A (Very) Unique Perspective on Food
Sometimes, when I need to satisfy the nerdier side of my food-loving self, I head over to the blog Inside Insides. If you want to see fruits and vegetables in a whole new way, then this is the site for you. By scanning produce in an MRI machine, Inside Insides creator Andy Ellison has put together pages and pages of mesmerizing images. Definitely worth a look!
Every time I visit this site, I wonder how these images were actually created. If you watch TV, you’ve probably seen someone get an MRI at some point or another. But what actually goes on in that crazy contraption? And how on earth does a giant magnet let you see the insides of people and produce?
Magnetic Resonance Imaging (MRI) takes advantage of a physical phenomenon called nuclear spin. All physical material is made up of atoms, which each contain a small compact nucleus surrounded by a cloud of electrons. Nuclear spin refers to the ability of an atomic nucleus to literally spin about some imaginary axis, much in the way the earth spins about the imaginary axis between the north and south poles. For an atom like hydrogen, there are two possible “spin states" for the nucleus. Normally these spin states have the same energy and are equally likely to occur, but they can also be influenced by external forces such as a magnetic field. For a set of hydrogen atoms in a magnetic field, both spin states can still exist; however, the spin state that is in line with the magnetic field will now have a lower energy than the other spin state and will predominate.
This is basically what happens when someone or something enters an MRI machine — the strong magnetic field inside the machine aligns the spin states of all the hydrogen atoms in whatever body, squash, or melon happens to be inside. At this point, specific radio wave frequencies are briefly used to “excite” or energize the hydrogen atoms. This causes the atoms to switch to the higher energy spin state out of line with the magnetic field. The machine then measures various “relaxation constants” that correspond to the time it takes the atoms to return to their original, low-energy spin states in line with the magnetic field.
Relaxation constants relate to the water content of different materials:
"The value of these constants are material dependent, specifically they depend on the water content of the material. Low water content materials, such as bone and other hard tissues, have very fast relaxation constants while in contrast soft tissues have a high water content to give long relaxation constants."
After some fancy computer magic, the relaxation constants can be mapped to specific locations and turned into a magnetic resonance image. In the image a higher signal (longer relaxation constant, lighter color) corresponds to a higher water content, while a lower signal (shorter relaxation constant, darker color) represents material with a lower water content. Try to keep this in mind as you check out Inside Insides!