Transcript The SMPTE Test Pattern (Society of Motion Picture and

The Leeds Teaching Hospitals
NHS Trust
Is Grey the New Black?
Image Display Optimisation & Consistency for
Softcopy Reporting
Mark Barnfield
St James’s University Hospital, Leeds
The Leeds Teaching Hospitals
NHS Trust
Softcopy Concerns…

Softcopy more often becoming last component
in the ‘Imaging chain’.

In NMed chain can cost in excess of £300K –
undertake well developed QA protocols.

… however, workstation monitors relatively
inexpensive ~£300 – possible weak link with
little or no QA system employed.
The Leeds Teaching Hospitals
NHS Trust
Image Quality Approach
St James’s NMed
 Optimisation

(currently qualitative)
To improve presentation of radiological images
and ensure that important image information is
not lost during visual inspection.
 Consistency

Images should appear similar on different
displays or on the same display at different
times.
The Leeds Teaching Hospitals
NHS Trust
First step - Display Preparation
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Monitor Cleanliness
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Display quality is compromised by dust,
fingerprints, ink, etc.
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Reduction in luminance.
Possible misinterpretation.
Needs cleaning on regular basis and on as-needed
basis.
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Lint free cloth to reduce static.
Never spray directly onto monitor.
Manufacturer may recommend special cleaner for
monitors coated with antireflective or antiglare coatings.
The Leeds Teaching Hospitals
NHS Trust
The SMPTE Test Pattern
Ref:Radiology 1985; 154: 519-527
Picture
Boarder
Uniformity
Mid-band
streaking
Linearity &
Geometric distortion
Brightness & Contrast
Resolution
response
Focus
The Leeds Teaching Hospitals
NHS Trust
An Optimal Contrast Range
Brightness & Contrast Adjustment
1.
Set
to ~50% and back off
2.
Bring up
until black just turns
grey and back off fraction
3.
Set
to give reasonably bright
white level but avoid loss of image
definition
The brightness and contrast of your monitor are adequately set if the
inner 5% squares at both ends of gray scale are visible.
The Leeds Teaching Hospitals
NHS Trust
Observations

17” Iiyama – Vision Master 403
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Visual
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Geometric (Aspect ratio) distortion –
squares  rectangles
Barrelling
Also observed pincushion on my
PC!
Refresh vertical rate 66Hz - <72Hz
some observers can perceive flicker
and greater eye stain is possible.
Known that nearly all parameters
are dependent on position on
screen - degrading from centre.
The Leeds Teaching Hospitals
NHS Trust
DICOM Part14: (GSDF)
Grey-Scale Standard Display Function
The Consistent image
Aims to mathematically define a display
function for all image presentation systems.
 Aims for similarity in grey-scale perception
between different display systems.
 Not a performance or image display standard.
 It does not define luminance range.

The Leeds Teaching Hospitals
NHS Trust
Measuring Monitor Characteristic Curve
Annex D - DICOM pt14 pp27-36
Background
(20% of max lum)
Target
(10% area of screen)
Photometer (Light-O-Meter
120
2
Luminance [cd/m ]
P10 Std)
Step target through greyscale range
100
80
60
40
20
0
0
0.2
0.4
0.6
0.8
Normalised Digital Driving Level
1
The Leeds Teaching Hospitals
NHS Trust
Curve Mapping
Measured
GSDF
2
Luminance [cd/m ]
120
100
80
60
40
20
0
0
0.2
0.4
0.6
0.8
Normalised Digital Driving Level
1
The Leeds Teaching Hospitals
NHS Trust
LUT set-up verification

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5% & 95%
contrast equally
perceptible.
Linear perception
along the colour
bar.
The Leeds Teaching Hospitals
NHS Trust
Effect of brightness & contrast setting on display
characteristic curves - PCs
The Leeds Teaching Hospitals
NHS Trust
Reproducibility of monitor set-up using SMPTE
test pattern
NB. A – B done as consecutive measurements, C – D on separate
occasions over a week.
The Leeds Teaching Hospitals
NHS Trust
Proposed Frequency of QC Tests
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Weekly
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Monthly
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Monitor preparation
Brightness & contrast adjustment
Geometry
Spatial resolution
Quarterly
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Spatial uniformity
Veiling glare
The Leeds Teaching Hospitals
NHS Trust
Acknowledgements
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.