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5th November 2014

This is an X-ray of a lobster

An insatiable curiosity for what goes on inside the human body has driven innovations in medicine and medical imaging for centuries.

In 1895, a German by the name of Wilhelm Röntgen accidentally discovered that X-ray waves could pass through flesh, but not through bone. X-rays work in much the same way that visible light rays do, but most importantly, with far more energy than visible light, they can pass through most objects.

When Röntgen asked his wife to place her hand between an X-ray source and a fluorescent screen, he saw that the screen became completely dark except for a white silhouette of all the bones in his wife’s hand. This is how the X-ray scan was born.

See inside your favorite crustacean. Don’t worry, he’s still alive just like you would be after a CT scan! (Photo: GE Healthcare)

Several iterations of the X-ray machine have been developed and improved upon ever since, but the basic principles of rays, shadows and silhouettes remain fundamentally unchanged.

However, X-ray scans were limited by offering only a two-dimensional view of a person’s bones, and little more. Even with an X-ray machine, doctors still had to cut a patient open if they wanted to examine their organs, or objects that were obscured on scans by bones in front of them.

In 1972, the idea of X-ray imaging was taken to the next level in the form of Computed Tomography, otherwise known as CT or CAT scanning. The modern CT scanner looks like a donut on its side, with the patient lying horizontally in the middle. An X-ray beam moves around the patient, scanning from hundreds of different angles. The data from each scanning point is compiled to form a whole image of a transverse section, or slice, through the body. This idea of ‘slicing’ through a patient and seeing full organs, bones and blood vessels from any angle marked another revolution in imaging technology.

What happens when you give a pineapple an MRI? This is what happens. (Photo: GE Healthcare)

For all its benefits, the use of X-ray and CT is limited by the amount of radiation one can be exposed to.  A series of experiments in 1977 involving giant magnets led to the next step in the evolution of medical imaging: the Magnetic Resonance Imaging (MRI) scanner. Unlike X-ray and CT, MRI generates no radiation at all. To understand how it works, you will need a brief lesson on magnetism in the human body.

Every rotating body in the universe generates a magnetic field, from planets to generators down to every single subatomic proton in your body. If you put a person inside a powerful magnetic field generated by a giant, super-cooled, donut shaped coil, the tiny magnetic fields of each and every proton inside their body will line up. Then, by adding a radio frequency pulse, the proton can be knocked out of alignment. This releases energy that is picked up by another magnetic field and processed by a supercomputer into an image. Different pulses of different strengths and moving in different directions generate information that helps radiologists see images of the body from every conceivable angle.

These days, few look inside the human body with more skill and care than the radiologist. Though often overlooked, radiology is a cornerstone of modern medical care. This Thursday 8th November, the world’s eyes will focus on imaging as we celebrate the International Day of Radiology (IDoR). Keep your eyes locked on twitter and #RSNA14 to see inside everything from lobsters to pineapples to electric guitars.