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Fluoroscopy Intro to EQUIPMENT

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Fluoroscopy Intro to EQUIPMENT RT 244 FALL 2008/9/10 rev Week 1 Mon day 1 Ref: Fluoroscopy Bushong s Ch. 24 Topics for WEEK 1 RT 244 Example of fluoroscopy ... – PowerPoint PPT presentation

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Title: Fluoroscopy Intro to EQUIPMENT


1
Fluoroscopy Intro to EQUIPMENT
  • RT 244
  • FALL 2008/9/10 rev
  • Week 1
  • Mon day 1

Ref Fluoroscopy Bushongs Ch. 24
2
Topics for WEEK 1 RT 244
  • Example of fluoroscopy systems
  • Components of the Imaging Chain
  • Image intensifier, Camera tubes
  • TV viewing system..etc
  • Recording systems
  • Digital Fluoroscopy (?)

3
(No Transcript)
4
Fluoro objectives
  • Draw a cross sectional view and identify the
    components of an image intensifier tube.
  • Describe the operation of an image intensifier
    tube, including the different image carriers
    (photons and electrons) that are utilized in the
    tube.
  • Describe the concepts of brightness gain,
    minification gain, and flux (electronic) gain as
    applied to an image intensifier.
  • Show how the total gain is computed from the
    minification gain and the flux (electronic) gain.

5
Fluoro objectives
  • Define conversion factor for an image
    intensifier.
  • A fluoroscopic system is switched to the
    enlargement mode so that the center 6 inches of
    the input screen is visualized in place of the
    entire 9 inch diameter screen. If the brightness
    of the output screen remains constant, estimate
    the relative increase in exposure rate that has
    occurred.

6
Fluoro objectives
  • Sketch and explain the function of the typical
    optical beam-splitter used to permit televised
    fluoroscopy and spot filming or cine-radiography.
  • Describe briefly the video process whereby an
    image on the output screen of an image
    intensifier is transferred to the screen of a
    television monitor.
  • Explain the process of video line interlacing and
    why it is used.

7
Fluoro objectives
  • Describe video image fields and frames and the
    times associated with each.
  • Describe the factors that influence the
    horizontal detail (blur) and the vertical detail
    (blur) of a fluoroscopic  image and how you can
    change detail during a procedure.
  • Describe the principles of operation of an
    automatic brightness control unit used with
    fluoroscopy.
  • Describe the principle factor that affects
    quantum noise in fluoroscopy.
  • Describe the process of evaluating a fluoroscopic
    system for quantum noise .
  • Explain how the quantum noise level can be
    changed.
  • State typical and regulatory maximum exposure
    rates to patients with normal fluoroscopy.
  • Identify the major factor that produces high
    patient and staff exposures during fluoroscopy.
  • Explain the purpose of the High Level Control
    (HLC) fluoroscopic mode, when is it used, and
    potential hazards.
  •  

8
Fluoro objectives
  • Describe video image fields and frames and the
    times associated with each.
  • Describe the factors that influence the
    horizontal detail (blur) and the vertical detail
    (blur) of a fluoroscopic  image and how you can
    change detail during a procedure.
  • Describe the principles of operation of an
    automatic brightness control unit used with
    fluoroscopy.

9
Fluoro objectives
  • Describe the principle factor that affects
    quantum noise in fluoroscopy.
  • Describe the process of evaluating a fluoroscopic
    system for quantum noise .
  • Explain how the quantum noise level can be
    changed.

10
Fluoro Rad Protection objectives
  • State typical and regulatory maximum exposure
    rates to patients with normal fluoroscopy.
  • Identify the major factor that produces high
    patient and staff exposures during fluoroscopy.
  • Explain the purpose of the High Level Control
    (HLC) fluoroscopic mode, when is it used, and
    potential hazards.
  •  Review the State Syllabus on Fluoroscopy and
    Radiation Protection with Title 17

11
SO, LETS GET STARTED!
  • Are you ready?

12
FLUOROSCOPY
  • Primary function dynamic motion studies
  • Motion of internal structures in real time
  • CONVENTIONAL FLUORO HAS BEEN REPLACED BY IMAGE
    INTENSIFICAITON
  • Conv Fluoro Rad directly observing images on a
    fluoroscopic screen

13
Basic Imaging Chain
14
Basic Componets of old Fluoroscopy Imaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Fiber Optics OR
Image Intensifier
ABC
LENS SPLIT
Cassette
Image Recording Devices
CINE
CONTROL UNIT
VIDICON Camera Tube
TV
15
Basic Componets of NEW DIGITAL FluoroImaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
Analog to Digital Converter ADC
Image Intensifier
ABC
CCD
TV
16
Fluoroscopy a see-through operation with motion
  • Used to visualize motion of internal fluid,
    structures
  • Operator controls activation of tube and position
    over patient
  • Early fluoroscopy gave dim image on fluorescent
    screen
  • Physician seared in dark room
  • Modern systems include image intensifier with
    television screen display and choice of recording
    devices

17
Fluoroscopy
  • X-ray transmitted trough patient
  • The photographic plate replaced by fluorescent
    screen
  • Screen fluoresces under irradiation and gives a
    life picture
  • Older systems direct viewing of screen
  • Nowadays screen part of an Image Intensifier
    system
  • Coupled to a television camera
  • Radiologist can watch the images live on
    TV-monitor images can be recorded
  • Fluoroscopy often used to observe digestive tract
  • Upper GI series, Barium Swallow
  • Lower GI series Barium Enema

18
Early Fluoroscopy
19
DIRECT FLUOROSCOPY
  • Early fluoroscopy the image was viewed directly
    the xray photons struck the fluoroscopic screen
    emitting light.
  • The Higher KVP brighter the light
  • DISADVANTAGES
  • ONLY ONE PERSON CAN VIEW IMAGE
  • ROOM NEED COMPLETE DARKNESS
  • PATIENT DOSE ( RADIOLOGIST) WAS VERY HIGH

20
Direct Fluoroscopy obsolete
In older fluoroscopic examinations radiologist
stands behind screen and view the
picture Radiologist receives high exposure
despite protective glass, lead shielding in
stand, apron and perhaps goggles
Main source staff exposure is NOT the patient but
direct beam
21
CONVENTIONAL FLUOROSCOPY INVENTED BY THOMAS EDISON
22
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23
Conventional Fluoroscopic Unit
  • Conventional fluoroscopy
  • User viewed faint image on screen
  • User in direct path of beam
  • Very high dose to user and patient
  • Excellent resolution
  • No longer used

24
Older Fluoroscopy
25
Older Fluoroscopic Equipment (still in use in
some countries)
Staff in DIRECT beam Even no protection
26
Red goggles for dark adaptation
More about the eye and vision later in unit.
27
Conventional older Fluoroscopy systems
30 min for dark adaptation RODS or CONES VISION?
28
Light Levels and Fluoroscopy
29
Early Image Intensified FLUORO
30
Conventional I I system
31
Types of Equipment
  • C-arm
  • Under table/over table units

32
Types of Equipment
  • Raise and lower image receptor for accuracy
  • Can vary beam geometry and image resolution
  • Full beam intercept

33
The main components of the fluoroscopy imaging
chain
  • Image Intensifier
  • Associated image
  • TV system

34
Basic Componets of old Fluoroscopy Imaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Image Intensifier
Image Recording Devices
ABC
Cassette
Fiber Optics OR
CINE
CONTROL UNIT
VIDICON Camera Tube
TV
35
NEWER SYSTEMS DIGITAL FLUORO
36
Basic Componets of NEW DIGITAL FluoroImaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
Analog to Digital Converter ADC
Image Intensifier
ABC
CCD
TV
37
IMAGE INTENSIFICAITON
  • IMAGES ARE VIEWED ON A TV SCREEN/MONITOR

38
FLUOROSCOPY IMAGES IN MOTION
39
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40
THE IMAGING CHAIN
  • Historical maybe
  • but you have to know this

41
Image Intensified Fluoroscopy
  • Electronic conversion of screen image to light
    image that can be viewed on a monitor
  • ? resolution
  • ? dose

42
Photons used Fluoro vs Radiography
43
Modern Image Intensifier based fluoroscopy system
44
Modern Fluoroscopic Unit
45
Modern fluoroscopic system components
46
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47
FLUORO TUBES
  • CAN BE LOCATED UNDER OR OVER THE TABLE..
  • FIRST COVERED UNDER THE TABLE

48
(No Transcript)
49
Remote over the table tube
50
Different fluoroscopy systems
  • Remote control systems
  • Not requiring the presence of medical specialists
    inside the X Ray room
  • Mobile C-arms
  • Mostly used in surgical theatres.

51
C-ARM UNIT -STATIONARY
52
MOBILE C-ARM UNIT
53
Mini c-arm
54
Basic Componets of old Fluoroscopy Imaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Fiber Optics OR
Image Intensifier
ABC
LENS SPLIT
Cassette
Image Recording Devices
CINE
CONTROL UNIT
VIDICON Camera Tube
TV
55
Fluoroscopy mA
  • Low, continuous exposures .05 5 ma
  • (usually ave 1 2 ma)
  • Radiographic Exposure
  • (for cassette spot films)
  • mA increased to 100 200 mA

56
I I
  • IMAGE INTENSIFIER

57
Basic Componets of old Fluoroscopy Imaging
Chain
Primary Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Fiber Optics OR
Image Intensifier
ABC
LENS SPLIT
Cassette
Image Recording Devices
CINE
CONTROL UNIT
VIDICON Camera Tube
TV
58
Image Intensifier
  • VACUUM TUBE
  • ENCASED IN A LEAD HOUSING
  • 2MM PB
  • (PRIMARY BARRIER)

59
Image intensifier systems
60
Image Intensification Tube Components
  • Input screen and photocathode
  • Electrostatic lenses
  • Magnification tubes

61
Image Intensification Tube Components
  • Anode and output screen
  • Total brightness gain
  • Minification gain x flux gain

62
INPUT PHOSPHOR
63
Functioning of Image Intensifier
64
IMAGE INTENSIFIER
  • INPUT PHOSPHOR CESIUM IODIDE
  • PHOTOCATHODE (LIGHT TO ES)
  • ELECTOSTATIC LENSES
  • FOCUSES AND ACCELERATES THE E
  • INTENSIFIES LIGHT BRIGHTNESS GAIN (BG)
  • BG MG X FG

65
YOU WILL HAVE TO DRAW THIS
66
IMAGE INTENSIFIER
  • CESIUM IODIDE Input Phosphor
  • ZINC CADMIUM SULFIDE Output phosphor
  • ELECTRON FOCUSING LENS
  • CURRENT ATTRACTS e TO ANODE
  • 25 35 KVP POTIENTIAL ACROSS TUBE
  • Output phosphor contains a thin al plate to
    prevent light returning to the photocathode

67
Input Screen and Photocathode
  • Input screen
  • 0.1 0.2 mm layer of sodium activated CsI
  • Converts intercepted x-ray beam to light
  • Photocathode
  • Emits electrons when struck by light emitted by
    input screen

68
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69
Cesium Iodide (CsI) Phosphor on Input Phosphor
  • CsI crystals grown linear and packed closely
    together
  • The column shaped pipes helps to direct the
    Light with less blurring
  • Converts x-ray photons to visible light

SIDE VIEW
70
II Image Intensifier
  • The input phosphor converts x-ray to light
  • Light from the input phosphor is sent to the
    photocathode made of cesium and antimony
    compounds
  • Photocathode turns light into electrons (called
    photoemission)
  • Now we have electrons that need to get to the
    anode.. this is done by the electrostatic
    lenses

71
Electrostatic Lenses
  • Accelerate and focus electron pattern across tube
    to anode
  • Primary source of brightness gain

72
Image intensifier component
  • Input screen conversion of incident X Rays into
    light photons (CsI)
  • 1 X Ray photon creates ? 3,000 light photons
  • Photocathode conversion of light photons into
    electrons
  • only 10 to 20 of light photons are converted
    into photoelectrons
  • Electrodes (lenses) focalization of electrons
    onto the output screen
  • electrodes provide the electronic magnification
  • Output screen conversion of accelerated
    electrons into light photons

73
The image intensifier (I.I.)
I.I. Input Screen
Electrode E1
Electrode E2
Electrode E3
Electrons Path
I.I.Output Screen
Photocathode

74
Image Intensifier Tube
  • Vacuum diode tube
  • 1. Input phosphor (CsI)
  • X-rays ? light
  • 2. Photocathode
  • Photoemission
  • Light ? electron beam
  • 3. Electrostatic lenses
  • Maintain minify e-
  • 4. Anode
  • Attracts e- in beam
  • 5. Output phosphor (ZnS-CdS)
  • e- ? light

75
Magnification
  • Input screen diameter
  • Diameter used
  • during exam

76
Multi-field II Units
  • II that allows selection of input phosphor size
  • 2 or 3 size selections
  • 25/17 cm
  • 25/17/12 or 23/15/10
  • Smaller input magnifies output by moving focal
    point away from output
  • Requires more x-rays to maintain brightness

77
STOPPING PLACE FOR DAY 1 - 2010
78
Magnification Tubes
  • Greater voltage to electrostatic lenses
  • Increases acceleration of electrons
  • Shifts focal point away from anode
  • Dual focus
  • 23/15 cm 9/6 inches
  • Tri focus
  • 12/9/6 inches

79
Intensifier Format and Modes
Note focal point moves farther from output in mag
mode
80
(No Transcript)
81
MAG MODE VS PT DOSE
  • MAG USED TO ENLARGE SMALL STRUCTURE OR TO
    PENETRATE THROUGH LARGER PARTS
  • FORMULA
  • PATIENT DOSE IS INCREASED IN THE MAG MODE
  • DEPENDANT ON SIZE OF INPUT PHOSPHOR

82
MAG MODE FORMULA
  • IP OLD SIZE
  • IP NEW SIZE mag

83
PT dose in MAG MODE
  • IP OLD SIZE 2
  • IP NEW SIZE 2 ? pt dose

84
Fluoroscopic Dose Rates may show as boost button
85
Intensifier Format and Mag Modes
86
Image Intensifier Performance
  • Conversion factor is the ratio of output
    phosphor image luminance (candelas/m2) to x-ray
    exposure rate entering the image intensifier
    (mR/second).
  • Very difficult to measure no access to output
    phosphor
  • No absolute performance criteria
  • Bushong pg 362 0.01 x brigtness gain
  • Usually 50-300 (BG 5000 to 30000

87
BG MG X FG
  • Brightness gain BG
  • MINIFICATION GAIN X FLUX GAIN
  • Brightness gain is a measure of the conversion
    factor that is the ratio of the intensity of the
    output phosphor to the input phosphor
  • conversion factor intensity of OP Ø

  • mR/sec

88
BRIGHTNESS GAIN can be expressed as
  • conversion factor intensity of OP Ø

  • mR/sec
  • conversion factor
  • Output phosphor illumination (candelas/m2 )
  • Input exposure rate (mR/sec)

89
Brightness gain
  • The II makes the image brighter because it
    minified it and more light photons.
  • Multiply the flux gain times the minification
    gain.
  • BG MG X FG

90
Intensifier Brightness Gain (BG)
  • BG MG x FG
  • Minification Gain x Flux Gain
  • Minification gain (MG) The ratio of the squares
    of the input and output phosphor diameters. This
    corresponds to concentrating the light into a
    smaller area, thus increasing brightness
  • MG (Input Diameter )2
  • (Output Diameter)2

91
Minification (? BRIGHTNESS OF LIGHT)
  • Electrons had to be focused down to fit through
    the hole at the anode Input phosphor is much
    bigger than the anode opening
  • Input phosphors are 10-35 cm in diameter
  • (6, 9 , 12
    inches)
  • Output phosphors are 2.5 to 5 cm (1 in) in
    diameter
  • Most fluoro tubes have the ability to operate in
    2 sizes (just like small and large focal spot
    sizes)
  • Bi focus - MNewer units - tri focus

92
Minification gain - again
  • BG MINIFICATION GAIN X FLUX GAIN
  • MINIFICATION GAIN same e at input condensed
    to output phosphor ratio of surface area on
    input screen over surface area of output screen
  • IP SIZE 2
  • OP SIZE 2

93
Flux gain
  • The ratio of the number of light photons striking
    the output screen to the ratio of the number of
    x-ray photons striking the input screen is called
    fluxgain

94
Intensifier Flux Gain
95
FLUX GAIN
  • 1000 light photons at the photocathode
  • from 1 x-ray photon
  • photocathode decreased the of ës so that they
    could fit through the anode
  • Output phosphor
  • 3000 light photons (3 X more than at the input
    phosphor!)
  • This increase is called the flux gain

96
BG MG X FG
  • FLUX GAIN increase of light brightness due to
    the conversion efficiency of the output screen
  • 1 electron 50 light photons is 50 FG
  • Can decrease as II ages
  • Output phosphor almost always 1 inch
  • Zinc cadnium phosphot
  • Flux gain is almost always 50

97
Intensifier Brightness Gain
  • Flux Gain (FG) Produced by accelerating the
    photoelectrons across a high voltage (gt20 keV),
    thus allowing each electron to produce many more
    light photons in the output phosphor than was
    required to eject them from the photcathode.
  • Summary Combining minification and flux gains

98
Intensifier Brightness Gain
  • Example
  • Input Phosphor Diameter 9
  • Output Phosphor Diameter 1
  • Flux Gain 75 (usually 50)
  • BG FG x MG 75 x (9/1)2 6075
  • Typical values a few thousand to gt10,000 for
    modern image intensifiers

99
Image Intensifier FORMULAS
  • Brightness Gain
  • Ability of II to increase illumination
  • Minification Gain
  • Flux Gain (usually stated rather than calculated)

MAGNIFICATION?????
100
MAG MODE FORMULA
  • IP OLD SIZE
  • IP NEW SIZE mag

101
PT dose in MAG MODE
  • IP OLD SIZE 2
  • IP NEW SIZE 2 ? pt dose
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