Medical Display Technologies

Medical Display Technologies
“Overview and Developments”
Ing. Juergen HECKEL
VP, Medical Business
Sales and Marketing, Global
© 2015 EIZO Corporation. All Rights Reserved.
Medical Monitors (Understanding)
Image Cycle and image Processing (Hybrid Viewing)
PACS / Modality
Monitor
Slide 2
Radiologist
Medical Monitors (Understanding)
Resolution / DICOM / Constancy
Standard Monitor Image
Medical Monitor Image
Slide 3
Expectations and Requirements?
Important to keep in mind “Human Visual System”
 Requirements / Expectations
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LCD Panel technology
DICOM Part 14 grade
Small Pixel pitch
High Resolution
High Brightness/Contrast
Stability (Brightness)
Uniformity Control (DUE)
Wide viewing angle
Hardware Calibration
Sharpness and no artifacts
Long and stable life time
Automatic calibration (QC)
Supporting medical standards
1000:1
750:1
Example
Comparison between 1,000:1 and 750:1.
(Black level)
Slide 4
Human Visual System
ACR-AAPM-SIIM Technical Standard for Electronic Practice
http://www.acr.org/~/media/AF1480B0F95842E7B163F09F1CE00977.pdf
 Display Characteristics:
 Ambient luminance should be less than ¼ of the
luminance of the darkest gray level
 Minimum Luminance should be at least 1.0 cd/m² for
diagnostic interpretation
 Maximum Luminance should be for diagnostic 420
cd/m² (on Mammography) and 350 cd/m² for others
 DICOM grayscale display function (GSDF) have to
be used to set the correct gray levels
 Color Temperature should be around 6500K with a
white point to the CIE daylight standard D65
 Pixel pitch for Diagnostic monitors should be not
larger than 0.210mm
Slide 5
Available Technologies for Medical?
Looking inside, Life Time, Accuracy, Power consumption…
 Display Technologies
 Current LCD / IPS
Technology
 Curved Displays
 OLED
 4K and 8K
 3D Display
Backlight Sensor (Stabilization)
Cold-Cathode Fluorescent (CCFL) or Light Emitting Diode (LED)
Slide 6
Available Technologies?
Comparison to LCD
• For TV Marlket
• Not yet ready for medical
applications as straight lines are
not straight visible
• Uncertain reliability and less
production efficiency
• VA technology more suitable for
curved
• Less black uniformity
• Good Contrast ratio
• Stable Greyscale and less
brightness shift
• Worse Uniformity and still TV
grade image quality
• Shorter lifetime than LCD
• Color Shift viewing angle &
• 1.2 times costs than LCD
CURVED
OLED
3D
4K/8K
• Glass-free 3D solutions are
under development
• Interesting for teaching purpose
for digital mammography
• No size limitations and good
image quality available
• Under development for various
future medical areas
• Could be interesting from
resolution point of view to show
more images
• For medical purpose viewer
adjustment is required
• Less Brightness than required for
medical diagnostic image viewing
• Under development could be
interesting for the future
Slide 7
Example Mammography Images
Accuracy important as cancer is growing fast
therefore accurate technology is key to detection / Detail visibility mandatory
20-mo later
Slide 8
more 25-mo
later
Importance of Ergonomics?
Effects and issues
 Negative Impacts
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Neck problems
Shoulder problems
Low back pain
Etc.
 Ergonomic Aspects
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Size of the monitor
Distance to the monitor
Anti-Reflection (Ambient Light)
Eye-Fatigue
Flicker Free
Uniform
Wide Viewing Angle
Stress Free
Slide 9
Technology Benefit: Hybrid Gamma
Image Adjustment & Color & Greyscale settings
 GAMMA 2.2 = COLOR
 DICOM = GREYSCALE
Slide 10
Technology Benefit: High Resolution / Size
More images can be displayed, avoid fragmented information = losing information
8.8MP vs 5MP/6MP
Slide 11
Technology Benefits: AR vs AG
Anti-Reflection Treatment
AR treatment reduces reflected images by light interference
Whereas AG (Anti-Glare) treatment just reflects incident light
diffusely, AR treatment reduces reflected light. In addition,
since AG treatment does not have any convexities, light from
backlight goes through without reflection, so AR treatment can
show sharper images than AG treatment.
Figure: AR treatment
AR improves sharpness and reduce black
brightness (=more black)
Slide 12
Technology Benefit: Quality
control mandatory
Medical grade monitors have to be quality controlled
 Integrated Calibration Sensor
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Automatic calibration functions (QC)
Schedule function / Self-QC
Remote calibration functions
 Ambient light sensor
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Adjustment to Ambient light
 Presence Sensor
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Power Save Options / Backlight Saver
 Digital Uniformity control (DUE)
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Luminance/Greyscale/Colors
Slide 13
www.eizoglobal.com
Slide 14
Technical developments in display
technology
David Hadden
15
Radiology market trend: “do more with less”
 Increasing image volumes
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Technology: CT, MRI, Tomo
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Multimodality examination
 Aging population
 Budgets are going down
16
A good read is a correct diagnosis done in a
productive and ergonomic way
*
17
* Independent survey by MarkeTech Group with large population of radiologists
Image quality is influenced in many ways (1/5)
 High calibrated luminance will
reveal subtle differences
18
Image quality is influenced in many ways (2/5)
 Uniformity correction on pixel level: DICOM from center to edge
19
Image quality is influenced in many ways (3/5)
 Ensuring crisp and in-focus moving images
20
Image quality is influenced in many ways (4/5)
 From GSDF to ColourSDF
Ultrasound
21
PET CT
Microscopy
Image quality is influenced in many ways (5/5)
 Integrated multi sensor technology to safeguard image
quality continuously
 Protected at all times
LCD Panel
22
How can a display solution improve productivity?
(1/2)
 Fusion displays allow for flexible image layout and multimodality
reading...
23
How can a display solution improve productivity?
(2/2)
 Luminance adjustments focused on area of interest
Diming the navigational display
Boosting to maximum
luminance renders
more JND’s
24
Focus on local
area of interest
Focus on ergonomics (1/2)
 All displays should be easily adjustable
Tilt, height adjustment
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 Fusion concept
500
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No intruding bezel
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Large viewing angle
Luminance ratio in function of viewing angle (L/R)
in normal reading position for 6MP display
450
Barco L
400
Barco R
350
Trad
IPS L
300
25
Trad
IPS R
250
0
10
20
30
40
Focus on ergonomics (2/2)
 Size does matter
26
Technical developments:
1. Image quality
2. Productivity
3. Ergonomics
27
Questions / Discussion
www.youtube.com/BarcoTV
www.twitter.com/Barco
www.facebook.com/Barco
Quality control of image display
monitors
Dr Kevin Robson
Regional Medical Physics Department
Freeman Hospital
Newcastle upon Tyne Hospitals NHS Foundation Trust
UKRC July 2015
Introduction
• Introduction
• User tests
• Physics tests
• Problems identified
Need for QC
•
The display is the last part of the
imaging chain.
•
Problems with display can adversely
impact on the improvements made in
image quality of the acquisition
system.
•
Incorrectly set up display can alter
appearance of the image
•
Impact on radiological opinion
Need for QC
• Reporting monitors
• Acquisition workstations
• Review monitors
• Ultrasound scanners – reporting and acquisition
• Portable/hand-held devices
Performance evaluation standards
• SMPTE RP-133-1991
• NEMA-DICOM standard (PS3)
• DIN V6868-57
• ISO 9241/ISO 13406 Series
• VESA Flat Panel Display Measurements Standard
AAPM Report OR-03 (TG18)
• Very large document
• Not practical to complete all the tests
• Specialist equipment and carefully
controlled environment
needed for some tests
• Which ones are important for QC?
•Two sections outline QC tests
• Guidance in UK closely follows these
• Designed for use with monochrome CRT and LCD
displays
• Test patterns developed as part of report
• Some of these are very useful
Real-world QC
• Characterising display screen is different from routine QC testing
• Has anything changed?
• Is the performance still within the recommended tolerance?
• Large numbers of individual display devices – Web-based PACS
access – all hospital PCs can potentially be used for viewing medical
images
• Targeted approach
• Primary displays
• Acquisition workstations/review monitors
• User QC is important
User QC tests
• Advice given in IPEM Report 91
- Level A tests
Display monitor condition
Greyscale
Distance and angle calibration (more PACS than display
device)
Resolution
• Advice given in NHSBSP 1303
Visual check to assess greyscale, resolution, viewing
conditions, geometry
Useful test patterns
User QC tests
• Routine tests with test patterns
• TG18-QC and SMPTE patterns
• Qualitative GSDF check
• Perceptual linearisation check
• Indirect check on viewing conditions
• Resolution and geometry check
• Quick and straightforward to carry out
• OK for radiology departments but what about
the hundreds of other monitors?
User QC tests
• Problem with ‘learning’ of test patterns
• MoniQA system developed at LUCMFR
(Leuven)
• Test patterns with fixed and variable features
• Centralised collation of QC results
User QC tests
• User challenge
E.g. system developed by David Brettle at Leeds
• Tests various aspects of performance
• Monitor
• Ambient light/viewing conditions
• Need to pass the test each time you log on
• Characters change at each log on
• Also checks observer’s contrast sensitivity as well
• Can be applied to all display devices inc. ‘non radiology’ ones
• Effective control of access to images from inappropriate workstations
Brettle DS and Bacon SE. A method for verified access when using soft copy display. Br J Radiol, 78 (2005) 749-751
User QC tests
• Manufacturer QC tests/calibration (eg Eizo
RadiCS and Barco Medical QAWeb)
• Built in sensors
• Clip on sensors
• Measure display parameters
• Calibration
• Can alter display LUT
• Know where to find the calibration set up
• It may change following software update etc and
may longer be correct.
Physics QC tests
• Guidance given in IPEM Report 91
• More detailed guidance given in NHSBSP Report 0604
• This is specifically mammo based but is a good protocol
• Luminance measurements – ie GSDF compliance and while you are at it you get Lmax
and Lmin
• Uniformity
• Resolution and artefacts
• Viewing conditions
Useful test patterns
Useful test patterns
TG18-MP
12-bit pixel range (0-4095)
Banding reflects the bit-depth of the
display system.
Display
8-bit (256 grey levels)
10-bit (1024 grey levels)
12-bit (4096 grey levels)
Bit depth
Limits etc.
•
•
a
OK for GSDF and matching of pairs of
workstations
Ambient light and Lamb is difficult for some
acquisition workstations – may be used for
degree of reporting (eg for stereotactic
localisation in mammography)
•
Conflict between reasonable working light
levels and monitor requirements.
What problems do we find?
• Keeping track of the monitors themselves – get moved from one workstation to another
• Difference between the two monitors in a pair – higher luminance on one than the other
– fiddling with controls by users? GSDF still OK.
• Resolution – I sometimes have difficulty with low contrast bars on some monitors
• Viewing conditions on acquisition and review workstations
• Simultaneous use of viewing boxes in reporting room/other room use
• Workstations sited opposite doorways
• What level of ambient light/monitor performance is acceptable for acquisition
workstations
• Repeating of images if thought to be of insufficient quality?
Some problems/issues identified
• One monitor completely defective – very low luminance
• Display bit-depth set wrongly / incorrect graphics card
• Severe banding on continuous greyscale wedge
• Very badly marked screen
• Looked like someone had opened a can of drink at the bottom of screen
• Finger marks on screen
• With test images on PACS, the PACS
introduced a degree of image processing on
some images - interpolation
• Great difficulty in resolving all the bar groups and Cx patterns look odd
• Display resolution bar pattern and zoom to v high magnification
• Bar patterns shown as sinusoidal rather than square wave
• Test using test patterns on workstation (or external drive)
• Change in calibration following upgrade of operating system
• Bad pixels
Effect of ambient light
• Adds luminance to display
• Creates diffuse reflection
• Alters display so that GSDF calibration may no
longer be correct
• Can create specular reflection
• Distracting to observer
• Different calibrations for different expected levels of
ambient light
• Some displays will auto-correct for ambient light
• Not generally a problem for diagnostic X-ray
reporting rooms
Effect of adding ambient light to display
(Lamb = 2cdm-2)
Total number of jnds = 646
Total number of jnds = 585
Effect of incorrect ambient light
correction
Some problems/issues identified
Physical inspection of monitors is very useful!
Acquisition monitor next to window
High ambient light (existing blinds make
some difference)
Specular reflection
Can see image of socket on
opposite wall
Increased diffuse reflection
Finger marks
Incorrect bit depth/incorrect graphics
card
Incorrect bit depth/incorrect graphics
card
Effect of interpolated display
Effect of correct monitor calibration
Effect of correct monitor calibration
Effect of correct monitor calibration
Normal
lcalibration curve
l
DICOM
calibration
curve
l
Conclusions
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•
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Pragmatic approach to QC needed
User tests are important
Reporting displays should pass all the tests
Some acquisition workstations will not pass
all tests.
•
Not all acquisition workstations are
calibrated
to the GSDF curve
•
Good viewing conditions more difficult to
maintain