Chapter 27 - Medical Physics

Question 1

What are the components of an X-ray tube

Answer 1

• Cathode
• Anode

Question 2

What is the role of an anode in an X-ray tube

Answer 2

A target metal, often tungsten, where the electron beam is aimed. It is propelled by a high voltage across the tube, which accelerates the electrons towards it.

Question 3

What is the role of a cathode in an X-ray tube

Answer 3

Emits a focused beam of electrons when heated by an electric current passing through the filament, shapes like a cup to direct electrons efficiently

Question 4

How do you increase the X-ray beam intensity

Answer 4

1) Increase the accelerating potential difference, heightening the energy of the electrons.
2) Boost the heating current of the filament to produce more electrons per second

Question 5

Why do X-rays diminish in intensity?

Answer 5

• Absorption
• Scattering

Question 6

Why do we X-ray bones?

Answer 6

Bones absorb X-rays more efficiently than soft tissue, making them more prominent on X-rays images.
Contrast can be further improved by administering contrast media, which are visible on X-rays and help in visualising internal structures

Question 7

How does CAT scans work?

Answer 7

• Rotating X-ray beam and detected to capture images of body slices
• These images are processed to produce detailed cross-sectional views of soft tissue
• Combining multiple slices generate 3D models of internal body structures

Question 8

What are the key features of medical tracers?

Answer 8

• Tracers provide insights into both the structures and function of organs, unlike traditional X-rays which only show structure
• They concentrate in areas with high metabolic rates, indicating active processes or abnormalities.
• Specific tracers are designed to target distinct tissues and biological functions

Question 9

Application of Medical tracers

Answer 9

• Areas with reduced blood flow can indicate heart tissue damage or blockages in the coronary artery.
  Tracers help identify heart attacks by highlighting areas of dead muscle tissue.
• Due to their high metabolic rate, cancer cells consume more glucose, making glucose-based tracers ideal for identifying tumours.
• Tracers are used to map cerebral blood flow and metabolic activity, valuable for diagnosing disorders like Alzheimer’s and Parkinson’s disease.

Question 10

Key properties of medical ultrasound

Answer 10

• Frequencies span from 1 to 15 MHz
• Upon encountering a boundary between different materials, ultrasound wave is subject to refraction and reflection
• It’s the reflected waves that are used to create images