Fluoroscopy (Meaghan Peretti) Flashcards
C-arm is considered:
Mobile Fluoroscopy
Fluoroscopy room is considered:
Stationary Fluoroscopy
The fluoroscopic x-ray tube is located:
under the fluoroscopic table
The C-arm x-ray source is located:
under the patient and/or surgical table
The Image Intensifier (II) is located:
over the patient
The Image Intensifier Job (II):
works similar to the Imaging plate by collecting the remnant or exit radiation after passing through the patient to create the radiographic image. The image is displayed on the monitor.
Fluoroscopy uses a technology referred to as:
Automatic Brightness Control (ABC) to control the kVp and mA
Purpose of ABC:
regulates the kVp and mA for fluoroscopy depending on the part being examined.
It will adjust as the radiologist moves the II over different areas of the body, as well as areas with or without contrast.
The maximum mA station for fluoroscopy is:
5 mA
(This will also control the brightness of the image)
kVp will vary by:
body part, thickness of body part, and type of contrast. This also may vary per equipment type/manufacturer.
Barium work kVp range:
100 range
Air Contrast kVp range:
90 range
Water soluble contrast kVp range:
70-80 range
Automatic Brightness Stabilization (ABS):
maintains image brightness
Automatic Exposure Rate Control (AERC):
maintains the radiation dose per frame at a predetermined level.
Automatic Brightness Control (ABC) controls:
kVp and mA
For a fluoroscopy of an arthrogram what do you do with technical factors?
nothing, do not set them.
What is the role of the Input phosphor?*
takes remnant beam and converts x-ray photons into light photons
What is the Input Phosphor made of?
Cesium Iodide
Photocathode purpose?
takes the light photons and converts them into electrons
Photoemission:
emitting electrons from light source
What is the photocathode made of?
Antimony compounds and cesium
The purpose of the electrostatic lenses:
focuses the electrons toward the anode
What is the anode in fluoroscopy made of?
Tungsten
What is the purpose of the output screen?
converts electrons into light photons
What is the output screen made of?
zinc cadmium sulfide
Put the image intensifier in order:
- Input phosphor (cesium iodide crystal)
a. x-rays to light - Photocathode
-light photons into electrons - Electrostatic lenses
-focuses electrons - Anode
-accelerates electrons - Output
-converts electrons into light photons - CCD
-converts light back to electrical signal - ADC
-converts to digital signal - Monitor
-see the image on the monitor screen
The ratio of light photons at the output phosphor divided by the number of input x-ray photons is the:
Flux Gain
total number of light photons produced by each electron
Flux Gain
a ratio of the size of the input phosphor compared to the size of the output phosphor.
Minification Gain
The output phosphor is _________ than the output, _________ brightness.
smaller, increasing
The ability of the image intensifier to increase the illumination level of the image is called the:
Brightness Gain
The brightness gain is simply the product of the:
minification gain x the flux gain
Total brightness gain ranges from:
5,000-20,000 and decreases as the tube ages
What does Flux Gain Compare:
of light photons (output)/# of x-rays (input)
Minification gain compares:
(input phosphor diameter/output phosphor diameter)^2
Brightness Gain=
minification gain x flux gain
A Radiologist needs to magnify up:
results in a smaller field of view
decreased input phosphor size
Increased Spatial Resolution
Increases Contrast Resolution
Increases Patient Dose
Smaller input phosphor size=
increased dose
Which input phosphor size would increase dose the most?
15 cm phosphor size=increased dose (smaller input phosphor size means magnification is more present)
As magnification increases:
the focal point moves forward
the size of the input phosphor decreases
The FOV decreases
Patient Dose Increases
(use it only when they need it)
If the patient is standing for a PA chest against the wall bucky:
decrease OID, decrease magnification of the heart
The patient is on the OR table what would you do?
Increase the SID, move the patient away from the x-ray source, closer to the II reduces dose.
Reducing magnification in flouroscopy:
decrease OID
bring the II closer to the patient
Newer C-arms are a:
FPD model
FPD improvements:
improve image quality
reduce patient dose
less cumbersome to move
reduces sterile field contamination
FPD=indirect conversion steps:
X-rays exit the patient, cesium iodide scintillator converts x-rays to light, amorphous silicon photodiode converts light to electrons. TFT collects electrical signal
Smaller DEL’s=
increased spatial resolution
For pediatric fluoroscopy __________ is recommended
removal of the grid
Fluoroscopic grids tend to be _____________ ratio grids due to the ________ mA values used in flouro imaging.
lower, low
the reduction of an image’s brightness or saturation toward the periphery compared to the image center.
Vignetting
image in a fluoroscopic system to distort with an “S” shape
S Shape Distortion
The loss of shape at the edges of the fluoro image
Pincushion Artifact
The exposure switch type in flouroscopy:
Dead Man Switch
X-rays are only generated when the operator actively pressed the switch (Button or Foot Pedal).
Dead Man Switch
Remote switch- mobile
2 meters
When fluoroscopy is stopped, an image continues to be displayed on the monitor.
Last Image Hold (LIH)
The last image hold/save grab feature:
allows the image to be saved, thus reducing the need for another exposure
The last image is digitally “frozen” on the monitor after x-ray exposure is terminated
Last Image Hold
The presence of a grid:
increases contrast, increases image quality, increase the dose to the patient
In pediatric cases, removal of the grid has resulted in dose reduction of up to:
1/3 to 1/2 with little or no loss in contrast and image quality
overlays a collimator blade on the last image hold so that one can adjust field dimensions without exposing the patient
Electronic Collimation
eye +
Boost
eye
Fluoro
Low dose reduces exposure by:
50%
Pulse reduces exposure by:
75-90%
Beam is emitted as a series of short pulses
Pulse Setting
there is a constant beam on time
Continuous Fluoro
Stepping on and off the foot pedal (dead man switch), usually for filling bladder
Intermittent Fluoroscopy
***Mobile Fluoroscopy (c-arm) SSD:
12” or 30 cm
(hint: take a lunch at 12:3- in the OR)
the distance between the tube and the patient during fluoroscopy
Source to Skin Distance (SSD)
***Stationary Fluoroscopy (flouro room) SSD:
14” or 38 cm
The largest amount of scatter produced on a c-arm is located:
where the x-ray beam enters the patient
In Fluoroscopy keep the _______ minimized when possible.
OID
The least scatter location is _______ to the patient where the II is placed over them.
90 degrees
The highest operator exposure is:
on the x-ray tube side
As patient size increases:
scatter radiation increases
The increase in scatter radiation will impact:
the radiographer and the patient
If you are doing a lateral C-arm examination, where should you be standing?
Behind the C-arm with an increased distance and use your remote and step back.
If the surgeon or radiologist is using flouro and not looking at the screen. Communication with the patient will improve efficiency of the exam.
Time
Move back from the flouro table or C-arm
Distance
Dosimeter placed outside the lead shield
Shielding
Lead apron and Thyroid shield minimum required:
.25 mm Pb
For fluoroscopy the minimum shield required:
.50 mm lead (Pb)
Bucky slot cover minimum:
.25 mm pb
Lead Curtain minimimum:
.25 mm pb
For fluoroscopy the exposure timer should be:
under 5 minutes
light must turn on to alert of exposure
radiation light
Keep the II Distance closer to the patient:
reduces scatter
