Unit Three: X-rays and Ultrasound

Question 1

What are X-rays?

Answer 1

High frequency, short wavelength electromagnetic waves - wavelength is roughly the same size as the diameter of an atom

Question 2

How do X-rays work?

What can they be used for?

Answer 2

They are transmitted by (pass through) healthy tissue, but are absorbed by bones and metal

X-ray photographs can be used to diagnose many medical conditions such as bone fractures or dental problems

Question 3

How are X-rays formed electronically?

Answer 3

Using charge-coupled devices (CCDS), which are silicon chips that are divided up into a grid of millions of identical pixels. CCDS detect X-rays and produce electronic signals which are used to form high resolution images

Question 4

What uses X-rays?

Answer 4

Computerised axial tomography (CT) scans use X-rays to produce high resolution images of soft and hard tissue

Question 5

How can X-rays be used to treat cancer?

Answer 5

X-rays can cause ionisation - high doses of X-rays will kill living cells, therefore they can be used to treat cancers as they are carefully focused and are at the the right disease to kill the cancer cells without damaging normal cells

1) X-rays are focuses on tumour using a wide beam
2) This beam is rotated round the patient with the tumour at the centre
3) This minimises the exposure of normal cells to radiation

Question 6

How do radiographers take precautions to minimise radiation dose?

Answer 6

• They wear lead lead aprons, stand behind a lead screen or leave the room during scans
• Lead is used to shield areas of the patient body that aren’t being scanned and the exposure time is kept to a minimum

Question 7

What is ultrasound?

Answer 7

A sound with a higher frequency than we can hear
Electrical systems are made which produce electrical oscillations of any frequency, these can be easily converted into mechanical vibrations to produce sound waves of a higher frequency that the upper limit of human hearing (this is called ultrasound)

Question 8

How are ultrasound waves used in medicine?

Answer 8

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 stones and turns it into sand-like particles. These particles then pass out of the body in the urine.

Pre-natal scanning of a fetus - ultrasound waves can pass through the body, but whenever they reach a boundary between two different media (like fluid in the womb and the skin of the fetus) some of the wave is reflected back and detected. The exact timing and distribution of these echoes are processed by a computer to produce a video image of the fetus

Question 9

Pros and cons of ultrasound, X-rays and CT scans:

Answer 9

Pros of ultrasound:
• The waves are non-ionising and safe

Cons of ultrasound:
• Images are fuzzy, which makes it harder to diagnose

Pros of X-rays:
• Images are clear (of bones and metal)

Cons of X-rays:
• X-rays are ionising and can cause cancer if you’re exposed to a high dosage
• Not safe to use on developing babies

Pros of CT scans:
• Images are detailed and can be used to diagnose complicated illnesses
• High quality 3D images can also be used in the planning of complicated surgery

Cons of CT scans:
• Use a lot more X-ray radiation, so the patient is exposed to even more ionising radiation