PACSnet Display Devices/Systems Evaluation Protocol
Bence-Jones Offices,
(Primeter Road)
St. George's Hospital
London
SW17 6QT
Tele: 020 8725 2619
Fax: 020 8725 3293
Version 1.02
0. Introduction and Explanation of why testing is important.
This protocol is designed to be used by PACSnet in its evaluation of image display devices used for the
display of medical images within a PACS. It covers both CRT and LCD displays.
The protocol does not cover workstation functionality, network connections or other features of a PACS.
1. Monitor description.
This section describes the monitor in terms of its physical attributes (size, weight, etc), its construction,
and its described display characteristics, all based on information supplied by the manufacturer.
2. Site-specific installation information.
Details of the ambient conditions during testing, e.g. of the reporting room, manufacturer’s test facility,
etc. It may also include information on warranties, service contracts, etc.
3. Test Results.
This section lists the results of various tests and measurement on the monitor. The tests are described
below. Note that before performing any of the tests, the screen should be cleaned and the monitor
should be allowed to warm up for 30 minutes (without screen-saver) before testing commences, and
should be cleaned before testing.
Veiling glare
This is caused by luminance energy reflected within the glass and phosphor structure from one location
to another, thus reducing the contrast modulation between dark and light pixels.
No existing protocol found. Suggest a method where screen is displaying a uniform grey level (peak
white?) apart from a central circle of black. Luminance at the centre of this black circle can be
measured, and measured again when the surrounding white area is reduced to black.
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PACS Evaluation Protocols: Evaluation of Display Monitors
0. Introduction.
This protocol is designed to be used by PACSnet in its evaluation of image display devices used for the
display of medical images within a PACS. It covers both CRT and LCD displays.
The protocol does not cover workstation functionality, network connections or other features of a PACS.
1. General monitor description and manufacturer’s specification
Physical size of monitor, footprint, any clearances required
Weight
Removable stand; adjustability of display height and angle (tilt, swivel), other mounting options
USB hub
Input signal
Analogue or digital
Signal cable
VESA DDC/Ci bi-directional control; sRGB support; VESA VCP support
Display Data Channel Command Interface Standard
(http://www.vesa.org/dload/summary/sumddcci.htm)
Dynamic or static?
Colour or black & white display
Backlight (for LCD)
Required specification of base unit, including video card
Any minimum specifications for CPU, memory, hard disk space, OS, etc.
Power supply requirements – voltage & frequency
Quote manufacturer’s figures.
Power consumption
Quote manufacturer’s figures.
Heat and noise output
Quote manufacturer’s figures.
Controls available for user adjustment
e.g. brightness, contrast, geometry. Ability to disable user adjustment facilities. On-screen manager.
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Controls available for engineer adjustment
Intended use
review, diagnosis, text-only, home, etc
First year sold, first year sold in UK
Territories sold to
Currently and ever.
Regulatory Approvals
CE Mark (ECM Directive, Medical Devices Directive), etc
Warranty and/or maintenance contracts available
Technical support
Response times, on-site engineer
Charges for spare parts
Time to supply spare parts
Self-calibration facilities
Bandwidth
Refresh rate
Scan rates
Horizontal synch (range)
Vertical synch (range)
Display Type
Shadow mask, aperture grille
Phosphor used for screen
Curvature of display surface
Portrait or landscape
Screen size – quoted, measured
Active area – quoted, measured
Dot pitch
Dot pitch, horizontal dot pitch, vertical dot pitch
Deflection angle
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Bulb transmission
Front panel transmission
Maximum input video bandwidth
Maximum resolution
Recommended resolution
Test images supplied
Screen cleaning recommendations
Response time
Dot clock
Optimum intended viewing angle (for LCD displays)
Aperture ratio
2. Site-specific Installation Information
Positioning of monitors within rooms
User space
Reflections, lighting, etc
Room lighting: Cornell: “monitor works best in a low-light environment. However, a low-light
environment does not equate to a dark room. Viewed in the dark, an on-screen image would appear
deficient in contrast.”
QA/QC programme in place; tools used.
Monitor cleanliness; tidiness of installation (cables, etc)
Maintenance contract for this installation
DICOM GSDF facility
3. Test Results
AAPM TG18 test results.
DICOM part 14
Veiling glare (aka “flare” or “surrounding field effect”)
Noise in image
Instability
Convergence
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Tone scale (e.g. Barten, default)
Resolution
Flat field uniformity, colour purity
Black level, peak white level – levels will depend on the area of the screen illuminated
Artefacts
Weak internal and external reflections
Focussing – test using only one primary colour (if colour monitor)
Contrast
Brightness
Spatial resolution
Aliasing
Ringing/overshoot
streaking
Average picture level/grey-level shift
Screen regulation
Ambient light sensors
Radiation levels, emissions certification
Power-saving features
Contrast ratio
Viewing angle
Screen reflection
Number of colours displayable (colour depth)
Gamma
Flicker – view an all-white screen using peripheral vision. Important in medical – monitors sit side-byside.
Geometric distortion: pincushion, barrel, trapezoidal (“keystone”), orthogonal, tilt, hook (“flagging”),
nonlinearity, line pairing, ringing (all from display measurement book).
Measurement of warm-up characteristics (“warm-up”) and luminance drift (“aging”)
Luminance stability (i.e. changes as greater or lesser areas of screen are white)
Number of defective pixels (LCD)
Phosphor artefacts (CRT)
Aspect ratio
Jitter
Phosphor persistence (decay)
SMPTE test image: constant increase in perceptual brightness (if using workstation software)
Test protocol.
Let monitor warm up (30 minutes). Set user-accessible adjustments to the settings used in the initial
tests.
Equipment needed.
Photometer
“a time constant of approx 100ms corresponds to that of the human eye”
Allow to warm up (1-2 minutes usually sufficient) and to stabilise temperature/drying of condensation if
necessary (30-60 mins).
Illuminance photometer to measure ambient light levels.
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Luminance probe
“A luminance meter of the reflex-viewer type with an accuracy of +/- 10% shall be used to check the
consistency of the luminance of the display. The measuring range shall be between 0.1 cd/sq m and
500 cd/sq m. The angle of measurement at the aperture of the meter should be 1 deg and shall not
exceed 5 deg.” (BSI 1994)
(to measure screen luminance)
Cloth tape measure (to measure distances off curved screens and to help with geometry tests))
Straight edge/ruler (to measure distances off screens, and to help with convergence tests and
geometry tests)
Darkroom with adjustable background lighting (to minimise effect of background illumination and
reflections)
Oscilloscope (to measure signals from video card, and flicker on screen
Detector suitable for measuring flicker
Test images
Dividers (to help with distance measurements off screen and with geometry tests)
Convergence gauge
Tests to be performed at the manufacturer’s recommended resolution, as well as at higher and lower
resolutions.
Test tools:
Display Mate: http://www.displaymate.com/intro.html
Image Smiths
Light source (for measurement of reflectance)
Microscope
Cleaning materials: cloth, etc
Rule
Tape measure
Film with printed grid
Magnifying glass
Berlin tests:
Background luminance level and luminance range
Luminance distribution
Spatial and low contrast resolution
Image geometry and motion
Monitor flickering
Artefacts
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