A little-known and harmless side effect of MRIs gives us an intriguing way to murder people. Tricking them into getting an MRI would be tough, but afterwards? It's almost too easy.
Magnetic resonance imaging machines are a safe, painless, and effective way to take a look at a person's insides. They put the person in a strong magnetic field, and then hit them with radio pulses. The magnetic field puts the person spin on a person's atoms in alignment, and the radio pulses throw them out of alignment. As they slowly realign, the give off their own signals, which the machine detects and interprets. Different tissues realign in different orders, so an MRI will not only give doctors a picture of the shapes in a person's body, but a picture of the material that makes up each shape.
While no one loves being shoved in a tube and magnetized, the experience is worse for some than for others. Some people feel a tingling sensation, a burning sensation, or a vibration along their skin. The process has come to be known as peripheral nerve stimulation. Basically, a changing magnetic field can induce an electric current. And electricity can stimulate nerve activity.
At low levels this nerve activity is minor. People feel the prickling of skin. Crank the machine up fifty percent higher than threshold level, and the "prickles" start to hurt – but at least the only nerves this level affects are sensation receptors. Muscles are also run via nerve impulses, and one of the most important muscles in the body is the heart. Get an MRI powerful enough, and it can stimulate the heart and the diaphragm, two fairly critical systems for those of us who want to continue to live. So far, there's no need for an image produced using the kind of power that would put a person's heart in danger, but that doesn't mean an MRI machine – suitably modified – couldn't do it. Anyone up for writing a medical murder mystery?