One of the questions I have been asked is how does MRI work? In this blog I will give a very simplified version, but in future blogs I will go into the physics in more depth.
MRI = Magnetic Resonance Imaging
In very simplified terms, when using a veterinary MRI Scanner, you are using a large magnet to interrogate the hydrogen protons within the patient’s body. The magnet forces the hydrogen protons within the patient to align roughly to the same position as the magnetic field. Radiofrequency (RF) pulses are then used to energise the hydrogen protons, which causes them to stop being aligned to the main magnet. Once the RF pulse stop the protons quickly realign themselves to the main magnet - as they do this very small amounts of energy are released, and the system listens to this echo, and forms an image, this is done by using a receiver coil wrapped around the region of interest.
As you can imagine each echo coming back is very small, so this process is repeated multiple times to for the image. Any outside RF will interfere, so scanning is always done in a shielded room.
Secondary magnets called gradients are used to help with imaging. One of the things the gradient magnets do is create slight variations in the magnetic field, which enables the system to locate where things are within the main magnet. This is where their name comes from, as they have created a gradient in the strength of the magnetic field. They also help improve image quality, by enabling you to quickly realign the protons within the scanner.
Hydrogen is used for a couple of reasons - mainly due to all tissues containing hydrogen, but also as hydrogen contains only one proton, making it easier to study. Research systems exist that can use MRI to help identify what is contained within a compound, but these don’t have a use in a clinical environment.
This image shows how the proton will behave- rather than spinning randomly or sitting in perfect alignment, each proton spins around the axis of the magnetic field, this is known as the plane of precession.
To find out more contact 3D sales manager Nigel Perry - [email protected] or 07876 202 016