Radiation Quality (3)

Question 1

Thermionic Emission

Answer 1

The electron emission from the filament - function of temperature.
- higher the current, greater the temperature, greater electron emission.

Question 2

What is the primary means of increasing beam intensity? (x-ray)

Answer 2

Adjusting milli-amperage

Question 3

How can we control the wavelngth or “quality” of x-radiation?

Answer 3

Adjusting voltage.

• higher voltage, greater electron velocity, enabling a greater penetration ability.
• more electrons striking the target per unit of time

Question 4

Mono-energetic

Answer 4

x-rays are not mono energetic, meaning they are not emitting having the same intensity in all directions from the focal spot.

Question 5

How are x-rays shaped when they are emitted?

Answer 5

• diverge in a conical shape
• amount of divergence depends on: target angle, target and focal spot size.
• central beam exhibits 100% beam intensity at 20° from the target.
• maximum intensity at 32°

Question 6

Heel effect

Answer 6

Intensities decrease rapidly toward the edge of the radiation cone,

intensities of the cathode side see a slight increase on the interior and steady decrease towards the edge - heel effect

Question 7

What occurs on film if an image is unsharp?

Answer 7

fuzziness around the outline also known as: Penumbra

Question 8

What is Penumbra dependant on?

Answer 8

• geometrical factors
• size of radiation source
• distance source-to-objects
• source-to-film distance
• top of object-to film distance

Question 9

What is ideal for the factors affecting Penumbra?

Answer 9

• radiation source is close to a point source (small)
• source-to-object distance is great
• top of object-to-film distance is small

Question 10

The radiation/source of energy should be _____ than the object

Answer 10

smaller

Question 11

Focal sizes for x-rays

Answer 11

1.5-5mm diameter

Question 12

Focal sizes for gamma rays

Answer 12

2.5-4.5mm diameter