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When was fluoroscopy discovered?
1896
Who discovered the fluoroscope?
Thomas Edison
Red Adaptation Goggles
Invented in 1916 by Wilhelm Trendelenburg to help physicians’ eyes adapt for greatest visual acuity
Who invented the image intensifier?
Dr. John Coltman in 1916
What can fluoro help diagnois?
Pathologies of soft tissue structures
Fluoro mA range
0.5-5.0 mA
Diagnostic tube mA range
50-1,200 mA
What is the purpose of the image intensifier?
Improve image brightness
Glass Envelope
Protective enclosure which maintains a vacuum seal and lined with 2mm of lead
What is the material of the input phosphor?
Cesium Iodide (Csl)
Input Phosphor (screen)
Converts x-ray photons into light photons
What is the material of the photocathode?
Cesium and antimony compounds
Photocathode
Bonded to input phosphors; converts light photons to electrons via photoemission
What is the charge of the electrostatic focusing lenses?
Negative
Electrostatic focusing lenses
Negatively charged; focus electrons towards the anode and accelerate the electrons
What is the charge of the anode?
Positive
Anode (accelerating)
Positively charged, layers of aluminum with hole in center to attract electrons from photocathode
What is the material of the output phosphor?
Cadmium sulfide
Output Phosphor
Small fluorescent screen that converts electrons back into light photons; the exit light carries the latent image in a minified form
Magnification
An increase in voltage causes a smaller diameter of input phosphor and shifts the focal point closer to the input phosphor
Benefits of magnification
Reduces contrast problems and increases spatial resolution
Magnification Factor
Input phosphor diameter / Input phosphor diameter during mag mode
What does magnification do the the x-ray tube?
Causes excessive heat
Minification gain
Input phosphor diamter2 / output phosphor diameter2
Flux gain
# of light photons from output phosphor / # of x-ray photons striking input phosphor
What does flux gain represent?
Tube’s conversion efficiency
Total brightness gain
The overall increase in image brightness achieved by an image intensifier
Total brightness gain will decrease roughly _____ each year due to aging of the tube
10%
Total brightness gain equation
Flux gain x minification gain
What is another method to identify brightness gain?
Conversion factor
Conversion factor
Intensity of output phosphor(cd/m2)/ exposure rate at input phosphor (mR/sec)
Conversion factor is equivalent to approximately _____ the brightness gain
1%
Coupling
Takes light from II to next component in imaging chain
Fiber optics
Bundle of glass fibers that connect to a camera tube/CCD
Charged-Couple Device (CCD)
In indirect DR, light sensitive semiconductor with fiber optics mounted to II or FPD with a high DQE and SNR, increased resolution
Complementary Metal-Oxide Semiconductor (CMOS)
In indirect DR, two stacked together to create electron hole pairs
Automatic brightness system (control)
Monitors the electrical current between the photocathode and anode of the II, or by measuring output intensity
Continuous fluoroscopy
30 frames a second, typically 0.5-4 mA
Low dose continuous fluoroscopy
Halves the mA value as selected by AERC; saves patient dose with minimal visualization of noise
High dose continuous fluoroscopy
Can be used for increased penetration of the patient; increased patient dose
Pulse width
Exposure length of each pulse (measured in msec)
Pulse interval
Beam off time
Pulse height
Determined by mA
Frame rate
Number of images obtained per second
