ISMRM24 - Surprising Aspects of MRI Physics: The Steady-State & Fast Spin Echo Beasts & Their Beauty

Surprising Aspects of MRI Physics: The Steady-State & Fast Spin Echo Beasts & Their Beauty

Sunrise Course

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

Thursday, 09 May 2024

Summit 2

07:00 - 08:00

Moderators: Congbo Cai & Ruixi Zhou

Skill Level: Intermediate to Advanced

Session Number: S-Th-02

CME Credit

Session Number: S-Th-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, 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		Transition Bands in Balanced SSFP: From Artifacts to Refined Method for fMRI Contrast View Presentation Video Rahel Heule Keywords: Contrast mechanisms: fMRI, Image acquisition: Sequences, Physics & Engineering: Physics Balanced steady-state free precession (bSSFP) signal formation exhibits a characteristic sensitivity to resonance frequency. Due to fully balanced gradients along all axes and thus the absence of any gradient-induced precession, bSSFP is highly sensitive to any source of off-resonance-induced precession. This strong dependency on off-resonance can constitute a confounder in the presence of magnetic field inhomogeneities or local susceptibility differences, causing signal voids (banding artifacts) in clinical images. On the other hand, the frequency sensitivity of bSSFP, which is prominent in the transition band, reveals interesting applications, e.g. as a refined fMRI contrast mechanism.
07:30		Spin-Echo Trains: Surprises & Facts View Presentation Video David Alsop Keywords: Image acquisition: Fast imaging, Image acquisition: Sequences, Physics & Engineering: Physics Trains of spin echoes have become essential parts of most imaging studies. They improve speed and signal-to-noise ratio and make possible 3D spin echo imaging in a feasible time. As more RF refocusing pulses are used, surprisingly complex effects arise that add new options and features for spin echo train imaging. We will review these surprising properties of echo trains and how they can be used to improve and optimize imaging.