Radiation physics 1 Flashcards
1
Q
What are x-rays
A
- Part of the electromagnetic spectrum
- Travel in straight lines at the speed of light
- Can travel through materials and through a vacuum
2
Q
How is the x-ray produced
A
An electron beam is produced from a cathode which hits an anode and produces an x-ray beam
3
Q
Describe what happens at the cathode
A
- An electric current is passed through the filament, heating it up
- Some electrons get enough energy to sit in a cloud surrounding it - this is called thermionic emission
- Electrons from the cathode at a high voltage are attracted to the positive anode
4
Q
What an increase in cause the number of x-rays to increase
A
- Increasing current
- Increasing time
- Increasing mass
5
Q
Explain how x-ray images are formed
A
X-rays can be
- Transmitted: travel through the patient to the detector
- Scattered: X-rays travel into the patient and scattered at different angles
- Absorbed: energy deposited into the patient; photoelectric effect; compton scatter
6
Q
Describe the photoelectric effect
A
- X-ray photon knocks an electron out, so a photon is scattered
- Reduces contrast in the image
7
Q
Describe the compton scatter
A
- Incoming x-ray photon knocks an electron out, so a photon is scattered
- Reduces contrast in the image
