Outline of the module
This module gives a basic introduction to the physical principles of Magnetic Resonance Imaging (MRI). It does not require detailed knowledge of classical physics or quantum mechanics. The module gives an overview at the beginner level. Knowledge of basic mathematical concepts (calculus, vectors, and complex numbers) is sufficient to attend the module. Additional important mathematical concepts will be taught in the beginning (Fourier Transform, Discrete Signals). The module starts with a physical description of the nuclear magnetic resonance effect, a brief coverage of its quantum mechanical treatment, followed by a detailed explanation of the semi-classical description given by the Bloch Equation, utilizing the concepts of polarisation, excitation, and relaxation of the spin system. The principles of MR imaging with magnetic field gradients are introduced, and finally the basic MRI sequences and their soft tissue contrast will be investigated. The MRI hardware will also briefly be discussed.
The module covers the following topics:
• What is Magnetic Resonance?
• Exciting the MR signal
• Encoding spatial information in MRI
• Generating basic soft-tissue contrasts with MRI
• What are the basic components of an MRI scanner?
Learning objectives
At the end of this module, students will have knowledge of:
• The basic theory and origin of nuclear magnetic resonance, and a brief introduction to the quantum mechanical description of MR
• Spin dynamics in MR experiments, T1 and T2 relaxation, and the description via the Bloch Equations and the Signal Equation
• The difference between gradient echoes and spin echoes and the difference between T2 and T2*
• On- and off-resonant excitation and the slice selection process
• Spatial encoding by means of gradient fields and the k-space formalism
• Basic imaging sequences and their basic contrasts, i.e. gradient echo sequence and spin echo sequence, and image contrast variation with repetition time, TR, and echo time, TE
• Basic imaging artifacts
• Concept of accelerated imaging with multiple receiver coils (parallel imaging)
• The basic hardware components of an MRI scanner
Content
MRI is an important medical imaging modality known for its superior soft tissue contrast and its capability to quantify many different tissue-characterising parameters. Therefore, in combination with the fact that MRI is completely noninvasive as no ionising radiation is involved, MRI is the imaging method of choice in neuroscience. In order to successfully participate in this highly interdisciplinary and fascinating field, a basic understanding of the physical principles of MRI is required.
This module gives an introduction to the mathematical basis of MR physics and the quantum mechanical and classical description of spins in a magnetic field. The latter is given by the fundamental Bloch equations, describing the interaction of the spins with external magnetic fields. In this context, spin precession at Larmor frequency, polarisation of the spin system, its excitation via radiofrequency pulses, and relaxation mechanisms are discussed. Then, the basic principles of imaging are covered by introducing the method of spatial encoding via gradient fields, the signal equation and k-space formalism, Fourier imaging, and selective excitation. Basic procedures such as spin echoes and gradient echoes and their contrast mechanisms are discussed. Examples of imaging artefacts are shown and their origin investigated. The utilisation of multiple receiver coils is nowadays standard on clinical MRI systems. Therefore the concept of parallel imaging is introduced. The module ends with an overview of the MR Hardware components, the super conducting coil, the gradient coils, the RF coils, the spectrometer, and the shimming devices.
Overview of tasks and lectures
There will be 10 lectures of 2 hours distributed over 5 days.
• Introduction and overview of MRI
• Mathematical Basics
• MR Fundamentals
• Excitation
• Imaging Principles 1
• Imaging Principles 2
• Sequences and Contrasts
• MRI Artefacts
• Parallel Imaging
• Hardware
Position within the programme
This is a unique module in this Master programme dealing with the basic principles of MRI. The knowledge is highly relevant for all subsequent modules. This module provides the foundation to the general modules dealing with MRI physics and Sequences.
Teaching format
Structure
The module is a one week-long residential module consisting of 10 lectures of 2 hours. Each day, the students will in addition solve mathematical and physical problems as well as implement computer algorithms relevant to the lecture guided by tutors. Furthermore, the residential part is combined with a preparatory reading phase and post-module marked assignments.
Grading
For passing the module, an 85% attendance to the lectures and practical sessions and a satisfactory completion of the practical sessions and the module assignments are required. The module assignments will be summarised by the students in a written form which will be evaluated by the module coordinator(s).