1. Basic Concepts of Other Imaging Modalities
Dent 5101

2. Body-section Radiography
A special radiographic technique that blurs out the shadows of superimposed structures
Object of interest less blurred
Does not improve the sharpness

3. Tube and Film Move in Opposite Direction

5. Tube and film move in opposite direction, and rotate about a fulcrum
The level of the fulcrum is the focal plain

6. Blurring Determined by: Distance of the tube travel
Distance from the focal plain
Distance from the film
Orientation of tube travel

7. Types of Tomographic Motions
Linear
Circular
Elliptical
Figure 8
Hypocycloidal
Trispiral

8. Panoramic Radiography

9. Panoramic Radiography
Obtained by rotating a narrow beam of radiation in the horizontal plane
The film is rotated in the opposite direction while the object (jaws) is stationary

11. Focal Trough
A 3-dimensional curved zone or image layer in which structures are reasonably well defined.

12. Types of Panoramic Machines
Panorex – Two centers of rotation. Interruption of exposure in the midline
Orthopantomogram – Three centers of rotation. Continuous image

13. Panorex Image

14. Orthopantpmograph

16. Image Intensification

17. Early Fluoroscopy Early fluoroscopy done by direct observation
Screen was poorly illuminated - image perception inadequate

18. Image Intensification
Image intensifier improved viewing of fluoroscopy

19. Intensifier Tube Four parts: Input phosphor and photocathode
Electrostatic focusing lens
Accelerating anode
Output phosphor

20. Intensifier Tube (Cont.)
Input phosphor: cesium iodide (CsI) or zinc-cadmium-sulfide.
Photocathode: A photo-emissive metal.
Electrostatic focusing lens: series of negatively charged electrodes—focuses the electron beam.
Output phosphor: Provides thousand-fold more light photons.

21. Intensifier Tube
Used in:
Sialography
Arthrography

22. Digital Imaging

23. Digital Imaging
Conventional film-intensifying screen radiograph - analog image.
Digital radiograph—film-less.
Conventional films can be digitized, with a likelihood of loss of information.

24. Photostimulable Phosphor (PSP)
Storage phosphor
Indirect Digital Radiography
Similar to the intensifying screen phosphors
Difference - PSP traps a significant number of electrons in its phosphor, which is later read by a laser beam

25. Photostimulable Phosphor (PSP)

29. Charge-coupled Devices
An amorphous silicon wafer containing an array of pixels (picture elements)
Each pixel acts as a capacitor storing charge
On radiation exposure, electric charge is deposited in the pixels proportional to the intensity of the beam
The variation in charge deposition can be digitally converted to an image

30. Pixels
Each square (pixel) has its own color (numerical value)

32. Pixel Array

33. CMOS Complimentary Metal Oxide Semiconductor Principle similar to CCD
Simpler circuit design

34. CCD, CMOS

35. Resolution
Ability to identify two different objects that are close to each other
D-speed films: >10 line pair/mm
Digital images:7-10 line pair/mm
Eyes: 4-6 line pair/mm

36. Digital Subtraction Shows changes in an area over time
Requires two films exposed with similar geometry

37. Digital Subtraction Two radiographs are obtained Identical position
One superimposed over another
Differences in two images identified digitally
Allows identifying changes in hard tissue that occurred between the two examinations

38. Radiation Dose Full Mouth Series D Round 8 days E 4 days Digital
Receptor
Collimation
Background equivalent D
Round
8 days E
4 days
Digital
2 days
Rectangular
1 day

39. Image Processing/Reconstruction
To improve diagnostic accuracy
May improve the diagnosis of one disease, while obscure another
Fraud

40. Digital Radiography: Advantages
Instant images
Consistent quality
High signal/noise ratio
Image Manipulation
Lower radiation dose

41. Disadvantages Lower resolution Quality depends on monitor and printer
Print quality often not optimal
Higher initial cost
Unwanted manipulation of images