Veterinary Imaging Past, Present and Future

Veterinary Imaging
Past, Present and FutureDigital Radiography
ROBERT H. WRIGLEY
Professor Veterinary Diagnostic Imaging
University of Sydney
Veterinary Teaching Hospital
Professor Emeritus Colorado State University
© Colostate Uni
Typical X-ray machine 1950s
© Colostate Uni
Restriction of X-ray field
Collimation
X-Ray
machine
with slide in
lead
diaphragms
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Light (projection) beam diaphragm
with adjustable Lead Shutters
X-RAY MACHINES
X-RAY MACHINES
Portable max output
20mA, 80KV
Ceiling mounted, 2000mA 150KV
50 mA 100KV
High Frequency
Automatic Film Processors 1960s
Dry, Processed Film in 90 seconds
• Underdevelopment
• From under replenishment per film
• From developer oxidization in too large a
storage tank
Courtesy Konica
2
Photographic film in
cassette
SINGLE EMULSION FILM
SINGLE ‘FINE’ SCREEN
• INCREASED DETAIL
• INCREASED
EXPOSURE
• INCREASED
RADIOGRAPHIC
CONTRAST
Radiology in the 20th Century
RARE EARTH SCREEN-FILM
Computerised X-ray machine
operating controls at the X-ray tube
Courtesy of SEDECAL USA Inc.
Diagnostic Imaging in the 21st Century
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Digital Radiography
Film Radiography
Digital Radiography
Film Radiography
• X-Ray Capture
Device
• Conversion to
DICOM computer
file
• Display on
Workstation Monitor
• Film
• Image optimization
software
• Computer file/folder
• PACS Computer
database/archive
•Electronic delivery
• Paper envelope
• File shelves
• Darkroom Film
Processing
• Light Box
•Digital Imaging & Communications in Medicine
• Hand/mail delivery
•Picture Archive & Communication Systems
ADVANTAGES
Image Auto correction of Image Whiteness
This feature is available on some Systems
-Simplifies X-ray Technique setting
Film/Screen
80 KVp 44mAs
-If not a feature vendor must provide an accurate technique
chart and patients measured and exposed as you would for
film. Latitude allows for some manual correction of mild over or
under exposure
DR Image
processed with
automatic
correction
selected
80 KVp 44mAs
Film/Screen
60 KVp
16mAs
Advantages of Filmless Digital
Imaging Versus Film Radiography
Gray Scale Latitude
Film
Digital
DR Image
processed with
automatic
correction
selected
60 KVp 16mAs
4
Gray Scale Processing
• Non-linear Gray scale transformation
using stored settings (Algorithms)
optimized for anatomical region imaged
Detail Enhancement
• Especially useful to improve visualization
of bone + lung detail
– Unsharp mask filtering
Unsharp Mask Filtering
• Can create black lines along radiolucent
structures such as metallic implants
– Artifact – halation, over-shoot, uberschwinger
• Customized for object size + level of enhancement
ADVANTAGES
• Eliminate darkroom and film processing
• Potential for patient side image viewing
ADVANTAGES
• Can use computer graphic software to optimize
image brightness & contrast.
• Whiten mildly overexposed images
• Darken mildly underexposed images
• Cost saving as eliminates
- Film
- Processing supplies
- Darkroom
- Film jackets & Files
• Electronic distribution of images via Networks
– For diagnosis
– For consultation/second opinions
– Input into an electronic medical record
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X-Ray exposure level effects Image detail
DISADVANTAGES
• Need to be a skilled computer user
• Need computer support personnel
• All systems more expensive than
film/screen cassettes and an automatic
processor
• Image detail less than good quality
radiographs
Exposure settings
- those appropriate for > 400
speed FS and faster result in
suboptimal CR image detail
- Exposure settings as used for
300 speed FS and higher
exposures are optimal for CR
imaging
- Newer systems using double
sided plates and other plate
halides now allow exposure to be
significantly reduced.
Courtesy Fuji Medical Syst.
Digital Image
Automatic Image
correction
Rectangular matrix of differing colored squares
(Pixels=Picture Elements)
Some systems provide
feed back information on
the radiation level to the
patient.
Fuji –Sensitivity S# =
equivalent FS
exposure level
S# 110
AGFA – LGM Exposure Index #
Optimal X-Ray Exposure = 2.1
2 X Recommended Exp = 2.4
½ Recommended Exp =1.9
What has been the
effect on resolution of
bony detail?
S# 2005
Detail Resolution dependent on:
• Pixel size – proportional to total number and size of pixels
-- physical size/quality of computer monitor
-- quality of computer video card
2000 Pixels
64 Pixels
2
5
0
8
0
0
P
P
I
I
X
X
E
E
L
L
S
Acquiston
Device
Film/screen
(all sizes)
Digital
Radiology
Detectors
5 x 7.5cm
22 x 27cm
35 x 43cm
Resolution
Matrix
# of Pixels
Crystals
Pixel size
Spacial Resolution
Line Pairs/mm
5-15 Lp/mm
Microscoptic
Diodes
Transistors
Dental
2,256x2878
2,208x2688
30 um2
100 um2
160 um2
~ 15 Lp/mm
~ 5 Lp/mm
~ 3 Lp/mm
S
6
Film/screen
(all sizes)
Crystals
Digital
Radiology
Detectors
5 x 7.5cm
22 x 27cm
35 x 43cm
Diodes
Transistors
Dental
2,256x2878
2,208x2688
Film/screen
(all sizes)
Crystals
Microscoptic
5-15 Lp/mm
Diodes
Transistors
30 um2
100 um2
160 um2
Digital
Radiology
Detectors
5 x 7.5cm
22 x 27cm
35 x 43cm
~ 15 Lp/mm
~ 5 Lp/mm
~ 3 Lp/mm
5-15 Lp/mm
Microscoptic
Dental
2,256x2878
2,208x2688
30 um2
100 um2
160 um2
~ 15 Lp/mm
~ 5 Lp/mm
~ 3 Lp/mm
Courtesy Eklin
Film/screen
(all sizes)
Crystals
Digital
Radiology
Detectors
5 x 7.5cm
22 x 27cm
35 x 43cm
Diodes
Transistors
5-15 Lp/mm
Microscoptic
Dental
2,256x2878
2,208x2688
30 um2
100 um2
160 um2
American College of Radiology
Teleradiology Display Monitor Standard (1999)
~ 15 Lp/mm
~ 5 Lp/mm
~ 3 Lp/mm
• Real size display of human
chest
= 35 x 43cm film ~monitor
53cm diagonal size
• Resolution not < 2.5 lead
lines per mm
> 2000K x 2500 pixels (5
Mega Pixels)
Courtesy Eklin
Resolution
Monochrome BW Medical DICOM factory calibrated LCD Monitors
2 Mega Pixels
1600 x 1200
3 M Pix
5 M Pix
ACR display
standard
DR detector
Computer Monitors
Consumer Level -------High End ----------------Medical-US,CT --------Radiographic
( not ACR std)
Size
35 x 43cm
35 x 43cm
22 x 27cm
Pixel Matrix
2000x2500
5 mega pixel
2,208x2688
2,256x2878
Variable
53cm
diagonal
35 x 43cm
Zoom x 2
Then Pan
600x800
1200x1600
2 Mega Pixel
2000x2500
1200 x1600
2400 x 3200
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Pan to view remainder of
the magnified image
Contrast Resolution dependent on:
Brightness of Light Boxes
• Brightness of monitor
• Number of colors per pixel (bits)
• Grey scale images (Radiographic images, grey scale is 1/3rd
of total number of colors)
• Dependent on -- quality of video card (number of colors)
-- quality of computer monitor
10 bits (1,024)
8 bits (256)
Monochrome BW Medical DICOM factory calibrated LCD Monitors
2 Mega Pixels
1600 x 1200
3 M Pix
5 M Pix
8
Liquid Crystal Display
LCD Grayscale Monitors
Monitor Display Test Pattern
Now preferred as brighter and more stable than TV type monitors
1022 Gray
tones
32cm x 43cm
Black/White
DICOM Calibrated Gray
Scale
$4-15,000
High Brightness
(>600 cd/mm2)
10 bit video card
Self calibrating
Courtesy of
Computed Radiography (CR=DR)
www.animalinsides.com
generates digital radiographic images
(computer files) from scanning a reusable
radiation sensitive imaging plate
Film
CR
SPATIAL RESOLUTION
6 pixels/mm (for 35 x 43cm )
8 pixels/mm (for 24 x 30cm)
10 pixels/mm (for 18 x 24cm)
Courtesy of IDEXX Labs. Inc
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Resolution
Reading the Imaging Plate
PM Tube
Rotating Prism
Laser
Light
Guide
Imaging Plate
Translation
Acquisition
Device
Matrix
(Pixels)
Pixels
Film/Screen Microscopic
Crystals
CR Plate Microscopic
Adjustable
Crystals by laser beam
35x43cm 3520x4280
10/mm
1760x2140
5/mm
24x30cm 3000x3750
15/mm
1770x2370
10/mm
Spatial
Resolution
Line
Pairs/mm
5-15 Lp/mm
~5 Lp/mm
~2.5Lp/mm
~7 Lp/mm
~5 Lp/mm
Melbourne and Camden
Uni Vet Hospital
Fuji CAPSULA
CR SCANNERS
Courtesy of IDEXX Labs. Inc
Courtesy
Agfa
HealthCare
Courtesy of IDEXX Labs. Inc
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Anatomic specific
Image Processing
Loading Cassette
Courtesy of IDEXX Labs. Inc
Courtesy of IDEXX Labs. Inc
CR Specific Image Artifacts
Scattered Radiation
Unloading Cassette
Courtesy of IDEXX Labs. Inc
CR Plate
Moiré Patterns
The term originates from moiré in its French form,
a type of textile, traditionally of silk but now also
of other fibers, creating a rippled appearance.
Effect of turning grid line sets
Superposition of 2 similar
patterns rotated by an angle α
2 sets of parallel lines inclined at an
angle 5 degrees to one another
Courtesy of: http://en.wikipedia.org/wiki/Moir%C3%A9_pattern
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CR image made with a stationary grid 110
lines per inch.
What is the image quality artifact?
Moire
problem
How to
stop
this?
* FOGGING BY SCATTERED X-RAYS &
BACKGROUND RADIATION
-Use a Bucky
-Turn the grid
lines right angle
to scan axis
-Replace with a
grid
recommended by
CR vendor,180230 lines per inch
EXPENSIVE
Erasing Plates
• Dirt on plate or in scanner will create white artifacts
• CR Plates and the Scanner need to be cleaned regularly
• Plus Image mottle from too low an X-ray exposure
Courtesy of IDEXX Labs. Inc
Non Automated system
Clipping of the thinnest densities of
the lungs from over exposure
Original
Clipping of the thickest densities of
the spine
Beyond the range of
manual correction
ORGINAL
Beyond
the range
of manual
correction
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ELECTRONIC PLATE X-RAY
DETECTORS
SMALL AREA DENTAL RADIOGRAPHY
“DR”
FILM LESS
Dental Digital Radiography
• Using Charge Coupled Device CCD (light detector
in digital cameras) – small size ~ 2”-3”
• SMALL AREA RADIOGRAPHY
- DENTAL RADIOGRAPHY
• X-Ray Intensifying Screen directly attached to CCD
under computer control
• Images displayed on computer in a few seconds
• Pixel size 30 um2
• Resolution 15 Lp/mm
Dental Radiography, “DR”
Courtesy Alameda Animal Hosp.
www.afpimaging.com
Digital Dental Radiographs
Large Area CCD “DR” Radiography
Aim to Record Image of a 14”x17” Region
(14” x 17” X-Ray Intensifying Screen)
Image Recorded on Small CCD Chip (camera technology)
Courtesy of SEDECAL USA Inc.
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Vet Ray Technology
Courtesy of www.innovet4vets.com
Courtesy of SEDECAL USA Inc.
Large Area Single CCD
Chip “DR” Radiography
• Problems:
– Bulky device
– Inefficient collection of light, limits resolution
– Built in grid will increase exposure need for
extremity imaging
– Precludes using horizontal beam radiography
– May require higher X-ray exposures than
film/screen and other digital acquisition
devices
Large Area Multiple (Tiled)
CCD Chips
– Smaller in size
– Improved collection of light
– Stitching of input from adjacent
CCD chips may create artifacts
4”
Courtesy of RF System Lab
Digital Radiology Plate Types
Indirect Types
Direct Types
Laser scanned
Anatomic
specific
image
processing
No
scanning
image
processing
No scanning
Anatomic
specific
processing
www.idexx.com/animalhealth/digital/dR
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ADVANTAGES
• Eliminate cassettes
• Patient side image viewing
Portable System Customized for Veterinary Imaging
Indirect DR detector
9” x 11” Plate
- Higher resolution
- 6.5 megapixels
- Pixel size 100 microns2
Table Mounted for Small Animal
Radiography
14” x 17” Plate
- Lower resolution
- 5.9 megapixels
- Pixel size 160 microns2
Courtesy of Eklin Medical Systems, Inc.
www.Eklin.com
Courtesy of Eklin Medical Systems, Inc.
www.Eklin.com
Small Animal Imaging
DR Electronic Plate Radiography
Advantages
Table top or in Grid tray
2232 x 3200 pixels
Pixel size 127 um2, 3.9 Lp/mm
• No processing, almost immediate
(5-10 sec) image acquisition
• No cassettes
• Potential for excellent image
quality when image processing is
optimized for animal anatomy
Courtesy of Sound Technologies Inc.
www.soundvet.com/pages/XRay/TruDR.html
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DR Electronic Plate
Disadvantages
• May require greater X-ray exposures than
for faster speed film screen radiographs
• Considerably more expensive than other
forms of “DR” & Computed Radiography
• Retrofitting to an existing X-Ray table may
be challenging
• Cannot perform cross table radiography
• The imaging sensor is very expensive to
replace
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