39358 - MRI Physics and Protection, Quality Controls

Learning outcomes

At the end of the module, the student knows the basic and  advanced physics of the Magnetic Resonance.

Course contents

Magnetic Field and SPIN
Slice, voxel, pixels.
The spectrum of the e.m. waves.
The modulations (amplitude, frequency and phase) and the transport of information.
The magnetic field.
The spin.

SPIN in a Fagnetic Field
Larmor equation.
Boltzmann Statistics.
Isotopic and biological abundance.

T1 and T2 Relaxation times
T1 and T2 Relaxation times.
Polarized e.m.Wave.
Free Induction Decay (pure and inhomogeneous).

Formation of the image contrast
Reference Systems for times T1 and T2 (TE and TR).
The signal (as the response of the spin system).
Saturation and flip angle.

Frequency and Phase Encodings
Rotating reference system.
Frequency encoding.
Passband of the transmission pulse and SYNC pulse.
Crosstalk and its minimization.
Structure of gradient coils.
Phase encoding.
Phase Equation.

The k-space
Fourier Series and Fourier Transform.
Structure of the k-space.
The chemical-shift. Structure of some artifacts in the k-space. Wrap-around.
Factors determining the image quality.
FOV, NEX, receiver bandwidth and Signal to Noise Ratio.
E.m. fields Protection and SAR.

Fourier Transform Imaging
Sequences and components of the sequences.
Excitation (slice selection).
Phase encoding.
Generation of the Echo.
Measurement of the signal.
Filling the k-space. Ways of filling the k-space.

The Fundamental Sequences
Spin-echo.
Inversion-recovery.
Gradient-echo.
The formation of the Echo in the three cases.

Structure of the MRI
Photo analysis of the structure of the MRI.
Functional block diagrams.
Structure and operation of the  more important coils and their applications.
An Overview of the superconductivity.

Insights
Electrical structure of the more used coils.
Slew rate, and its importance.
Sequences that require very high slew-rates.
Techniques for tissues suppression.
Techniques for the visualization of blood flows.
Outlines on some advanced sequences.

Readings/Bibliography

Lecture Note
The matter is particularly complex and the texts on the market are either too elementary
for the level of knowledge of a  Medical Radiology Expert Thecnician with a Degree or too
detailed in mathematics and/or physics. We have therefore prepared - and improved over the
years, a series of slides very detailed that, together with a constant presence during the lectures
and the supplementary notes taken by the student, should cover all (or almost all) the training
requirements.

A text easily understandable but, in many ways, insufficient, is the following:
Weishaupt, Kochli, Marincek - How does MRI work ? - Springer

The student interested in a discussion of more in-depth level can read the text:
Liang, Lauterbur - Principles of Magnetic Resonance Imaging - IEEE Press

A text more general (with a mathematical discussion not too extensive) dedicated
to the medical imaging specialist is:
Princes, Links - Medical Imaging Signals and Systems - Pearson Prentice Hall

Teaching methods

Frontal Lectures.
We will seek to stimulate the interaction between student and teacher in order to
enhance the understanding of the subject.
Educational programs, java applets, simulation programs will also be used.

Assessment methods

Oral examination in which the student is invited to discuss the topics covered during lessons, exposed in recommended texts and in teaching material presented and discussed in class.
The interview will be assessed on the basis of the following parameters:
-knowledge, mastery and depth of content
-critical ability and expository skills
-scientific and technical correct terminology.

Teaching tools

Frontal Lectures.
We will use simulation programs of the physical and mathematical phenomena
(modulations, harmonic decomposition of signals and images) to make them
more easily understandable.
An image processing program (ImageJ) will be used  to show the phenomena
in the frequency space.
Will be used a simulation program of the MRI to encourage the learning of the
operating parameters and their influence on the diagnostic image.

Office hours

See the website of Giuseppe Baldazzi