MRI-based dynamic tracking of an untethered ferromagnetic microcapsule navigating in liquid

Abstract

The propulsion of ferromagnetic objects by means of MRI gradients is a promising approach to enable new forms of therapy. In this work, necessary techniques are presented to make this approach work. This includes path planning algorithms working on MRI data, ferromagnetic artifact imaging and a tracking algorithm which delivers position feedback for the ferromagnetic objects, and a propulsion sequence to enable interleaved magnetic propulsion and imaging. Using a dedicated software environment, integrating path-planning methods and real-time tracking, a clinical MRI system is adapted to provide this new functionality for controlled interventional targeted therapeutic applications. Through MRI-based sensing analysis, this article aims to propose a framework to plan a robust pathway to enhance the navigation ability to reach deep locations in the human body. The proposed approaches are validated with different experiments.

Magnetic Resonance Imaging System–Driven Medical Robotics

“…The most correlated slice gives the out‐of‐plane distance of the robot to the slice of the image. Later, Dahmen et al demonstrated that the template stack matching method can be performed faster by k ‐space reduction …”

“…Tracking and localization data acquired by MRI systems can be around 100 Hz when simultaneous imaging and actuation sequences are used; however, it lacks the true position information since these frequencies can be achieved when only single 1D line scans are used. Typically, the feedback rates are at around 10–30 Hz for sequential actuation and tracking sequences . Unlike standard robotic approaches, where high‐speed cameras or high‐performance computers provide very accurate estimation at much higher frequencies, the limited feedback data could be one of the challenges for medical applications under highly dynamic environments.…”

“…Answering when and which one of this information is required is crucial for the appropriate choice of imaging strategy. Currently, most studies are using standard imaging procedures such as FLASH for feedback and localization . However, for this innovative use of MRI devices, the typical imaging sequences that are optimized for diagnostic imaging may not be the best choice.…”

“…Later, Dahmen et al demonstrated that the template stack matching method can be performed faster by k-space reduction. [32]…”

“…Typically, the feedback rates are at around 10-30 Hz for sequential actuation and tracking sequences. [9,13,20,32] Unlike standard robotic approaches, where high-speed cameras or high-performance computers provide very accurate estimation at much higher frequencies, the limited feedback data could be one of the challenges for medical applications under highly dynamic environments. Combining MRI devices with complementary imaging modalities, such as PET and ultrasound, could be a potential solution to the low feedback rate of MRI systems.…”