1. Digital Imaging

2. Week 10 Week 9 Image Receptors Image Receptors Digital Imaging
Film Imaging
Film Construction
Cassette Construction
Film Handling
Darkroom
Digital Imaging
Cassette Digital Imaging
Direct Digital Imaging
Week 9
Week 10

3. Digital Radiography Computed Direct-to-Digital Radiography Radiography
Capture
Indirect
Capture
Computed
Radiography
(CR)
Direct-to-Digital
Radiography
(DDR)

4. Computed Radiography Similar to F/S
Uses cassettes as imaging plate (IP)
Imaging plate is termed PSP

5. History of CR
INDUSTRY
Theory of “filmless radiography” first introduced in 1970
1981 Fuji introduced special cassettes with PSP plates (replaces film)
Technology could not support system
First clinical use in Japan

6. Predictions
1980 – Bell Labs believed that Unix would be the worlds dominant operating system
1982 – Bill Gates thought 640K of main memory would suffice for workplace operating systems ( This presentation is 80,000 kb)
1984 – IBM predicted that personal computers would not amount to anything

7. How does it differ ?
Uses the same general
equipment as F/S

8. Computed Radiography How is it different from F/S?
How the image is captured
How the image is stored
How the image is viewed
How the image is processed after taken

9. Computed Radiography Review of F/S image production: Primary beam
Exit radiation
Hits phosphors of intensifying screens, lights helps form image-latent image
Some photons hit film directly-latent image
Film is processed to develop manifest image
Film stored, duplicated to be seen by others

10. Computed Radiography Computed Radiography Image Production:
Primary beam-same as film
Exit radiation-same as film
Interacts with CR cassette image plate- latent image -similar to film
CR cassette is place in CR reader, laser translates image to analog signal-different
Analog signal converted to digital signal
Image can be viewed on computer monitor-manifest image
Image can be post-processed-not possible with F/S
Image is stored in computer system (PACS)
Image can be viewed by anyone with access to system
Image can be printed on film with a laser printer

11. Cassette with film CR with PSP
Film Cassette
CR cassette with PSP

12. Photostimulable Phosphor
Computed Radiography
Photostimulable Phosphor
Responds to radiation by trapping energy in the locations where x-rays strike, creating the latent image
PSP run scanned by a CR reader, converted to analog image, then to digital image, then image viewed on monitor.

13. Photostimulable Phosphor
CR Reader- scans the PSP plate using a RED laser light, releases trapped electrons which then emit BLUE light which is converted to analog image.

14. Computed Radiography Exit radiation exposes CR cassette
Uses red light to scan
Detects the Blue light emitted

15. CR – PSP plate Stimulated by a RED LIGHT
Energy is RELEASED in a form of BLUE light
LIGHT captured by photomultiplier tube (PMT)
Changed to a digital signal

16. Computed Radiography
The CR system is not much faster than film screen cassettes. It is really not faster it is just different. We can manipulate the image and it is better quality images.

17. CR Phosphor Plates ABSORPTION EMISSION X-RAY LIGHT LASER STIMULATION
ELECTRON
TRAP
ELECTRON
TRAP
X-RAY
LIGHT
Raster pattern scans the phosphor plate.

18. How CR works
Blue released light is captured by a PMT (photo multiplier tube)(laser reader)
This light is sent as a digital signal to the computer
The intensity (brightness) of the light – correlates to the density on the image

19. ERASING PLATE After image is recorded
Plate is erased with high intensity white light
Cassettes are reused
Remember RED, WHITE AND BLUE…..but really it goes Red, Blue White…

20. Digital Radiography Computed Direct-to-Digital Radiography Radiography
Capture
Indirect
Capture
Computed
Radiography
(CR)
Direct-to-Digital
Radiography
(DDR)

21. Directed Digital Radiography (DDR)
Directed digital radiography, a
term used to describe total
electronic imaging capturing.
Eliminates the need for an image plate altogether.
There is no cassette at all. Supposed to be faster, digital is faster the CR.

22. Direct Digital Radiography
Cassette-less imaging
Uses TFT-Thin Film Transistor
No film, so no developing,
No PSP, so CR reader needed
Immediate image viewing
Post Processing capabilities
Multiple viewing stations

23. Amorphous Selenium detector technology for
DR Direct Radiography
Transitors are coated with amorphous selenium.

24. Direct Digital Radiography
No cassette used, device similar to Bucky used
Contains thin film transistor
Captures x-ray photons, converts to electron energy,
Electron energy transferred to digital image
Displayed on monitor for IMMEDIATE viewing

25. Patient is missing a shield
Patient is missing a shield. This is a lot faster but it is a problem for an educator. It is hard to know if they always have someone around with them when they do repeats.

26. Imaging Systems
Be able to compare all the different imaging systems. Compare the advantages, disadvantages of each system.

27. COMPUTED RADIOGRAPHY & DIRECT RADIOGRAPHY & FILM SCREEN IMAGE CAPTURE
FS - Film inside of cassette
CR – Photostimulable Phosphor Plate (PSP)
DR(DDR) - Thin Film Transistor (TFT)
Don’t forget about Direct Exposure !!

28. FS vs. CR CR FILM PSP in cassette Film in cassette Digital image
Scanned & read- CR reader
COMPUTER
Image stored on computer
Viewed on a Monitor
Hard copy (film) can be made with laser printer
FILM
Film in cassette
loaded in a darkroom
Processed in a processor
Hard copy image – stores the image
Viewboxes – view the images

29. CR vs DR CR Imaging plate Processed in a Digital Reader
Signal sent to computer
Viewed on a monitor DR
Transistor receiver (like bucky)
Directly into digital signal
Seen immediately on monitor

30. COMPUTED RADIOGRAPHY & DIRECT RADIOGRAPHY & FILM SCREEN IMAGE CAPTURE

31. Image Resolution (how sharply is the image seen)
CR 2 -5 lp/mm
RAD 10 lp/mm
DR ?
IMAGE APPEARS SHARPER BECAUSE CONTRAST CAN BE ADJUSTED BY THE COMPUTER –
(DIFFERENCES IN DENSITY) CR
4000 x 4000
Image only as good a monitor*
More pixels = more memory needed to store

32. ADVANTAGE OF CR/DR Can optimize image quality
Can manipulate digital data
Improves visualization of anatomy and pathology
AFTER EXPOSURE TO PATIENT

33. CR/DR VS FILM/SCREEN FILM- these can not be modified once processed
If copied – lose quality
DR/CR – print from file – no loss of quality

34. “No fault” TECHNIQUES F/S: RT must choose technical factors
(mAs & kVp) to optimally visualize anatomic detail
CR: the selection of processing algorithms and anatomical regions controls how the acquired latent image is presented for display
HOW THE IMAGE LOOKS CAN BE ALTERED BY THE COMPUTER – EVEN WHEN “BAD” TECHNIQUES ARE SET
F/S: RT must choose technical factors
(mAs & kvp) to optimally visualize anatomic detail
CR: the selection of processing algorithms and anatomical regions controls how the acquired latent image is presented for display
HOW THE IMAGE LOOKS CAN BE ALTERED BY THE COMPUTER – EVEN WHEN “BAD” TECHNIQUES ARE SET

35. Storage /Archiving FILM/SCREEN Films: bulky Deteriorates over time
Requires large storage & expense
Environmental concerns
CR & DR
8000 images stored on CD-R
Jukebox CD storage
No deterioration of images
Easy access

37. ADVANTAGE OF CR/DR vs FS
Rapid storage
Retrieval of images NO LOST FILMS!
PACS- DICOM (storage management)
Teleradiology - long distance transmission of image information
Economic advantage - at least in the long run?

38. Transmission of Images
PACS - Picture Archiving & Communications System
DICOM - Digital Images & Communication in Medicine
TELERADIOGRAPHY -Remote Transmission of Images

39. Basics of Digital Images
Digital images are a (matrix) of pixel (picture element) values
Computer can see 256 shades of gray.

40. Analog vs Digital Analog - one value blends into another
like a thermometer
Digital - distinct separation
98.6
exact
Analog is not exact. Where digital is an exaxt.

41. CONTRAST & DENSITY
Most digital systems are capable of 1024 shades of gray –
but the human eye can see only about 30 shades of gray
The Optical Density and Contrast can be adjusted after the exposure by the Radiographer.
This is POST - PROCESSING

42. High displayed contrast – narrow window width
Short scale of contrast. Different algorithms
High displayed contrast – narrow window width

43. Low displayed contrast (stretched) – wide window width
Long scale of contrast
Low displayed contrast (stretched) – wide window width

44. Basics of Digital Images
Pixel values can be any bit depth (values from 0 to 1023)
Image contrast can be manipulated to stretched or contracted to alter the displayed contrast.
Typically use “window width” and “window level” to alter displayed contrast

45. 80 KVP 5 30 5 15
100
200
500
These all look the same regardless of the dosage given to the patient. This a a concern because technologists can overexpose patients.

46. Danger of Digital Then the COMPUTER corrects any exposure errors
Therefore almost ANY technique can be used on the patient –
The computer will fix it

47. DOSE IMPLICATIONS More exposure to the patient
Techniques established-F/S techniques
Higher kVp = Less mAs
Less patient dose
Goes Contrary to what good techs have been taught

48. 80 kvp 200mas
10 mas 80 kvp
Note
Quantum Mottle

49. Dose Implications
Images nearly always look better at higher exposures.
Huge dynamic range means nearly impossible to overexpose.

50. POST PROCESSING
These are all from one exposure.

51. TECHNIQUE CONSIDERATIONS
kVp Dependent
Now COMPUTER controls CONTRAST
Higher kVp to stimulate electron traps

52. (replaces film, storage & viewboxes)
CR – Reader (replaces Darkroom & Processor & Chemicals
Diagnostic Viewer
(replaces film, storage & viewboxes)
EXPLAIN EQUIPMENT

53. EMERGING PROBLEMS Better – not necessarily faster
Learning curve for technologists and physicians-increase repeat rate?
Student applications and issues
Pitfalls of CR

54. Learning Curve
Positioning and proper collimation are critical to good imaging outcomes
Just like Phototiming, it can magnify your mistakes

55. COLLIMATION CRITICAL
As the computer reads the density value of each pixel- it is averaged into the total
Close collimation= Better contrast
Bad collimation= more grays and less detail

56. To Produce Quality Images
For Conventional Radiography
or CR Radiography:
The same rules, theories, and laws still apply and can not be overlooked SID, Inverse Square Law, Beam Alignment ,Tube-Part-Film Alignment, Collimation, Grid, Exposure Factors: kVp, mAs
Patient Positioning
PATIENT POSITIONING
Accounts for 85% of the total number of repeat exposures.
Has a direct affect on exposure technique.

57. Quality Images Patient positioning
Accounts for 85% of the total number of repeat exposures.
Has a direct affect on exposure technique.

58. Towel that was used to help in positioning a child
CR/DR is MORE sensitive to ARTIFACTS

59. Digital Imaging