(Nuclear) Magnetic Resonance Imaging

Aaron Rios
March 22, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: A modern MRI Scanner (Source: Wikimedia Commons)

Nuclear Magnetic Resonance Imaging (NMRI) has proven itself to be a crucial technology in modern diagnostics, especially involving soft tissue diagnostics. It is interesting to note that, due to stigma around terminology and an interest in preventing negative connotations around nuclear processes, the term 'nuclear' was dropped. [1] NMRI is now more commonly known as MRI.

The history of the MRI is a controversial one, as are other breakthrough in medicine and health. Paul Lauterbur ( University of Illinois in Urbana-Champaign) and Sir Peter Mansfield (University of Nottingham) received the Nobel prize in medicine for their contributions to the modern day MRI. Raymond Damadian, however, credits himself with being the true founder of MRI. Dr. Damadian was the first to find that the relaxation times (described below) of hydrogen atoms differed between healthy and cancerous cells, publishing his findings in Science in 1971. Not long after, Dr. Lauterbur published his idea to use NMR for diagnostics in Nature, without citing Dr. Damadian. Several scientists contributed to the progression of this technology moving forward, but the first clinical MRI scanner was built by a team lead by Professor John Mallard at the University of Aberdeen in 1980. [2] Fig. 1 shows a modern day MRI Scanner. [3,4]

How It Works

In 1956, Felix Bloch (Stanford University) and Edward Purcell (Harvard University) were awarded the Nobel Prize for finding a way to measure nuclear magnetic resonance. [1] The nuclei of some atoms possess a magnetic moment, allowing them to behave similarly to a compass needle. [3] An MRI applies a strong magnetic field to the patient, forcing these nuclei to align with the field. Specifically, hydrogen atoms, which are present in water and fat, are aligned. Next, in order to study the atomic nuclei and their surroundings, an electromagnetic energy of the same frequency of the nuclei affected by the magnetism. This causes the atomic nuclei to flip. Nuclear magnetic resonance occurs as these nuclei correct themselves and relax. During relaxation, they emit radio signals, allowing medical practitioners to determine density of the hydrogen nuclei in specific parts of the body. By repeating this concept throughout the body at different dimensions, it is possible to elucidate a scan with different distributions of nuclei throughout the body, and therefore tissue delineation and imaging. [3-5]

© Aaron Rios. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] A. Khalis, "The Future of Nuclear Medicine," Physics 241, Stanford University, Winter 2016.

[2] J. R. Mallard, "Magnetic Resonance Imaging - the Aberdeen Perspective on Developments in the Early Years," Phys. Med. Biol. 51, R45 (2006).

[3] "MRI's Inside Story, The Economist, 4 Dec 03.

[4] S. S. Rajan, MRI: A Conceptual Overview, (Springer, 1998)

[5] C. L. Partain, Nuclear Magnetic Resonance Imaging, (Saunders, 1983).