MR Physics for Clinicians: Spins & Sequences
ORGANIZERS: Maxime Guye, Mark Ladd
Tuesday, 18 May 2021
||14:00 - 14:30
||Moderators: Patrick Cozzone & Ivan Jambor
Skill Level: Basic to Intermediate
Session Number: WD-08
Parent Session: MR Physics for Clinicians: Spins & Sequences
Session Number: WD-08
This session is part of a series that will be a basic and comprehensive review of MRI physics and techniques; each session can be attended independent of the others. The presentations will be non-mathematical and suitable for clinicians and physicists new to the field and will cover topics including basic MRI physics, pulse sequence design, contrast weightings, and image reconstruction.
Those interested may include: radiologists and clinicians relatively new to MR imaging (including residents and fellows), experienced radiologists and clinicians wanting a refresher course in MR physics, and physicists and engineers wanting an introduction to the field.
As a result of attending this course, participants should be able to:
- Define and describe the fundamental principles of MR imaging including the definition of spin magnetization, the Larmor relationship, relaxation phenomena, the process of using spin magnetization to produce an image, and k-space;
- Explain the basic physics and properties of pulse sequences based upon spin and gradient echoes; and
- Describe the fundamentals of capturing and reconstructing multiple image contrasts.
SYNOPSIS: “SPIN GYMNASTICS” There are two main principles in the MRI process: the basic physics of NMR, and spatial encoding of signal. The basic physics deals with spin, angular momentum, resonance, bulk magnetization, excitation and signal detection. The second describes the application of magnetic field gradients in three dimensions for encoding the location of the signal. 3D animations are used to illustrate complex concepts in a graphically intuitive manner. The overall goal is to provide a working knowledge of the basic physics of MRI in a way that is both intuitive and true to the physics of MRI.
||Basic Pulse Sequences: Gradient & Spin Echo Imaging
MRI techniques are often classified into Spin and Gradient echo sequences. This talk will introduce the basic concepts and elements of both sequences, highlight differences in terms of contrast, such as the T2 signal decay in Spin echo sequences and the T2* signal decay in Gradient echo sequences. It will introduce and motivate the concepts of gradient and RF spoiling, balanced sequences and magnetization preparation and finish with a short outlook on accelerating spin and gradient echo sequences using echo trains.
This presentation presents an overview of multi-contrasts approaches in MRI, from a simple but technical point of view. The presentation starts from two simple examples of multi-contrasts approaches and continues with quantitative multi-contrast approaches. The presentation compares all these approaches in 3 points: 1/ the acquisition schemes that allows to probe multiple contrasts at once, 2/ the underlying model that maps MR signal onto multiple contrasts and allows to disentangle them and 3/ the output contrasts that are eventually provided by the approach of interest. Finally, we will review extensions of multi-contrast approaches with synthetic imaging, segmentation, and standardized reporting.