOL can detect movements in all six degrees of freedom and with significantly higher signal quality. Given its reliance on weak magnetic fields, it poses no risk to human health, offers wireless operation, and seamlessly integrates with a wide variety of existing medical devices and imaging technologies, heralding a new era in the precision and safety of internal medical procedures.

"There are many possible applications for the SMOL method," said research scientist Felix Fischer. "We have already integrated the system into miniature robots and instruments for minimally invasive surgery. A combination with capsule endoscopes or the marking of tumor tissue for very precise radiotherapy would be conceivable. Our method could also provide a decisive advantage for fully automated surgical robotics or augmented reality applications." 

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