X-rays are part of the electromagentic spectrum (EM waves)
They have a short wavelength, same size as the siameter of an atom.
They cause ionisation
They are transmitted (pass through)by healthy tissue.
They are absorbed by dense materials - metal and bone
They affect a photgraphic film in the same way as light, so they can be used to take photographs.
The plate starts off all white, so were the X-rays are absorbed by dense materials it produces a negative image.
X-rays in Medicine
- X-rays can be used to diagnose many medical conditions, such as bone fractures or dental problems.
- X-rays can be formed electronically using charged-coupled devices (CCDs).
- They detect X-rays and produce signals which are used to prosuce high resolution images.
- CCDs are also used to take photos in digital cameras.
- Computerised axial tomography (CT) scans use X-rays to produce high resolution images of soft and hard tissue.
- The patient is put inside the sylundrical scanner and an X-ray beam is fired through the body from an X-ray tube and picked up by detectors on the opposite side.
- The X-ray tube and detectors are rotated during the scan.
- A computer interprets the signals form the detectors to form and image of a two-dimensional slice through the body.
- Multiple 2D CT scans can be put together to make a 3D image of the inside of the body.
X-rays Can Be Used to Treat Cancer
- High doses of X-rays will kill living cells due to their ionising effect.
- They can therfore be used to treat cancers, by killing the cancerous cells.
- The X-rays have to be carefully focused and at the right dosage to kill the cancer cells without damaging too many healthy cells.
- 1) The X-rays are focused on the tumour using a wide beam.
- 2) The beam is rotated round the patient with the tumour at the centre.
- 3) This minimises the exposure of healthy cells to radiation and so reduces the chances of damaging the rest of the body.
- Prolonged exposure to ionising radiation can be very dangerous to your health.
- Radiographers wear lead aprons, stand behind lead screens or leave the room while scans are being done, to minimise their X-ray dose.
- Lead is used to shield areas of the patients body that aren't being scanned, and exposure time to X-rays is kept to a minimum.
Electronic systems can be used to produce ultrasound waves, which have a higher frequency than the upper limit of the hearing for a human. 20Hz to 20,00Hz
Ultrasound waves are partially reflected when they met a boundary between two different medias.
The time taken for the reflections to reach a detector can be used to determine how far away a boundary is. This is how ultrasound imagery works.
Oscilloscope traces can be used to show an ultrasound wave reflecting off two seperate boundaries.
Use the formula: distance = velocity x time. to find the distance between two boundaries.
Uses Of Ultrasound Waves
Ultrasound waves can pass through the body, but whenever they reach a boundary between two different media some of the wave is reflected back, and detected.
The exact timing and distribution of theses echos are processed by a computer to produce a video image of the foetus.
Breaking Down Kidney Stones:
Kidney stones are hard masses that can block the urinary tract.
An ultrasound beam concentrates high-energy waves at the kidney stone and turns it into sand-like particles. These particles then pass out of the body in urine.
It is good as it is relatively painless and doesn't involve surgery.
Cleaning Delicate Items
Comparing Medical Imaging
Ultrasound waves are non-ionising and safe,as far as anyone can tell.
X-rays are ionising. They can cause cancer if exposed to too high a dose, and not safe to use on developing babies.
CT scans us a lot more X-ray radiation than the normal X-ray photographs, so patients are exposed to even more ionising radiation. They are not used unless essential sue to the increased radiation dose.
Ultrasound imagery is fuzzy, making the diagnostics of some conditions difficult.
X-ray photographs produce clear images of bones and metal, but not tissue.
CT scans produce detailed, high resolution images which make it easier to diagnose complicated illnesses. The high quality 3D images can also be used to plan complicated surgery.