LO3

Question 1

What factors affect images?

Answer 1

Intensity of X-ray beam.

Operator variables:

• Exposure time
• mA vs time
• kVp - intensity
• Set up of film/sensor

Question 2

How does exposure time affect images?

Answer 2

Directly proportional to the effect on X-rays.

Question 3

How does mA vs time affect images?

Answer 3

Direct effect on quantity of photons.

mA x time (seconds) = mAs
- mA and seconds = inversely proportional to maintain same quantity of radiation.

Question 4

How does kVp affect images?

Answer 4

• Homogeneous – photons of identical energy.
• Heterogeneous – photons of varying energy.
• Quality – energy of photons.
• Quantity – number of photons.
• Intensity – total energy in beam (quality x quantity/area x time).
• kVp determines maximum energy of X-rays produced (quality).
• Higher kVp = higher kinetic energy of electrons higher energy in X-rays.

Hard X-rays = more penetrating.
Soft X-rays = low energy.

Question 5

How does setup of film/sensor affect images?

Answer 5

Intensity of beam decreases as distance from source increases.

Question 6

Describe the structure of the X-ray tube

Answer 6

• Cathode (-ve) = heated lament of tungsten – electron source.
• Anode (+ve) = target (small piece of tungsten) in angled face of large copper block to allow efficient heat removal.
• Focusing/position indicating device (PID) aims stream of electrons at focal spot on target.
• Kilovoltage peak - high-voltage between cathode and anode accelerates electrons from negative filament to positive target.
• Current flows from cathode to anode – measure of quantity of electrons being accelerated.
• Surrounding lead casing absorbs unwanted X-rays as radiation protection measure (X-rays emitted in all directions).
• Surrounding oil = heat removal.

Question 7

What are bitewings for?

Answer 7

• Interproximal caries.

- Condition of crestal alveolar bone.

Question 8

What are vertical bitewings for?

Answer 8

Patients with advanced periodontal disease.

Question 9

What are technique errors associated with bitewings?

Answer 9

• Overlap.
• Improper film placement.
• Cone cutting.

Question 10

How does cone cutting occur?

Answer 10

If X-ray tube isn’t positioned properly, X-ray beam may not cover entire film – results in white area on film.

Question 11

How does radiolucent areas show up?

Answer 11

Remnant radiation collected by sensor produces darker density areas or radiolucent areas.

Question 12

What are periodicals used for?

Answer 12

Show alveolar bone and root structure.
Endodontics.
Before extractions/crown/bridge prep.
Trauma.
Periodontal disease.

Question 13

What techniques are associated with PAs?

Answer 13

• Paralleling.

- Bisected angle.

Question 14

What difficulties are associated with PAs?

Answer 14

Mandibular 3rd molars.
Gagging.
Endodontics.
Edentulous alveolar ridges.
Children.
Patients with disabilities.