Transcript Slide 1

RAD 354 Chapt. 25 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 xrays exiting the patient to low level light the
radiologist could view
Image Intensified Fluoro
II
II Tube Parts
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Input phosphor
Photocathode (photo emission)
Evacuated glass envelope
Electrostatic focusing lens (neg. charged!!!)
Anode
Output phosphor
II Fluoro
• Increased image brightness with II over
“direct” fluoro is the biggest advantage of II
– Maintains OD 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 mA and uses
highest optimum kVp
• Back up timer = 5 minutes
• Protective Fluoro measures
– Bucky slot cover
– Lead curtain
– Lead gloves and aprons (secondary barriers)
– Distance
Gain
• Minification gain (ratio of input to output
sizes)
• Flux gain – ratio of # of inpupt 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” {27/17cm})
– Some have TRI sizes input (trifield tubes
27/17/12cm)
• The crossover of the electron stream distance from the
output phosphor determines the amount of
magnification
• Mag mode = BETTER SPATIAL RESOLUTION, better
contrast, HIGHER pt. dose!
TV Monitoring
• Must “couple” the output phosphor to a TV
camera tube or photomultiplier tube
– Vidicon is the MOST frequently used tube –
plubicon and image orthocon are also tube types
– Fiber optics and beam splitters are used to help
direct the digitized image to the various
destinations (TV monitor, photo spot film, VCR/CD
recorder, cine camera)
Vidicon Camera (tube)