Gwangju Institute of Science and Technology researchers improve the scanning capability of magnetic particle imaging systems used for medical imaging

Magnetic particle imaging (MPI) is an emerging imaging modality that is based on the detection of superparamagnetic iron oxide nanoparticles that have been injected into the body. The magnetic particles act like tracers and are detected in response to a moving magnetic field free point (FFP), which changes their magnetic direction. As these particles do not naturally exist in the human body, it makes MPI highly sensitive and free from background noise. MPI could potentially transform medical imaging. However, currently available commercial scanners often compromise between coverage volume and imaging resolution.

In a new study published online on 29 April 2022 in IEEE Transactions on Industrial Electronics, researchers from Gwangju Institute of Science and Technology (GIST) in South Korea have now addressed this issue. They have developed a rabbit-scale three-dimensional (3D) MPI system that can scan a large volume at a high resolution. “For a large bore size of MPI, it is important to achieve a high magnetic gradient for high image resolution along with a large field-of-view (FOV), while allowing fast scanning and high sensitivity,” explains Prof. Jungwon Yoon, the corresponding author of the study.

This had to be done without increasing the magnetic field strength or the size of the system, since high magnetic fields can cause undesirable peripheral nerve stimulation in the patient’s body and large systems incur higher cooling expenses. To realize this feat, the researchers turned to a technique called “amplitude modulation” (AM), which uses low-amplitude, high-frequency excitation fields in combination with low-frequency, high-amplitude drive fields to quickly scan the FFP and detect the magnetic nanoparticles. “The AM MPI can enable a large FOV and good resolution while minimizing the peripheral nerve stimulation constraint and hardware requirements,” says Tuan-Anh Le, a postdoctoral researcher at GIST who was involved in the study.

To this end, they developed an AM MPI system with a bore size of 90 mm and seven coils that included selection coils, drive coils (along x, y, z), excitation coil, receiver coil, copy of drive-z coil, copy of the excitation coil, and a cancellation coil. In this configuration, the selection coils generate magnetic fields that produce an FFP, while the drive and excitation coils produce the drive and excitation fields that scan the FFP and generate signals from the magnetic tracer, which are then measured by the receiver coil. A 3D image is created by converting the 3D slice images obtained from scanning the FFP to MPI images using the AM technique.

By testing the imaging capabilities of their system with a 3D phantom, the researchers demonstrated that it had a higher magnetic gradient scanner (4 T/m/µ₀ vs 2.5 T/m/µ₀) and a larger coverage volume (175,616 mm³ vs 117,440 mm³) than commercially available MPI scanners. Using the AM technique, they developed a low-cost, small MPI scanner to demonstrate the method's potential for enabling high-resolution 3D human-scale scanners.

Hopefully, it won’t be long before such MPI scanners are realized in practice!

***

Reference

Authors: Tuan-Anh Le*, Minh Phu Bui, and Jungwon Yoon

DOI: https://doi.org/10.1109/TIE.2022.3169715  

Affiliations: Gwangju Institute of Science and Technology, the Republic of Korea

About the Gwangju Institute of Science and Technology (GIST)

The Gwangju Institute of Science and Technology (GIST) is a research-oriented university situated in Gwangju, South Korea. Founded in 1993, GIST has become one of the most prestigious schools in South Korea. The university aims to create a strong research environment to spur advancements in science and technology and to promote collaboration between international and domestic research programs. With its motto of “A Proud Creator of Future Science and Technology,” GIST has consistently received one of the highest university rankings in Korea.

Website: http://www.gist.ac.kr/

About the authors

Tuan-Anh Le received his Ph.D. degree in the School of Integrated Technology at Gwangju Institute of Science and Technology, Korea, in 2021, where he is currently a Postdoctoral Researcher. His current research interests include electromagnetics, magnetic particle imaging, bio-nano robot control, magnetic hyperthermia, and medical imaging.

Jungwon Yoon received his Ph.D. degree in the Department of Mechatronics, Gwangju Institute of Science and Technology (GIST), Korea, in 2005. In 2017, he joined the School of Integrated Technology at GIST where he is currently a Professor. He is a Technical Editor of the IEEE/ASME Transactions on Mechatronics and an Associate Editor of Frontiers in Robotics and AI. His current research interests include bio-nano robot control, virtual reality haptic devices, and rehabilitation robots. He has authored or coauthored more than 160 peer-reviewed journal and conference articles.