1. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
L16.1: Optimization of protection in fluoroscopy
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. Part No...., Module No....Lesson No
Module title
Introduction
Subject matter : fluoroscopy equipment and accessories
Different electronic component contribute to the image formation in fluoroscopy.
Good knowledge of their respective role and consistent Quality Control policy are the essential tools for an appropriate use of such equipment.
Explanation or/and additional information
Instructions for the lecturer/trainer
16.1: Optimization of protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

3. Part No...., Module No....Lesson No
Module title
Topics
Example of fluoroscopy systems
Image intensifier component and parameters
Image intensifier and TV system
Explanation or/and additional information
Instructions for the lecturer/trainer
16.1: Optimization of protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

4. Part No...., Module No....Lesson No
Module title
Overview
To become familiar with the components of the fluoroscopy system (design, technical parameters that affect the fluoroscopic image quality and Quality Control).
Lecture notes: ( about 100 words)
Instructions for the lecturer/trainer
16.1: Optimization of protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

5. Part 16.1: Optimization of protection in fluoroscopy
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 16.1: Optimization of protection in fluoroscopy
Topic 1: Example of fluoroscopy systems
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

6. 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
Modern systems include image intensifier with television screen display and choice of recording devices
16.1: Optimization of protection in fluoroscopy

7. Fluoroscopy X-ray transmitted trough patient
The photographic plate replaced by fluorescent screen
Screen fluoresces under irradiation and gives a live image
Older systems— direct viewing of screen
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
16.1: Optimization of protection in fluoroscopy

8. Main source of 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 of staff exposure is NOT the patient but direct beam
16.1: Optimization of protection in fluoroscopy

9. Older Fluoroscopic Equipment (still in use in some countries)
Staff in DIRECT beam
16.1: Optimization of protection in fluoroscopy

10. Direct fluoroscopy AVOID USE OF DIRECT FLUOROSCOPY
Directive 97/43Euratom Art 8.4.
In the case of fluoroscopy, examinations without an image intensification or equivalent techniques are not justified and shall therefore be prohibited.
Direct fluoroscopy will not comply with BSS
“… performance of diagnostic radiography and fluoroscopy equipment and of nuclear medicine equipment should be assessed on the basis of comparison with the diagnostic reference levels
16.1: Optimization of protection in fluoroscopy

11. Modern Image Intensifier based fluoroscopy system
16.1: Optimization of protection in fluoroscopy

12. Modern fluoroscopic system components
Automatic control
display brightness
radiation dose
film exposure
Timer
Display control
16.1: Optimization of protection in fluoroscopy

13. 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.
16.1: Optimization of protection in fluoroscopy

14. Different fluoroscopy systems
Interventional radiology systems
Requires specific safety considerations.
In interventional radiology the physician can be near the patient during the procedure.
Multipurpose fluoroscopy systems
Can be used as a remote control system or as a system to perform simple interventional procedures
16.1: Optimization of protection in fluoroscopy

15. Part 16.1: Optimization of protection in fluoroscopy
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 16.1: Optimization of protection in fluoroscopy
Topic 2: Image Intensifier component and parameters
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

16. The image intensifier (I.I.)
I.I. Input Screen
Electrode E1
Electrode E2
Electrode E3
Electrons Path
I.I.Output Screen
Photocathode +
16.1: Optimization of protection in fluoroscopy

17. Image intensifier systems
16.1: Optimization of protection in fluoroscopy

18. 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 : focusing of electrons onto the output screen
electrodes provide the electronic de-magnification
Output screen: conversion of accelerated electrons into light photons
16.1: Optimization of protection in fluoroscopy

19. Image intensifier parameters (I)
Conversion coefficient (Gx): the ratio of the output screen brightness to the input screen dose rate—
Gx = cd.m-2Gys-1
Gx depends on :
the applied tube potential
the diameter () of the input screen
I.I. input screen () of 22 cm  Gx = 200
I.I. input screen () of 16 cm  Gx = 200 x (16/22)2 = 105
I.I. input screen () of 11 cm  Gx = 200 x (11/22)2 = 50
16.1: Optimization of protection in fluoroscopy

20. Image intensifier parameters (II)
Brightness Uniformity: the input screen brightness may vary from the center of the image intensifier to the periphery
Uniformity = (Brightness(c) - Brightness(p)) x 100 / Brightness(c)
Geometrical distortion: all X Ray image intensifiers exhibit some degree of pincushion distortion. This is usually caused by a local magnetic field.
16.1: Optimization of protection in fluoroscopy

21. Image distortion
16.1: Optimization of protection in fluoroscopy

22. Image intensifier parameters (III)
Spatial resolution limit: the value of the highest spatial frequency that can be visually detected
it provides a sensitive measure of the state of focusing of a system
it is quoted by manufacturer and usually measured optically and under fully optimized conditions. This value correlates well with the high frequency limit of the Modulation Transfer Function (MTF)
it can be assessed with a resolution pattern which contains several sets of patterns at various frequency
16.1: Optimization of protection in fluoroscopy

23. Line pair gauges
16.1: Optimization of protection in fluoroscopy

24. Line pair gauges GOOD RESOLUTION POOR RESOLUTION
16.1: Optimization of protection in fluoroscopy

25. Image intensifier parameters (IV)
Overall image quality - threshold contrast-detail detection
X Ray, electrons and light scatter process in an I.I. can result in a significant loss of contrast of radiological detail. The degree of contrast exhibited by an I.I. is defined by the design of the image tube and coupling optics.
Spurious sources of contrast loss are:
accumulation of dust and dirt on the various optical surfaces
reduction in the quality of the vacuum
aging process (deterioration of phosphor screen)
Sources of noise are:
X Ray quantum mottle
photon-conversion processes, film granularity, film processing
16.1: Optimization of protection in fluoroscopy

26. Image intensifier parameters (V)
Overall image quality can be assessed using a suitable threshold contrast-detail detectability test object which comprises an array of disc-shaped metal details and gives a range of diameters and X Ray transmission
Sources of image degradation such as contrast loss, noise and unsharpness limit the number of details that are visible.
If performance is regularly monitored using this test, any sudden or gradual deterioration in image quality can be detected as a reduction in the number of low contrast or small details.
16.1: Optimization of protection in fluoroscopy

27. Overall image quality
16.1: Optimization of protection in fluoroscopy

28. Part 16.1: Optimization of protection in fluoroscopy
Part No...., Module No....Lesson No
Module title
IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 16.1: Optimization of protection in fluoroscopy
Topic 3: Image Intensifier and TV system
Part …: (Add part number and title)
Module…: (Add module number and title)
Lesson …: (Add session number and title)
Learning objectives: Upon completion of this lesson, the students will be able to: …
. (Add a list of what the students are expected to learn or be able to do upon completion of the session)
Activity: (Add the method used for presenting or conducting the lesson – lecture, demonstration, exercise, laboratory exercise, case study, simulation, etc.)
Duration: (Add presentation time or duration of the session – hrs)
Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate)
References: (List the references for the session)
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

29. Image intensifier - TV system
Output screen image can be transferred to different optical displaying systems:
conventional TV
262,5 odd lines and 262,5 even lines generating a full frame of 525 lines (in USA)
625 lines and 25 full frames/s up to 1000 lines (in Europe)
interlaced mode is used to prevent flickering
Cine film
35 mm film format: from 25 to 150 images/s
photography
roll film,105 mm: max 6 images/s
film of 100 mm x 100 mm
16.1: Optimization of protection in fluoroscopy

30. GENERAL SCHEME OF FLUOROSCOPY
VIDICON
FILM PM
REFERENCE kV
CONTROLLER
X Ray TUBE
GENERAL SCHEME OF FLUOROSCOPY
16.1: Optimization of protection in fluoroscopy

31. CINE MODE kV X Ray TUBE FILM VIDICON PM I2 Ref. I3 C1 I1 C2 CONTROLLER
16.1: Optimization of protection in fluoroscopy

32. Type of TV camera VIDICON TV camera
improvement of contrast
improvement of signal to noise ratio
high image lag
PLUMBICON TV camera (suitable for cardiology)
lower image lag (follow up of organ motion)
higher quantum noise level
CCD TV camera (digital fluoroscopy)
digital fluoroscopy spot films are limited in resolution, since they depend on the TV camera (no better than about 2 c/mm) for a 1000 line TV system
16.1: Optimization of protection in fluoroscopy

33. TV camera and video signal (I)
The output phosphor of the image intensifier is optically coupled to a television camera system. A pair of lenses focuses the output image onto the input surface of the television camera.
Often a beam splitting mirror is interposed between the two lenses. The purpose of this mirror is to reflect part of the light produced by the image intensifier onto a 100 mm camera or cine camera.
Typically, the mirror will reflect 90% of the incident light and transmit 10% onto the television camera.
16.1: Optimization of protection in fluoroscopy

34. TV camera and video signal (II)
Older fluoroscopy equipment will have a television system using a camera tube.
The camera tube has a glass envelope containing a thin conductive layer coated onto the inside surface of the glass envelope.
In a PLUMBICON tube, this material is made out of lead oxide, whereas antimony trisulphide is used in a VIDICON tube.
16.1: Optimization of protection in fluoroscopy

35. Photoconductive camera tube
Focussing optical lens
Input plate
Steering coils
Deviation coil
Alignement coil
Accelarator grids
Control grid
Electron beam
Video Signal
Signal electrode
Field grid
Electrode
Electron gun
Iris
Photoconductive layer
16.1: Optimization of protection in fluoroscopy

36. TV camera and video signal (III)
The surface of the photoconductor is scanned with an electron beam and the amount of current flowing is related to the amount of light falling on the television camera input surface.
The scanning electron beam is produced by a heated photocathode. Electrons are emitted into the vacuum and accelerated across the television camera tube by applying a voltage. The electron beam is focussed by a set of focussing coils.
16.1: Optimization of protection in fluoroscopy

37. TV camera and video signal (IV)
This scanning electron beam moves across the surface of the TV camera tube in a series of lines.
This is achieved by a series of external coils, which are placed on the outside of the camera tube. In a typical television system, the image is formed from a set of 625 lines. On the first pass the set of odd numbered lines are scanned followed by the even numbers. This type of image is called interlaced.
The purpose of interlacing is to prevent flickering of the television image on the monitor, by increasing the apparent frequency of frames (50 half frames/second).
In Europe, 25 frames are updated every second.
16.1: Optimization of protection in fluoroscopy

38. Different types of scanning11 1
INTERLACED
SCANNING 13 12 3 2 15 14 5
625 lines in 40 ms
i.e. : 25 frames/s 4 17 16 7 6 19 18 9 8 21 20 10 1 2 3 4 5 6 7
PROGRESSIVE
SCANNING 8 9 10 11 12 13 14 15 16 17 18
16.1: Optimization of protection in fluoroscopy

39. TV camera and video signal (V)
On most fluoroscopy units, the resolution of the system is governed by the number of lines of the television system.
Thus, it is possible to improve the high contrast resolution by increasing the number of television lines.
Some systems have 1,000 or 2,000
16.1: Optimization of protection in fluoroscopy

40. TV camera and video signal (VI)
Many modern fluoroscopy systems used CCD (charge coupled devices) TV cameras.
The front surface is a mosaic of detectors from which a signal is derived.
The video signal comprises a set of repetitive synchronizing pulses. In between there is a signal that is produced by the light falling on the camera surface. The synchronizing voltage is used to trigger the TV system to begin sweeping across a raster line.
Another voltage pulse is used to trigger the system to start rescanning the television field.
16.1: Optimization of protection in fluoroscopy

41. Schematic structure of a charged couple device (CCD)
16.1: Optimization of protection in fluoroscopy

42. TV camera and video signal (VII)
A series of electronic circuits move the scanning beams of the TV camera and monitor in synchronism. This is achieved by the synchronizing voltage pulses. The current, which flows down the scanning beam in the TV monitor, is related to that in the TV camera.
Consequently, the brightness of the image on the video display is proportional to the amount of light falling on the corresponding position on the TV camera.
16.1: Optimization of protection in fluoroscopy

43. TV image sampling IMAGE 512 x 512 PIXELS 64 µs IMAGE LINE 52 µs 12 µs
HEIGHT 512
WIDTH 512
ONE LINE
VIDEO
SIGNAL
(1 LINE)
64 µs
IMAGE LINE
52 µs
SYNCHRO
12 µs
DIGITIZED SIGNAL
LIGHT INTENSITY
SAMPLING
SINGLE LINE TIME
16.1: Optimization of protection in fluoroscopy

44. Digital radiography principle
ANALOGUE
SIGNAL I t
ADC
Memory
DIGITAL
SIGNAL
Iris
Clock t
See more in Lecture L20
16.1: Optimization of protection in fluoroscopy

45. Digital Image recording
In newer fluoroscopic systems film recording is replaced with digital image recording.
Digital photospots are acquired by recording a digitized video signal and storing it in computer memory.
Operation— fast, convenient.
Image quality can be enhanced by application of various image processing techniques, including window-level, frame averaging, and edge enhancement.
But the spatial resolution of digital photospots is less than that of film images.
16.1: Optimization of protection in fluoroscopy

46. TV camera and video signal (VIII)
It is possible to adjust the brightness and contrast settings of the TV monitor to improve the quality of the displayed image.
16.1: Optimization of protection in fluoroscopy

47. Part No...., Module No....Lesson No
Module title
Summary
The main components of the fluoroscopy imaging chain and their role are explained:
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)
16.1: Optimization of protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

48. Where to Get More Information
Part No...., Module No....Lesson No
Module title
Where to Get More Information
The Essential Physics of Medical Imaging. JT Bushberg, JA Seibert, EM Leidholdt, JM Boone. Lippincott Williams & Wilkins, Philadelphia, 2011
The physics of diagnostic imaging, Dowsett et al, Hodder Arnold, 2006
Interventional Fluoroscopy: Physics, Technology, Safety, S. Balter, Wiley-Liss, 2001
16.1: Optimization of protection in fluoroscopy
IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources