What's an mri?

Question

What's an mri?

Answer 1

Nuclear magnetic resonance imaging (MRI) is primarily a medical imaging technique most commonly used in Radiology to visualize the structure and function of the body. It provides detailed images of the body in any plane. MRI provides much greater contrast between the different soft tissues of the body than does computed tomography (CT), making it especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer) imaging. Unlike CT it uses no ionizing radiation, but uses a powerful magnetic field to align the nuclear magnetization of (usually) hydrogen atoms in water in the body. Radiofrequency fields are used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to reconstruct an image of the body.

Answer 2

Spoofer is absolutely correct, Magnetic Resonance Imagine is a method of imaging the body (in clinical medicine) which provide brilliant, high-contrast images with multiplanar capacity.  The MRI (closed magnet) is a big machine with a ridiculously powerful magnetic field (typically 1.5 or 3.0 Tesla) and a relatively narrow tunnel in the center for the patient to slide in.  The physics of image acquisition and the mathematics governing how data acquired is rather complicated and was worthy of a Nobel Award for the men who came up with the complex mathematics which enable images to be rendered from source data.  Besides being in a very strong magnetic field associated with the used of RF signals to generate various "sequences" to help with identification of anatomy (e.g. T1WS) versus pathology (e.g. anything where the TR & TE produce essentially a T2/FLAIR sequence), the patient undergoing the MR will hear loud, and very strange noises which are the result of gradient coils which also partake in image acquisition.  You have to lay still, there are a number of reasons why a patient may not be able to have an MRI peformed (because of the strength of the magnet), and it takes quite some time to acquire all the necessary images as compared to modern CT (which employs ionizing radiation to acquire images).  Ear plugs are highly recommended as the gradient coils make it really loud.  If you're claustrophobic, a closed magnet isn't suitable, you'd need to be scanned in an open magnet so long as there are no other contraindications.

Everything that Spoofer has mentioned is absolutely correct.