Fluoroscopy week 3 Flashcards
Fluoro is what type of exam
Dynamic Radiographic
Fluoro involves _ during the exam
active diagnosis
Fluoro is primarily the domain of the
Radiologist
Radiographers should perform fluoroscope only for _ examinations
static
Fluoro was invention is credited to _ and when
Edison in 1896
Fluoroscopic screen consists of a
specialized x-ray tube with an image receptor
What was held by hand and put in front of the patient and x-ray tube (1st Fluoro)
a viewing hood
when was image intensification tubes were developed in
1948
what allow to view safely
digital monitoring system
Fluoro is currently used only for studies that require
observation of dynamic physiological function
ex-. the flow of barium through the GI tract
ex.2- injection of a contrast medium into the heart
what is the arm that supports the equipment suspended over the table
carriage
the carriage includes an
image intensification tube
what is the image intensifier
increases the brightness
in order to gain access the the patient what can be done
the carriage can be disengaged and pushed away
exposure cannot continue until the
the carriage is returned and locked into position
Fluoroscopic x-ray tubes are very similar to what
Diagnostic tubes
Fluoroscopic x-ray tubes are different from diagnostic tubes how
they are designed to operate for longer periods of time at much lower mA
4 parts of a fluoro system
- II
- tube
- carriage or gantry
- monitor
what is the Fluoroscopic mA range is
0.5-5.0 mA
Fluoroscopic tubes are equipped with
electrically controlled shutters
Fluoro tubes are equipped with electrically controlled shutters that permit _ both Fluoro and spot imaging
maintenance of close collimation from the Fluoro carriage
Early Fluoroscopic screens were
very dim
what is dark adaptation
a procedure in which light levels are reduced for a pd. of at least 10-15 min
Dark adaptation, why are the light levels are reduced for a pd. of at least 10-15 min.
to permit the rods of the eye to become activated
The brightness of the fluoro image was not raided to daylight levels until
image intensification technology was developed in 1948
an image intensification tube is designed to
electronically amplify the brightness of an image
modern image intensifiers are capable of increasing image brightness _ times
500-8,000
The primary x-ray beam exits the patient and strikes the
input screen of the II tube
what is the image intensifier tube
vacuum tube w.a cathode and an anode
fluorescent screen is an
input screen
The fluorescent screen absorbs
the x-ray photons and emits light photons
photocathode is a
cathode of the tube
the photocathode absorbs
the light photons and emits electrons
electrons are accelerated from the
cathode to anode
the same time the electron beam is focused onto the
output screen, which is much smaller than the input screen
what are electrostatic lenses used for
to accelerate and focus the electrons
The primaryBRIGHTNESS GAIN occurs from the
acceleration and focusing of the electron beam
The output screen absorbs the _ and emits
electrons
light photons
viewed on
video monitor
The input screen consists of
0.1 - 0.2 mm layer of sodium-activated cesium iodide (Csl) phosphors
For the input screen, the sodium-activated cesium (CsI) phosphors coated onto the
concave surface of the II tube
the surface of the II tube of the input screen may be made of _ and ranges from
glass titanium, steel aluminum 6" - 23" in diameter
the screen is
concave
The cesium iodide (CsL) phosphors are packed together very tightly so they absorb about _ of _ producing a good
66% of the incident beam
conversion efficiency or quantum yield
What is applied to the input screen to prevent a chemical interaction with the photocathode
extremely thin protective coating
the photo emissive materials absorb the light photons and emit electrons in a process called
photoemission
what are electrostatic lenses
series of charged electrodes located inside the glass envelope of the tube
the electrons are
negative
what reverses the image so the output screen image is reversed from the input screen image
focal point
The focal point reverses the image so the output screen image is
reversed from the input screen image
Image intensification tubes can be designed to magnify
the image electronically by changing the voltage on the electrostatic lenses
By changing the voltage on the electrostatic lenses they are know by these 4 types of intensifier fields
multi-field
dual-field
triple field
quad-field
magnification image intensifiers are capable of _ magnification
1.5 -4x
The magnification image intensifiers are controlled at the
fluoro carriage
The mag factor is calculated as
Magnification= input screen diameter/
diameter if input screen
used during magnification
The anode is _ charged and is normally supplied with about
+
25 kV
This charge causes a tremendous attraction of the
negative electrons from the photocathode
The anode is positioned inside the
glass envelope
electrons pass through the
anode field and onto the output screen
The output screen is also a _.
fluorescent screen
The output screen consists of
silver-activated zinc-cadmium sulfide phosphor
the electrons that strike the screen are converted into
green light photons that exit the tube
what transmit the image some distance without loss of resolution
fiber optics
what is a measurement of the increase in image intensity achieved by an image intensification tube
total Brightness Gain
The total brightness gain is determined by 2 factors
minification gain
flux gain
Minification gain occurs as a result of the
same number of electrons that were produced at the large input screen being compressed into the area of the sm. output screen
out put screens, most are how big
6” or 9”
typical output screens are
1” in diameter
Minification gains formula
Minification gain=input screen diameter2
output screen diameter2
minification gain is simply an _
not an improvement in the quality or # of photons making up the image
increase in brightness/intensity
Photocathode converts
photon to electrons
The Flux Gain is a measurement of the
increase in light photons due to the conversion efficiency of the output screen
Flux gain does not take into account the
conversion efficiency of the input screen
The flux Gain only deals with the _ and is accomplished by the
gain
electron to light conversion at the output screen
total brightness gain formula
brightness gain=minification gain x flux gain
Brightness gain deteriorates as much as _ per year because the
10%
input and output screen phosphors age
