A fluoroscope uses x-rays and a fluorescent screen to enable direct observation of internal organs. It consists of an x-ray tube, table, and image intensifier. The image intensifier converts x-rays into visible light images and amplifies them for viewing. It works by accelerating photoelectrons emitted from a photocathode onto a phosphor screen, producing light photons and gaining brightness. Newer generations of image intensifiers use additional electron multiplication for higher sensitivity. Fluoroscopy provides real-time moving images for procedures while fluorography captures still diagnostic images.

2. Fluoroscope
– – A fluorescent screen for observing the
shadows cast by objects placed in the path of the
x- -rays
– – An x- -ray machine that combines an x- -ray
source and a fluorescent screen to enable direct
observation of internal organs
-- Examination of an organ or body structure
using a fluoroscope is FLUOROSCOPY

3. FLUOROSCOPY
 Refers to use of low (i.e. 0.5 to 2
mA), continuous x-ray exposures.
The resultant images have a relatively
low signal-to-noise ratio (SNR), because of
the low XRT current, but are of sufficient
quality for applications such as patient
positioning or monitoring catheter
placement.

4. FLUOROGRAPHY
 Refers to the use of relatively intense
(e.g.50 to 500 mA or greater), pulsed
exposures.
The pulses are typically of short
duration and are applied at, for example,
1 to 12 pulses per second. The resultant
images have a relatively high SNR and are
used for diagnostic purposes.

5. HISTORY
Fluoroscopy was done for the first time
by Dr.W.C. Roentgen when he first
discovered the new kind of rays in 1895
Thomas Edison is credited with the
designing and producing of the first
commercially available fluoroscope
1950’s ----- introduction of Image
Intensifiers

7. Fluoroscope
consists of
 X ray tube
 X ray table
 IMAGE
INTENSIFIER

8. IMAGE INTENSIFIER DESIGN
VACCUM
GLASS TUBE
[ 2 – 4 mm
THICK ]
ENCLOSED
IN A LEAD
LINED METAL
CONTAINER

9. IMAGE INTENSIFIER TUBE
PARTS
 INPUT PHOSPHUR AND THE PHOTO CATHODE
 ELECTROSTATIC FOCUSING LENS
 ACCELERATING ANODE
 OUTPUT PHOSPHUR

11. INPUT PHOSPHUR
CESIUM IODIDE
 VERTICAL ORIENTATION OF CsI CRYSTALS
 Vapour deposited on thin aluminium substrate --
0.5 micrometre thick
 CsI grow as tiny needles 150 to 400 micrometre
high and 5 micrometer in diameter
 Grow perpendicular to the substrate
 Prevent lateral diffusion of light

12. CESIUM CRYSTALS

13. GREATER PACKING DENSITY
 CsI HAS 3 TIMES MORE PACKING
DENSITY WHEN COMPARED TO Zn
Cd sulphide
 REDUCE PHOSPHUR LAYER
THICKNESS
 IMPROVE RESOLUTION OF THE
IMAGE
 THE RESOLUTION OF CsI IMAGE
INTENSIFIER IS ABOUT 4 lp/mm

14.  FAVOURABLE ATOMIC NUMBER
 ATOMIC NUMBER OF CESIUM IS 55
 K EDGE OF Cs IS 36keV AND THAT OF IODIDE IS
33.2keV
 CLOSE TO THE MEAN ENERGY OF X RAY BEAM
USED IN FLUOROSCOPY i.e 30 to 40 keV
 FOR MAXIMUM PHOTOELECTRIC ABSORPTION
THE K EDGE SHOULD BE AS CLOSE TO THE KV
OF THE X RAY BEAM AS POSSIBLE

15. PHOTOCATHODE
IS APPLIED DIRECTLY TO THE INPUT
PHOSPHUR
PHOTOEMISSIVE METAL
COMBINATION OF CESIUM AND ANTIMONY

16.  LIGHT FROM INPUT PHOSPHUR >>>>
PHOTOCATHODE >>>>>
PHOTOELECTRONS ARE EMITTED
 NO: OF ELECTRONS EMITTED IS
PROPORTIONAL TO BRIGHTNESS OF
SCREEN

18. ACCELERATING ANODE
 HAS POSITIVE POTENTIAL OF 25 TO 35 kV
RELATIVE TO PHOTOCATHODE
 ACCELERATE ELECTRONS
 BECAUSE OF THE POTENTIAL
DIFFERENCE THE ELECTRONS ARE
ACCELERATED TO VERY HIGH VELOCITY

19. ELECTROSTATIC FOCUSING
LENS
 SERIES OF POSITIVELY CHARGED
ELECTRODES
 JOB- TO FOCUS BEAM OF ELECTRONS
 POINT INVERSION- ALL ELECTRONS
PASS THROUGH A COMMON FOCAL
POINT ON THEIR PATHWAY

20. OUTPUT PHOSPHUR
 SILVER ACTIVATED ZINC CADMIUM SULPHIDE
 HAS DIAMETER OF ½ TO 1 INCH
 SINCE ELECTRONS ARE ACCELERATED >>>
MORE LIGHT PHOTONS ARE EMITTED FOR
EVERY ELECTRON.
 NO: OF LIGHT PHOTONS ARE INCREASED 50
FOLD

22. WORKING OF INTENSIFIER
TUBES

24.  EACH POINT IN INPUT PHOSPHUR IS
FOCUSED ON A SPECIFIC POINT ON THE
OUTPUT PHOSPHUR
 FOR UNDISTORTED FOCUSSING OF THE
IMAGE

25.  INPUT PHOSPHUR IS CURVED SO THAT
ELECTRONS EMITTED FROM THE
PERIPHERY ALSO TRAVELS THE SAME
DISTANCE
 OUTPUT IMAGE IS SMALLER IN SIZE
>>>> MORE BRIGHTNESS

26.  THIN LAYER OF ALUMINIUM ON THE INSIDE
SURFACE OF OUTPUT PHOSPHUR
 JOB--- TO PREVENT RETROGRADE
PASSAGE OF LIGHT FROM THE OUT PUT
PHOSPHUR TO PHOTOCATHODE

27. IMAGE CARRIERS
X RAY PHOTONS
LIGHT PHOTONS
PHOTOELECTRONS
LIGHT PHOTONS

28. MINIFICATION GAIN
 PRICE PAID FOR INCREASED
BRIGHTNESS IS THAT THE IMAGE IS
CORRESPONDINGLY SMALLER
 THE QUANTITY OF THIS GAIN DEPENDS
ON DIAMETER OF THE INPUT AND
OUTPUT SCREENS

29.  THE DIAMETER OF THE OUTPUT SCREEN
IS ABOUT ONE FIFTH AS THAT OF THE
INPUT SCREEN
 THE PHOTONS THAT MAKE UP THE IMAGE
ON BOTH SCREENS ARE THE SAME
 THE PHOTONS ARE COMPRESSED
TOGETHER ON A SMALLER SCREEN>>>>
BRIGHTER IMAGE

30. MINIFICATION GAIN =
- DIAMETER OF THE INPUT SCREEN
- DIAMETER OF THE OUTPUT
SCREEN

32. FLUX GAIN/ ELECTRON GAIN
 RATIO OF NUMBER OF LIGHT PHOTONS AT
THE OUTPUT PHOSPHUR TO THE NUMBER
OF X RAY PHOTONS AT THE INPUT
PHOSPHUR
 INCREASAE BRIGHTNESS BY A FACTOR
OF 50

33. BRIGHTNESS GAIN
 THE TOTAL BRIGHTNESS GAIN OF AN
IMAGE =
MINIFICATION GAIN X FLUX GAIN
 TENDS TO DETERIORATE AS THE IMAGE
INTENSIFIER AGES
 THEN THE PATIENT DOSE WILL BE
HIGHER
 DETERIORATON AT THE RATE OF 10 %
PER YEAR

34. CONVERSION FACTOR
RATIO OF THE LUMINANCE OF THE OUT
PUT PHOSPHUR TO THE INPUT XRAY
EXPOSURE RATE
LUMINANCE IS MEASURED IN candelas
{cd}
CONVERSION FACTOR =

35. IMAGING CHARACTERISTICS
CONTRAST
STATISTICAL FLUCTUATIONS
IMAGE DISTORTION

36. CONTRAST
BRIGHTNESS RATIO OF THE PERIPHERY TO
THE CENTRE OF THE OUTPUT SCREEN
THREE FACTORS DIMINISH CONTRAST

37. 1
THE INPUT PHOSPHUR DOES NOT
ABSORB ALL THE INCIDENT PHOTONS
 SOME OF THE TRANSMITTED ONES CAN
BE ABSORBED BY THE OUPUT
PHOSPHUR

38.  THESE PHOTONS INCREASE THE
BRIGHTNESS AT THE OUTPUT PHOSPHUR
BUT DOESN’T CONTRIBUTE TO IMAGE
FORMATION
 THESE PHOTONS WILL PRODUCE A
BACKGROUND OF FOG AND WILL REDUCE
THE CONTRAST

39. RETROGRADE FLOW OF LIGHT PHOTONS
FROM THE OUTPUT PHOSPHUR
 MOST OF THESE ARE BLOCKED BY THE
THIN ALUMINIUM LAYER
2

40.  THESE PHOTONS REACH THE
PHOTOCATHODE WHICH THEN EMITS
PHOTOELECTRONS WHICH AGAIN COME
AND STRIKE THE OUTPUT PHOSPHUR
 THEY INCREASE THE BRIGHTNNESS BUT
PRODUCE FOG SINCE THE DISTRIBUTION
OF THE ELECTRONS BEARS NO
RELATIONSHIP TO THE PRINCIPAL IMAGE

41. SIDEWAYS LIGHT SCATTERING IN THE
INPUT PHOSPHUR PRIOR TO ENTERING
THE PHOTOCATHODE
3

42. LAG
PERSISTENCE OF LUMINESCENCE AFTER
TERMINATION OF OF X RAY STIMULATION
PERSISTENCE OF IMAGES
USUALLY OF SHORT DURATION
DOESN’T INTERFERE WITH THE ACQUISITION
OF IMAGES

43. Eg :
FOR ZINC CADMIUM SULPHIDE 1% OF
IMAGE RETAINS AFTER 0.1 sec AND O.1%
IMAGE AFTER 0.5 sec
FOR CsI THE LAG TIMES ARE AROUND 1
ms

44. IMAGE DISTORTION
PIN CUSHION EFFECT
 APPEARANCE OF STRAIGHT LINES
CURVING TOWARDS THE EDGES
 THE ELECTRONS IN THE PERIPHERY OF
THE BEAM FLARE OUT FROM THE IDEAL
COURSE
 THE ELECTRIC FIELD CAN ACCURATELY
CONTROL THE ELECTRONS IN THE
CENTRE OF THE IMAGE BUT NOT THOSE
IN THE PERIPHERY

45. EFFECT
 FLARING OUT OF THE ELECTRONS
CAUSE UNEQUAL MAGNIFICATION >>>>
PERIPHERAL DISTORTION
 EFFECT IS MORE WITH LARGE
INTENSIFIERS

47. VIGNETTING
FALL OFF IN BRIGHTNESS AT THE
PERIPHERY OF IMAGE
UNEQUAL MAGNIFICATION PRODUCE
UNEQUAL ILLUMINATION
THE CENTER OF THE OUTPUT SCREEN IS
BRIGHTER THAN THE PERIPHERY

48. PERIPHERAL IMAGE DISPLAYED OVER A LARGE
AREA OF THE OUT PUT SCREEN
BRIGHTNESS GAIN FROM MINIFICATION IS LESS
THAN AT THE CENTER

49. VIGNETTING

50. MULTIPLE FIELD IMAGE
INTENSIFIERS
 ALWAYS BUILT-IN IN DIGITAL UNITS
 ALLOW FOCAL POINT CHANGE TO
REDUCE FIELD OF VIEW AND MAGNIFY
IMAGE
 DONE BY CHANGING THE VOLTAGE OF
THE ELECTROSTSATIC FOCUSING LENS

51. MULTIFIELD IMAGE INTENSIFIERS
 SMALLER DIMENSIONS – VOLTAGE OF
THE FOCUSING LENS IS INCREASED
 ELECTRON FOCAL SPOT MOVES AWAY
FROM THE OUT PUT SCREEN
 AS THE ELECTRONS CROSS THEY WILL
DIVERGE---- RESULTS IN MAGNIFIED
IMAGE

52.  ONLY THE ELCTRONS FROM THE CENTER
OF THE INPUT WILL STRIKE THE OUTPUT
 SPATIAL RESOLUTION IS BETTER
 LOW NOISE
 HIGH CONTRAST RESOLUTION

53. DUAL FIELD IMAGE
INTENSIFIER

54.  SEVERAL MODES 4.5” , 6” , 9”
 LARGE ANATOMICAL AREAS --- 9”
 WE REDUCE THE VOLTAGE OF THE FOCUSING
LENS
 THE ELECTRONS FOCUS OR CROSS OVER AT A
POINT CLOSE TO THE OUTPUT PHOSPHUR
 FINAL IMAGE IS SMALLER

55. MULTIFIELD IMAGE
INTENSIFIERS
 NO CHANGE IN THE PHYSICAL SIZE OF THE
INPUT AND OUT PUT SCREENS
 CHANGE IS ONLY IN THE SIZE OF THE OUTPUT
IMAGE
 DISADV: AS MAGNIFICATION THE
BRIGHTNESS
 TO COMPENSATE , HAVE TO INCREASE mA
 INCREASE PATIENT DOSE

56. 1st generation
 Utilize only a single potential difference to
accelerate electrons from the cathode to the
anode (screen). Focusing is achieved by two
methods:
by placing the screen in close proximity to the
photocathode (proximity diode)
by using an electron lens to focus electrons
originating from the photocathode onto the screen
(inverter diode)

57. 2nd generation
 The major difference between first and second
generation tubes is the use of electron multipliers
 Not only the energy but also the number of
electrons between input and output is significantly
increased.
 Multiplication is achieved by use of a device
called PHOTOELECTRON MULTIPLIER TUBES ---
MICRO CHANNEL PLATE DETECTORS

58. 3rd generation
 Employ proximity focus MCP
intensifiers with Gallium-Arsenide
photocathodes.

59. PHOTOMULTIPLIER TUBE
 A photomultiplier tube is useful for light
detection of very weak signals
 These detectors work by amplifying the
electrons generated by a photocathode
exposed to a photon flux.

60. Consists of
A TYPICAL PMT TUBE is a vaccum tube
 PHOTOEMISSIVE CATHODE
 FOCUSING ELECTRODES
 ELECTRON MULTIPLIER
 ELECRON COLLECTOR -- ANODE

61.  WHEN LIGHT ENTERS PHOTOCATHODE
>>> PHOTOELECTRONS ARE EMITTTED
INTO THE VACCUM
 THESE ELECTRONS ARE FOCUSED BY
FOCUSING ELECTRODE TOWARDS THE
ELECTRON MULTIPLIER
 CONSISTS OF A SERIES OF METAL
CHANNEL ELECTRODES – DYNODES --
EACH MAINTAINED AT A MORE POSITIVE
POTENTIAL

62.  14 TO 16 DYNODE ELEMENTS IN A PMT TUBE
 FOCUSING ELECTRODE DIRECT THE
PHOTOELECTRONS ON TO THE 1ST DYNODE
 THIS WILL INVOKE THE RELEASE OF
ADDITIONAL ELECTRONS THAT ARE
ACCELERATED TOWARDS THE NEXT DYNODE
AND SO ON…
SECONDARY EMISSION
 THESE ELECTRONS ARE THEN COLLECTED BY
THE ANODE AS AN OUTPUT SIGNAL

64.  THE SURFACE COMPOSITION AND THE
GEOMETRY OF THE DYNODES DETERMINE
THEIR ABILITY TO SERVE AS ELECTRON
MULTIPLIERS
 GAIN VARIES WITH THE VOLTAGE ACROSS THE
DYNODES AND THEIR TOTAL NUMBER
 ELECTRON GAINS OF 10 MILLION ARE POSSIBLE
IF 12 TO 14 DYNODE ELEMENTS ARE EMPLOYED

65. DUE TO
SECONDARY
EMISSION
MULTIPLICATON
PMT’S HAVE
EXTREMELY
HIGH SENSITIVITY
AND
EXCEPTIONALLY
LOW NOISE

67. 1. CIRCULAR – CAGE TYPE
HIGH GAIN AND FAST RESPONSE AT A
RELATIVELY LOW SUPPLY VOLTAGE

68. 2. BOX AND GRID TYPE
A TRAIN OF QUARTER CYLINDRICAL DYNODES.
HAS GOOD ELECTRON COLLECTION
EFFICIENCYAND EXCELLENT UNIFORMITY

69. 3. LINEAR – FOCUS TYPE
EXTREMELY FAST RESPONSE TIME
RELATIVELY LARGE OUTPUT CURRENT

70. 4. MICRO CHANNEL PLATE

71. MICROCHANNEL PLATE
 CONSISITS OF MILLIONS OF MICRO GLASS
TUBES FUSED IN PARALLEL WITH EACH OTHER
 THESE TUBES CONTAIN SECONDARY ELECTRON
EMITTTER ON THEIR INNER WALLS eg: CESIUM
IODODE ; COPPER IODIDE
 EACH CHANNEL ACT AS AN INDEPENDENT
ELECTRON MULTIPLIER

72.  ELECTRONS GENERATED BY THE PHOTOCATHODE
ARE DRIVEN THROUGH THE CHANNELS BY A
CONSTANT FIELD FROM VOLTAGE 600 TO 900
VOLTS APPLIED TO THE MCP
 THE ACHIEVABLE IMAGE RESOLUTION AND
DYNAMIC RANGE ARE LESS WHEN COMPARED TO
1ST GEN. INTENSIFIERS.
 BUT LUMINOUS GAIN IS TREMENDOUSLY
INCREASED

75. VIEWING AND RECORDING
OF
FLUOROSCOPIC IMAGING

76. OPTICAL SYSTEM
USED TO COUPLE XII TO PHOTOGRAPHIC
DEVICES AND / OR A VIDEO CAMERA
TWO METHODS :
LENS COUPLING
FIBRE OPTIC COUPLING

77. LENS COUPLING
 USUALLY COMPLEX ARRANGEMENTS OF LENSES
AND PRISMS
 LIGHT FROM THE OUTPUT PHOSPHUR IS
COLLECTED BY THE LENS SYSTEM ; CONVERTED
INTO A PARALLEL BEAM AND TRANSMITTED TO
THE LENS SYSTEM OF VIDEO CAMERA FOR
FOCUSSING ONTO ITS TARGET
 ADVANTAGE OF LENS COUPLING IS THAT IT
CAN BE USED TO ACCOMMODATE MORE THAN ONE
CAMERA

78.  APERTURE OR IRIS : IS USED TO
COLLIMATE THE OPTICAL IMAGE AND
TO CONTROL THE EXPOSURE OF CAMERA
 LOW INPUT EXPOSURE – OUTPUT
LUMINANCE LOW – AMOUNT OF LIGHT
AVAILABLE TO THE CAMERA IS LOW –
WIDE APERTURE TO OPTIMISE THE
LIGHT STRIKING THE CAMERA

79. SEMI- TRANSPARENT MIRROR
 PLACED BETWEEN THE APERTURE AND THE
CAMERA LENSES
 ACTS AS A BEAM SPLITTER WHICH DISTRIBUTES
THE LIGHT FROM THE OUT PUT PHOSPHUR TO A
CINE OR SPOT FILM CAMERA AND A VIDEO
CAMERA SIMULTANEOUSLY

81. FIBRE OPTIC COUPLING
 A fibre-optic bundle relays the
light from the output phosphor
directly to the video camera.
 Consists of a coherent bundle of
glass fibre light guides; each fibre
around 10 micrometer in diameter
Advantages
a smaller sized coupling system
increased efficiency and improved
image quality relative to lens-based
coupling

82. VIEWING A FLUOROSCOPIC
IMAGE
CLOSE CIRCUIT TELEVISION SYSTEM
Consists of
VIDEO CAMERA
VIDEO MONITOR

84. VIDEO CAMERA TUBES
 Translate the output image from an x-ray image
intensifier (XII) into an electronic signal which can
be:
 displayed on a video monitor,
 recorded by a video tape or disc recorder,
 fed to a computer for manipulation, analysis
and storage.
 Convert a two-dimensional spatial image
distribution to a one-dimensional temporal, voltage
distribution.

85. TYPES OF VIDEO CAMERA
Two types
PHOTOCONDUCTIVE CAMERAS –
Vaccum tube TV Cameras
SEMI CONDUCTOR VIDEO CAMERAS --
CCD Cameras, CMOS cameras
BOTH PRODUCE VIDEO SIGNAL BUT IN SUBSTANTIALLY
DIFFERENT WAYS

86. CAMERA TUBES
 VIDICON– USUALLY EMPLOYED
Good resolution , moderate lag and low image distortion
SEVERAL OTHER TYPES:
 PLUMBICON – trade mark of Philips
high performance tube ,very high resolution and low lag.
particularly suited to use with X-ray image intensifiers in
digital subtraction and angiographic applications.
 CHALNICON -- trade mark of Toshiba
 SATICON -- trade mark of Hitachi

87. CAMERA TUBE
SMALL ELECTRONIC VACCUM TUBE
1 inch in diameter and 6 inches in length
MAINLY 4 PARTS
o CATHODE
o CONTROL GRID
o ANODE
o TARGET ASSEMBLY
 ELECTROMAGNETIC FOCUSING COILS
 ELECTROSTATIC DEFLECTING COILS

89. VIDICON CAMERA
 CATHODE – AT THE OPPOSITE END OF THE
TUBE FROM TARGET
HEATED INDIRECTLY BY INTERNAL ELECTRIC
COILS – ELECTRONS ARE EMITTED ----
THERMIONIC EMISSION
 ANODE – EXTENDS ACROSS THE TARGET END
OF THE TUBE AS A THIN WIRE MESH
HAS A POSITIVE POTENTIAL OF OF ABOUT
250 V WITH RESPECT TO THE CATHODE

90. TARGET ASSEMBLY
3 LAYERS
 GLASS FACE PLATE
 SIGNAL PLATE
 TARGET

91. SIGNAL PLATE
 LOCATED ON THE INNER SURFACE OF
THE FACE PLATE
 THIN TRANSPARENT FILM OF GRAPHITE
POSITIVE POTENTIAL OF 25 V

92. TARGET
 THIN FILM OF PHOTOCONDUCTIVE MATERIAL–
ANTIMONY SULPHIDE
 ANTIMONY SULPHIDE SUSPENDED AS TINY GLOBULES
IN MICA MATRIX
 EACH GLOBULE IS ABOUT 0.001 inch IN DIAMETER
 GLOBULES ARE INSULATED FROM ITS NEIGHBOURS
AND FROM THE SIGNAL PLATE BY THE MICA MATRIX
 IN PLUMBICON – LEAD MONO OXIDE

93.  ELECTRONS EMITTED FROM CATHODE
 FORMED INTO A BEAM BY CONTROL GRID
 GRID INITIATE ACCELERATION OF THE
ELECTRONS TOWARDS TARGET
 ELECTRONS MOVE INTO THE
ELECTROSTATIC FIELD OF THE ANODE

94.  DUE TO THE 250 V POTENTIAL DIFFERENCE
THE ELECTRONS ARE ACCELERATED TO VERY
HIGH VELOCITY
 THE ANODE WIRE MESH AND THE SIGNAL PLATE
SET UP A DECCELERATING FIELD FOR THE
ELECTRONS
 THE ELECTRON BEAM IS DEFLECTED SLIGHTLY
UPWARDS AND VELOCITY DECREASES

95.  COMES TO A NEAR STAND STILL AS THEY
REACH THE TARGET
 THE DECCELERATING FIELD STRAIGHTENS THE
FINAL PATH OF ELECTRON BEAM SO THAT THEY
STRIKE THE TARGET PERPENDICULARLY
 ELECTROMANETIC COILS KEEPS THE BEAM OF
ELECTRONS IN A NARROW BUNDLE

96.  THE ELECTRONS PROGRESS IN A SERIES OF
OSCILLATING SPIRALS AND STRIKE THE
TARGET AS A NARROW BEAM
DEFLECTING COILS - 2 PAIRS
 VERTICAL – MOVES BEAM UP AND DOWN
 HORIZONTAL – MOVES BEAM SIDE TO SIDE

98. FORMATION OF VIDEO SIGNAL
 THE FLUOROSCOPIC IMAGE FROM THE XII IS
MADE TO FOCUS ONTO THE TARGET ASSEMBLY
 GLOBULE ABSORBS LIGHT >>>>
PHOTOELECTRONS ARE EMITTED >>>>
GLOBULES BECOME POSITIVELY CHARGED
 SINCE INSULATED FROM EACH OTHER AND FROM
THE SIGNAL PLATE IT BEHAVES LIKE HALF
OF A TINY CAPACITOR >>>> DRAWS
CURRENT ONTO THE SIGNAL PLATE
 THIS CURRENT IS IGNORED… NOT RECORDED

99. VIDEO SIGNAL
 THIS CHANGE IS OCCURING OVER THE ENTIRE
TARGET PLATE SURFACE
 A BRIGHTER AREA IN THE LIGHT IMAGE EMITS
MORE PHOTOELECTRONS WHEN COMPARED TO A
DIM AREA >>> PRODUCES A STRONGER
CHARGE ON THE TINY CAPACITORS
 A MOSAIC OF CHARGED GLOBULES THAT STORE
AN ELECTRICAL IMAGE WHICH IS AN EXACT
REPLICA OF THE LIGHT IMAGE FOCUSED ON TO
THE TARGET

100.  ELECTRON BEAM SCAN THE ELECTRONIC IMAGE
STORED ON THE TARGET >>> HOLES
LEFT BY THE EMITTED PHOTOELECTRONS GET
FILLED >>> NEUTRALISE / DISCHARGE
THE TINY GLOBULE CAPACITORS
 ELECTRONS IN THE SIGNAL PLATE NO LONGER
HAVE ELECTROSTATIC FORCE TO HOLD THEM ON
TO THE PLATE >>> THEY LEAVE THE
PLATE VIA THE RESISTOR >>>
PRODUCING A CURRENT

101.  THIS VOLTAGE WHEN COLLECTED FOR EACH
NEUTRALISED GLOBULE CONSTITUTES A
VIDEO SIGNAL
 EACH INSTANT ONLY A DOT IS GETTING
DISCHARGED >>> THEN THE BEAM MOVES
ON TO THE NEXT DOT
 SERIES OF VIDEO PULSES >>> EACH PULSE
CORRESPONDS TO EXACT LOCATION ON THE
TARGET

103. TV MONITOR
REASSEMBLING OF VIDEO PULSES BACK TO
LIGHT IMAGE IS DONE BY THE TV MONITOR
MAIN PART IS THE PICTURE TUBE
ELECTRONIC VACCUM TUBE
ELECTRON GUN [ CATHODE + CONTROL GRID]
ANODE– 10, 000 V
FLUORESCENT SCREEN
FOCUSING COILS
DEFLECTING COILS

104.  THE VIDEO SIGNAL IS RECEIVED BY THE
CONTROL GRID
 THE BRIGHTNESS OF THE INDIVIDUAL DOTS IS
REGULATED BY THE CONTROL GRID
 LARGE NUMBER OF ELECTRONS --- BRIGHTER
AREA OF IMAGE
 COILS CONTROL THE ELECTRON BEAM IN
EXACT SYNCHRONY WITH THE CAMERA TUBE

105. ELECTRONS STRIKE THE FLUORESCENT SCREEN
>>> EMITS LIGHT PHOTONS >>> VISIBLE
TELEVISION IMAGE
COLOUR MONITOR
 3 ELECTRON GUNS
 3 FLUOROSCENT MATERIALS
RED BLUE YELLOW

106. TELEVISION IMAGE QUALITY
RESOLUTION : depends on the size of the
input image
525 line TV SYSTEM with total resolution of
185 lp/ mm
LAG : when camera moved rapidly –
‘stickiness of image’ = image blur
Time for the image to build up and decay on
the vidicon target

107. TELEVISION IMAGE
BRIGHTNESS :
 AUTOMATIC BRIGHTNESS CONTROL
 AUTOMATIC GAIN CONTROL
: VARYING THE GAIN OF
TELEVISION AMPLIFICATION SYSTEM

108. AUTOMATIC BRIGHTNESS CONTROL
 An optical sensor - called the ABC sensor is
used in a feedback loop to the x-ray generator to
automatically adjust the radiation exposure in order
to maintain a constant image brightness
 This small photodetector senses the output
luminance and its output is used to appropriately
adjust the kVp, the mA or both factors, when the XII
is moved to screen a different part of the body.

109.  In fluorography, it can be used to
terminate an exposure pulse and to set an
appropriate kVp and mAs for the next
image.
 The ABC sensor is also useful when the
XII field size is changed so that, for
example, the exposure factors can be
increased automatically when a smaller
field size is chosen.

110. ABC SENSOR

111. SEMICONDUCTOR CAMERAS
CHARGED – COUPLED DEVICES
 Small photoelectronic imaging device
(typically 1.5 cm square) made from a crystal
of silicon in which numerous (at least
250,000) individual light-sensitive picture
elements (pixels) have been fabricated.
 These pixels are tiny capacitors
 Each pixel (less than 0.03 mm in size) is
capable of storing electronic charges created
by the absorption of light

113.  Extraction of the locally stored charges from
each pixel, is done by transferring or "coupling"
charges from one pixel to the next by the
controlled collapse and growth of adjacent
storage sites or potential wells
 Each well is formed inside the silicon crystal by
the electric field generated by voltages applied
to tiny, semi-transparent metallic electrodes on
the CCD surface--- CLOCKING GATES.

114.  An image is projected by a lens on the capacitor array,
causing each capacitor to accumulate an electric
charge proportional to the light intensity at that
location.
 Once the array has been exposed to the image, a
control circuit causes each capacitor to transfer its
contents to its neighbour.
 The last capacitor in the array dumps its charge into
an amplifier that converts the charge into a voltage

115.  The control circuit converts the entire contents
of the array to a varying voltage, which it
samples, digitizes and stores in memory.
 Stored images can be transferred to a printer,
storage device or video display.

117. CMOS CAMERAS
COMPLEMENTARY METAL- OXIDE SEMICONDUCTOR
DEVICES
Eg : flat panel detectors
LARGER PIXEL SIZE
ALL CIRCUITARY WITHIN CHIP
CREATES DIGITAL SIGNAL ON THE CHIP

118. RECORDING OF
FLUOROSCOPIC IMAGES

119. TWO METHODS
DIRECT METHODS : USE THE LIGHT IMAGE
FROM THE OUTPUT PHOSPHUR OF THE IMAGE
INTENSIFIER
SPOT FILM RECORDER
CINEFLUOROGRAPHY
INDIRECT METHODS : USE THE ELECTRICAL
SIGNAL FROM THE TV CAMERA
TAPE RECORDER
DIGITAL FLUOROSCOPY

120. SPOT FILM RECORDING
 THIS ALLOWS A CONVENTIONAL SCREEN FILM
CASSETTE EXPOSURE IN CONJUNCTION WITH
FLUOROSCOPIC VIEWING
 AN X RAY FILM CASSETTE IS INTERPOSED
BETWEEN THE X RAY BEAM AND IMAGE
INTENSIFIER TUBE
 CONDUCTED AT ABOUT 80 TO 90 kVp and
1 to 3 mA of TUBE CURRENT
 THERE IS A PHOTO TIMER THAT CONTROLS THE
LENGTH OF EXPOSURE

121. DIFFERENCES FROM GENERAL RADIOGRAPHY
 LIMITATION IN THE FILM SIZES – USUALLY
USE 10”- 8” FILM
 SPOT FILMS ALLOW MORE THAN ONE IMAGE TO
BE OBTAINED ON A SINGLE FILM
 SCREEN FILM COMBINATIONS WITH A SPEED OF
AROUND 400 ARE USED
 SLIGHTLY MORE MAGNIFICATION OF PATIENTS
FEATURES

122. CINE FLUOROGRAPHY
 PROCESS OF RECORDING
FLUOROSCOPIC IMAGES ON A MOVING
FILM
 2 FILM SIZES ARE USED , 16 MM AND 35
MM
 35 mm USED FOR CARDIAC CINE
FLUOROGRAPHY