The Leeds Teaching Hospitals NHS Trust Is Grey the New Black? Image Display Optimisation & Consistency for Softcopy Reporting Mark Barnfield St James’s

The Leeds Teaching HospitalsNHS Trust

Is Grey the New Black?Is Grey the New Black?Image Display Optimisation & Consistency for Image Display Optimisation & Consistency for

Softcopy ReportingSoftcopy Reporting

Mark BarnfieldMark BarnfieldSt James’s University Hospital, LeedsSt James’s University Hospital, Leeds


Softcopy Concerns…Softcopy Concerns…

Softcopy more often becoming last Softcopy more often becoming last component in the component in the ‘Imaging chain’‘Imaging chain’..

In NMed chain can cost in excess of £300K In NMed chain can cost in excess of £300K – undertake well developed QA protocols.– undertake well developed QA protocols.

… … however, workstation monitors however, workstation monitors relatively inexpensive ~£300 – possible relatively inexpensive ~£300 – possible weak link with little or no QA system weak link with little or no QA system employed.employed.


Image Quality ApproachImage Quality ApproachSt James’s NMedSt James’s NMed

Optimisation Optimisation (currently qualitative) (currently qualitative) To improve presentation of radiological To improve presentation of radiological

images and ensure that important image images and ensure that important image information is not lost during visual information is not lost during visual inspection.inspection.

ConsistencyConsistency Images should appear similar on different Images should appear similar on different

displays or on the same display at displays or on the same display at different times.different times.


First step - Display PreparationFirst step - Display Preparation

Monitor CleanlinessMonitor Cleanliness

Display quality is compromised by dust, Display quality is compromised by dust, fingerprints, ink, etc. fingerprints, ink, etc.

Reduction in luminance.Reduction in luminance. Possible misinterpretation.Possible misinterpretation.

Needs cleaning on regular basis and on as-Needs cleaning on regular basis and on as-needed basis.needed basis.

Lint free cloth to reduce static.Lint free cloth to reduce static. Never spray directly onto monitor.Never spray directly onto monitor. Manufacturer may recommend special cleaner for Manufacturer may recommend special cleaner for

monitors coated with antireflective or antiglare monitors coated with antireflective or antiglare coatings.coatings.


The SMPTE Test Pattern The SMPTE Test Pattern Ref:Radiology 1985; 154: 519-527Ref:Radiology 1985; 154: 519-527

Mid-band Mid-band streakingstreaking

Brightness Brightness && Contrast Contrast

UniformityUniformity

ResolutionResolutionresponseresponse

Linearity & Linearity & Geometric distortionGeometric distortion

FocusFocus

Picture BoarderBoarder


An Optimal Contrast Range An Optimal Contrast Range Brightness & Contrast AdjustmentBrightness & Contrast Adjustment

1.1. SetSet to to ~~50% and back off50% and back off

2.2. Bring up until Bring up until blackblack just just turnsturns grey and back off fractiongrey and back off fraction

3.3. Set to give reasonably bright Set to give reasonably bright whitewhite level but avoid loss of image level but avoid loss of image definitiondefinition

The brightness and contrast of yourThe brightness and contrast of your monitor are adequately set monitor are adequately set if the if the inner inner 5% squares at both ends of gray scale are visible.5% squares at both ends of gray scale are visible.


ObservationsObservations

17” Iiyama – 17” Iiyama – Vision Master 403Vision Master 403 VisualVisual

Geometric Geometric (Aspect ratio)(Aspect ratio) distortion – distortion – squares squares rectangles rectangles

BarrellingBarrelling Also observed pincushion on my Also observed pincushion on my

PC!PC! RefreshRefresh verticalvertical raterate 66Hz - 66Hz -

<72Hz <72Hz somesome observers can observers can perceive flicker and greater eye perceive flicker and greater eye stain is possible.stain is possible.

Known that nearly all parameters Known that nearly all parameters are dependent on position on are dependent on position on screen - degrading from centre.screen - degrading from centre.


DICOM Part14: (GSDF) DICOM Part14: (GSDF) Grey-Scale Standard Display FunctionGrey-Scale Standard Display Function

The Consistent imageThe Consistent image

Aims to mathematically define a display Aims to mathematically define a display function for all image presentation systems. function for all image presentation systems.

Aims for similarity in grey-scale Aims for similarity in grey-scale perceptionperception between different display systems.between different display systems.

Not a performance or image display Not a performance or image display standard.standard.

It does not define luminance range.It does not define luminance range.

The Leeds Teaching HospitalsNHS TrustMeasuring Monitor Characteristic Measuring Monitor Characteristic

CurveCurveAnnex D - DICOM pt14 pp27-36Annex D - DICOM pt14 pp27-36

0

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1

Normalised Digital Driving Level

Lum

inan

ce [c

d/m

2 ]

Step target through greyscale range

Background(20% of max lum)

Target (10% area of screen)

Photometer (Light-O-Meter P10

Std)


Curve MappingCurve Mapping

0

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1

Normalised Digital Driving Level

Lu

min

an

ce

[c

d/m

2 ]

Measured

GSDF


LUT set-up verificationLUT set-up verification

5% & 95% 5% & 95% contrast contrast equally equally perceptible.perceptible.

Linear Linear perception perception along the along the colour bar.colour bar.


Effect of brightness & contrast setting on Effect of brightness & contrast setting on display characteristic curves - PCsdisplay characteristic curves - PCs


Reproducibility of monitor set-up using Reproducibility of monitor set-up using SMPTE test patternSMPTE test pattern

NB. A – B done as consecutive measurements, C – D on NB. A – B done as consecutive measurements, C – D on separate occasions over a week.separate occasions over a week.


Proposed Frequency of QC TestsProposed Frequency of QC Tests

WeeklyWeekly Monitor preparationMonitor preparation Brightness & contrast adjustmentBrightness & contrast adjustment

MonthlyMonthly GeometryGeometry Spatial resolutionSpatial resolution

QuarterlyQuarterly Spatial uniformitySpatial uniformity Veiling glareVeiling glare


I would like to thank,

Sarah Jervis for allowing the use of her SMPTE and DICOM 14 Matlab programs;

David Brettle for guidance and technical support.

AcknowledgementsAcknowledgements

Documents

The Leeds Teaching Hospitals NHS Trust Is Grey the New Black? Image Display Optimisation & Consistency for Softcopy Reporting Mark Barnfield St James’s