fluoroscopy and technique FINAL Flashcards
1
Q
who discovered fluoroscopy
A
Roentgen noticed fingers moving, but thomas edison is credited for inventing fluoro
2
Q
what equipment makes up the fluoro machine
A
xray tube, image intensifier, C-arm, carriage
3
Q
C-arm
A
allows the IR to be raised and lowered
4
Q
carriage
A
the arm that supports the equipment suspended over the table
5
Q
Image intesification tube
A
makes the image brighter so we don’t need the dark adaptation
6
Q
brightness control
A
regulates tube mA
7
Q
tube shutters
A
control colimation
8
Q
how much mA is used for fluoro
A
less than 5 mA (0.5-5.0)
9
Q
what’s the biggest advantage of image intensified fluoroscopy over earlier fluoroscopy?
A
increased image brightness due to the image intensifier
10
Q
brightness depends on what?
A
anatomy, kV, and mA
11
Q
ABC =
A
automatic brightness control
12
Q
ABC
A
just like phototiming
varies the kVp and mA automatically according to subject contrast and density
13
Q
What is ABC also called
A
ADC - automatic dose control
ABS - automatic brightness stabilization
14
Q
the fluorescent screen is filled with?
A
cesium iodide crystals
15
Q
image intensifying tube contains
A
cathode, anode, fluorescent screen, input phosphor screen, cesium iodide crystals
16
Q
fluorescent screen
A
absorbs the xray photons and emits light photons
17
Q
photocathode
A
absorbs light photons and emits electrons
18
Q
electrostatic lenses
A
used to accelerate and focus the electrons
19
Q
output screen
A
absorbs the electrons and emits light photons
20
Q
input phosphor screen
A
absorbs 2/3 incident beam by producing good conversion efficiency
21
Q
photoemission
A
the emission of electrons when stimulated by light
22
Q
what is the output screen made of
A
cadmium sulfide
23
Q
flux gain
A
the ratio of the number of light photons at the output phosphor to the number of light photons from the input phosphor #of output light photons/#of input light photons
24
Q
minification gain
A
when the amount of electrons that were produced at the large input screen are being compressed into the area of the small output screen
ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor.
disquared /dOsquared
makes the image brighter
25
the increased illumination of the image is due to 2 factors
1. flux gain
| 2. minification gain
26
brightness gain
the ability of the I.I. to increase the illumination level of the image
brightness gain = minification gain * flux gain
27
as the intensifier ages....
patient dose increases
28
conversion factor
the illumination intensity at the output phosphor compared to the radiation intensity incident on the input phosphor
conversion factor = output phosphor illumination/input exposure rate
29
magnification
by increasing the voltage on the electrostatic lenses the electrons are focused at a point closer tot eh input screen causing the image to be magnified.
magnification = input screen diameter/input screen diameter used during magnification
30
magnification mode results in?
better spatial resolution
better contrast resolution
higher patient dose
31
veil glare
when the intensely bright light floods the eye
32
vignetting
a reduction in brightness at the edges of an image
33
pincushion effect
distortion of lines which curve inward at the edges of the output screen
34
viewing systems
systems to deliver the image from the output screen to teh viewer
some are real time, some are static
35
types of viewing systems
digital
video
cine
spot imaging
36
video viewing
includes video camera attached to the I.I tube
37
types of camera tubes
1. vidicon
2. plumbicon
3. CCD charge coupled device
38
what types of camera tubes are used most often?
vidicon and plumbicon
39
video camera tube elements
cathode
electrostatic grids
electron gun
target assembly (anode)
40
Electron gun
a heated filament that supplies constant electron current by thermionic emission
41
control grids
form electrons into an electron beam and help to accelerate the electrons to the anode
ACTS AS A FOCUSING CUP
42
accelerator grids
electrostatic grids that also aid in accelerating and focusing the electron beam
43
3 layers of the target
1. glass face plate (outside layer/window)
2. signal plate (creates video signal)
3. photoconductive layer (target plate) emits electrons when hit with light
44
CCD
charge coupled devices
device that converts visible light into an electric charge
like a computer chip
45
2 methods used to couple the camera to the I.I tube
1. fiber optics
| 2. lens system
46
fiber optics
bundles of extremely small light conducting cables
47
advantages of fiber optics
compact
| very durable
48
disadvantages of fiber optics
cant accommodate cine/spot films
49
lens system
accepts the light from output phosphor and converts into beam
50
lens system advantages
allows Rad to view image while its being recorded
51
lens system disadvantages
much larger than fiber optics and more delicate
52
TV monitor
video signal from the tv camera is transmitted by cable to the tv monitor
the signal is then transformed into a visible image
53
parts of the tv monitor
tv picture tube
| cathode ray tube
54
tv picture tube consists of
glass envelope
electron gun (cathode)
external coils
anode
55
tv picture tube
the monitor creates an image as the gun sprays a stream of electrons from the camera onto screen phosphor
56
active sweep
the first sweep in the upper left corner of the screen and moves across almost horizontally
57
horizontal retrace sweep
the second sweep the beam returns to the left side of the screen to a point slightly below the first line
58
interlacing
the scanning beam does a vertical retrace and repeats the entire sweeping pattern, however the lines are placed between the first set of lines
59
raster
the horizontal linear pattern
60
the entire 525 line raster pattern is scanned every
1/30 of a second
61
the frame rate is
30 times per second
62
each frame is
33ms long
63
HDTV
has better detail and 1050 scan lines opposed to 525
64
cine
highest dose to the patient
| used mostly in cardiac studies
65
what is the weakest link in the I.I. fluoro
the TV monitor
66
quantum mottle
blotchy or grainy appearance caused by insufficient radiation to create a uniform image
67
what is the most common solution for quantum mottle
to increase the fluoro tube mA
68
audible alarm
in the U.S federal law requires an audible alarm at 5 minutes
69
Minimum source to skin distance in stationary fluoro
15 inches
70
minimum source to skin distance in mobile fluoro
12 inches
71
tabletop exposure rate should not exceed
10 R/min
72
lead apron and gloves
0.25 mm Pb/eq
73
a single step away from the table
decreases exposure exponentially
74
who's responsibility is it to inform others to wear a lead apron?
the radiographer
75
body habitus
sthenic
hyposthenic
hypersthenic
asthenic
76
soft tissue
use lower kVp because radioluscent tissue needs less xrays
77
extremities
low kVp because body part is thin
78
radiopaque tissue
absorbs x rays so it needs more
79
when the image requires less density
the mAs should be decreased
80
pathology can be
```
destructive
constructive (additive)
```
81
Destructive (more radioluscent)
```
more easy to penetrate must decrease technique
metastases
emphysema
pneumothorax
osteoporosis
paget's disease
```
82
constructive/additive
```
must increase technique more difficult to penetrate
pneumonia
ascites
cirrhosis
congestive heart failure
malignancy
pleural effustion
```
83
casts and splints
exposure factors will change due to the material used
84
fiberglass casts
usually do not require a change in technique
85
plaster casts
requires an increase in exposure factors
86
rule of thumb for casts
double the mAs for dry casts and triple for wet
87
position
the position determines how much tissue you will be penetrating
a lateral chest requires more than an AP chest
88
if you position a lateral ankle will you increase or decrease technique from the AP?
decrease because less to go through
89
OD is controlled by two factors
1. mAs
| 2. SID
90
to change the density of the image you must change the
mAs
91
to change the contrast of the image you must change the
kVp
92
for every increase of 4-5 cm of part thickness the mAs should be
doubled
| 15% rule
93
for every decrease of 4-5 cm of part thickness the mAs should be
halved
| 15% rule
94
high contrast =
short scale black and white
| obtained using low kVp
95
low contrast =
long scale many shades of gray
| obtained using high kvp
96
advantages of technique charts
consistency in exposure from one tech to another
| comparison of exams on the same pt. on different dates with different techs.
97
variable kVp chart
```
uses a fixed mAs
kVp varies according to the thickness of the part
usually short scale
higher pt. dose
less exposure latitude
measurement of part is critical
```
98
fixed kVp chart
```
utilizes exposures that produce radiograps with a longer scale of contrast
for each part there is an optimum kVp
usually higher kVp than variable
lower pt dose
more consistency of exposures
greater latitude
measurement not as critical
```
99
exposure rates for age 0-5
when setting techniques for children use 25% of the mAs you would use on an adult
100
exposure rates for age 6-12
use 50% of the mAs you would on an adult
101
AEC
uses a device to sense the amount of radiation falling on the IR
the radiation exposure is terminated when enough xrays have reached the IR to produce proper OD
102
if the AEC fails
secondary safety circuit terminates at 600 mAs
