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Veterinary Imaging Past, Present and Future-

Digital RadiographyROBERT H. WRIGLEY

Professor Veterinary Diagnostic ImagingUniversity of Sydney

Veterinary Teaching HospitalProfessor Emeritus Colorado State University

© Colostate Uni

© Colostate Uni

Typical X-ray machine 1950s

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 MACHINESPortable max output 20mA, 80KV

50 mA 100KVHigh Frequency

X-RAY MACHINESCeiling mounted, 2000mA 150KV

Automatic Film Processors 1960sDry, Processed Film in 90 seconds

Courtesy Konica

• Underdevelopment• From under replenishment per film• From developer oxidization in too large a

storage tank

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Photographic film incassette

RARE EARTH SCREEN-FILM

SINGLE EMULSION FILM SINGLE ‘FINE’ SCREEN • INCREASED DETAIL• INCREASED

EXPOSURE• INCREASED

RADIOGRAPHIC CONTRAST

Computerised X-ray machine operating controls at the X-ray tube

Courtesy of SEDECAL USA Inc.

Radiology in the 20th Century Diagnostic Imaging in the 21st Century

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Digital Radiography Film Radiography

• Film

• Darkroom Film Processing

• Light Box

• X-Ray Capture Device

• Conversion to DICOM computer file

• Display on Workstation Monitor

•Digital Imaging & Communications in Medicine

Digital Radiography Film Radiography

• Paper envelope• File shelves

• Hand/mail delivery

• Image optimization software

• Computer file/folder• PACS Computer

database/archive•Electronic delivery

•Picture Archive & Communication Systems

Image Auto correction of Image WhitenessThis feature is available on some Systems

-Simplifies X-ray Technique setting

-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 orunder exposure

ADVANTAGESFilm/Screen

80 KVp 44mAs

DR Image processed with automatic correction selected80 KVp 44mAs

Film/Screen60 KVp16mAs

DR Image processed with automatic correction selected60 KVp 16mAs

Advantages of Filmless Digital Imaging Versus Film Radiography

Gray Scale Latitude

Film Digital

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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

• Customized for object size + level of enhancement

Unsharp Mask Filtering

• Can create black lines along radiolucent structures such as metallic implants– Artifact – halation, over-shoot, uberschwinger

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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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

Courtesy Fuji Medical Syst.

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.

X-Ray exposure level effects Image detail

Some systems provide feed back information on the radiation level to the patient.

Fuji –Sensitivity S# = equivalent FS exposure level S# 110

S# 2005

AGFA – LGM Exposure Index #

Optimal X-Ray Exposure = 2.1

2 X Recommended Exp = 2.4

½ Recommended Exp =1.9

Automatic Image correction

What has been the effect on resolution of bony detail?

Digital ImageRectangular matrix of differing colored squares

(Pixels=Picture Elements)

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

0

P

I

X

E

L

S

80

P

I

X

E

L

S

Resolution

~ 15 Lp/mm~ 5 Lp/mm~ 3 Lp/mm

30 um2

100 um2

160 um2

DiodesTransistors

Dental2,256x28782,208x2688

Digital RadiologyDetectors5 x 7.5cm22 x 27cm35 x 43cm

5-15 Lp/mmMicroscoptic

CrystalsFilm/screen(all sizes)

Spacial ResolutionLine Pairs/mm

Pixel sizeMatrix# of Pixels

AcquistonDevice

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30 um2

100 um2

160 um2

DiodesTransistors

Dental2,256x28782,208x2688





30 um2

100 um2

160 um2

DiodesTransistors

Dental2,256x28782,208x2688




Courtesy Eklin


30 um2

100 um2

160 um2

DiodesTransistors

Dental2,256x28782,208x2688




Courtesy Eklin

American College of RadiologyTeleradiology Display Monitor Standard (1999)

• 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)

2 Mega Pixels

1600 x 1200 3 M Pix 5 M Pix

Monochrome BW Medical DICOM factory calibrated LCD MonitorsResolution

600x8001200x1600

2 Mega Pixel2000x25001200 x16002400 x 3200

Variable53cm

diagonal35 x 43cmZoom x 2Then Pan

Computer MonitorsConsumer Level --------High End -----------------Medical-US,CT ---------Radiographic ( not ACR std)

2,208x26882,256x2878

35 x 43cm22 x 27cm

DR detector

2000x25005 mega pixel

35 x 43cmACR displaystandard

Pixel MatrixSize

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Pan to view remainder of the magnified image

Contrast Resolution dependent on:• 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 monitor10 bits (1,024) 8 bits (256)

Brightness of Light Boxes

2 Mega Pixels

1600 x 1200 3 M Pix 5 M Pix

Monochrome BW Medical DICOM factory calibrated LCD Monitors

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Liquid Crystal DisplayLCD Grayscale Monitors

Now preferred as brighter and more stable than TV type monitors

32cm x 43cm

Black/White

DICOM Calibrated Gray Scale

High Brightness

(>600 cd/mm2)

10 bit video card

Self calibrating

1022 Gray tones

$4-15,000

Monitor Display Test Pattern

Courtesy of www.animalinsides.com

generates digital radiographic images (computer files) from scanning a reusable

radiation sensitive imaging plate

Computed Radiography (CR=DR)

Film CR SPATIAL RESOLUTION6 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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Reading the Imaging Plate

TranslationTranslation

LaserLaser

PM TubePM TubeRotating PrismRotating Prism

Imaging PlateImaging Plate

LightLightGuideGuide

Resolution

~5 Lp/mm~2.5Lp/mm~7 Lp/mm~5 Lp/mm

Adjustableby laser beam

10/mm5/mm

15/mm10/mm

MicroscopicCrystals

3520x42801760x21403000x37501770x2370

CR Plate

35x43cm

24x30cm

5-15 Lp/mmMicroscopicCrystals

Film/Screen

SpatialResolution

Line Pairs/mm

PixelsMatrix(Pixels)

Acquisition Device

CR SCANNERS

Melbourne and CamdenUni Vet Hospital Fuji CAPSULA


Courtesy Agfa HealthCare


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Loading Cassette


Anatomic specific Image Processing


Unloading Cassette


Scattered Radiation

CR Plate

CR Specific Image Artifacts

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.

Superposition of 2 similar patterns rotated by an angle α

2 sets of parallel lines inclined at an angle 5 degrees to one another

Moiré Patterns Effect of turning grid line sets

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?

Moireproblem

How to stop this?

-Use a Bucky

-Turn the grid lines right angle to scan axis

-Replace with a grid recommended by CR vendor,180-230 lines per inch EXPENSIVE

* FOGGING BY SCATTERED X-RAYS & BACKGROUND RADIATION

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

Clipping of the thinnest densities of the lungs from over exposure

OriginalBeyond the range of manual correction

Non Automated system Clipping of the thickest densities of the spine

ORGINAL

Beyond the range of manual correction

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SMALL AREA DENTAL RADIOGRAPHY “DR”

ELECTRONIC PLATE X-RAY DETECTORS

FILM LESSDental 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” RadiographyAim 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 SEDECAL USA Inc.Courtesy of www.innovet4vets.com

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 TypesIndirect Types Direct Types

www.idexx.com/animalhealth/digital/dR

Laser scanned

No scanning

image processing

No scanning

Anatomic specific

processing

Anatomic specific image

processing

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ADVANTAGES• Eliminate cassettes• Patient side image viewing

Portable System Customized for Veterinary Imaging Indirect DR detector

14” x 17” Plate- Lower resolution- 5.9 megapixels - Pixel size 160 microns2

9” x 11” Plate- Higher resolution- 6.5 megapixels - Pixel size 100 microns2

Courtesy of Eklin Medical Systems, Inc. www.Eklin.com

Table Mounted for Small Animal Radiography

Courtesy of Eklin Medical Systems, Inc. www.Eklin.com

Small Animal Imaging

Table top or in Grid tray

2232 x 3200 pixels Pixel size 127 um2, 3.9 Lp/mm

Courtesy of Sound Technologies Inc.www.soundvet.com/pages/XRay/TruDR.html

DR Electronic Plate Radiography Advantages

• No processing, almost immediate (5-10 sec) image acquisition

• No cassettes• Potential for excellent image

quality when image processing is optimized for animal anatomy

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DR Electronic PlateDisadvantages

• 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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