ISMRM23 - Relaxation: Principles & Acquisition/Reconstruction Strategies

ISMRM & ISMRT Annual Meeting & Exhibition • 03-08 June 2023 • Toronto, ON, Canada

Relaxation: Principles & Acquisition/Reconstruction Strategies

Weekday Course

ORGANIZERS: Noam Ben-Eliezer, Sune Jespersen

Thursday, 08 June 2023

701A

08:15 - 10:15

Moderators: Dafna Ben Bashat & Moti Freiman

Skill Level: Basic to Advanced

Session Number: Th-02

CME Credit

Session Number: Th-02

Overview
This course will cover the basic principles, data acquisition strategies, and image reconstruction methods for the estimation of T1, T2, T1ρ, and T2ρ relaxation parameters, as well as magnetization transfer (MT) and inhomogeneous MT (ihMT).

Target Audience
Clinicians and basic scientists who would like to: be familiar with what T1, T2, T1ρ, T2ρ, MT, and ihMT are; know how to quantify these parameters (as well as scientists who are interested in developing/improving quantitative relaxation parameter mapping approaches); and understand how are they being employed in the clinic.

Educational Objectives
As a result of attending this course, participants should be able to:
- Describe conventional (T1, T2, MT) and less conventional (T1ρ, T2ρ, ihMT) types of relaxation;
- Explain how to quantify the above parameters, i.e., which pulse sequences and reconstruction methods to use; and
- Describe how these contrast mechanisms are being used for clinical applications and how to incorporate them in future studies.

08:15		T1, T2: Quantification Techniques & Applications View Presentation Video Shir Filo Keywords: Contrast mechanisms: Relaxometry T1 and T2 relaxation: biophysical basis, quantification techniques, limitations & applications.
08:45		MT and ihMT: basic principles and applications View Presentation Video Olivier Girard Keywords: Contrast mechanisms: CEST & MT, Contrast mechanisms: Relaxometry, Contrast mechanisms: Microstructure This course will cover the basic principles of MT and ihMT and will describe the associated biophysical modelling used to measure tissue macromolecular content using MRI. Following this lecture, the attendees should 1/ understand the origin of magnetization transfer effects within heterogeneous spin systems, 2/ understand that MT mechanisms and T1 longitudinal relaxation are tightly related, 3/ gain intuition on biophysical models aiming to describe MT and ihMT effects, especially in central nervous system tissues, and 4/ know the usual MT and ihMT acquisition methods and applications in neuroimaging studies.
09:15		T1ρ, T2ρ: Definition & Quantification View Presentation Video Shalom Michaeli Keywords: Contrast mechanisms: Rotating Frame Relaxometry, Contrast mechanisms: Microstructure, Image acquisition: Quantification Rotating frame relaxation methods based on FS pulses, including T1ρ and T2ρ using adiabatic pulses, and the non-adiabatic method entitled Relaxation Along a Fictitious Field (RAFF) in the rotating frame of rank n (RAFFn), offer sensitivity to a broad range of motional regimes. The reduced power deposition of RAFFn, along with the opportunity of enhancing sensitivity to exchange by tuning the periodicity of irradiation, are distinct advantages of the methodology. The methodologies for detection of fast relaxing spins using asymptotic relaxation mapping and alternating Look-Locker sequence are described. Applications of T1ρ, T2ρ and RAFFn for detecting pathological conditions are presented.
09:45		T1ρ, T2ρ: Applications No Video Available Weitian Chen Keywords: Contrast mechanisms: Rotating frame relaxometry MRI can be used for non-invasive imaging and characterization of metabolites and macromolecules in human tissues based on chemical exchange (CE) and magnetization transfer (MT). It is popular to use off-resonance saturation radiofrequency (RF) pulses to study CE and MT based contrasts. Alternatively, relaxation times in the presence of a spin-lock field can also be used to measure CE and MT signal. This leads to many promising applications of spin-lock MRI, including, but not limited to, diagnosis of brain cancer, Alzheimer’s’ disease, demyelination, MSK diseases, cardiac diseases, and fibrosis.