Download Improving Medical Imaging Display Performance

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Top Ten Issues and Best Practices
Improving Medical Imaging Display Per formance
By David So re n s e n
Director of Engineering/Prod Development/Sourcing
Ca nvy s - Vis ual Technolog y S olu ti ons
Today, LCD-based displays are more stable than ever, and many issues and
artifacts relating specifically to CRT monitors have been resolved. The useful
life of these displays is longer resulting in longer warranties from the
manufacturers. However, the relative stability of the displays gives rise to
some false premises and confidences ...
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Im provin g M e d ica l I m a g i n g D i s p l a y
Pe r forma nce
T op T en Issues a n d Best Pr a ct ice s
Objective
world class health care facilities, large
The objective of this paper is to cite
common issues, clarify misconceptions and
to offer solutions, via best practices, to
those who are tasked with maintaining
display quality and conformance in medical
imaging environments.
The experts at
Canvys believe that the medical diagnostic
community should strive to maintain the
highest quality of diagnostic and clinical
displays
with
the
goal
of
promoting
positive patient outcomes.
If the information in this paper helps solve
one or two current issues the reader is
experiencing, we believe our goal will have
been accomplished.
first-hand
experiences,
formal
education and training along with their
“view from the trenches” - crawling under,
around and behind desks and dismantling
and cleaning workstations - has revealed
some
interesting
perspectives
and
that
eye-opening
most
healthcare
medical LCDs are not exposed to.
experiences
have
provided
These
insight
into
display quality, wear and tear, set up, and
calibration and maintenance procedures.
the best practices to overcome them.
an
organization
of
display
and supplied thousands of medical displays
to healthcare providers and manufacturers
of healthcare equipment throughout North
America and Europe including products
variety
of
manufacturers
of
displays, work stations, graphics cards,
and software.
—
Dedicated field engineers and technical
services team members support, maintain
and
—
Their
The outcome is a list of top ten issues and
solutions technology experts, has installed
a
community hospitals.
—
Background
from
mid-sized hospitals and clinics, and small
professionals on the viewing side of a
—
Canvys,
multi-site institutions, teaching hospitals,
calibrate
displays
from
multiple
manufacturers in all kinds of institutions:
Diagnostic Displays
For
our
purposes,
we
define
medical
imaging LCDs as those displays that are
used
to
view
medical
images
in
a
diagnostic or clinical environment. These
diagnostic displays are typically arranged
in PACS (Picture Archiving Communication
System)
workstation
connected
directly
to
configurations,
medical
imaging
equipment for image quality control or are
integrated into complete medical imaging
systems. These displays can be located in
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a variety of places within a healthcare
facility including radiology reading rooms,
operating rooms, cath labs, ICUs, etc.
than ever, and many issues and artifacts
relating specifically to CRT monitors have
displays
is
warranties
However,
The useful life of these
longer
from
the
resulting
the
relative
in
longer
manufacturers.
stability
Below are the top 10 issues affecting
Medical Imaging LCDs and best practices to
Today, LCD-based displays are more stable
been resolved.
The List
of
the
displays gives rise to some false premises
and confidences such as:
address them. Most issues are surprisingly
simple and are a result of limited resources
(impacted
by
the
current
challenging
economy) or purely inexperience and/or
lack of basic knowledge about medical
imaging displays. The issues listed can be
commonly found at small practices as well
as world class multi facility institutions.
The items on the list primarily relate to the
set up or maintenance of the display, work-
“We can just hook them up and start
using them...”
Yes it is possible, but generally one should
follow set up procedures to insure proper
calibration.
station, graphics cards, drivers and proper
calibration of displays.
#10
(Workstation) Incorrect setup of
display resolution and/or color bit
depth.
“These are LCD monitors; they don’t
For best image quality, the display
need any maintenance...”
resolution called out by the operating
The maintenance is not as demanding as
system on the workstation should match
CRT displays, but there is maintenance to
the native resolution of the display.
be done.
•
1600 x 1200, then the display resolution
“If they go bad we can just throw them
should be set up to 1600 x 1200—peri-
out and purchase new ones...”
Medical
imaging
displays
allowed
to
bad”
“go
should
rather
not
they
od.
be
need
If the native resolution of the display is
•
Displays are tolerant to accepting other
calibration and maintenance in order to
non-native resolutions, but if this is
insure the best patient care possible. Poorly
done interpolation is required to fill in or
performing displays may result in misdiag-
toss away the extra pixels and can
nosis or comprised medical care. Further-
cause less than optimal image quality.
more improper disposal has environmental
impacts that could be costly in some states.
•
Similarly, the color bit depth (8 bit,
24 bit,
properly
32
bit,
called
capabilities
of
etc.)
needs
out
to
the
graphics
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to
match
be
the
card.
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The wrong setting can limit the number
of
gray
scales
negatively
impact
displayed
or
performance.
If
Windows OS is being used you can find
these
settings
easily
under
never matched at the new location.
can
Best Practices:
a) For
Display
Properties/Settings.
gray
resolution
of
the
to
calibrate
the
c) Record and mark displays with their
color coordinates to aid in future move-
mended settings and make this a check
point at the time of initial setup.
b) Alternatively,
contract
the
display
ment.
d) Provide the color coordinate target to
the
manufacturer or integrator to perform
the initial setup of the display, workstation, and graphics cards.
have
not
changed
manufacture
when
obtaining
replacement units.
e) Be aware of new generation grayscale
display
c) Perform a periodic audit to ensure that
settings
software
color point.
native
display and the manufacturer’s recom-
the
displays:
b) For color medical displays: utilize color
calibration
the
medical
buy them in color matched pairs.
Best Practices:
a) Know
scale
technology
that
will
enable
tweaking of the color point in the field.
and
consider hiding the Display Properties
d) Pay particular attention to any new or
rogue workstations that get introduced.
e) Utilize
analyze
a
network
these
tool
settings
to
on
view
and
deployed
workstations from a remote site.
management controls to prolong LCD
panel life.
Use of DPMS (Display Power Management
System) prolongs LCD panel life and
reduces energy consumption.
•
#9
(Displays) Poor color match.
The target luminance setting needed by
medical
imaging
applications
is
generally higher than that of general
When two or more displays are used
office applications. The useful life of the
side-by-side it is best if their colors and
display
more specifically their white points are
(the
ability
to
achieve
the
desired target luminance) is primarily a
similar.
•
#8
(Workstation) Not enabling power
Settings tab.
function of the hours on the backlight.
When this issue is seen in the field,
either the displays were never properly
color matched (common with commercial displays), or perhaps one of the
displays was subsequently moved and
•
Reduced target luminance levels (due to
aging
ratios,
digital
backlights)
affects
driving
decreases
calibration
levels
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contrast
and
limits
which
may
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ultimately violate guidelines governing
•
specific imaging procedures.
•
Implementation of a screen saver will
usually prevent image retention, and
even if a persistent image develops, it is
Properly implemented power manage-
usually not permanent and will go away
ment controls shut down the monitor
if exercised with a proper screen saver.
backlight after periods of inactivity and
thus extend the useful of the display.
Best Practices:
a) Setup
Best Practices:
a) Setup
all
new
workstations
organizational-acceptable
with
default
from
disabling
with
an
moving image, screen saver to kick in.
b) Perform periodic audits of workstations
to ensure screen saver settings are
the monitor will shut down.
users
workstations
agreed upon time with an appropriate,
set-
ting for medical imaging displays for the
b) Prevent
new
acceptable default setting for a specific
an
amount of time of non-use after which
all
maintained.
power
management settings by policy or by
#6
(Graphics card) Poorly performing
user controls.
c) Perform periodic audits of workstations
(old) graphics cards and drivers.
to ensure power management settings
Graphics cards and driver technologies
are maintained.
change rapidly. Older graphics cards may
cause performance issues as other parts
#7
(Workstation)Not enabling a screen
of the system change, evolve, and
saver to minimize image burn-in/
improve.
retention.
•
More video RAM on the card may be
LCDs can suffer from “image retention” or
needed
“image persistence” where the LCD
systems change and a faster GPU may
crystals develop memory when a static
boost performance.
image is displayed in one place for too
long.
•
Task
•
as
software
or
operating
The graphics driver needs to be setup
correctly upon initial install using the
bars,
icons,
and
other
recommended driver (not a Windows
static
default driver).
images are at risk of retaining a faint
image. If the faint image is in an area
•
Newer
drivers
may
be
required
to
of the screen where medical images are
support
viewed, it can negatively impact image
processing using the latest DirectX or
quality.
OpenGL
new
software,
commands,
or
perform
support
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3D
new
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operating
systems
(XP
to
Vista
to
Windows 7, 32 bit to 64 bit, etc.).
•
•
(Workstation) Poor airflow on vents
Graphics cards companies continually
fans are used.
update their drivers, making improve-
This issue can be “out of sight, out of
ments and correcting bugs/issues.
mind” as workstations are often
Using a newer driver may solve an issue
or
result
in
better
however,
be
careful
performance;
of
updating
positioned where they are not easily
seen or cleaned.
•
For machines that have been deployed
graphics drivers too quickly such
for long periods of time, it is common to
that they may be unsupported by
have vent holes that are partially or
the hardware or software in use on
nearly completely covered up with dust
the system.
and lint.
•
Blocked vent holes limit air flow and can
cause
Best Practices:
of
both
the
CPU
graphics card.
If you are adding or
upgrading workstations, it is a good
overheating
processor as well as the GPU chip on the
a) Look for opportunities to upgrade your
graphics boards.
•
Overheating
is
a
potential
reliability
time to upgrade graphics boards. In
problem that can cause loss of video,
addition, if you have a major planned
crashes, restarts, slow downs, or render
upgrade
in
the workstation completely unusable.
system,
consider
software,
a
or
operating
graphics
board
the
graphics
drivers
on
your
deployed hardware and bring them all
up to a pre-defined level.
c) Communicate with your display vendor
for
recommended
Overheating can also be a cause of poor
video or video artifacts.
upgrade as well.
b) Audit
#5
or dust/lint covering up vents where
and
supported
updates to the graphics drivers.
Best Practices:
a) Schedule routine maintenance on the
workstations that includes clearing and
cleaning ventilation holes.
b) Consider utilizing utilities that monitor
GPU and CPU operating temperatures.
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#4
(Calibration) Not taking advantage of
d) Monitor the performance of the displays
the functions/features available in
utilizing
software.
outsourcing this to a third party.
Quite often sites do not set-up or properly
the
available
tools
or
by
e) Refer to the Appendix in this paper for
implement calibration and conformance
recommended
reference
articles
and
software that is available from display
governing standards regarding confor-
vendors.
mance and calibration of medical imaging displays.
•
Many medical grade displays come with
software that not only can calibrate a
•
#3
display, but also include many other
(Calibration) The displays are not
functions and features that can provide
calibrated and could or should be.
feedback and help monitor, control, and
There really is no excuse for using
maintain deployed displays.
non-calibrated displays in medical imaging
Software can be set up to schedule
applications.
periodic conformance tests, recalibrate
•
Medical
grade
gray
scale
and
color
displays, keep white levels consistent
displays
across platforms, monitor temperatures
calibrated
and
loading the calibration file (a look-up
usage,
and
provide
logs
for
objective evidence that the displays are
typically
and
are
have
meant
a
to
be
provision
for
table) directly into the display.
setup and performing properly.
•
Even most commercial color displays
can be calibrated to the DICOM Gray
Best Practices:
a) Purchase your display hardware from a
manufacturer who specializes in medical
displays and offers software solutions
Scale Display Function with the proper
software
and
luminance
sensor,
by
loading the look-up table to the graphic
card or to an ICC profile.
that help monitor and control performance.
Best Practices:
b) Consider having your display provider
install the displays to ensure proper
setup and implementation.
c) Utilize support services for training and
follow-up to ensure that the functions
and features of the displays and the
software are fully and properly used.
a) Ensure that all displays used for diagnostic purposes are properly calibrated
and that records are maintained to show
calibration conformance to applicable
(DICOM) standards
b) It is highly recommended that displays
used
for
clinical
purposes
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are
also
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calibrated to DICOM standards. (Why
should
a
clinician
substandard
have
images
to
when
look
it
is
•
at
Diagnostic
displays
need
to
be
calibrated in order to compensate for
not
the
necessary?)
idiosyncrasies
of
the
native
luminance response of a liquid crystal
display, which is particularly important
c) Refer to the Appendix in this paper for
recommended
reference
articles
in
and
the
lower
level
shades
of
gray.
regarding
(Failure to do so may result in the
conformance and calibration of medical
inability to discern a luminance differ-
imaging displays.
ence between pixels that have differing
governing
standards
digital driving levels which could (worst
#2
case) result in false diagnosis).
(Display) Use of common commercial
•
color displays for diagnostic work.
There
needs
to
be
enough
native
resolution over the face of the display to
For most diagnostic work this should not
properly
be done – period.
5 mega-pixels for mammography). The
•
Commercial color displays can be used
viewing angle needs to be wide enough
for many clinical applications.
that the gray levels and colors do not
shift
•
with
the
image
horizontal
(typically
or
vertical
On lower resolution modalities (ultra-
movement
sound or 3D reconstructed images) it is
(be careful with TN type LCD panels).
possible
The luminance uniformity needs to be
to
undertake
diagnostic
imaging work.
•
show
For
the
uniform
higher
resolution
modalities
quality
of
the
enough
does
so
not
head
that
vary
or
the
position
image
significantly
commonly viewed by a radiologist, it is
depending on image position on the
inappropriate
a
screen. And it is helpful to minimize the
violation of specifications, guidelines,
noise, artifacts, and pixel defects that
and laws to utilize a display with the
can detract from an optimal image.
and
in
some
cases
performance of a common commercial
color display.
Best Practices:
•
Diagnostic
imaging
displays
need
a
minimum luminance and contrast ratio
in
order
to
have
enough
luminance
range to assign to each digital driving
level (and have enough “overhead” to
have adequate life as the display ages).
a) Establish and enforce a policy for the
procurement of displays used in diagnostic imaging that requires them to
meet
minimum
performance
require-
ments as well as all applicable specifications, guidelines, and laws.
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b) Utilize
your
local
medical
physicist
(if available) to approve the displays
used in diagnostic work
imaging
to
a) Provide
easy
access
to
approved
cleaning materials for users.
c) Utilize a display provider experienced in
medical
Best Practices:
recommend
b) Schedule routine cleaning by in-house
or third party personnel.
appropriate displays for your application
d) Monitor and audit the displays used in
diagnostic work to ensure no rogue
displays or displays intended for other
uses (navigation displays, 3D workstation displays, etc.) get used improperly.
A ND
NOW ,
AFFECTING
THE
DISPLAYS IS
#1
THE
IMAGE
NUMBER
QUALITY
ONE
ON
ISSUE
MEDICAL
…
(Display) Dirty Displays.
This was by far the most common issue
to be found negatively affecting medical
imaging display performance. The
incidence of this issue is widespread and
is commonly found on displays used
throughout healthcare facilities.
•
Dirt and dust, fingerprints, marks, food,
coffee, and other sources of debris find
their way on to displays and cut down
on the image quality.
•
While it is often a function of other
priorities, we have found some users
are hesitant to clean an LCD because
they are unsure of or don’t have access
to proper cleaning materials.
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David Sorensen was formerly the President/CEO and a principle of Image Systems Corporation.
He is currently the Director of Engineering/Product Development/Sourcing for Canvys –
Visual Technology Solutions and can be reached at [email protected].
Canvys is a division of Richardson Electronics, Ltd and is a provider of PACS, Surgical, and Custom
display solutions for Healthcare as well as Teklink service and support.
Appendix
A lot of people still don’t “get” calibration with regard to medical imaging displays.
“Why do we need to use a calibrated display?”
“Can’t we see what we want to see on a standard display?”
“Why can’t we just use a standard display out of the box?”
“How does calibration work and is it really all that important?”
A simple demonstration toggling the calibration on and off is often all it takes to show the difference
in what can be seen in an image, especially in the low digital driving levels. It is amazing to see and
hear about both clinical and diagnostic work being done on non-calibrated displays. One can view
medical images on non-calibrated displays, but it is not ideal (and in some cases violates
specifications, guidelines, and laws pertaining to particular areas of medical imaging).
The following articles and standards will lend more insight into the critical importance of calibration
of medical imaging displays and conformance to guidelines and standards.
•
ACR/NEMA DICOM Standard Part 3.14 Grayscale Standard Display Function
•
American Association of Physicists in Medicine, Task Group 18 Report (AAPM TG18)
•
NEMA XR23-2006 Quality Control Manual Template for Manufacturers of Hardcopy Output Devices
Labeled for Final Interpretation in Full-Field Digital Mammography (FFDM)
•
DIN 6868-57 Deutsches Institute fur Normung-German Standard Institute.
•
IEC 61223-2-5 International Electrotechnical Commission
•
Paper: “Digital Mammography Image Quality: Image Display” - 2006 ACR by Siegel, Krupinski,
Samei, Flynn et all with an excellent list of references
•
ACR Technical Standard for the Electronic Practice of Medical Imaging
•
FDA MQSA Guidelines
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©2009 Canvys | All brands and trademarks are the property of their respective owners. | EU4USv.2009/10/14
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