X - Rays in Medicine

X-Rays:

  • High frequency
  • Short wavelength
  • Electromagnetic wave
  • Are absorbed by bones and pass through tissues
  • Are ionising

CCD'S are silicon chips (the size of postage stamps) with identical pixels. They detect X-rays and produce electronic signals, used to produce an image.

CT scans use X-Rays (Computerised Axial Tomography) A patient is put in a cylindrical scanner which rotates around them, firing an X-Ray beam through them. It is recieved at a detector the other side. An image like a 2 - D slice is formed.

X-Rays can be used to treat cancer. High doses of X-Rays will kill living cells.

  1. X-Rays are focuse on the tumour using a wide beam.
  2. The beam is rotated around the patient keeping the tumour at the centre.

Radiographers wear lead aprons or stand behind a screen to shield themselves. Areas of the patient's body which aren't being scanned are shielded by lead. 

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  • Created by: rubyfleur
  • Created on: 16-05-14 17:03

Ultrasound

ULTRASOUND = Sound with a higher frequency than we can hear.

They are made by converting electrical oscillations into mechanical vibrations with a frequency of over 20,000 Hz.

Ultrasound waves get partially reflected at a boundary between media.

  • This is partial reflection.
  • So, you can point a pulse of ultrasound at any object - whenever there are boundaries between one substance and another, some of the ultrasound gets reflected back.
  • This can be used to measure how far away the boundary is.

Oscilloscope traces can be used to find boundaries.

s = v x t       

s = Distance in metres, m. v = Speed in metres per second, m/s. t = Time in seconds, s.


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Ultrasound Uses

1. Breaking down kidney stones.

Ultrasound beams concentrate high-energy waves at the kidney stones, turning them into small patticles which can be passed out in the urine.

2. Pre-natal scanning of a fetus.

US waves can pass through the body and bounce between the baby's skin and another boundary to give a video image of the fetus.

MEDICAL IMAGING - SAFE?

  • US waves are non-ionising, so are safe.
  • X-Rays are ionising, so can cause cancer.
  • CT Scans expose patients to a high dose of radiation.

IMAGE QUALITY

  • US images are fuzzy and would be hard to use to diagnose conditions.
  • X-Rays produce clear images but only of bones and metal.
  • CT Scans produce detailed images and can be used to diagnose conditions and in the planning of complicated surgery.

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