The Anonymous Widower

Experiencing an MRI Scan

I’ve heard from several people that they don’t like MRI scans.  My late wife didn’t, as she found them claustrophobic and noisy.  I’ve had two; one on my shoulder and the other yesterday on my brain.  They are both, but at least in the second, I was able to see out through a mirror.  I’ve also had a CT scan in Naples and apart from the technology, that was a similar experience, although less noisy.

So how does an MRI scan work.  This is the first paragraph of an excellent article in Wikipedia.

Magnetic resonance imaging (MRI), or nuclear magnetic resonance imaging (NMRI), is primarily a medical imaging technique most commonly used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, 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. Radio frequency (RF) 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 construct an image of the body.

Note that they call the technique by its real name NMRI.  It was called that when I worked on an NMR machine in 1969 at ICI Mond Division.  I seem to remember that the guy who ran the department, Eddie Clayton, claimed that one day it will be used instead of X-rays.  I don’t think he was believed, but then the first images were taken in 1973, so it wasn’t far off.

The Wikipedia article also explains all the noise.

…These fields are created by passing electric currents through solenoids, known as gradient coils. Since these coils are within the bore of the scanner, there will be large forces between them and the main field coils, producing most of the noise that is heard during operation. Without efforts to dampen this noise, it can approach 130 decibels (the human pain threshold) with strong fields.

So it’s just mechanical interaction and not somebody trying to operate on your head with a road drill.  I’m partly deaf, or rather I have frequencies missing, so it doesn’t bother me.

But the real power of MRI scans is that show the body in amazing detail that enables problems to really be diagnosed.  In the first use of the technique they looked at my shoulder that had given me trouble all my life.  They ascertained that there was no serious problem and that exercise rather than surgery was the best way to proceed.  That was good news, not like yesterday’s. 

But only a few years ago, neither diagnosis would have been possible.

March 16, 2010 - Posted by AnonW | Health | Engineering, MRI Scan, Stroke