Transcript RAD 350 Chapt. 25 Fluoroscopy

RAD 350 Chapt. 25 Fluoroscopy
• Fluoro’s primary function is to enable one to
view the patient in “real time” with dynamic
motion
• Invented by Thomas Edison in 1896
– Utilized a conventional x-ray unit with a
fluorescent screen that would convert the x-rays
(remnant beam) 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 control)
Image Intensifier
• Dang it – I couldn’t find a picture, so draw the
dang thing!
– Input phosphore
– Photocathode (photo emission)
– Evacuated glass envelope
– Electrostatic focusing lens (neg. charge)
– Anode
– Output phosphor
Image intensifier
(I lied – here is the picture)
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’s distance from
the output phosphor determines the amount of
magnification
• Mag mode = better spatial resolution, better contrast
resolution and HIGHER PT. DOSE!!!
TV/Monitor Viewing
• Must “couple” the output phosphor to a TV
camera tube or CCD/TFT
– Vidicon tube is the MOST frequently used tube
• Image orthocon and plumbicon are also used
Other viewing/imaging devices
• Fiber optics and beam splitters are used to
help direct the digitized image to the various
destinations (TV monitor, photospot film
camera, VCR/DVD recorder, cine camera)
Eyes use rods and cones
• Photopic vision – daylight vision uses the
CONES
• Scotopic Vision - night time vision and uses
the RODS
Conventional Fluoro Techniques
(not digital fluoro)
• Fluoro usually is operated at 5 mA and uses the
highest OPTIMUM kVp
• Protective Fluoro Measures
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Bucky slot cover
Lead curtain
5 min. back up timer
Lead gloves and aprons (5mm pb) – secondary
barriers
– Distance