ISMRM24 - Surprising Aspects of MRI Physics: Beware or Befriend Eddy Currents & Lorenz Force

Surprising Aspects of MRI Physics: Beware or Befriend Eddy Currents & Lorenz Force

Sunrise Course

ORGANIZERS: Brian Hargreaves, Shaoying Huang, Rita Schmidt, Rolf Schulte, Ramesh Venkatesan, Andrew Webb

Wednesday, 08 May 2024

Summit 2

07:00 - 08:00

Moderators: Silvia De Santis

Skill Level: Intermediate to Advanced

Session Number: S-W-02

CME Credit

Session Number: S-W-02

Overview
In this sunrise session, we want to get a glimpse of some of the surprising and unexpected aspects of MR physics, to motivate thinking out of the box – for example, how one can look in the MRI room, pick up an existing tool and use it for an unconventional purpose; or how we can get an image without having gradients; or even how we can use Eddy currents and Lorenz force for our advantage. Finally, we will deepen our understanding of sequences in our daily use and bring up some of the special aspects of steady state and spin echo acquisitions.

Target Audience
Scientists and engineers.

Educational Objectives
As a result of attending this course, participants should be able to:
- Explain MR physics;
- Describe how to use RF coils as respiratory and motion sensor and use coils sensitivities for B0 mapping;
- Identify how to get an image without gradients;
- Identify what contrast one can get using Eddy currents and Lorentz force for imaging;
- Describe how one can use a feature of a steady state acquisition that usually results in an artifact to a sensitive approach for fMRI contrast; and
- Examine special cases of spin echo acquisition.

07:00		Lorenz Force on Conductors: From Nuisance to Driver Actuation for MRE & Music Composition View Presentation Video Ralph Sinkus Keywords: Physics & Engineering: Gradient & B0 Safety The Lorenz Force refers to the force exerted on moving electrons within conductors when placed in a magnetic field. This phenomenon is critical as it influences the behavior of conductive materials within the magnetic field of the scanner. When a conductor, such as the human body or components of the MRI machine, is exposed to the rapidly changing magnetic fields used in MRI, currents are induced within these conductors due to the Lorenz Force. This can affect the quality of the MRI images by introducing artifacts or even pose safety risks by heating tissues or affecting implanted medical devices.
07:30		Eddy Currents: From Artifacts to Conductivity Imaging View Presentation Video Jiaen Liu Keywords: Contrast mechanisms: Electromagnetic Tissue Properties, Physics & Engineering: Gradient & B0 Safety Electrical conductivity and permittivity are fundamentally related to tissue properties, including cell volume fraction, ion & water distribution and cell membrane permeability. Imaging the electrical properties at the kilo-hertz range can be useful for diagnosis, functional imaging and electromagnetic modeling in biomedical engineering applications. It is theoretically possible to obtain conductivity maps utilizing the eddy current effect in MRI. In this lecture, we will introduce methods for conductivity mapping based on the eddy current effect and other principles.