Medical Central: MRI

I read more on Medical Imaging. The subject went from radiation to magnetic. Today's subject is another familiar term: MRI--Magnetic Resonance Imaging--machines.

MRI
MRI came from NMR (Nuclear Magnetic Resonance), which chemists used to figure out which atoms made up a substance. Someone realized the potential for looking inside the human body, and began to develop the MRI. The first machine, made by Damadian (who went to an university in Brooklyn, New York) was impressive, but it took the work of many scientists to create a good MRI machine (especially one who figured out how to make the image using data and showed it using math).
MRI scanners started coming into use in the mid-1980's. They were expensive, but worth it. They can do something PET and CT Scanners can't... they can see tissues!
MRI works by detecting hydrogen. Since this is primarily in water, it tracks water in the body. The MRI uses radio waves and magnets (primary one makes magnetic field stronger than Earth's natural one!) to trigger hydrogen atoms into releasing their own magnetic signals. Now, the book says these are weak signals, but the MRI can pick them up. Thanks to the atoms surrounding the hydrogen atoms, the hydrogen atoms send out slightly-different signals (according to book), but a machine attached to the MRI figures out these signals and makes an image (according to book). Now, substances with little water--like primarily-calcium bones--don't come up as well. But a lot of stuff can be seen... especially stuff surrounding by bone and cartilage. In fact, it's great for finding tumors in the pituitary gland, right under the brain and surrounded by bone, according to the book.
The book also pops up an interesting fact... this machine was also used for checking out the brain at first! In fact, today, there's something called functional MRI... AKA fMRI. This is a way of studying the brain. Japanese scientists figured out that MRI could trace blood flow in the brain. Since when a section of the brain is working it needs energy and oxygen, and therefore the blood flow increases (according to the book), this was a good way to figure out which part of the brain did what while someone was doing something. Book says that the scientists first get a baseline in which the brain rests, and then they scan the patient while doing some simple task, and then subtract the baseline, and figure out which parts of the brain were active when doing the activity. Now, there are debates on whether or not this is effective (some of it is on technique use, reports, experiments, and the fact that the brain changes functions faster than a machine can make an image) according to the book, but it's still pretty cool to me!
Like other machines in modern times, MRI machines can now make 3D images. Using pits called voxels (according to book: "volume" and "pixels" combined), a 3D image can be made. A surgeon can play around with this image as much as he wants, cutting "slices", looking at something (like a tumor) from every angle, and whatever, according to the book. The book states that this increases the chances of a successful surgery.
Now, to people with pacemakers and the little metal nets that keep an artery open, MRI machines can be dangerous because of the high-powered magnetic field. The book even says that patients going through an MRI are usually stripped of magnetic objects first. The book says that scientists once even thought that the high-powered magnetic field made the MRI dangerous, though they are now considered safe (and safer than a PET or CT Scanner, since those use radiation, according to the book).