Image Intensified Fluoroscopy Flashcards
To aid the radiologist dynamic studies of the human body, “real time” imaging
Fluoroscopy
who invented the fluoroscope (calcium tungsten screen)
Thomas Edison
When did Thomas Edison invent the fluoroscope
1896
studied on poor illumination from fluoroscopic screen
William Chamberlain
When did William Chamberlain studied on the poor illumination from fluoroscopic screen
1941
development of image intensifier tube
1950s
measured in units of Lamberts (L) and millilamberts (mL)
Illumination
Radiographs are viewed under illumination level to?
10 to 1000 mL
Human Vision
- Rods and cones
- Photopic and scotopic vision
- Visual acuity
When light appears, the Iris?
The iris contracts
When dark, the iris?
dilates
primarily used in daylight vision
Cones
otherwise called as daylight vision
photopic vision
Cones can perceive?
color
while cones can perceive color, rods are?
color blind
are for night vision
Rods
otherwise called as night vision
scotopic vision
the ability to perceive fine details
Visual acquity
Components of the Fluoroscopic Chain
- Image Intensifier
- Recording System
- Viewing System
Electronic vacuum tube that converts the remnant beam to light then to electrons, then back to light, increasing thhe light intensity in the process
Image Intensifier
The Image intensifier converts the remnant beam to?
light then back to electrons, the back to light, increasing the light intensity in the process
It is a complex electronic device that receives the remnant x-ray beam, converts it into light and increases the light intensity
Image Intensifier
The Image Intensifier allows a means to indirectly view the?
Fluoroscopic Image
The image intensifier tube is approximately ?
50 cm long
A potential difference of about ________ is maitained across the tube between photocathode and the anode so that electrons will be accelerated to the anode
25,000 volts
Basic Parts of an Image Intensifier
- Input Phosphor
- Photocathode
- Accelerating Anode
- Output Phosphor
- Electrostatic Focusing lenses
Converts energy to visible light
Input Phosphor
Material used in Input Phosphor
Cesium Iodide (CsI)
CsI crystals are tightly packed as
100 to 200 micrometer layer
Composed of Cesium and antimony compounds
Photocathode
Emission of electrons when stimulated by light from the Photocathode
Photoemission
Maintains constant potential of approximately 25 kV
Accelerating Anode
Electrons interact to produce light
Output Phosphor
Output Phosphor is usually made of?
silver-activated zinc-cadmium sulfide
Engineering aspects of maintaining proper electron travel.
Electron Optics
Not really lenses, but are negatively charged plates along the length of the II tube.
Electrostatic Focusing Lens
The Electrostatic Focusing Lens are located along the?
length of image intensifier tube
High energy electrons that interact with the output phosphor each result in substantially more light photon than was necessary to cause their release at the photocathode.
Image Intensifier Tube
The length of the Image Intensifier Tube is?
50 cm in length
The diameter of the Image Intensifier Tube is approximately ?
15 to 56 cm
represents the tube’s conversion efficiency
Flux Gain
Flux gain is the ratio of?
number of light photons at the output phosphor to the number of x-rays at the input phosphor
number of output light photons
——————————————-
number of input x-ray photons
is due to the multiplication of the light photons at the output phosphor compared with the x-rays at the input phosphor and the minification from the input phosphor to output phosphor
increased illumination of the image
The ratio of Minification Gain is the
the square of the diameter of the input phosphor to the square of the diameter of the output phosphor.
input phosphor diameter^2
—————————————
output phosphor diameter^2
Minification Gain as a characteristic makes the image brigher because the same number of electrons is being?
concetrated on a smaller surface area
In Minification Gain, the output phosphor size is fairly standard at
2.5 or 5 cm
In Minification Gain, the Input phosphor size varies from?
10 to 35 cm
Brightness gain of most image intensifiers is
5000 to 20,000
Is an expression of the ability of an image intensifier tube to convert x-ray energy into light energy and increase the brightness of the image in the process
Brightness Gain
Formula of Brightness gain
Brightness Gain = minification gain x flux gain
is an expression of the luminance at the output phosphor divided by the input exposure rate
Conversion Factor
Recommended by the ICRU to quantify the increase in brightness created by II.
Conversion Factor
Exposure Rate and Age of the II
an image intensifier ages, the exposure rate to the patient increases to maintain brightness.
