ITMO: ITMO Researchers Propose New Wireless Power Transfer System For MRI Scanners
Scientists from ITMO’s Faculty of Physics have an antenna capable of capturing energy from alternating magnetic fields within MRI scanners and relaying it to additional devices used inside such systems. The technology can harvest nearly twice as much energy as its counterparts, thus representing a new significant step towards eliminating wires and expensive batteries from MRI equipment.
Improving the experience of both patients and specialists
Conducted as part of the Russian Science Foundation megagrant project entitled Controllable Metasurfaces for Wireless Technologies, the study aims to create a new generation of devices for 5G, wireless power transfer, and magnetic resonance imaging (MRI) systems that are safe, efficient, compact, and, above all, wireless.
Although various devices (e.g. special additional antennas such as the so-called local coils) are widely used in MRI to accelerate the scanning process and improve the quality of images, they have to be connected to a power supply via cables, which is often extremely uncomfortable for patients. Some of these devices, such as those used for spine, knee, and breast scans, are also too heavy to lift, causing challenges for medical specialists. In this sense, moving away from unwieldy equipment and wires would make scanning easier and more manageable.
Wireless technologies are actively developing nowadays due to the trend towards compact setups and higher energy efficiency. An example of such a technology is energy harvesting, which relies on converting ambient electromagnetic fields readily present in the surrounding environment. Within the present study, this technique was combined with the specific features of MRI scanners.
“It takes rather short yet quite intense pulses to generate an excitation field in an MRI scanner. Such power levels cannot be achieved by most conventional wireless power suppliers present. Moreover, such setups with dedicated power-transmitting antennas are not suitable for MRI scanners since they can distort their constant magnetic field. Even if we could use them, there would be a number of problems associated with their use. For instance, we would have to find our way around without redesigning the MRI scanner and decreasing the field distribution while at the same time keeping it safe for people,” says Pavel Seregin, one of the paper’s authors and a junior research fellow at ITMO’s Faculty of Physics.
Circular polarization
The proposed model includes a receiving structure, i.e., a near-field antenna, and a frequency-to-voltage converter. The device works on the principle of harvesting energy from circular polarization, which makes it possible to increase the efficiency of the system by almost two times compared to its alternatives, which mainly use linear polarization.
“The variable magnetic field has a vector that is directed in a certain way at any given time. Wireless systems today are based on linear polarization, which means that the vector can only move along one line (e.g. up or down). We suggested using circular polarization, which is when the electric field’s vector rotates akin to a clock hand. This kind of polarization corresponds exactly to the movement of the field vector inside an MRI, thus significantly increasing its performance. Our product can take almost double the energy as opposed to previously available devices,” explains Oleg Burmistrov, one of the paper’s authors and a PhD student at ITMO’s Faculty of Physics.
On the way to wireless devices
As noted by the developers, they managed to obtain a power density of over 1,000 mW, which is enough for gadgets like wearable heart rate monitors or respiration sensors. The device can also be used as a secondary power source. Although it can be already implemented in power systems of wireless local antennas, the researchers want to achieve even greater performance so that the technology could be used to power a wider range of MRI equipment.
“Numerical simulations have demonstrated the safety of our system and ensured that our antenna doesn’t affect the homogeneity of the magnetic field; in other words, that it doesn’t decrease the quality of MRI images. The same results were obtained when testing the system on phantoms (vessels with liquid that imitate the human body) that were placed inside an MRI unit,” says Pavel Seregin.
Both Master’s and PhD students were involved in the study. As stressed by Pavel Seregin, students of the Master’s program Radiofrequency Systems and Devices study specialized disciplines related to MRI technologies. Thanks to this, the students have the chance to participate in cutting-edge research and contribute to the development of the field at their alma mater.