Special Radiographic Procedures

1
Special Radiographic Procedures

• Chapter 21

2
Tomography

• An examination designed to bring into focus only
  the anatomic structure lying in a plane of
  interest while blurring structures on either side
  of that plane
• Use the movement of the tube and film to create
  image

3
5 types of Tomography

• Linear
• Circular
• Elliptical
• Hypocycloidal
• Trispiral

4
Terms

• Fulcrum
• The imaginary pivot point about which the x-ray
  tube moves
• Objective plane
• The plane that is imaged clearly

5
Terms

• Tomographic angle or arch
• The angle of movement between the tube and the
  image receptor
• Section thickness
• Determined by the tomographic angle and the
  amount of movement in the tube
• The larger the angle the thinner the cut
• The more the tube moves, the thinner the cut

6
Zonography

• Tomography which uses a very small (less than 10
  degree angle)
• Produces a very thick cut
• Mainly used as survey instruments

7
Panoramic Tomography

• Developed to study curved structures of the head
• Today mainly used in evaluating the mandible and
  in dental radiography
• Uses a special film in which the film and tube
  rotates around the patients head to produce
  image

8
Magnification radiography

• Enhances visualization of small vessels by
  increasing OID or decreasing SID
• Useful to use a small focal spot for detail
• Biggest disadvantage, is often an increase in
  patient does
• Still widely used in mammography

9
Calculating Magnification and Magnification
factors

• MF SID Image Size
• SOD Object Size

10

• Given an SID or 100 cm, an OID of 10 cm and an
  image size of 3.2 cm, what is the true object
  size?
• MF SID Image Size
• SOD Object Size

11

• 100 3.2
• 100-10 OS
• 100x 3.2 x 90
• 100 x 288
• x 288/100
• x 2.88 cm is the object size

12

• What is the magnification factor?
• MF SID
• SOD
• MF 100
• 100-10
• MF 1.1.