Fluoroscopy Flashcards
Fluoroscopy
a DYNAMIC radiographic examination which makes possible the visualization of internal organs in MOTION
Xrays were initially discovered by ___________ because of their ability to cause _________.
Roentgen, Fluorescence
who invented the fluoroscope and in what year?
Thomas edison in 1896
First generation Fluoroscope consist of:
x-ray tube, table, and fluoroscopic screen
Light from the fluoroscopic screen was so faint that exams were performed in ________ -________.
Darkened room
How long did it take for the radiologist to dark adapt their eyes?
20-30 min
A sheet of ____ covered the florescent screen so the radiologist could look directly at the screen.
lead glass
what does the human eye have the ability to adapt to?
low levels of illumination
Where are type of receptors located within?
retina
where are cones located?
densely concentrated in the posterior of the retina which is called the fovea centralis
Cones function most efficiently in:
bright light
cones are used for _______ vision.
daylight or photopic
where cones sparsely scattered and what are they used for?
over the rest of the retina and used for peripheral vision during daylight
where are rods located?
located around the periphery of the retina. none are located in the fovea centailis
where do the rods function best?
best with low level of illumination, dim vision
what are rods used for?
night vision which is peripheral
night vision is also called:
scotopic vision
rods are most sensitive to which kind of wave-length light?
blue-green
what color goggles do you wear to dark adapt and why?
red goggles which filter out blue-green wavelength
dim fluoroscopic images require the use of _____ vision.
rod
Using rod vision leads to:
poor visual acuity, poor ability to detect shade of grey (contrast)
what led to the development of the image intensifier?
the need to produce a bright image to allow the use of cone vision w/o giving the patient an excessive radiation exposure
What is an image intensifier?
an ELECTRONIC vacuum tube that converts the pattern of the x-ray beam to a BRIGHT LIGHT IMAGE
what are the 5 basic elements of an image intensifier?
Input phosphor, photocathode, electrostatic focusing lens, accelerating anode, output phosphor
What is the input phosphor(IP) made of?
Cesium Iodide (Csl)
What the input phosphor increase and decrease?
Increases image quality and resolution, decrease phosphor thickness
Older screens were made up of:
Zinc Cadmium Sulfide (ZnCdS)
When the input phosphor is stuck by xrays what is produced?
Bright light
The intensity of the light produced be the IP is __________ to the number of x-rays incident on it.
Proportional
Photocathode (PC) is made up of a
photoemissive metal (combination of Cs and Sb)
Photocathode responds to light from IP and emits _______.
electrons (e-)
For the photocathode, the number of e- produced is _____________ to the intensity of light sticking the PC.
Proportional
What prevents chemical reaction between Photocathode and Input phosphor?
a thin transparent layer
what is resolution?
the ability of a system to image an object faithfully
Both IP & PC are ________ for undistorted focusing of the e- beam.
Curved
Since IP & PC are curved this allows the electrons to travel _________ __________ to the output phosphor.
same Distance
What is the electrostatic focusing lens?
series of negatively charged electrodes on the inside surface of the tube
The purpose of the electrostatic focusing lens.
To focus electron beam as it flows toward the output phosphor
All electrons meet/ converge at ____ ______.
focal point.
Because they are traveling in straight lines, this results in __________ and __________ the image
Inverting and reversing
Where does point inversion occur at?
focal point
Where is the accelerating tube located?
in the neck of the tube
purpose of the accelerating anode
functions to accelerate electrons toward the output phosphor
Accelerating anode has a ____ to ______ kv positive potential relative to PC.
25-35
Output phosphor (OP) is made of
Zinc Cadmium sulfide (ZnCdS)
Output phosphor is ____ to ____ inches in diameter.
1/2 inches to 1 inch
electrons arrive at OP at very high kinetic energy. they contain the image of the IP in __________ form.
minified
Input phosphor is _______ then output phosphor
bigger
How much more light does output phosphor produce compare input phosphor? and this is due to?
50 times; high kinetic energy of e- beam
The image from the OP, in the form of ___ _____, is the same image that was carried to the IP via the _____ x-ray beam.
light photons; remnant
what is brightness gain?
The ability of the image intensifier to increase the ILLUMINATION LEVEL of the image
Brightness gain is dependent on what two sources?
minification gain and flux gain
What is minification gain?
occurs due to the same number of light photons produced on IP being compressed to the small area of the OP
minification gain is dependent on:
diameter of IP &OP
the formula of minification
ratio of the square of the diameter of the IP to the square of the diameter of the OP
what is the range for the input phosphor diameter?
4” to 20”
What is the usual diameter of the output phosphor?
1” or 2.5cm
Minification gain is simply an increase in _________ or __________, not an improvement in the ______ or number of light photons making up the image.
Brightness; intensity; quality
what is the flux gain?
ratio of the number of light photons at the output phosphor to the number of x-ray at the input phosphor
Flux gain formula
of light photons at OP over # of light photons at IP
Brightness gain (BG) formula
BG= (MG)(FG)
Dim objects can be viewed better with _______ vision.
peripheral
purpose of angiography
to visualize vessels
in general, during fluoroscopy as compared with radiography:
the mA will be lower
radiation can cause cataracts in what part of the eye?
lens
During a fluoro exam, static images are obtained on:
spot film
Visual acuity
the ability to perceive fine detail
The fluoro tube is located:
under or over the table
As compared with radiography, the x-ray technique required for fluoroscopy calls for:
lower mA
what properties is associated with rods but not with cones
scotopic vision
what is the ocular structures immediately precedes the vitreous humor along the path of incident light?
lens
Radiographic images are viewed under
photopic conditions
The fovea centralis is part of the ______
retina
Fluoroscopy normally requires a tube current of
1 to 5 mA
During fluoroscopic imaging, Reducing ____ increases _________ ____________.
kVp; image contrast
Automatic brightness stabilization (ABS) is designed to compensate for
patient composition
Video viewing of the fluoroscopic image is advantageous because __________.
the image is brighter
what structure of the eye is most sensitive to colors?
cones
the fluoroscopic system designed to maintain a constant image intensity
Automatic brightness control (ABC)
function of the iris
Control the light level
Photoelectric emission
the emission of electrons from an illuminated surface
At what stage of image intensified fluoroscopy is the number of image forming photons lowest?
Entering the input phosphor
image intensifier brightness gain increases when ________ ______increases
flux gain
when an image intensifier receives x-rays at the input phosphor, what is emitted at the output phosphor?
visible light
What does the photocathode convert?
visible light into electrons
The minification gain of an image intensifier increases when ______ increases
input phosphor size
sequence for image intensified fluoroscopy
- X-rays to light
- Light-to-electrons
- Electrons-to-light
- light-to-electric signal
- Electric signal to light
in output phosphor _________ is emitted
light
when does the photocathode emit electrons?
when its illuminated by the input phosphor
what is modulation?
a change in a quality or signal in a response to another quantity or signal
video monitoring uses how many frames per a second?
30 frames per sec
