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