PACS Workstations: appropriateness, PACS Workstations: appropriateness, performance & value for moneyperformance & value for money

Alan McBrideAlan McBride**PACSnetPACSnet

St. Georges Hospital, LondonSt. Georges Hospital, London

*A Department of Health, Medicines and Healthcare Products Regulatory Agency, National Evaluation Centre

Workstation TypesWorkstation Types

Reporting (Radiology)Reporting (Radiology) Typically 2048 x 2560 portraitTypically 2048 x 2560 portrait

Review (Wards)Review (Wards) Typically 1280 x 1024 landscapeTypically 1280 x 1024 landscape

CRT DisplayCRT Display

Defining a Pixel by Defining a Pixel by Industry StandardsIndustry Standards

Pixel is viewed as a Gaussian distributionPixel is viewed as a Gaussian distribution This is a convenience that ignores halationThis is a convenience that ignores halation

when describing the spot size in literaturewhen describing the spot size in literature

Pixel size is measured at the 50% point of Pixel size is measured at the 50% point of luminance energy (FWHM) for Medicalluminance energy (FWHM) for Medical 5% point is generally not included5% point is generally not included Measurement on a single white pixelMeasurement on a single white pixel

Gaussian Spot ProfileGaussian Spot Profile

P45 Phosphor

Microvision Scan

50%

5%

Spot of P104 PhosphorSpot of P104 Phosphor

5%

50%

Ageing CRTAgeing CRT

Ikeda M. Ikeda M. et alet al (2003), (2003), Inves. RadiolInves. Radiol, , 3838, pp57-63, pp57-63Kuprinski E.A. & Roehrig H. (2002), Kuprinski E.A. & Roehrig H. (2002), Acad. Radiol.,Acad. Radiol., 99, pp638-645, pp638-645

82

84

86

88

90

92

94

96

98

100

102

0 1000 2000 3000 4000 5000 6000 7000

Hours of Operation

% o

f In

itia

l L

um

ina

nc

e

Cathode

P45 Phosphor

P104 Phosphor

2 - 6% drop in 2Khr (~12wks)2 - 6% drop in 2Khr (~12wks)

Long Term ageing in CRT display

Flat Panel DisplayFlat Panel Display

Structure AMLCDStructure AMLCD

Flynn et al (1999), Radiographics, 19, pp1653-1669Blume H. et al (2002), Proceedings of SPIE, 4681, pp271-292

Transmission: • Colour 6- 8%• Monochrome 24%

Viewing Angle DependenceViewing Angle Dependence

Ageing LCD Ageing LCD

White level goes down,White level goes down,

black level goes up.black level goes up.

- contrast level drops.- contrast level drops.- less gray levels.- less gray levels.

Power save systems Power save systems (e.g. DPMS) help a lot !(e.g. DPMS) help a lot !

Screensavers do not Screensavers do not help for LCD’s !help for LCD’s !

In the old days – static In the old days – static text displays, would text displays, would ‘burn’ their image into ‘burn’ their image into the display phosphors the display phosphors

Luminance as a function of Runtime

50

55

60

65

70

75

80

85

90

95

100

1 10 100 1000 10000 100000

Backlight Operation (Hours)

Lu

min

an

ce

(%

)

LCD Vendor Data Data Measured by Barco

Long term ageing in a LCD displayLong term ageing in a LCD display

10% drop in 2Khr (~12wks)10% drop in 2Khr (~12wks)50% drop in 30Khr (~3.5yrs)50% drop in 30Khr (~3.5yrs)

Display Technology Display Technology LimitationsLimitations

Luminance UniformityLuminance Uniformity

h1 h2 h3 h4 h5v1

v4150170190210230250270290

310

Luminance

Screen postion X

Screenpostion Y h1 h2 h3 h4 h5

v1

v4150

170

190

210

230

250

270

290

310

Luminance

Screen position X

Screen

position Y

LCD:LCD:Only P104 alike

CRT:CRT:Depends on phosphor type used (P45 > P104)

Ambient LightAmbient LightAmbient light adds to the Ambient light adds to the image luminanceimage luminance

Sources are:Sources are: Specular = single point

source, a lamp Diffuse = scattered,

unstructured light

Thin LCD offers more Thin LCD offers more flexibility.flexibility.

No direct or indirect sunlight.No direct or indirect sunlight.

No direct light source.No direct light source.

Contrast may drop drastically.Contrast may drop drastically.

LCD’s and CRT’s behave differently under LCD’s and CRT’s behave differently under changing ambient conditions.changing ambient conditions.

Typical illuminance in reading rooms is Typical illuminance in reading rooms is 300-500 Lux.300-500 Lux.

Contrast Ratio LCD - CRT

0

50

100

150

200

250

300

350

400

450

500

0 200 400 600 800 1000

I lluminance

Co

ntr

ast

Rati

oLCDCRT

DIN

AAPM

Ishihara S. Ishihara S. et alet al (2002), (2002), Comp. Med. Imag. & Graph.,Comp. Med. Imag. & Graph., 2626, pp181-185, pp181-185

Differences Between CRT & AMLCDDifferences Between CRT & AMLCD

CRT AMLCD

Mechanism Light-emitting Light-modulating

Front panel Curved Flat

Array formation Scanning beam Active-matrix discrete addressing

Emission Near-Lambertian Non-Lambertian

Long-range interactions

Veiling glare Crosstalk

Pixel structure Gaussian spot Rectangular with sub-pixel domains

Noise Phosphor noise LC variationsCell thickness

variationsSpacers

Structured noise Raster Non-active pixel regions

Artifacts Deflection Landing

Cell voltage variationBacklight non-

uniformity

Temporal Flicker Flicker and LC ghosting

REVIEW IMAGE DISPLAYS - Below 2 Mega Pixel & Standard PC Displays

REPORTING and REVIEW IMAGE DISPLAYS – Above 2 Mega Pixel but Below 3 Mega Pixel

REPORTING IMAGE DISPLAYS – Above 3 Mega Pixel

CR

T LC

D

PRICE

DESIRABILITYR

ES

OLU

TIO

N

Matrix for Image Display Evaluations

Landscape

LandscapePortrait

Portrait

SC

REEN

SIZ

E

17”

21”Siemens SMM21200PClinton DS5100PBarco MGD521-P45-75R

Siemens SMM21200PClinton DS5100PBarco MGD521-P45-75R

Siemens SMM21140PClinton DS2190PBarco MGD2621P

Siemens SMM21140PClinton DS2190PBarco MGD2621P

IBM ? (9 Mega Pixel)IBM ? (9 Mega Pixel)

Dome C3G-1/C3G-2Barco Coronis 3MP1H/2HDome C3G-1/C3G-2Barco Coronis 3MP1H/2H

Dome C5G-1/C5G-2Dome C5G-1/C5G-2

Siemens SMM2182LImage Systems M21LV-65MAXPhilips Fimi MGD203

Siemens SMM2182LImage Systems M21LV-65MAXPhilips Fimi MGD203

NEC LCD-2010XNEC LCD-2010X

Barco MVD1218Siemens SMD1898DELL 17 SXGA

Barco MVD1218Siemens SMD1898DELL 17 SXGA

Vid

eo

card

s?

Human Computer InterfaceHuman Computer Interface

After 2 Yrs softcopy reportingAfter 2 Yrs softcopy reporting

1.1. Regular 2 monitors for reporting Regular 2 monitors for reporting 2.2. Presentation Software & roller ball view CT in Presentation Software & roller ball view CT in

stack modestack mode3.3. PACS Software Optimized for 2 monitors PACS Software Optimized for 2 monitors

Bennet W.F. et al, (2002), Bennet W.F. et al, (2002), J. Digit ImagingJ. Digit Imaging; ; 15 15 Suppl 1, pp171-174Suppl 1, pp171-174Ohio State University Medical CentreOhio State University Medical Centre

Monitor ResolutionMonitor Resolution

1K vs 2K monitors1K vs 2K monitors

Steckel R.J. Steckel R.J. et alet al (1995), (1995), AJRAJR, , 164164, pp837-841, pp837-841 Graf B.Graf B. et al et al (2000),(2000), AJR, AJR, 174174, pp1067–1074, pp1067–1074

Otto D. Otto D. et alet al (1998), (1998), RadiologyRadiology, , 207207, pp237-242, pp237-242 Peer S. Peer S. et alet al (2003), (2003), Eur Radiol,Eur Radiol, 1313, pp413-417, pp413-417

CDRAD Phantom

Image Manipulation toolsImage Manipulation tools

Window width/levelWindow width/levelMagnifyMagnifyPan/zoomPan/zoomFlip/rotateFlip/rotateInvert greyscaleInvert greyscaleLocal window Local window width/levelwidth/levelHistogramHistogramProfileProfile

Pseudo colourPseudo colourImage filtersImage filtersDSADSAImage mergeImage mergeImage cropImage cropImage stitchImage stitchToggle overlayToggle overlayToggle annotationsToggle annotationsPatient anonymizationPatient anonymization

Window Width/LevelWindow Width/Level

Native Image File16 bit per pixel, 65,536 tonal steps

Displayed Image8 bit per pixel video at 1.5 to 270 cd/m2

Selected Window Width and Level from native image mapped to CRT display.

Digital World DAC CRT Display

Window Level

3D Study

Monitor Quality ControlMonitor Quality Control

Monitor Calibration (GSDF)Monitor Calibration (GSDF)

Weekly testing Reporting WorkstationsWeekly testing Reporting Workstations

Clinical Acceptance TestingClinical Acceptance Testing

Parr L.F. et al (2001), J. Digit Imag., 14 (Suppl 1) , pp22-26Groth S. et al (2001), Radiographics, 21 , pp719-732

Conclusion

Fitness for purposeFitness for purpose

Set up a Quality Control regime (Medical Set up a Quality Control regime (Medical Physics, Vendor, 3Physics, Vendor, 3rdrd Party...) Party...)

Ensure that your display systems adhere to Ensure that your display systems adhere to the GSDF at all timesthe GSDF at all times

AcknowledgementsAcknowledgements

Mr. Ken Compton. (Clinton Electronics)Mr. Ken Compton. (Clinton Electronics)

Mr. Ivan Boeykens. (BarcoView)Mr. Ivan Boeykens. (BarcoView)

Mr. Dewinder Bhachu (PACSnet)Mr. Dewinder Bhachu (PACSnet)

ReferencesGraf B. et al (2000), AJR,174, pp1067–1074

Bennet W.F. et al (2002), J. Digit Imag; 15 Suppl 1, pp171-174

Ishihara S. et al (2002), Comp. Med. Imag. & Graph., 26, pp181-185

Ikeda M. et al (2003), Inves. Radiol, 38, pp57-63

Peer S. et al (2003), Eur Radiol, 13, pp413-417

Kuprinski E.A. & Roehrig H. (2002), Acad. Radiol., 9, pp638-645

Flynn et al (1999), Radiographics, 19, pp1653-1669

Steckel R.J. et al (1995), AJR, 164, pp837-841

Parr L.F. et al (2001), J. Digit Imag., 14 (Suppl 1) , pp22-26

Blume H. et al (2002), Proceedings of SPIE, 4681, pp271-292

Groth S. et al (2001), Radiographics, 21 , pp719-732