L1 Introduction to X-Ray Physics and Equipment

Question 1

What is dosimetry?

Answer 1

The measurement of ionising radiation in a given place or on a person.

Question 2

What is X-radiation?

Answer 2

High energy electromagnetic radiation.
High frequency.
Low wavelength.

Question 3

Define intensity.

Answer 3

Amount of radiation (per unit time and area)

Question 4

Define quality.

Answer 4

A measurement of the penetrating power (how likely is a photon to be absorbed)

Question 5

Define exposure.

Answer 5

Amount of radiation in a beam

Question 6

Define dose.

Answer 6

Amount of energy deposited in a subject (closely linked to exposure but not identical)

Question 7

Define a photon.

Answer 7

Photon = 1 individual X-ray

Question 8

Define attenuation.

Answer 8

Reduction in intensity

Question 9

How do X-rays work?

Answer 9

• X-rays ionise atoms within tissue, remove electrons from atoms

Ionisation is the basic cause of harm from radiation, it is the start point for cellular and tissue damage

Question 10

What are the 3 exposure factors?

Answer 10

• kVp: the tube volatge, often shorted to kV, 60kVp and higher used in dentistry, ideally 70kVp
• mA: the tube current (in milliamps, usually 15-20mA)
• s: exposure time

Question 11

What does a higher kV indicate?

Answer 11

More photons, and photons of highery energy.

Therefore increased beam quality and intensity.

Question 12

What does a higher mAs indicate?

Answer 12

More photons.

Therefore increased beam intensity.