Module 2

Question 1

An atom is a ______ with a ________ and _________ that are _______

Answer 1

Fundamental unit of matter
Central nucleus (positively charged)
Orbiting electrons
Negatively charged

Question 2

Describe ionization (production of ions)

Answer 2

Process of converting an atom (neutrally charged) into ions (electrically unbalanced) by loosing an electron

Question 3

Differentiate radiation from radioactivity

Answer 3

Radiation: formation of energy in the form of waves or particles

Radioactivity: a substance with unstable atoms or elements that undergo spontaneous disintegration or decay

Question 4

Describe x-radiation

Answer 4

Conversion of electric energy to radiation

Question 5

List the properties of x-radiation

Answer 5

Invisible
Consists of energy (photons)
Travels in lines at the speed of light
Moves in form of transverse (small) waves
Penetrates tissues/structures
Affects film emulsion producing latent image
Can affect/impact living tissue

Question 6

Review parts of the x-ray tube head and the x-ray tube

Answer 6

Tube head: Aluminum disks, lead collimator, PID, tube head seal, x-ray tube, insulating oil, unleaded glass window, and metal housing of x-ray tube head

X-ray tube: Tungsten filament, molybdenum cup, electron stream, tungsten target, copper stem, vacuum, x-ray beam, and lead-glass housing

Question 7

Describe the purpose of transformers

Answer 7

Transformers change the alternating current in the machine to decrease/increase the typical 110 volts that enter the machine when plugged into the wall

Question 8

Describe the step-down transformer

Answer 8

mA circuit is part of the step-down transformer
Decrease the wall outlet voltage from 110 volts to 3-5 volts in the filament circuit
When turned on the filament in the cathode (-) terminal heats up and produces an electron cloud

Question 9

Describe the step-up transformer

Answer 9

kVp circuit is part of the step-up transformer
Increases house voltage of 110 volts to 65,000-100,000 volts (65-100 kVp)
When exposure button is hit, the (-) electrons are attracted to the anode (+) and high speed electrons hit the tungsten target and then leave the tube

Question 10

Explain the process in which x-rays are produced within the x-ray tube

Answer 10

Machine is turned on
The tungsten filament in the cathode (-) forms and electron cloud
When the exposure button is activated the high voltage circuit is completed
Electrons are attracted across the tube head to the tungsten target on the anode (+)
X-rays are produced when the high speed electrons strike the tungsten target
X-rays are then directed out of the tube head because of the angled tungsten target so you can take an image on the film/sensor

Question 11

In the process of x-ray production, how much energy is converted into x-rays and how much is converted into heat?

Answer 11

1% x-rays

99% heat

Question 12

Explain Bremsstrahlung (general) and characteristic radiation

Answer 12

Bremsstrahlung: “braking radiation” high-speed electrons suddenly stop when they hit the tungsten target in the anode

Characteristic: produced when a high-speed electron dislodges an inner-shell electron from the tungsten atom and causes ionization of that atom

Question 13

Which type of radiation occurs most frequently within the dental x-ray tube?

Answer 13

Bremsstrahlung (70%)

Question 14

When does Characteristic radiation occur?

Answer 14

70 kVp or above

Question 15

Describe primary radiation

Answer 15

Penetrating x-ray beam that is produced at the target and exits the tube head; useful beam

Question 16

Describe secondary radiation

Answer 16

Created when the primary beam interacts with matter (skin, bones, teeth, etc); less penetrating than primary radiation

Question 17

Describe scatter radiation

Answer 17

Form of secondary radiation and is the result of x-rays that have been deflected by interaction with matter; usually absorbed by construction materials

Question 18

Describe the possible interactions of x-rays with matter

Answer 18

X-rays can pass through the pt without any interaction
X-ray photons can be completely absorbed by the pt
X-ray photons my be scattered