Exposures II > Chapter 33: Fluoroscopy > Flashcards

Chapter 33: Fluoroscopy Flashcards

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1
Q

who was the fluoroscope invented by and when

A

Thomas Edison in 1896

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2
Q

where is the xray tube and image intensifier loacted in fluoro

A

xray tube is below table and image intensifier is on top

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3
Q

dynamic imaging modality designed to observe moving structures in the body

A

Fluoroscopy

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4
Q

what should the SSD be for mobile equipment

A

30 cm (12 inches)

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5
Q

what should the SSD be for fixed fluoroscopic

A

38 cm (15inches)

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6
Q

What is the mA range for the fluoroscopic xray tube

A

0.5 to 5 mA

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7
Q

purpose of the image itensification

A

increase brightness of fluoroscopic images by thousands (8,000 times)

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8
Q

Electronic devise mounted above the table and patient and permantely attched to the xray tube

A

Image Intensifier

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9
Q

components of the image intensifier

A

Input phosphor
photocathode
electrostatic lenses
anode
output phosphor

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10
Q

Function of the input phosphor

A

converts xray photons to light photons

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11
Q

coated with cesium iodide

A

Input phosphor

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12
Q

*concave surface
*approx. 10-35 cm in diameter
*coated with cesium iodide
* converts xray photons to light photons

A

input phosphor

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13
Q

made of cesium antimony

A

photocathode

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14
Q

function of photocathode

A

converts light photons to electrons ; called photoemission

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15
Q

Mimics the pattern of light demonstrating the anatomy of the patient emitted by the input phosphor (latent image)

A

Photocathode

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16
Q

narrowing the electron beam

A

electrostatic lenses

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17
Q

very high exposures directly into :

A

eyes, neck, hands

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18
Q

*positively charged end of the image intensifier
*attracts the photoelectrons due to elctrostatic charger
*contains the output phosphor at end

A

Anode

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19
Q

function of the elctrostatic lenses :

A

accelerate and focus the electrons toward the output phosophor

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20
Q

made of zinc cadmium
sulfide
glass fluorescent screen

A

Output phosphor

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21
Q

function of the output phosphor

A

Converts photoelectrons to visible light

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22
Q

what type of diagnosis is fluoroscopy

A

Active

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23
Q

what type of examination is fluoroscopy

A

Dynamic

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24
Q

image intensification tubes dveleoped in 1948. there was mirror optics for viewing what was that replaced with

A

replaced with closed circuit TV systems

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25
fluoroscopic uses for functional studies:
o Gastrointestinal (GI) tract studies o Angiograms o Line placements o Orthopedic surgeries
26
total brightness gain
minification gain * flux gain
27
o 0.1–0.2 mm layer of sodium activated cesium iodide (CsI) o Converts intercepted x-ray beam to light
Input screen
28
Emits electrons when struck by light emitted by input screen
Photocathode
29
audible timer, radiation protection
five minute timer
30
where should the patient be shielded
from behind since the xray tube is below
31
what is the last image hold for
to decrease dose pt. protection
32
measurment of the increase in image brightness due to the conversions of energy in the image intensifier
Total brightness gain
33
* Accelerate and focus electron pattern across tube to anode *primary source of brightness gain (due to acceleration of electron stream and increased kinetic energy)
electrostatic lenses
34
what is increased in magnification mode
increased resolution increased patient dose
35
magnification =
input screen diamter/ diamater of input screen used during magnification
36
distortion in fluoro
vignetting
37
where is the focal point in magmode
focal point closer to input phosphor in magmode
38
what size surface area is during magmode
smaller surface area
39
measurement of increased image intensity achieved by image intensifier
Brightness gain
40
results from concentration of large electron volume from input phosphor, being focused down onto small area of output phosphor
Minfication gain
41
input over output
minification gain
42
measurement of conversion efficiently of output screen
Flug gain
43
Automatically adjusting the contrast , takes account the thickness
Automatic Brightness control
44
help to see in bright lights, phototopic
Cones
45
help to see in low light, scotopic
rods
46
is input or output bigger
input is bigger vs. output
47
how much lead is in the bucky slot cover
0.25 mm
48
how much lead is in the curtain
0.25mm
49
how much lead is in the lead aprons
0.25mm
50
how much lead is in the lead aprons in fluoro
0.5mm
51
image intensification was introduced in 1948. What was modified.
-higher visual acuity -uses photopic vision (cones) -reduced fluoroscopic dose
52
Image intensification tube components:
-input screen and photocathode -electrostatic lenses -magnification tubes -anode and output screen -total brightness gain (minification gain * flux gain)
53
what does greater voltage to electrostatic lenses do
-increases acceleration of electrons -shifts focal point away from anode
54
hole in center allows electrons to pass through to output screen
Anode
55
Results from concentration of large electron volume from input phosphor, being focused down onto small area of output phosphor
Minification gain
56
minification gain =
input screen diameter ^2/output screen diameter^2
57
Measurement of conversion efficiency of output screen ex. one electron strikes output screen -50 light photons emitted per electron striking output phosphor -flug gain 50
Flux gain
58
Image quality
Contrast, resolution, distortion, quantum mottle
59
-controlled by amplitude of video signal -digital systems use post processing (window width and filtering algorithm) Affected by: -scattered ionizing radiation -penumbral light scatter
Contrast
60
Which is better? Fluoroscopic or static radiography resolution
Static radiography
61
Resolution varies depending on geometric Factors:
SID, OID, minification gain longer sid, smaller oid
62
Edges of image intensifier have lower resolution due to:
Vignetting
63
Automatically adjusting the contrast takes account of the thickness
Automatic brightness control
64
penumbra
unsharpness
65
numbra
sharpness
66
What does more scatter do to the contrast
Decrease contrast
67
Size distortion
-affected by same parameters as static radiography (primarily oid) - geometric problems in shape of image intensifier input screen -concave shape helps reduce distortion -vignetting or pincushion effect -not a problem with TFT matrices -uniform resolution across flat panel detector array
68
blotchy, grainy appearance -caused by too little exposure -most commonly remedied by increases mA
Quantum Mottle
69
Improved by increasing total exposure to intensifier input phosphor -increase mA -reduce distance between patient and image intensifier -increase kvp
Quantum Mottle
70
Most common viewing system:
Video -video camera attched to output phosphor -fluoro video camera uses CCD -display monitor for viewing
71
Highest energy scatter
-90 degrees angle to incident beam - same level as radiographer / radiologists gonads
72
What is the difference with flat panel fluoroscopy ?
-No intensifier tube -no vignetting -no dose increase in mag mode
73
C- arm fluoroscopic units
- populary for surgery, er, orthopedic studies - operates the same as stationary units -pary particular attention to radiation dose when using mobile fluoroscopy
74
what generator is used for digital fluoroscopy
High power generator
75
in digital, Image intensifier output screen coupled to :
TFT
76
in digital fluoroscopy, what is connected to each pixel
Photodiodes
77
what is used in digital fluoroscopy to lower noise
pixel binning
78
Use C C D to generate electronic signal Signal sent to A D C Allows for post-processing and electronic storage and distribution Last image hold function Post-exposure image processing
digital fluoroscopy
79
patient protection for fluoroscopy
-audible alarm at 5 minutes -same rules for collimation -last image hold
80
how much aluminum for filtration for fluoro
2.5mm
81
how often should the fluoro system and lead aprons be checked
the fluoro system should be checked every 6 months the lead gowns should be checked yearly
82
What is the mR for xray tube and fluoro
Xray tube = 100mR fluoro= 10mR
83
purpose of intensifier tube :
To increase image brightness
84
-converts xray to photons -cesium iodide
Input phosphor
85
-converts light to photons to electrons -cesium and antimony
Photocathode
86
-focuses the photoelectrons to the output phosphor 25-35kvp -located on the inside of the image intensifier
Electrostatic lenses
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