NMR vs. MRI - When Should We Use Each Acronym?

Your Guide to The Acronyms Used For Magnetic Imaging

The medical industry is filled with acronyms that can be a little confusing at times, especially when different acronyms seem to be interchangeable. For example, a magnetic imaging system is typically known as an MRI (Magnetic Resonance Imaging), but it's also been referred to as an NMR (Nuclear Magnetic Resonance). You're probably wondering whether MRIs and NMRs are actually the same thing-- and if they are, which term should you be using? It's important to know the proper term so that everybody in your facility is on the same page when referring to your hospital's equipment.

The Terms NMR and MRI: Are They Interchangeable?

NMRs and MRIs are exactly the same. They refer to the same process that the machine performs. The process was called an NMR from its inception because of the involvement of the hydrogen nuclei. The "nuclear" part of the name was eventually dropped and the acronym was changed to MRI instead. So technically, NMR and MRI are interchangeable because they refer to the exact same process, but these days, MRI is the more commonly used term.

Why Is MRI the Preferred Term?

The process was first described in 1938 by Isidor Rabi, who went on to win the Nobel Prize in Physics for the work. The acronym NMR was commonly used because it described what the process involved. However, the acronym became less used because of the word "nuclear," which gained more and more negative connotations throughout the next few decades.

Not only was there a societal fear about a potential nuclear war, but there had been several nuclear plant accidents emblazoned into the memory of society as a whole, including incidents at Chernobyl and Three Mile Island. Not surprisingly, the term NMR was replaced with the less dangerous sounding MRI, which is the term most used to describe the machine and the process to this day.

Do MRIs Expose Patients to Nuclear Danger?

There is zero nuclear danger involved in the MRI process. Like previously mentioned, the term "Nuclear Magnetic Resonance" was used to describe the process involving hydrogen nuclei and had nothing to do with radiation. Unfortunately, due to the threat of nuclear war and the high profile failure of several nuclear power plants, a negative connotation was attached to the word. In fact, unlike other diagnostic imaging systems, MRIs do not expose patients to any kind of radiation since they do not use X-rays at all.

Breaking Down The Term Nuclear

The NMR (or MRI) process involves aligning the hydrogen nuclei in the body's water molecules using a strong magnetic field. A varying magnetic field is generated using a radio frequency produced by the machine. The hydrogen nuclei absorb the energy and flip their spins. The magnetic field is then turned off, causing the nuclei to return to their normal spins. This return process creates a radio signal that the scanner receives and converts to an image. It's for this reason that the process was once called NMR.

It's unfortunate that the acronym had to be changed due to the negative connotations of the word "nuclear." The word certainly has plenty of positive connotations as well. Yes, the word's presence in phrases such as "nuclear war" and "nuclear fallout" are scary, but the understanding of the word "nuclear" depends on context. For example, even though nuclear plants rarely conjure up positive connotations, they are actually incredibly safe ways to generate electricity.

According to the World Nuclear Association, there have only been three major accidents involving nuclear power plants in 33 countries over 17,000 cumulative reactor-years of commercial operation. In fact, the only deaths that occurred as a result of a commercial nuclear reactor incident occurred during Chernobyl.

In the term Nuclear Magnetic Resonance, the word nuclear refers to the way all nucleons/nuclei (protons and neutrons) respond to the strong magnetic fields produced during this process. There are plenty of other terms that use the word "nuclear" that have positive connotations as well; for example:

• Nuclear physics - A branch of physics focusing on the nucleus of the atom as well as its internal structure and components.
• Nuclear energy - A type of energy used to generate electricity.
• Nuclear family - Refers to a family unit consisting of two parents and their children.
• Nuclear medicine - A branch of medicine focusing on the use of radioactive isotopes in diagnosing and treating diseases.
• Nuclear spectroscopic telescope array - A type of telescope used by NASA in space that uses high energy X-rays to further our understanding of the universe.

Is the Term NMR in Use These Days?

Although our collective culture has a much better understanding of the word "nuclear" in this day and age, the acronym NMR has largely been replaced by MRI in almost every respect. However, NMR is still sometimes used when referring to the process in regards to chemical analysis or laboratory imaging. There are also some scientific terminology purists out there who prefer the term NMR as it encompasses a more specific description of the process than the term MRI.

When Can We Use Each Term?

Because the acronym MRI is interchangeable with NMR, it might be confusing which term you should use. Generally speaking, the term MRI is more commonly used throughout the medical industry, especially when referring to the actual imaging or spectroscopic techniques for both human and animal patients. The typical patient is also more familiar with the term MRI, and most manufacturers use it to describe their systems as well.

As a result, NMR is a mostly outdated acronym. However, there are still a few cases in which it can be used. For example, it's most commonly used to refer to nuclear induction signal measurements in physics or chemistry labs as well as when describing the actual physical process itself.