Physical Properties Of An X-ray Beam

Question 1

What is radiation?

Answer 1

-transfer of kinetic energy that passes from one location to another
🔹x-ray is the emission of energy through matter as a wave and/or particle
🔹matter that intercepts or absorbs radiation is said to be irradiated
-when sound waves for through a wall is that considered radiation?
🔹yes! it is a transfer of energy

Question 2

Amplitude

Answer 2

Intensity of wave defined by its maximum height

Question 3

Period

Answer 3

Time required to complete one cycle

Question 4

Electromagnetic spectrum

Answer 4

• low frequencies, long wavelengths are at the bottom of the spectrum: radio waves, microwaves, light and ultraviolet
• high frequencies, short wavelengths are at the top of the spectrum: x-rays, gamma rays

Question 5

Wave particle duality

Answer 5

• x-ray photons can be described as both waves or particles
• can travel through space in the form of a wave
• can interact with matter as a particle of energy

Question 6

Wave theory

Answer 6

• electromagnetic waves do not require a medium

- electromagnetic waves travel in a vacuum

Question 7

Ionizing radiation

Answer 7

• ionizing radiation causes ionization of atoms
  
  • causes electrons to be ejected from an atom
  • this is the foundation of interactions in human tissue
• ion
  
  • electrically charged atom
  • caused by a loss or a gain of one or more electrons

Question 8

Ionization of an atom

Answer 8

• orbital electron and the atom are called an ion pair
  
  • electron is a negative ion, remaining atom is a positive ion
• orbital electron can:
  
  • bind with “+” ion of the original pair
  • bond with another atom
• last possibility can cause biological damage

Question 9

Excitation of an atom

Answer 9

-occurs with both ionizing and non ionizing radiation
🔹electrons are infused with energy
🔹jump to a higher energy shell
🔹electron will return to its original location
🔹excess energy is released as non-ionizing radiation
-difference from ionization
🔹electrons are not ejected
🔹just moved to a different level and then returned

Question 10

Alpha particle

Answer 10

• highly ionizing, short range in tissue
• less penetrating that beta particles
• external source of radiation (harmless)
• internal source of radiation (can be very damaging when absorbed, can intensely irradiate local tissue)

Question 11

Beta particle

Answer 11

• very high energy ejected at high speed

- penetrates matter to a greater depth than alpha with less ionization

Question 12

Sources of radiation

Answer 12

Natural
-terrestrial: earth, uranium and radium, radon (largest contributor of background radiation), bricks, concrete and gypsum all contain radon
-cosmic: sun and stars
-internal: human tissue has naturally occurring radionuclides
Man made
-medical imaging, industrial (nuclear accidents, mining etc)

Question 13

Absorbed dose

Answer 13

Measurement of energy transferred from ionizing radiation per unit mass of irradiated material

Question 14

Dose equivalent

Answer 14

Determined by multiplying the absorbed dose but a quality factor of the type of radiation. Used to compare dose of different types of radiation

Question 15

Inverse square law

Answer 15

Distance
-most effective means of protection from ionizing radiation
-more distance, less radiation intensity (spreads out like a flashlight beam)
-ISL states beam intensity is inversely proportional to square of the distance
-SID and radiation intensity
🔹2 x SID= 1/4th of radiation intensity
🔹3 x SID= 1/9th of radiation intensity
🔹4 x SID= 1/16th of radiation intensity