MR Physics for Clinicians: Contrast Mechanisms
ORGANIZERS: Noam Ben-Eliezer, C. C. Tchoyoson Lim, Hai-Ling Cheng
Monday, 17 May 2021
||14:00 - 14:30
||Moderators: Noam Ben-Eliezer & C. C. Tchoyoson Lim
Skill Level: Basic
Session Number: WD-03
Parent Session: MR Physics for Clinicians: Contrast Mechanisms
Session Number: WD-03
This course will cover fundamental physical concepts of MR imaging. The topics include:
1. T1 Relaxation
2. T2 and T2* Relaxation (audience should already be familiar with the spin-echo and gradient echo)
3. Diffusion MRI
4. From biology to radiology: a bird's-eye review on how tissue biology is reflected in changes to the contrast mechanisms detected in the MR images. Namely:
- How do biological tissues' properties translate to differences in the acquired images
- How do pathological changes reflect in changes to the image contrast
The talk will not focus on specific physical/mathematical calculations (and does not demand advanced physics degrees), but on the link between tissue properties → MR parameters → MR contrast. For example, in what way are T1, T2, and T2* involved in FLAIR contrast, and how do pathological changes affect the physical properties, which, in turn, change the image contrast?
This course is primarily designed for clinicians who would like to better understand the "hows" and "whys" of MR imaging. While it requires no prior experience with MR, those with some familiarity and experience will also benefit.
Target audience includes 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;
- Explain the Larmor relationship, relaxation phenomena, and the process of using the spin magnetization to produce an image; and
- Describe how changing acquisition parameters impacts image quality and contrast, and understand the parameters relationships.
This talk will cover the physical origins of T1 relaxation, present biophysical models for it in tissue, and explain why it is an important biomarker for many pathologies. It will then present some common techniques and sequences for measuring it, the most common of which are saturation and inversion recovery. Finally, it will present some of how obtaining T1 maps can be used both clinically and, to a lesser extent, as a tool in more basic research.
||From Biology to Radiology
||Relaxation: T2 & T2*
We will discuss the basic physical concepts of T2-relaxation and its distinction from T2*-relaxation, learn how to measure and quantify T2-relaxation, hear about pitfalls and challenges to access T2-relaxtion, understand what makes T2-contrast in a clinical MR-image, and brief over some fundamental clinical applications for T2-relaxation contrast (weighted T2- and T2*-contrast, quantitative relaxation time measurements).
This talk will cover the basic physics of diffusion MRI and how it can be used to study tissue microstructure. We will learn how to measure diffusion in MRI and the various parameters that effect diffusion measurements, such as b-value and diffusion gradient directions, and how to obtain DWI images and ADC maps. Finally, we will present the concept of diffusion tensor imaging and the information obtained by it.