Home > chemistry, Science > Apparently A through W were taken

Apparently A through W were taken

February 13, 2010 Leave a comment Go to comments

I’m around X-rays all of the time at the hospital. They’re a common instrument used by the docs, so common that I don’t think that many people how appreciate them. I mean, every school kid learns about X-rays when they match objects to a corresponding letter, unless your teach is weird and makes you use xylophone. No one ever seems to uses xenon, our noble friend. It’s not like they’re new and exciting, though. They’ve been around for over 100 years. Still, it’s amazing that through a relatively safe, quick and  inexpensive method we can get a picture of a person’s skeleton and find problems with major organs.

One day when I was about 20, I developed chest pressure. It felt like there was a boulder on my chest. My mom took me to the ER, we got an X-ray and were told by the doctor that I had probably  an inflammation of the lining surrounding the lungs. I was sent home and told to take some ibuprofen (if I’m remembering things correctly, it turns out the doctor who told me this really doesn’t know his stuff because this is a symptom of a bigger problem, at least according to this). The next day we were called back to the hospital. The radiologist discovered something. He showed us the x-ray and told me to look at the top of my left lung. It looked exactly like the right one to me, then he pointed to a little black smudge at the top of the lung, which I couldn’t find distinguishable from any of the other black smudges on the x-ray. Two percent of my lung had deflated or collapsed. TWO PERCENT! The little smudge that he was pointing out was the “flat” part. No wonder the OR doc didn’t pick up on it.

But how do X-rays see what they see and why can they show through some things better than others? It turns out that X-rays work because of atomic energy states, kinda. When atoms are hit by photons (like from visible light) the electrons can absorb the energy from the photon and jump to a higher energy state. If the photon then drops to a lower energy state it has to give off the same amount of energy in the form of a photon. This is what happens when it’s said that light reflects off of objects, and explains how we see things. We’re not seeing the light wave bouncing off the object, we’re seeing the light given off by the object after the energy from the light source moves the electrons to a higher state. The larger an atom is, the more energy that’s required to move the electron to a higher state.

X-rays have a higher energy than visible light. When they hit atoms, instead of knocking an electron into a higher energy state, X-rays tend to knock the electrons completely away from the atom.  However, since electrons have such a high energy, they have a hard time hitting smaller atoms. Most of the rays pass right by smaller atoms while hitting larger ones. The soft tissue of the body is mostly made up of smaller atoms. Bones are made up of calcium which are big enough to absorb some of the x-rays. This also explains why lead is used to shield people from X-rays; it’s one of the largest atoms and absorbs x-rays like the sham-wow absorbs stains. When we look at an X-ray image, we’re actually looking at the negative. This is why the soft tissues, which most X-rays just pass through, appear darker than bones.

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Categories: chemistry, Science Tags: , ,
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