Transcript RAD 254 Fluoroscopy

RAD 150
Fluoroscopy
Fluoro’s primary function is to
enable one to view the patient in
“real time” with dynamic (motion)
Fluoro was first invented by
Thomas Edison in 1896
• Utilized a conventional x-ray unit with a
fluorescent screen that would convert the
x-rays exiting the patient to low level light
the radiologist could view
Image Intensified Fluoro
II Fluoro
• Increased image brightness with II over
direct fluoro is the biggest advantage of II
– Usually controlled by “automatic brightness
control” (ABC) that the radiologist can preset
and control
Eyes use rods and cones
• Photopic vision – daylight vision uses the
CONES
• Scotopic vision - night time vision and
uses the RODS
Fluoro Techniques
• Fluoro usually is operated at 5 mAs and
uses highest optimum kVp
• Protective Fluoro measures
– Bucky slot cover
– Lead curtain
– 5 min back up timer
– Lead gloves and aprons (secondary barriers!)
– Distance
Image intensifier tube
• Dang it – I couldn’t find a diagram to
import here!!!!!!!
– Input phosphor
– Photocathode (photo emission)
– Evacuated glass envelope
– Electrostatic focusing lens (neg. charged!!!!)
– Anode
– Output phosphor
Gain
• Minification gain – ratio of input to output
sizes
• Flux gain – ratio of # of input PHOTONS to
output LIGHT PHOTONS
• Brightness gain (total brightness gain)=
minification gain X flux gain
Fluoro Magnification
• Most fluoro II units have dual input
phosphor sizes (9” and 6” [27/17 cm]
– Some have TRI – input (trifield tubes 27/17/12
cm)
• The crossover of the electron stream distance from
the output phosphor determines the amount of
magnification
• Mag mode = better spatial resolution,
better contrast resolution, HIGHER pt.
dose
TV Monitoring
• Must “couple” the output phosphor to a TV
camera tube
– Vidicon tube is MOST frequently used –
plumbicon also can be used
– Fiber optics and beam splitters are used to
help direct the digitized image to the various
destinations (TV monitor, photo spot film
camera, VCR/CD recorder, cine camera)