Radiographic Imaging (3) Flashcards
What are the two radiographic imaging methods?
- filmless
- permanent
List the three early methods of filmless radiography:
- Fluoroscopy
- Electronic Fluoroscopy
- Xeroradiography
List the three types of permanent radiography:
- Photographic films and screens
- Fluorescent and Phosphorescent imaging plates
- Direct Digital and Computed
Fluoroscopy
Examined by direct observation of the fluorescent screen, using shielded cabinets.
- viewed from the backside of the screen or mirror
Electronic Fluoroscopy
Fluoroscopy with increased brightness and definition, increased safety, viewed on a close-circuit television
Xeroradiography
Photocopy machine like, selenium coated electro-statically charged plate, produced when the charge was depleted and a developing powder was applied to an imaging paper.
Photographic films and screens
viewed as photonegative, transparent polyester material coated with emulsion that is light sensitive, used with screens to aid in image formation.
- film is sandwiched between screens
Types of screens
- lead
- fluorescent
- fluoro-metallic
Intensification factor of lead screens
2-3
Effects of lead screens (3)
- increases photographic action, electrons emitted and secondary radiation generated in lead
- absorb longer wavelengths
- intensify primary radiation
Alloys for lead screens
6% antimony and 94% lead, providing better wear and abrasion resistance.
Use of lead screens below ___kV may actually provide an image quality reduction and overall poor contrast
150kV
When not using screens at voltages above 150kV image may appear to be ____.
mottled
Fluorescent screens
Also referred to as Fluorescent salt-screens made of finely powdered or crystallized phosphor crystals miked with a binder to form a coating.
- absorb radiation and immediately emit light
Intensification factor for Fluorescent screens
10-200
Why aren’t Fluorescent screens used often?
produce a screen mottle, softer outline and graininess due to non-uniform distribution of light
Fluorescent screens should not be exposed to the ____ _____ of primary radiation.
Full intensity of the primary radiation, the tend to develop and afterglow or become discoloured.
Fluoro-metallic Screens
Middle ground between lead and fluorescent.
lead foil coated with phosphor
Intensification factor of Fluoro-Metallic screens
5-150
Screens for high energy radiation
energy ranges greater than 1MeV use copper or steel screens.
Linear accelerators 5-8MeV use thick copper screens.
Digital Radiography
Filmless
flat curved panels constructed of micro-electric sensors or phosphor screens
Benefits of Digital Radiography
- requires less radiation for image generation
- images can be enhanced digitally
- easy to save and share
- instantaneous
- built in recognition programs
- use panels repeatedly
Flat panel detectors are referred to as:
Digital Detector Arrays (DDA’s)
- Complementary metal-oxide-semiconductor
- Linear diode arrays
- Amorphous selenium flat panel
- Amorphous silicon flat panel
What are DDA’s
Electronic devices that convert radiation into an array of analog signals, digitalized and transferred to a computer display.
radiation penetrates into an electronic signal, converted into visible light, converts light into an electronic charge, photodiode signifies as pixel digitally read by low-noise electronics.
Computed Radiography
Flexible phosphor imaging plate used with a laser scanning device for image processing.
- plate is flexible, placing an a standard film cassette, utilized similarly
- phosphors when exposed absorb radiation, scanned by a laser to make phosphors emit blue light, which is collected by a photomultiplier, amplified and digitalized for a computer (photo-stimulated luminescence)
