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Basic Concepts of Other Imaging Modalities. Dent 5101. 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. Tube and Film Move in Opposite Direction.

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body section radiography
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
slide5
Tube and film move in opposite direction, and rotate about a fulcrum
  • The level of the fulcrum is the focal plain
blurring
Blurring
  • Determined by:
    • Distance of the tube travel
    • Distance from the focal plain
    • Distance from the film
    • Orientation of tube travel
types of tomographic motions
Types of Tomographic Motions

Linear

Circular

Elliptical

Trispiral

Hypocycloidal

Figure 8

panoramic radiography1
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
focal trough
Focal Trough
  • A 3-dimensional curved zone or image layer in which structures are reasonably well defined.
types of panoramic machines
Types of Panoramic Machines
  • Panorex – Two centers of rotation. Interruption of exposure in the midline
  • Orthopantomogram – Three centers of rotation. Continuous image
early fluoroscopy
Early Fluoroscopy
  • Early fluoroscopy done by direct observation
  • Screen was poorly illuminated - image perception inadequate
image intensification1
Image Intensification
  • Image intensifier improved viewing of fluoroscopy
intensifier tube
Intensifier Tube
  • Four parts:
    • Input phosphor and photocathode
    • Electrostatic focusing lens
    • Accelerating anode
    • Output phosphor
intensifier tube cont
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.
intensifier tube1
Intensifier Tube
  • Used in:
    • Sialography
    • Arthrography
digital imaging1
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.
photostimulable phosphor psp
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
charge coupled devices
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
pixels
Pixels
  • Each square (pixel) has its own color (numerical value)
slide33
CMOS
  • Complimentary Metal Oxide Semiconductor
  • Principle similar to CCD
  • Simpler circuit design
resolution
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
digital subtraction
Digital Subtraction
  • Shows changes in an area over time
  • Requires two films exposed with similar geometry
digital subtraction1
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
image processing reconstruction
Image Processing/Reconstruction
  • To improve diagnostic accuracy
  • May improve the diagnosis of one disease, while obscure another
  • Fraud
digital radiography advantages
Digital Radiography: Advantages
  • Instant images
  • Consistent quality
  • High signal/noise ratio
  • Image Manipulation
  • Lower radiation dose
disadvantages
Disadvantages
  • Lower resolution
  • Quality depends on monitor and printer
  • Print quality often not optimal
  • Higher initial cost
  • Unwanted manipulation of images