1. Fluoroscopy Intro to EQUIPMENT
RT 244
FALL 2008/9/10 rev
Week 1
Mon – day 1
Ref: Fluoroscopy – Bushong’s 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 (?)
Explanation or/and additional information
Instructions for the lecturer/trainer

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, LET’S 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” Fluoro“Imaging 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. Main source staff exposure is NOT the patient but direct beam
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

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
Let’s summarize the main subjects we did cover in this session. (List the main subjects covered and stress again the important features of the session)

34. Basic Componets of “old” Fluoroscopy “Imaging Chain”
Primary
Radiation
EXIT Radiation
Fluoro TUBE
PATIENT
105 Photospot
Image Intensifier
Image Recording Devices
Cassette
ABC
Fiber Optics OR
CINE
CONTROL
UNIT
VIDICON
Camera Tube TV

35. NEWER SYSTEMS – DIGITAL FLUORO

36. Basic Componets of “NEW DIGITAL” Fluoro“Imaging 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

40. Historical maybe– but you have to know this………
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

47. FLUORO TUBES CAN BE LOCATED UNDER OR OVER THE TABLE…..
FIRST COVERED – UNDER THE TABLE

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 E’S)
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
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

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 70

71. Accelerate and focus electron pattern across tube to anode
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 5 4 3 1 2

75. Magnification
Input screen diameter
Diameter used
during exam

76. Multi-field II Units II that allows selection of input phosphor size
25 cm vs. 17 cm
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 Dual focus
Increases acceleration of electrons
Shifts focal point away from anode
Dual focus
23/15 cm /6 inches
Tri focus
12/9/6 inches

79. Intensifier Format and Modes
Note focal point moves farther from output in mag mode

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 = ↑ 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 (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. BG = MG X FG 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 89

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 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 M=Newer units - tri focus 91

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. 1000 light photons at the photocathode from 1 x-ray photon
FLUX GAIN
1000 light photons at the photocathode
from 1 x-ray photon
photocathode decreased the # of ë’s 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 (>20 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 >10,000 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 = ↑ pt dose