1. Flouroscopic imaging

2. Fluoroscopy Purpose To visualize, in real time: organ motion
ingested or injected contrast agents
insert stents
cathetarize small blood vessels
REAL TIME IMAGING

3. X-rays were discovered because of there ability to cause fluorescence .
The first x-ray image of human part was observed fluoroscopically-Dr. Glasser.

4. FLUOROSCOPE

5. THE FLUOROSCOPE
First generation fluoroscopes consisted of an x-ray tube, an x-ray table and a fluoroscopic screen.
A sheet of lead glass covered the screen, so that radiologist could stare directly into the screen with out having the x-ray beam strike his eyes.

6. The fluorescent material used in screen was copper activated zinc cadmium sulfide that emitted light in yellow-green spectrum.
Screen fluoroscence was very faint so, the examination was carried out in a dark room by the radiologist who had to adapt his eyes by wearing red goggles for mins prior to the examination  technique is now obsolete & gone.

7. Photograph shows an early (1933) fluoroscopic system in use before the development of image intensification. An actual fluoroscopic examination with this device would have occurred in a darkened room.

8. IMAGE INTENSIFIER DESIGN
Image intensifier was discovered in 1950s-to produce an image bright enough to allow cone vision without giving the pt an excess radiation exposure.
The tube itself is an evacuated glass envelope ,a vacuum tube containing-
1.input phosphor and photocathode .
2.electrostatic focusing lens.
3.accelerating anode.
4.out put phosphor.

9. IMAGE INTENSIFIER

10. After an x-ray beam passes the pt it enters the image intensifier tube the input fluorescent screen absorbs x-ray photons and converts their energy into light photons.
The light photons strike the photo cathode, causing it to emit photoelectrons  these electrons are immediately drawn away from the photocathode by the high potential difference betn it &the accelerating anode.
As the electrons flow from the cathode towards the anode, they are focused by an electrostatic lens which guides them to the output fluorescent screen without distorting their geometric configuration.

11. The electrons strike the output screen, which emits the light photons that carry the fluoroscopic images to the eye of the observer.
In intensifier tube, the image is first carried by the x-ray photons, then by the light photons, next by the electrons &finally by the light photons.

13. INPUT PHOSPHOR & PHOTO CATHODE:
The input fluorescent screen in image intensifiers is cesium iodide (CsI). (older intensifier- silver activated zinc cadmium sulfide).
CsI is deposited on a thin aluminum substrate by a process called “vapor deposition”.  an interesting & useful characteristic of CsI is that during the deposition process the crystals of CsI grow in tiny needles perpendicular to the substrate.  There by reducing scattering.

14. INPUT PHOSPHOR & PHOTO CATHODE:
Image quality is dramatically better with CSI input screen than it was with zinc cadmium sulfide screens.
Three physical characteristics of CsI make it superior.
1. vertical orientation of the crystals.
2. A greater packing density &
3. A more favorable effective atomic number.
Phosphor thickness have been reduced comparably from app. 0.3mm with Zn-Cd su to 0.1mm with CsI. The principal advantage of thinner phosphor layer combined with needle shaped crystals is improved resolution.

15. The photo cathode is applied directly to the CsI input phosphor.
The photo cathode is a photoemissive metal (commonly a combination of antimony & cesium compounds).
The photo cathode is applied directly to the CsI input phosphor.

16. ELECTROSTATIC FOCUSING CUP:
series positively charged electrodes that are usually plated on to the inside surface of the glass envelope.
These electrodes focus the electron beam as it flows from the photocathode toward the output phosphor.
Electron focusing inverts & reverses the image which is called “point inversion” because all the electrons pass through a common focal point on their way to output phosphor.

17. The input phosphor is curved to ensure that electrons emitted at the peripheral regions of the photocathode travel the same distance as those emitted from the central region.
The image on the output phosphor is reduced in size ,which is one of the principle reasons why it is brighter.

18. The anode is located in the neck of the image tube.
ACCELERATING ANODE :
The anode is located in the neck of the image tube.
Its function is to accelerate electrons emitted from the photocathode towards the output screen. the anode has a +ve potential of 25 to 35 kv relative to the photocathode, so it accelerates electrons to a tremendous velocity.

19. OUTPUT PHOSPHOR:
silver activated zn-cd sulfide, the same used in Ist generation input phosphor.
Crystal size and layer thickness are reduced to maintain resolution in the minified image.
A thin layer of aluminum is plated onto the fluorescent screen prevent light from moving retrograde through the tube & activating the photocathode.

20. The glass tube of the image intensifier is 2 to 4mm thick & enclosed in a lead lined metal container protects the operator from stray radiation.
The output phosphor image is viewed either directly through a series of lenses and mirrors or indirectly through closed circuit TV.

21. BRIGHTNESS GAIN:
Two methods are used to evaluate the brightness gain of image intensifiers.
First compares the luminance of an intensifier output screen to that of a Patterson type B2 fluoroscopy screen when both are exposed to same quantity of radiation.
The brightness gain is the ratio of the two illuminations.
Brightness gain=intensifier luminance/Patterson b-2 lumin.

22. Another way is “conversion factor”
Another way is “conversion factor”. The method is accurate & reproducible.
Conversion factor =cd/m2 by mR/sec
The brightness gain tends to deteriorate as the image intensifier ages. ie the pt dose with an older image intensifier tends to be higher than with a new intensifier of the same type.
The brightness gain of an II comes from 2 completely unrelated sources called minification gain &flux gain.

23. MINIFICATION GAIN:
The brightness gain from minification is produced by a reduction in image size.
Depends on the relative areas of input &output screens. coz the size of the intensifier is usually indicated by its diameter.
MG=(d1/d0)2.d1=diameter of input screen,d0=diameter of output screen.
Most II have an input screen from 5 to9 in. & an output screen of app 1 inch diameter.

24. Theoretically minification can be increased indefinitely but as the minification is increased the image becomes smaller.-disadvantage.
Hence image has to be magnified and viewed which will result in reduce brightness & precipitous drop in resolution.

25. Brightness gain =minification gain x flux gain.
FLUX gain increases the brightness of the fluoroscopic image by a factor of app 50.
The total brightness of an II is product of minification & flux gain: ie
Brightness gain =minification gain x flux gain.

26. MULTIPLE-FIELD IMAGE INTENSIFIERS
Dual field or triple field II attempt to resolve the conflicts btn image size & quality.
They can be operated in several modes, including the 4.5in, a 6in, or a 9in mode. the 9in mode is used to view large anatomic areas. When size is unimportant the 4.5in or 6in mode is used coz of better resultant image quality.
Field size is changed by a simple electronic principle: the higher the voltage on the electrostatic focusing lens, the more the electron beam is focused.

27. This figure shows this principle applied to a dual field II.
In the 9in mode, the electrostatic focusing voltage is decreased. the electrons focus to a point or cross, close to the output phosphor & the final image is actually smaller than the phosphor.
In 6in mode the electrostatic focusing voltage is increased & the electrons focus farther away from the output phosphor. after the electrons cross they diverge, so the image on the output phosphor is larger than in the 9in mode.

28. Optical coupling

29. Optical coupling
Optical system transmits the output of the image intensifier to the light sensitive area of the video camera
The optical distributor include beam-splitting mirror, which directs a portion of the light from the image intensifier output window to an accessory device for image recording and passes the remainder to the video camera.
Two lenses are mounted in tandem
The II and the vidicon are placed at the focal planes of the two lenses

30. Closed-circuit Television System
used to view the image intensifier output image
Consists of
1)Television camera
2) Camera control unit
3) Monitor
The television system allows for real-time viewing of the fluoroscopic image by several people at once from one monitor or multiple monitors

31. Television Camera Tube
Output phosphor is directly coupled to a TV camera tube
Plumbicon
Vidicon
CCD

32. a) Glass plate assembly
The basic video camera consists of
1) vacuum tube cylinder (approximately 2.5 cm in diameter) surrounded by electromagnetic focusing coils ,2 pairs of electrostatic deflecting coils
2) photoconductive target
3) a scanning electron beam
Target assembly:
a) Glass plate assembly
b) signal plate
c) Target

34. Target Functionally most important in tube
Thin film of photoconductive material, antimony sulfide suspended as globules in mica matrix.
The optical coupling lens focuses the image intensifier output image onto the target, forming a charge image within the photoconductive layer

35. This latent image is read out by the electron beam, which scans across the target in a series of horizontal raster lines.
As the scanning electron beam moves across the target, a current signal is produced that represents the two-dimensional image as a continuous series of raster lines with varying voltage levels.

38. Video signal When globules absorbs light ,photoelectrons are emitted
The globule becomes positively charged
The electron beam scans the electrical image stored on the target & fills in the holes left by the emitted photoelectrons, discharging the tiny globular capacitors

39. When the electrons in beam neutralize the positive charge in the globules , the electrons on the signal plate leave the plate via resistor
These moving electrons form a current flowing through a resistor and voltage across the resistor
This voltage ,when collected for each neutralized globule, constitutes the video signal

40. CCD Same resolution as vidicon No electron beam needed for reading
Stores negative charge
PLUMBICON- PbO is the photoconductive material

41. Camera control unit
Reassembling the pulses to a visible image

42. Television monitor
The video signal produced by the video camera is converted into a visible image by the monitor
Contains picture tube & controls for regulating brightness & contrast
Picture tube contains-
Electron gun
control grid
anode
focusing coil, deflecting coil-control the electron beam
synchrony with the camera tube

44. Control grid-receive video signal from Camera control unit ,uses this signal to regulate the no. of electrons in electron beam
Anode –carries higher potential (10,000V) accelerates the electron beam to much higher velocity
The electron Strike the fluorescent screen ,emit large number of light photons.

46. Image Recording Two modes of recording the fluoroscopic image -
1) light image from output phosphor of II recorded on film with a photospot camera or cine camera
2) electrical signal generated by TV camera-includes magnetic tape, magnetic discs & optical discs

47.    DIRECT FILM RECORDING
SPOT FILM DEVICES:
Fluoroscopic systems designed for gastrointestinal imaging are generally equipped with a spot film device.
The spot film device allows exposure of a conventional screen-film cassette in conjunction with fluoroscopic viewing. This rather familiar system, located in front of the image intensifier, accepts the screen-film cassette and "parks" it out of the way during fluoroscopy
Cassettes may be loaded from the front or rear depending on the design of the system.

48.   Standard spot film imaging configuration typical of gastrointestinal fluoroscopy equipment. The screen-film cassette is parked out of the x-ray field until the spot film trigger is pressed, causing both the cassette and the formatting mask to move into position.

49. The x-ray field size is also reduced automatically by the collimators at the time of exposure to minimize scattered radiation and patient radiation dose.
Spot film imaging uses essentially the same technology as conventional screen-film radiography.
Differences and limitations of spot film imaging compared with general radiography.
One major limitation is the range of film sizes available for spot film imaging. Although some older fluoroscopy equipment is limited to a single size, usually 24 x 24 cm, current equipment allows a range of film sizes to be used, from 20 x 25 cm to 24 x 35 cm.
Spot film devices usually allow more than one image to be obtained on a single film.
Formats typically include one, two, three, four, or six images on a film.

50. A number of factors affect patient doses in spot film imaging.
Moving the spot film device closer to the patient reduces the amount of magnification and decreases the patient radiation dose.
A number of factors affect patient doses in spot film imaging.
The source-to-skin distance is shorter in spot film imaging than in general radiography.
Although the automatic exposure control system fixes the exposure to the screen, the shorter source-to-skin distance increases the inverse square reduction in radiation intensity as it passes through the patient.
This increase tends to make the skin entrance exposure higher.
The field size in spot film imaging is generally smaller than that used in general radiography.
This smaller field size reduces scatter and therefore tends to reduce dose. For the same reason, grids used in fluoroscopy generally have a lower grid ratio and therefore a smaller Bucky factor, which also leads to lower dose.
These effects tend to offset each other to a large extent.

51. One of the major shortcomings of conventional spot film devices is the delay involved in moving the cassette into position for exposure.
In vascular imaging, more rapid film movement is achieved with automatic film changers.

52. Photospot camera Records the the image output of an II on a film
Film – role film/cut film(10 cm)
Advantage –1)reduction in pt exposure
2)film does not have to be changed
b/w exposures
3)exposure times are shorter-motion is less likely problem
4)films can be taken more rapidly
5)possible to record & view image at same time

53. Framing with spot film cameras:
Framing –utilisation of available area on film
The output phosphor of II tube is round, shape of film is square
4 framing patterns
1) Exact framing
2) Equal area framing
3) mean diameter framing
4) total area framing
Equal area framing or mean diameter framing is recommended for most clinical situations.

55. Cineflourography
Process of recording fluoroscopic images on movie (cine) film
Two film sizes- 16 mm, 35 mm
Cine camera-components are lens, iris diaphragm, shutter, aperture, pressure plate, pull down arm & film transport mechanism

57. TV image recorders :
TAPE RECORDER : used for both recoding& playback
as a recorder receives video signal from camera control unit
for playback transmits the signal to one or more several TV monitors
Components:1)magnetic tube
2)writing head
3) tape transport system
Writing head converts an electrical signal in to magnetic field for recoding & converts magnetic signal to electric signal for replay

62. DIGITAL FLUOROGRAPHY
Digital charge-coupled device (CCD) TV cameras are rapidly replacing conventional TV cameras in fluoroscopic systems. An analog, high-resolution (1,023-line) TV camera has a vertical resolution of about 358 line pairs. A high-resolution CCD camera with a 1,024 x 1,024 matrix will provide equivalent vertical resolution. However, the digital camera will have the same vertical and horizontal resolution, whereas the horizontal resolution of the analog camera is defined by its electronic band-pass.

63. For a 15-cm-diameter intensifier input, the limiting resolution of the CCD camera would be 358 lp/150 mm or 2.4 lp/mm. This result is about half the resolution of a photospot film.
This resolution loss is made up for by the ability to digitally increase display contrast, reduce noise, and enhance the edges of digital images.
There are several other advantages to digital photospot images. Mechanical devices are not needed for film transport. Film processing is not required. Images can be viewed immediately. The linear response of the digital system makes it very forgiving of under- or overexposure.

64. Fluoroscopic Equipment Configurations
The basic configurations include radiography/fluoroscopy (R/F) tables with either an under-table or over-table x-ray tube and fixed C-arm, mobile C-arm, and mini C-arm
R/F Units with Under-Table X-ray Tube:
most common fluoroscopic equipment configuration
The x-ray tube and collimator are mounted below the tabletop with the image intensifier tower mounted above the table on a carriage that can be panned over the patient.
In addition, R/F systems include an overhead x-ray tube that can be used for regular radiography with a Bucky incorporated into the table.
Other common features include a tilting table and image recording devices.

65. R/F Units with Over-Table X-ray Tube
x-ray tube mounted over the table with the image intensifier below.
this configuration results in increased patient access, which is helpful for interventional procedures.
Radiography can be performed with the same x-ray tube and a Bucky incorporated into the table.
The x-ray tube can be angled to acquire angulated projections or tomograms.

66. THANK U