medical application of physics

X-rays:

X-rays are short wavelength, high frequency electromagnetic waves. Their wavelength is roughly the same size as the diameter of an atom.

Properties of x-rays include:

• they affect photographic film in the same way as light- this means they can be used to take photographs. (The brighter parts of the film are where fewer x-rays get through)
• they are absorbed by denser materials (both metal and bone)
• they are transmitted by (healthy) tissue
• they have a range of frequencies (lower frequency X-rays have less energy and are therefore less penetrating and ionising)
• x-rays are ionising- they kill or damage living cells.

X-rays can be used to diagnose medical problems such as bone fractures and dental problems. This is done by forming x-ray images through use of charge coupled devices (CCDs). CCDs detect x-rays and produce electronic signals which form high resolution images. These can then be used to diagnose bone or dental problemss (as bones absorb x-rays).

X-rays can be used in CT scans to produce high resolution images of both soft and hard tissue. The patient is put inside a cylindrical scanner and an x-ray beam is fired through the body from an x-ray tube and picked up by detectors on the other side. Both the x-ray tube and the detectors are rotated during the scan. A computer intercepts the signals from the dectectors and an image od a two dimensional slice through the body is formed. Multiple images can be put together, enabling a three dimensional image to be formed illustrating the inside of the body.

X-rays can be used to treat cancer. This is due to the fact that they are ionising, meaning they kill living cells. However the x-rays must be carefully focused at the right dosage, lest they damage any normal cells. To treat cancer the x-ray beam is first focused on the tumor, using a wide beam. Then the beam is rotated around the patient whilst the tumor is at the centre. This is to minimise the exposure of normal cells to radiation, minimising the chance of damage to the rest of the body.

Precautions must be taken to minimise the risk…