Physics P3 - X-rays vs. CT scans

A detailed comparison and explanation of X-rays and CT Scans. Feel free to ask questions!

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Alan Zajac 15/09/13
X-rays vs. CT scans
X-rays are part of the electromagnetic spectrum. It travels at the speed of light, has a very high energy and frequency,
also it has a very short wavelength- the same order of magnitude as the diameter of an atom,
lastly is causes ionisation (causes electrons to split from their atoms). X-rays are particularly useful
in medicine, for diagnosing and treating problems. X-rays allow doctors to see inside the patient
as the rays are abso rbed by dense materials, such as
bones. Therefore if a patient is hit by a stream of
X-rays then the bones and other materials which
absorb the radiation will cast a shadow onto
photographic film. However, because they are
ionising, X-rays can damage living cells and can cause
cancer. This is because the rays are powerful enough to manipulate our
DNA and cause it to mutate. X-rays used to be very common in circuses
and children's shoe shops, however, this unnecessary exposure proved
very damaging to the body. Now X-rays are handled very seriously, doctors monitor how many times a year their
patients were exposed to X-rays, radiographers are protected by lead screens during the scan.
There are two main types of X-ray scans: single X-ray images and CT or CAT scans (computed tomography or computer
assisted tomography).
Single X-ray images are the most common, these are the simple 2D images produced. In
the past people would use photographic film to capture the shadow image. Nowadays,
computed radiography is used. Theses work by using CCDs. The X-rays are detected
using the charge-coupled devices (CCDs) and are turned into an electronic image. The
CCD contains semiconductor material that is ionised by the X-rays. These electrons form
a current that can be measured.
CT scans are very similar to the single images,
however, they have one main difference: the CT
scanner many photos compared to one allowing the
computers to put together a 3D image of the body.
The CT scan consists of a rotating scanner taking X-ray
images from many different directions. The moving
bed carries the patient slowly through the scanner machine. The main
computer will combine the images and build a 3D image.
Advantages and disadvantages of single X-ray images:
Cheap to buy and maintain compared to CT scan.
Very simple to use.
Less exposure to X-rays compared to CT scan
Not very detailed and can only give image of bones.
Not as helpful to doctors.
Advantages and disadvantages of CT scan.
Unbeatable detail and precision of scan.
Gives doctors ability to not only scan the bones but other soft tissue by varying
the X-ray hardness.
Every expensive and difficult to use, requires trained professionals
More radiation exposure compared to the single image X-ray.
Able to destroy infected tissue.

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