1. X-RAYS IN MOTION “Viewing dynamic studies of the human body”
FLUOROSCOPY
X-RAYS IN MOTION
“Viewing dynamic studies of the human body”

2. HISTORY
Thomas Edison, 1896
Screen (zinc-cadmium sulfide) placed over patient’s body in x-ray beam
Radiologist looked directly at screen
Red goggles-30 minutes before exam
1950 image intensifiers developed

3. PRESENTLY….
Fluoro viewed at same level of brightness as radiographs ( lux)
X-ray tube under table/over table or in c-arm
Image intensifier above patient in carriage
Carriage also has the power drive control, spot film selection and tube shutters

4. RED GOGGLES? The eye Light passes thru the cornea
Between the cornea and lens is iris
Iris acts as a diaphragm
Contracts in bright, dilates in dark

5. Light hits lens which focuses the light onto the retina where the cones and rods await
Cones- central
Rods - periphery

6. RODS CONES Sensitive to low light
Used in night vision (scotopic vision)
Dims objects seen better peripherally
Color blind
Do not perceive detail
Less sensitive to light (threshold of 100 lux)
Will respond to bright light
Daylight vision (phototopic vision)
Perceive color, differences in brightness
Perceive fine detail

7. IN FLUOROSCOPY
The winner is……
CONES!!

8. FLUORO X-RAY TUBES
Operate at .5 to 5mA. Why do they operate at such low mA stations?
They are designed to operate for a longer period of time with higher kVp for longer scale contrast.
kVp dependent on body section
kVp and mA can be controlled to select image brightness
Maintaining (automatic) of the brightness us called ABC or ABS or AGC (control,stabilization gain control)

9. Fluoro X-ray Tubes
Fixed…may be mounted no closer than 15 inches or 38 cm to patient
Mobile may be brought no closer than 12 inches or 30 cm to patient

10. IMAGE INTENSIFIER RECEIVE REMNANT X-RAY BEAM, CONVERT IT TO LIGHT…INCREASE THE LIGHT INTENSITY ,000 TIMES

11. THE SEQUENCE Beam exits the patient
Hits the input phosphore(cesium iodide CsI tightly packed needles…produce excellent spatial resolution)
Converts x-rays to visible light

12. The sequence cont. Hits photocathode (Cesium and antimony components)
Emits electrons when struck by light (photoemission)

13. The sequence cont
The potential difference within the image intensifier tube is a constant 25,000 volts
Electrons are accelerated to anode
Anode is a circular plate with hole for electrons to go thru.
Hits output phosphor which interact with electrons and produce light

14. The Electron Path MUST BE FOCUSED FOR ACCURATE IMAGE PATTERN
Electrostatic lenses (focusing devices)
Accelerate and focus electron beam
“The engineering aspect of maintaining proper electron travel is called electron optics”

15. Continuing the sequence
Electrons hit output phosphor (zinc cadmium sulfide) with high kinetic energy producing an increased amount of light
Each photoelectron at the output phosphor has more light photons

16. FLUX GAIN
Ratio of number of light photons at the output phosphor to the number of x-rays at the input phosphor
Flux gain =
# of output light photon
# of input x-ray photons

17. MINIFICATION GAIN
Ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor OR
# of electrons produces at large input screen ( 6 inches) squared, compressed into the area of small output screen ( 1 inch) squared
Try the math
6 inches squared = 36
1 inch squared = 1
Minification gain = 36

18. BRIGHTNESS GAIN Minification gain x flux gain
Increases illumination level of an image
Ratio of the intensity of the illumination ot the output phosphor to the radiation intensity at the input phosphor
Brightness gain of ,000
Maintaining (automatic) of the brightness us called ABC or ABS or AGC (control,stabilization gain control)

19. CONVERSION FACTOR
Ratio of intensity of illumination at the output phosphor (measured in Candela per meter squared) to the radiation intensity at the input phosphor (mR per sec)
Cd/mr squared
mr/s

20. MULTIFIELD IMAGE INTENSIFICATION Allows focal point change to reduce field of view and magnify the image

21. Some facts about multifield image intensifiers
Standard component on most machines
Always built in in digital units
Most popular is 25/17
Trifield tubes are 25/17/12 or 23/15/10

22. MULTIFIELD IMAGE INTENSIFICATION
Numeric dimensions refer to the input phosphor (25/17)
Smaller dimension (25/17) result in magnified images
At 25-all photoelectrons are accelerated to output phosphor

23. MULTIFIELD IMAGE INTENSIFICATION
Smaller dimension – voltage of focusing lenses is increased
Electron focal spot moves away from the output.
Only the electrons from the center of input strike the output

24. PROS CONS Only central region of input is used
Spatial resolution is better (think of it as the umbra!)
Lower noise, higher contrast resolution
Minification gain is reduced = dimmer image
To compensate must increase mA
Increase patient dose

25. VIGNETTING: REDUCTION OF PERIPHERAL BRIGHTNESS

26. COMING SOON Coupling (Vidicon, Plumbicon) Fiber Optics Lens coupling
Beam splitting
Modulation
Size of the video signal directly proportion to the light intensity received by x-ray tube. The signal received by the TV tube is modulated

27. Image recording Cassette loaded spot film Photospot camera
When recording image, the radiographic mA goes from a low mA to high mA. Why?
Photospot camera
Patient dose increases with size of film

28. DIGITAL FLUOROSCOPY Bushong, Chapter 27 pgs 437-441
Reference: Chapter 12, Fauber pg to include figure 12-6

29. Why is it easy to convert a conventional fluoro unit to a digital one?
QUESTION
Why is it easy to convert a conventional fluoro unit to a digital one?

30. Facts about digital fluoro
Image acquisition is faster
Can post process
Similar equipment to a conventional fluoro room except
two monitors
Operates in radiographic mode

31. DF and radiographic mode
Hundreds of mA vs 5 mA
Due to the high generator required for DF
the x-ray beam is pulsed progressive fluoroscopy

32. PULSED PROGRESSIVE FLUOROSCOPY
Generator can be switched on and off rapidly
Interrogation time
Tube switched on and meets selected levels of kVp and mA
Extinction time
Time required for the tube to be switched off
Each must have times of less than one 1 ms.

33. CCD
Instead of a vidicom or plumbicom (see figure 27-8, pg 440 Bushong)
Discuss Box 27-1 on pg 441

34. FPIR (pg 440-442) Flat panel Image receptor Replacing CCD’s
Made of cesium Iodide pixel detectors
Lighter, smaller than image intensifiers
No cassette needed

35. FPIR CONT.
Improvement to image as the spatial resolution is uniform and distortion free
High DQE
Improved contrast
Rectangular image
See page 442 Box 27-2