Quantification and 3D Localization of Magnetically Navigated Superparamagnetic Particles Using MRI in Phantom and Swine Chemoembolization Models

Abstract

Objec0ve: Superparamagne0c nanopar0cles (SPIONs) can be combined with tumor chemoemboliza-0on agents to form magne0c drug-elu0ng beads (MDEBs), which are navigated magne0cally in the MRI scanner through the vascular system. We aim to develop a method to accurately quan0fy and localize these par0cles and to validate the method in phantoms and swine models. Meth-ods: MDEBs were made of Fe3O4 SPIONs. Aaer injected known numbers of MDEBs, suscep0bility ar0facts in three-dimensional (3D) volumetric interpolated breath-hold ex-amina0on (VIBE) sequences were acquired in glass and Polyvinyl alcohol (PVA) phantoms, and two living swine. Image processing of VIBE images provided the volume rela0onship between MDEBs and their ar0fact at different VIBE acquisi0ons and post-processing parameters. Sim-ulated hepa0c-artery emboliza0on was performed in vivo with an MRI-condi0onal magne0c-injec0on system, using the volume rela0onship to locate and quan0fy MDEB distri-bu0on. Results: Individual MDEBs were spa0ally identified, and their ar0facts quan0fied, showing no correla0on with magne0c-field orienta0on or sequence bandwidth, but ex-hibi0ng a rela0onship with echo 0me and providing a lin-ear volume rela0onship. Two MDEB aggregates were mag-ne0cally steered into desired liver regions while the other 19 had no steering, and 25 aggregates were injected into another swine without steering. The MDEBs were spa0ally iden0fied and the volume rela0onship showed accuracy in assessing the number of the MDEBs, with small errors (≤ 8.8%). Conclusion and Significance: MDEBs were able to be steered into desired body regions and then localized using 3D VIBE sequences. The resul0ng volume rela0onship was linear, robust, and allowed for quan0ta0ve analysis of the MDEB distribu0on.

Improved magnetic drug targeting with maximized magnetic forces and limited particle spreading

“…In this part, we demonstrate the dynamic optimization problem (11) for steering particles from an initial to a target location. The problem solution yields the magnetic currents and hence forces required for this movement.…”

“…Typically for in-vivo use, particles are administered to the bloodstream through intravenous or intraarterial injection. The injection can occur into a large vein before entering the arterial network or directly through a catheter in the arteries near the target (e.g., hepatic artery [9][10][11] ). As soon as the particles arrive in smaller arterial vessels with lower blood velocities (orders of magnitude reported by Cherry et al 12 ), magnetic gradients are applied to force them toward the desired location.…”

“…These can be obtained from state-of -the-art imaging procedures such as magnetic resonance (MR) and computed tomography. 11 The particle locations can be imaged with MR and magnetic particle imaging (MPI). 23 MPI or MRI scanner topologies have been used to locate particles in combination with navigating them, with or without additional electromagnets.…”

“…For MDT application in the human body, detailed images of the geometry of the vascular system are required. These can be obtained from state‐of‐the‐art imaging procedures such as magnetic resonance (MR) and computed tomography 11 . The particle locations can be imaged with MR and magnetic particle imaging (MPI) 23 .…”

Micro/Nanorobotic Swarms: From Fundamentals to Functionalities

“…To date, most of the medical micro/nanorobotic swarms reported result in zero-flow and 2D environments. To yield promising efficacy for clinical use, the capability for swarms to maintain their structural integrity and motion in physiological environments, such as pulsatile biofluid flow and organ motion, must be considered. ,,,, The navigation of micro/nanorobotic swarms in 3D environments must also be taken into considerations (Figure A). ,,, Microrobotic swarms have been shown to be capable of rolling up circular channels [Figure A­(i)] and performing adaptive locomotion in 3D environments, such as climbing up stairs and crossing gaps [Figure A­(ii)] . However, swarm navigation in a 3D environment without relying on interfaces or solid boundaries requires further research.…”