We hope you will find this site useful, whether you are an MRI radiographer, radiography student, radiologist, medical student or just plain curious…. Our aim is to provide a clear and easily accessible guide to many of the practical aspects of MRI, available at the click of a button on a single site.
Mrimaster.com is easy to find your way around using the tabs at the top of this page. In the Planning section you will find full explanations and illustrations of how to plan MRI scans of different parts of the body, together with suitable protocols and parameters. The Technical section will tell you how to manipulate parameters to produce good diagnostic scans, and how to deal with artefacts. By clicking on the Characterized Images tab, you will be able to look at typical images produced by the different sequences and learn about the basic physics of each one. In the Anatomy section, labelled images give a clear guide to cross-sectional anatomy in different planes, while the Pathology section will show the distinctive characteristics of particular pathologies as imaged using different sequences. A final section gives basic, but crucial information on maintaining safety for MRI patients, staff and visitors.
History of magnetic resonance imaging
Magnets were first discovered by the Romans more than 2000 years ago. Over the years, the understanding of magnet has increased and many applications have developed.
The history of NMR (known as MRI) begins with a french mathematician Jean Baptiste Joseph Fourier (1768–1830) who developed a mathematical method to analyze the heat transfer between solid bodies. Later this discovery made rapid processing of phase and frequency signals possible in NMR.
The unit strength of a magnetic field is the Tesla (1 Tesla = 1 Newton/Ampere-meter) and is named after Serbian inventor Nikola Tesla (1856–1943) who discovered the rotating magnetic field.
An Irish physicist, Sir Joseph Larmor (1857–1942) discovered a way to calculate the rate at which energy is radiated by an accelerated electron. He also explained the splitting of spectrum lines by a magnetic field. He is famous in the field of NMR for the so-called larmor equation, which states that the frequency of precession of the nuclear magnetic moment (ω) is directly proportional to the product of the magnetic field strength (B0) and the gyromagnetic ratio (γ ): ω = γB0.
An Austrian, Isidor Rabi (1898–1988) working in the Department of Physics at Columbia University in New York, discovered a way to detect and measure single states of rotation of atoms and molecules. He also succeeded in determining the magnetic moments of the nuclei. For his discoveries, he was awarded the Nobel Prize in Physics in 1944.
In 1940s, Felix Bloch working at stanford university and Edward Purcell from harvard university independent of each other, described a physicochemical phenomenon which was based on the magnetic properties of certain nuclei in the periodic system. They found that when certain nuclei were placed in a magnetic field they absorbed energy in the electromagnetic spectrum and re-emitted this energy when they returned to their original state. The strength of the magnetic field and the radiofrequency matched each other according to the Larmor relationship. For this discovery, Bloch and Purcell were awarded with the nobel prize for physics in 1952.
In 1971, Raymond Damadian from Downstate Medical Center in New York measured T1 and T2 relaxation times of normal and cancerous rat tissues and found that normal tissue had shorter relaxation times than the tumour tissue.
In 1974, Paul C. Lauterbur, a professor of chemistry and radiology at New York University and Peter Mansfield from the department of physics at the Nottingham University England independent of each other, described the use of magnetic field gradients for spatial localization of NMR signals. These discoveries led to the foundation for Magnetic Resonance Imaging (MRI). For this discovery, Lauterbur and Mansfield were awarded with the nobel prize for physiology or medicine in 2003.
In 1975, a Swiss physical chemist Richard Ernst described the use of Fourier transform of phase and frequency encoding to reconstruct 2D images. For this discovery he was awarded with the nobel prize for chemistry in 1991.
Later in 1975, Peter Mansfield and Andrew Maudsley proposed a line scan technique, which led to the first cross sectional imaging of human anatomy (cross section through a finger). In 1978, Hugh Clow and Ian R. Young worked at a British company called EMI, created the first transverse NMR image through a human head.