Melissa Paul
Imaging Technology in Medicine
12/13/10
Imaging technology in medicine started in 1895 completely by accident. A
German physicist named Wilhelm Roentgen made the discovery while working with a
gas discharge tube or cathode ray generator.
He noticed that when he turned it on a
fluorescent screen that he had in his lab would
glow. He thought that this was odd as heavy
cardboard blocked the tube, so he used other
things to block the radiation. This eventually
led to him using his wife’s hand this was
when the image of her bones appeared on the
fluorescent light (howstuffworks.com). The
technology discovered by Roentgen was used
until 1913 when William Coolidge created the
reich-chemistry.wikispaces.com 1
cathode ray tube, otherwise known as the
Coolidge tube. Even though this new technology was created in 1913, it didn’t start
being used until the 1920s. The Coolidge tube offered stability and allowed the intensity
of the x-rays to be controlled. This is why today the Coolidge tube technology is still
used. Obviously the materials used to make it and the overall aesthetic of it is different,
but the principles that control it are the same (orau.org).
Although the history behind the x-ray is interesting, what is even more interesting
is how x-rays work. X-rays themselves are a form of electromagnetic energy that is
transported by photons. The reason X-rays produce pictures of bones so well is
because bones absorb x-rays extremely well. That is why the image of bones comes
across so wells, but tissues don’t show as well. The thicker tissues do show slightly, but
not as well as bones. The machine itself works by having a glass
vacuum tube containing both a cathode and an anode (howstuffworks.com). A cathode is
the part where the electrons enter a device (negative charge) and the anode is the part
where the electrons leave a device (positive charge) (dictionary.com). The cathode is
made of a heated filament and the anode is made out of tungsten, which makes sense as
William Coolidge also created the tungsten piece used in light bulbs. The electrons pass
through the heated filament heating it up and then pass down to the tungsten piece. The
differences in voltage between cathode and anode are specifically far apart so that the
electrons move at an extremely rapid speed. This high speed creates a lot of collisions
between the particles so it is necessary for there to be both a motor spinning and cool oil
flowing around it in order to keep the mechanism cool. The whole system has to be
covered in lead because as Roentgen proved when discovering the technology, x-rays
have a tendency to be able to pass through anything and go everywhere. There is a small
opening at the bottom to allow the light through. The
camera itself is on the underside of the patient so that the xrays pass completely through the patient creating the image
on the camera underneath them (howstuffworks.com).
After discovering the technology behind x-rays. I wanted to know how many xrays is it safe to have. It turns out that a person can have up to 300 x-rays before it starts
affecting them negatively (schoolforchampions.com). The information in the chart below
represents the data collected when I polled twenty people about how many x-rays they
had received. Out of the twenty people polled, ten have had only one x-ray, 5 have only
had two x-rays, one only three, and four have had five x-rays taken.
The Number of X-Rays Received
By Twenty People
12
10
8
Number of X-Rays
Received
6
Number of People
4
2
0
0
1
2
3
4
5