Lecture1 MRI...You are either fat or you are water!!!

The most important reason why I am an MRI Radiographer today is that the first time I met an MRI scanner, it “wowed” me. I have been a cross sectional radiographer for about 8 years now and I must tell you that MRI still “wows” me. Throughout your career long encounter with MRI, it promises to keep "wowing" you because MRI is like a river of fascination that never runs dry.

I like to learn and share. And that has proven to be the best way to learn more and be better. I am not an expert in MRI. But I do know a few things that I hope could benefit those are new to MRI or struggling to get their feet in the practice. My blogs will be mostly beneficial to newbies in MRI or persons with growing interest in the practice. However, more experienced radiographers are not immune to learning from my blogs but I bet they will find my simple way of explaining what goes on with and in MRI very interesting.

It is often very difficult to explain MRI in very simple terms. I will try.  In doing so, I may dilute the information that I pass across. You will find this helpful as you read more, do more and learn more. My blog will be very helpful in understanding the basic physics behind MRI before you can appreciate it clinical application.


There are two very essential questions whose answers are very important in understanding the physics of MRI as a newbie.

1    1.    What are the compositions of the body that makes MRI possible?

2    2.    What are the interactions possible in MRI?

To answer the first question, the only two  compositions of the body that make MRI possible are fat and water. At this level, it is very important to note that anything you see on an MRI image is either fat or water or  a composition of both or none of the two. From basic biology, cells make up tissues which make up organs. For the purpose of your discussion, we can look at components of the body at the tissue level. So in essence, every tissue has either fat or water or a combination of both in unique proportions. Understanding MRI physics with its clinical application is very easy if we narrow down our dealings to tissues that are fat or water or a make of both or none at all. This is important because the primary essence of imaging is to differentiate tissues from one another. The very interesting thing about fat and water is that they both contain hydrogen particles and these hydrogen particles have a different physical property in fat or water that is exploited for the benefit of MRI . I won’t discuss the properties of hydrogen in this blog as this is an introductory one but in subsequent blogs, we will discuss those properties and it will become clearer how hydrogen play a major role in MR image formation. But it important to note that hydrogen is perhaps the single most important element in MRI.

To recap what we have said so far, every tissue has a composition of either fat or water or a combination of both that are unique to them and makes them different from other tissues on an MRI image. This also applies to diseases. A disease is differentiated from another or normal tissues on the basis of its unique composition of fat or water or a combination of both. As we go deeper into our learning, we will learn about MR signals and how they are generated and only then will we appreciate the significance of our narrowing this down to fat and water.


Now lets look at question number two. The interactions possible in MRI are magnetization and transfer of energy in the form of radiofrequency. This is possible by having a strong external magnetic field and a device capable of transmitting and receiving radiofrequencies. We are not going into this now. But also, it is important to note that these two interaction are only useful with the hydrogen particles in the body. We will be looking deeper into these interaction in subsequent blogs. But again, it is important to note that the interaction of hydrogen in water and fat with magnetization and radiofrequencies are different and this forms the basis of what I refer to as differential MR signal formation.


As a brief summary, when you make a strong magnetic field, put the body under the magnetic field, the hydrogen in the tissues in the body interact with the magnetic field. When radiofrequency pulses are applied, another form of interaction is possible. Depending on certain conditions which we will look at later, the hydrogen particles in fat and water are able to take up energy and return these energies as signals that are used to form the images we see from an MRI scan.


I have tried not to introduce any technical terms which sadly are many in MRI. The reason being that I want you to appreciate that MRI is all about differentiating fat and water. And that hydrogen is the most valuable player in the game.

Thank you for reading and I hope to see you in my next blog