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– Bucky slot cover– Lead curtain– 5 min. back up timer– Lead gloves and aprons (5mm pb) – secondary barriers– Distance