ABCs of The Magnetic Resonace Imaging – MRI
The human body is opaques and a well-designed mystery. To understand the diseases that afflict humans and treat them appropriately, we need to be able to see inside the body and visualize what goes on in there. In earlier days, physicians could only rely on their experience and intuition. Thankfully for us, around 1975 a powerful technique was created known as Magnetic Resonance Imaging or MRI. In this article, I will explain the ABCs of the MRI, how it works, what it is for, and why it was invented.
A – Anatomy of MRI
Between 55 to 78 percent of the human body is made up of water molecules. The water molecule has two hydrogen atoms and one oxygen atom. Inside each of these atoms, there is a nucleus. This nucleus contains a particle called a proton on the inside. Another particle, called an electron, revolves around the nucleus just like the earth revolves around the sun. The hydrogen atom has one electron and one proton. The planet Earth rotates about its own axis, and this is what causes day and night. Similarly, the particle proton inside the nucleus rotates about its own axis. This causes the particle to possess a property called “spin”. This property of spin is utilized in the technique of Magnetic Resonance Imagining.
Some important facts about the Anatomy of the MRI include:
This involves randomly oriented spinning protons.
The protons align along the magnetic field direction.
The protons are activated when the radio waves of the MRI are turned on.
The protons are inactivated when the radio waves are turned off.
B – Behavior of the MRI
- With the MRI technique of imaging, a person is brought under the influence of a strong magnetic field. The direction in which this magnetic field is applied serves as a reference direction (the blue arrow). During this stage of the MRI, the protons present in the water molecules of the body and are randomly directed (image 1). When the magnetic field is applied, the randomly oriented protons get aligned along its direction in an orderly fashion (image 2). Once this occurs, the energy in the form of radio waves is turned on and the protons absorb this energy to get newly oriented (image 3). However, at this time the orientation is with respect to the reference direction, that that is of the applied magnetic field. Once the energy is turned to the off position, the protons go back to their original ordered direction (image 4). The shift in direction then generates a signal that is detected by an instrument called a scanner. This signal is used to create an image of the internal organs and structures or the affected site of the body.
C – Causes for use of the MRI
MRI is performed for many reasons. It can be used to find problems such as bleeding, injury, tumors, blood vessel disease, or infection. MRI may also be done to provide your doctor with information about problems seen on an ultrasound scan, a CT scan, or even an X-Ray. A MRI can be done for:
Head – A MRI can assess for aneurysms, bleeding of the brain, tumors, nerve injury, and damage caused from a stroke. It can also find problems of the eyes and the optic (seeing) nerves as well as of the ears and auditory (hearing) nerves.
Chest – The MRI can examine the heart, the valves, and the coronary blood vessels. It can also see if the lungs are damaged or have tumors. Many doctors order an MRI to assess for breast cancer.
Abdomen and Pelvis – The MRI can look at the blood vessels and the flow of blood through them by way of a magnetic resonance angiography, or MRA. This helps doctors see aneurysms, blocked blood vessels, or torn lining of a blood vessel (dissection).
Bones and Joints – The MRI can be used to check for issues with bones and joints such as arthritis, bone marrow problems, cartilage issues, torn tendons or ligaments, and infection.
Spine – Many doctors use the MRI to assess for conditions that affect the spine, such as spinal tumors, disc bulges and herniation, and stenosis of the spine.