Coulter BME Seminar Series

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“In Vivo Quantitative Imaging of Nanoparticles and Cells Using Magnetic Particle Imaging”

Carlos Rinaldi-Ramos, Ph.D.
Dean’s Leadership Professor and Chair of Chemical Engineering
Professor, J. Crayton Pruitt Family Department of Biomedical Engineering
Member, UF Health Cancer Center
University of Florida

Magnetic Particle Imaging (MPI) is a new molecular imaging technology capable of unambiguous and quantitative tomographic imaging of the distribution of superparamagnetic nanoparticle tracers in vivo. While the term MPI may be confused with that for Magnetic Resonance Imaging (MRI), the two rely on distinct physics. In MPI, a tomographic image of the distribution of superparamagnetic nanoparticles is constructed by scanning a so-called field free region (FFR) through the domain of interest. Outside the FFR there is a quasi-static bias field strong enough to saturate the magnetic moments of the nanoparticles. But inside the FFR the dipole moments of the nanoparticles respond to the superimposed alternating excitation field. The signal used to construct an image in MPI arises due to the non-linear dynamic magnetization response of the nanoparticle dipole moments to the excitation field inside the FFR. At the field amplitudes and frequencies used in MPI there is no appreciable attenuation in field or signal strength in tissue. Further, while there are magnetic species in the body (e.g., ferritin), they do not contribute an appreciable signal for MPI, allowing for unambiguous imaging of the distribution of one of the superparamagnetic nanoparticle tracers. In this talk I will explain the physics of image generation in MPI, discuss work to understand how imaging performance relates to physical and magnetic properties of the nanoparticles, and discuss our work developing tracers and using MPI to quantify biodistribution of iron oxide nanoparticles in vivo, in the context of tracking nanoparticles and cell therapies.

Carlos M. Rinaldi-Ramos is the Chair and Dean’s Leadership Professor in the Department of Chemical Engineering at the University of Florida. He is also a Professor in the J. Crayton Pruitt Family Department of Biomedical Engineering. He received his bachelor’s degree in Chemical Engineering at the University of Puerto Rico, Mayagüez, and completed degrees in Master of Science in Chemical Engineering, Master of Science in Chemical Engineering Practice, and Doctor of Philosophy in Chemical Engineering at the Massachusetts Institute of Technology. Prior to the University of Florida, Dr. Rinaldi-Ramos was a Professor in the Department of Chemical Engineering at the University of Puerto Rico, Mayagüez. Dr. Rinaldi-Ramos is a leading scientist in the areas of ferrohydrodynamics, biomedical applications of magnetic nanoparticles, and transport of nanoparticles in complex and biological fluids. His research spans theory and simulation of magnetic nanoparticle response to dynamic magnetic fields, nanoparticle synthesis and surface modification, and characterization of nanoparticle interactions with biological environments. In the field of ferrohydrodynamics, Dr. Rinaldi-Ramos has made fundamental contributions to understanding of suspension-scale flows of ferrofluids in time-varying and rotating magnetic fields. Through a combination of theoretical and experimental work, his group demonstrated that description of ferrofluid flows in rotating magnetic fields requires consideration of internal angular momentum transport through the so-called couple stress and spin viscosity, unique features in the description of flows of structured continua. In the field of nanomedicine, Dr. Rinaldi-Ramos has made outstanding contributions to harnessing localized nanoscale heating for magnetic nanoparticle thermal cancer therapy. His group was the first to demonstrate that receptor-targeted nanoparticles can kill cancer cells without a perceptible macroscopic temperature rise through disruption of lysosomes and activation of lysosomal death pathways. He has also contributed to understanding the synergistic interactions of nanoscale thermal therapy and traditional chemotherapeutics. Dr. Rinaldi-Ramos has pioneered development and application of new methods to evaluate nanoparticle stability and diffusion in complex and biological fluids. Based on non-invasive monitoring of nanoparticle response to oscillating magnetic fields, these methods permit quantitative measurements of nanoparticle aggregation state, hydrodynamic size, and diffusion in complex environments such as polymer melts, polymer solutions, highly-concentrated protein solutions, whole blood, and tissues. More recently, Dr. Rinaldi-Ramos has contributed to understanding the physics of magnetic nanoparticle response to alternating magnetic fields, enabling rational design of high-sensitivity and high-resolution tracers for magnetic particle imaging, an emerging biomedical imaging technology. Dr. Rinaldi-Ramos is committed to mentoring new generations of scientists and engineers seeking solutions to biomedical problems and to broadening participation of women and minorities in science and engineering.



  • Workflow Status: Published
  • Created By: Christina Wessels
  • Created: 12/14/2022
  • Modified By: Christina Wessels
  • Modified: 12/14/2022