-
What is the primary function of fluroscopy?
visualize the motion of internal structures and fluids
-
What is C-arm usually referred to?
Usually referred to mobile fluroscopy
-
What does the C-arm do to the image receptor?
Allows image receptor to vary the OFD and gain maximum resolution while x-ray tube remains in position.
-
What part of flouroscopy equipment is the Carriage?
Arm that supports the equipment suspended over the table.
-
What is scotopic vision?
Rod vision used in dim light or complete darkness.
-
What is phototopic vision?
Vision that requires bright light or day light.
-
What does the carriage typically have?
Includes an image intesnifier, control for power to drive the cirrage, spot film selection, tube shutters, on/off dead man switch, blah blah
-
What is fluoro carriage usually referred to?
Usually refers to fluro room c arm.
-
Exposure will not occur until..
Carriage is returned to a full beam intercept position
-
What is the flouroscopic ma range? Why is it lower than typical diagnostic tubes?
Between .5 to 5.0 mA. It is lower because fluroscopic tubes are designed to operate for longer periods of time
-
Why is the tube target usually Fixed?
Its fixed to prevent a SOD of less than 15 inches.
-
Tubes can be operated by a foot pedal so that...
Operators will have both hands free to move the carriage and maniplate the patient.
-
What are imaging intesnficiation tubes for?
Designed to amplify the brightness of an image and to reduce patient dose while maintaining quality.
-
What kind of exposure technique is usually preferred in flurosocopy?
High kvp and low MA
-
How does the x-ray beam for fluroscopy work?
After it exits the patient, bema strieks the input screen of intesnifier.
-
What is the input phosphor screen intensifier composed of?
Cesium Iodide
-
What does the input screens do?
Absorbs the x-ray photons and emits light photons.
-
Where is the photocathode and what does it do?
It is in contact with the input screen to prevent divergence.
-
What is the photocathode composed of?
Cesium and antimony compounds that absorb light photons and emit ELECTRONS. ( photo emission )
-
What is photoemission?
When photocathode absorbs light and emits electrons.
-
What happens to the electrons emitted from photoemission?
Electrons are accelerated towards the anode and output screen
-
How does the electrons from photoemission go towards the anode and output screen?
Potential difference ( 25,000 v) that exists in both input side and output side.
-
What are electrostratic lenses used for?
Their used to accelerate and focus electrons to the anode an output screen.
-
What focuses the electron stream?
The opposite charge between the elcetrons and the lenses.
-
What is the output phosphor screen composed of?
Zinc cadmium sulfide that absorbs the electrons and emit light photons.
-
How many times larger are the photoelectrons that arrived at the output phosphor screens than they were originally created with?
50 to 70 times more than they were created with.
-
What happens to the electrons if you have greater voltage supplied to the lenses? What happens to the focal point?
You have greater acceleration and the focal point moves toward the input screen
-
What range of size sdo triple field intensifiers come in?
14, 7 and 5 inch fields.
-
What range of sizes do dual fields often come in?
9 and 6 inch fields
-
What is the disadvantage of using magnification?
When intsiferier is focused to a smaller field size, image suffers a loss of birghtness
-
What is total brightness gain?
Measurement of the increanse in image intesnity achieved by an image intensifier.
-
What determines brightness gain?
Determined by minimification gain and flux gain.
-
What are the ranges of contemporary image intensifiers?
1000 to 5000.
-
When does minification gain occur?
Occurs as the result of the same number of electrons that were produced at the large input screen being compressed into the area on the small output screen
Basically, number of electrons being compressed into small output area.
-
What is minification gain?
increase in the brightness o rintensity of an image and NOT an improvement in quality or number of photons making up the image.
-
What is the equaition for minification gain?
Input screen diameter^2 / output screen diameter^2
-
What is flux gain?
Measurement of the increase in light pohotns due to converssion efficiency of output screen
-
What is conversion efficiency? How does it affect patient dose?
Ability of the phosphor to emit as much light per x-ray photon interaction aspossible.
As conversion efficient increases, patient exposure dose decrease
-
How do you calculate total brightness gain?
Total brightness gain = minification gain x flux gain
-
What is brightness control used for?
To automttically maintain satisfactory fluro image density and contrast.Known as ABC ( automatic brightness control )
-
What is lag?
persistence of luminescence after x-ray stimulation has been terminated.
-
What causes size distortion in fluoro?
OFD
-
What causes shape distortion in flouro?
Caused by geometric problem in the shape of the image intesification tube.Peripheral electrons do not strike output screen where they are focused resulting in unequal magnification producing peripheral distortion.
|
|