1. Digital FLUORO
Summer 2008

2. DIGITAL FLUORO

3. Digital fluoroscopy is currently most commonly configured as a conventional fluoroscopy system in which the analog video signal is converted to a digital format with an analog-to-digital converter (ADC). An in-depth discussion of digital detector technologies (eg, flat-panel "direct" detection of x rays and charge-coupled device technology) is beyond the scope of this article. After a review of several fundamental digital imaging concepts including binary numbers, pixels, and gray levels, emphasis will be placed on discussions of the digital imaging tools specific to digital fluoroscopy and digital subtraction angiography (DSA).

4. Digital fluoroscopy is currently most commonly configured as a conventional fluoroscopy system in which the analog video signal is converted to a digital format with an analog-to-digital converter (ADC).
With discussions of the digital imaging tools specific to digital fluoroscopy and digital subtraction angiography (DSA).

5. Early Fluoroscopy

6. CONVENTIONAL FLUOROSCOPY INVENTED BY THOMAS EDISON

7. 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

10. pixels the smallest element of a digital image.
A digital image is normally composed of a two-dimensional (square) matrix of pixels.
The matrix size of an image is used to describe the number of pixels in each row and column of the image.

11. The size of a pixel determines the smallest detail visible in the image,
the number of pixels (of a given size) determines the field of view of the image.
pixel value is assigned to a certain color or gray level for visualization.
The imaged object is more faithfully reproduced as matrix size increases and pixel size decreases.

13. 63 K
1024

14. Digital fluoroscopy
is most commonly configured as a conventional fluoroscopy system (tube, table, image intensifier, video system) in which the analog video signal has been digitized with an ADC.
Alternatively, digitization may be accomplished with a digital video camera (eg, a charge-coupled device) or via direct capture of x rays with a flat-panel detector.
For digital fluoroscopy systems in which the analog video signal is digitized with an ADC, the resolution is limited by the resolution of the video camera, which is typically 1–2 line pairs per millimeter.

19. Digital Image recording
In newer fluoroscopic systems film recording replaced with digital image recording.
Digital photospots 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.

20. Digital radiography principle
Clock
Memory
ADC I
Iris t
ANALOGUE
SIGNAL
DIGITAL
See more in Lecture L20

21. Digital spot film images
and photospot images may be acquired by using the same digital fluoroscopy system.
Individual frames from a digital fluoroscopy sequence can be stored digitally and can be used instead of conventional spot film and photospot images.
Digital photospot images will have the same characteristics (eg, resolution) as digital fluoroscopic images.

22. Digital format – print to film

23. Remote – over the table tube

24. 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.

30. The digital image data from digital fluoroscopy may be processed by using many useful image processing techniques.
These techniques may serve to decrease radiation exposure to the patient and medical imaging staff or improve visualization of anatomy.
Processing options include last image hold, gray-scale processing, temporal frame averaging, and edge enhancement.
Additional processing is available when digital fluoroscopy data are used to perform DSA.

41. STAT CH 7 & 8 DHS-RHB RAD PROT/FLUORO SYLLABUS
RADIATION PROTECTION
STAT CH 7 & 8
DHS-RHB
RAD PROT/FLUORO SYLLABUS

42. Radiation Safety and Fluoroscopy
Time
Distance
Shielding
Also see Intro to Fluoro Lecture
From RT 124 Spring 2007

43. Patient Protection Tabletop exposure rate Maximum 10 R/min
Typically 1 – 3 R/min

44. Patient Protection Minimum source-to-skin distance
12” for mobile equipment
15” for stationary systems
Audible alarm at 5 mins.
Same rules for collimation

45. Patient Protection Typical exposure rates Cinefluorography Cassettes
7.2 R/min
Cassettes
30 mR/exposure
105 mm film
10 mR/exposure

46. Protection of Radiographer and Radiologist
Lead apron
0.25 mm Pb/eq
Highest energy scatter
90o angle to the incident beam
Same level as radiographer /radiologist’s gonads

47. The Patient & Scatter

48. WHATS WRONG?

50. Remote – over the table tube

51. Under table tube vs Over table tube (remote units) Need moving shield for Remote rooms

52. IsoExposure Curves Where is it SAFE??

53. ISOEXPOSURE CURVES

54. Patient entrance skin exposure (ESE) is higher when the fluoroscopic x-ray tube is too close to the tabletop.

55. KEEP I.I. CLOSE TO PATIENT

57. REDUCE DISTANCE OF IMAGE INTESIFIER
PATIENT EXPOSURE
REDUCE DISTANCE OF IMAGE INTESIFIER
INCREASE DISTANCE FROM THE TUBE

59. PATIENT EXPOSURE
REDUCE SIZE OF
COLLIMATED BEAM
WHEN POSSIBLE

60. ESE FOR FLUORO TLD PLACED AT SKIN ENTRACE POINT
1 – 5 R/MINUTE AVE IS 4 R/MIN
INTERGRAL DOSE –
100 ERGS OF TISSUE = 1 RAD EXPOSURE
OR 1 GM RAD = 100 ERGS

61. 1 rad (of ionizing radiation) deposits 100 ergs of energy per gram
1 RAD -100 ERGS – 1 GRAM
1 rad (of ionizing radiation) deposits 100 ergs of energy per gram

62. DOSE REGULATIONS BEFORE 1974 - AT TABLETOP 5R/MIN (WITHOUT AEC)
5R/MIN (WITHOUT AEC) – BOOST MODE
After with AEC
10 R/MIN R/MIN BOOST

63. SSD – TUBE TO SKIN DISTANCE
FIXED UNITS
18” PREFERRED
15 “ MINIMUM
MOBILE UNITS ( C-ARMS)
12’ MINIMUM

64. Conventional “FIXED” Fluoro

66. Mobile – C- arm fluoro

74. FLUOROSCOPY –
ABOVE AND BELOW THE TABLE TUBE EXPOSURE TO TECH

77. Pulsed Fluoro
Some fluoroscopic equipment is designed for pulsed-mode operation. With the pulsed mode, it can be set to produce less than the conventional 25 or 30 images per second. This reduces the exposure rate.
Collimation of the X ray beam to the smallest practical size and keeping the distance between the patient and image receptor as short as possible contribute to good exposure management.

79. Dose rate to patients

82. Mini c-arm