Radiology-Pan Principles

Question 1

Tomography

Answer 1

• Images one layer/section of body and blurs other planes

Question 2

Focal Trough

Answer 2

• 3D curved zone or image layer
• structures within zone are well defines
  
  • Outside zone=Blurred
• determined by imaging mechanism
• some units, can select shape and size to better fit maxillomandibular anatomy

Question 3

Center of rotation

Answer 3

• tube head and detector rotate around
• contemporary Pan use continuously moving center of rotation
• located off side of arch
  
  • away from area being imaged
  • structures close to image receptor=sharp image
  • Structures close to x-ray tube=distorrted & out-focused shadow

Question 4

How is the image formed?

Answer 4

Sequentially

Question 5

Advantages

Answer 5

• Broad coverage of facial bones and teeth
• quick and easy acquisition
• works for limited mouth opening or can’t tolerate intraoral imaging
• low radiation dose
• good for patient education

Question 6

Disadvantages

Answer 6

• Lower resolution than intraoral
• Distortion
• Magnification
• Superimposition
• requires accurate patient positioning

Question 7

Image distortion

Answer 7

• distortion of shape and size
• distortion affected by:
  
  • beam angle
  • location of objects relative to focal trough
  • patient positioning
• Limitations for linear measurements
  
  • horizontal
  • angular

Question 8

Image distortion: Metal ring positioned:

in focal trough

5mm posterior to focal trough

5mm anterior to focal trough

Answer 8

• In focal trough
  
  • round ring
• 5mm posterior:
  
  • flattened ring
• 5mm anterior:
  
  • ovoid ring

Question 9

Magnification

Answer 9

• magnified 20% horizontal & Vertical when in focal trough
• Horizontal magnification
  
  • object move away from focal trough
  • degree of magnification is greater in anterior than posterior
  • horizontal measurements unreliable on pan
• Vertical magnification
  
  • constant throughout image if positioning is correct

Question 10

Applications of Pan

Answer 10

• overall eval of dentition
• eval:
  
  • tooth eruption, impaction
  • TMJ
  • intraosseous pathology
    
    • infection
    • cysts
    • tumors
  • Dentomaxillofacial trauma
  • Abnormal developement

Question 12

Real Image

Answer 12

• lying b/w center of rotation & receptor

Question 13

Ghost Image

Answer 13

• b/w center of rotation & x-ray tube

Question 14

Double Image vs Real Image vs Ghost Image

Answer 14

• Real Image
  
  • b/w center of rotation & receptor
• Ghost Image
  
  • b/w center of rotation and x-ray tube
• Double image
  
  • b/w center of rotation and receptor and posterior to center of rotation

Question 15

Features of Ghost Image

Answer 15

• Opposite side of real image
• Higher
• larger
• blurry

Question 16

What structures may generate Ghost images

Answer 16

• Ascending ramus
• Mandibular body and angle
• Hard palate
• Hyoid bone
• Cervical spine
• Metal accessories
  
  • earrings
  • hairpins
  • necklace

Question 17

Single vs Double Images: Midline structures may be projected in 2 ways

Answer 17

1. Single midline image
   
   1. anterior to center of rotation
2. Bilateral double image
   
   1. posterior to center of rotation

Question 18

Structures shown as single midline image

Answer 18

• Incisors
• anterior nasal spine
• Nasal Septum
• inferior nasal concha
• Soft tissue outline of nose
• incisive foramen

Question 19

Structures shown as bilateral double images

Answer 19

• Hard palate
• Soft palate
• Uvula
• Hyoid bone
• Epiglottis
• Cervical spine

Question 20

Systemic Viewing Zones of Interpretation: Draw

Answer 20