Lecture

Bloch equations: MR signal basics

Graph Chat

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Description

This lecture covers the Bloch equations, which describe the change in magnetization in MRI, by adding relaxation terms (T₁, T₂) to the fundamental equation of motion. It explains the basic MR signal, including free induction decay, precession, and relaxation. The lecture also discusses how T₁ changes can be measured through repetitive pulsing and multipulse experiments, emphasizing the impact of T₁ and T₂ relaxation on signal intensity. The summary highlights the equilibrium magnetization, the effect of T₁ and T₂ on image contrast, and the factors influencing the precession of transverse magnetization in MRI.

In MOOC

Fundamentals of Biomedical Imaging: Magnetic Resonance Imaging (MRI)

This physics course covers the physical principles of major in vivo bio-imaging modalities. This course will focus on magnetic resonance imaging, also known as an MRI. In the first part of the course, the dynamic of spins in a magnetic field is described, leading to the essential notions of magnetic resonance (MR), excitation and relaxation. We will also discuss the basic mechanisms of image reconstruction, MR spectroscopy and functional MRI. You will learn how existing physical principles transcend into bi

Official source

Quiz

Related concepts (28)

Spin–spin relaxation

In physics, the spin–spin relaxation is the mechanism by which Mxy, the transverse component of the magnetization vector, exponentially decays towards its equilibrium value in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). It is characterized by the spin–spin relaxation time, known as T2, a time constant characterizing the signal decay. It is named in contrast to T1, the spin–lattice relaxation time.

Spin–lattice relaxation

During nuclear magnetic resonance observations, spin–lattice relaxation is the mechanism by which the longitudinal component of the total nuclear magnetic moment vector (parallel to the constant magnetic field) exponentially relaxes from a higher energy, non-equilibrium state to thermodynamic equilibrium with its surroundings (the "lattice"). It is characterized by the spin–lattice relaxation time, a time constant known as T1.

Nuclear magnetic resonance

Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans.

Nuclear Overhauser effect

The nuclear Overhauser effect (NOE) is the transfer of nuclear spin polarization from one population of spin-active nuclei (e.g. 1H, 13C, 15N etc.) to another via cross-relaxation. A phenomenological definition of the NOE in nuclear magnetic resonance spectroscopy (NMR) is the change in the integrated intensity (positive or negative) of one NMR resonance that occurs when another is saturated by irradiation with an RF field. The change in resonance intensity of a nucleus is a consequence of the nucleus being close in space to those directly affected by the RF perturbation.

Related lectures (35)

Spin Relaxation in Magnetic Resonance

Introduces the fundamentals of spin relaxation in magnetic resonance, covering spin-lattice and spin-spin relaxation, and rotational motion in liquids.

Spin Relaxation: Examples and Mechanisms

Explores spin relaxation mechanisms in magnetic resonance, with examples like protein structure determination and solid benzene.

NMR Experiments: Basics and Applications

Explores the basic steps in magnetic resonance, including INEPT pulse sequences and two-dimensional NMR experiments like COSY and NOESY.

Spin Qubits in Quantum Dots

Explores spin qubits in quantum dots, including coherence, exchange interactions, and spin-orbit coupling.

Basic Steps in Magnetic Resonance