Proposal for New Work Item for Working Group Eleven on Extending Image
Quality Support
Introduction
The intended scope and primary subject of the work item includes two components:
 First, a proposed new service class that will support retrieving display system
characteristics and performance information, and also to configure certain aspects
of display operations.
 Second, an extension of the current Printer Configuration Retrieval SOP Class to
include additional image quality factors.
It is proposed that the DICOM Committee approve a Work Item for the development of a
new supplement on (a) a new service class (referred to as “Display Performance Service
Class” in this document) for communication and control of image quality information
factors between applications and display devices, and (b) additional image quality factors
to added to the Printer Configuration Retrieval SOP Class.
Limitations of Current Standard
Medical image quality and quality control are system-wide challenges involving multiple
devices. In particular, it is necessary to continually track image quality performance
factors of output devices, including modality consoles as well as PACS softcopy and
hardcopy output. Although display and print devices are increasingly calibrated
automatically, quality control, maintenance and record keeping are still largely manual
processes, partly due to lack of standards for communication and control between display
systems and image display application programs.
At this time, DICOM offers little help with the technical and management aspects of
image quality and quality control. The limitations of the current standard include:
 DICOM does not support management of softcopy displays.
 The DICOM Grayscale Standard Display Function (GSDF), while a successful
definition, does not provide methods for applications to determine the level of
conformance to GSDF or even to query the actual display function of a display
device.
 DICOM does not include any way for display applications to determine other
characteristics of the output devices on which images will be shown.
 Unlike DICOM Print, there is no way to control the characteristics of display
systems such as luminance and the display function of the output device.
 DICOM’s Printer Configuration Retrieval SOP Class does not currently support
detailed information on performance and spatial characteristics of the printer.
As a Display Performance Service Class User (DPSCU), an application can gather
critical image quality information from any display system acting as service class
provider (DPSCP). A few examples include:
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Enterprise Display / Print Manager: retrieves and monitors performance
parameters of all output devices, supports quality control, maintenance, and
management functions. May distribute information to display applications.
Standardized output for display application: uses tonescale and spatial
characteristics of display system to standardize presentation of images.
Consultation: applications share display device capabilities, adjusting output to
ensure visibility of key clinical information at all stations in the collaboration.
Capture Console Quality Control and Standardization: applications can
ensure image similarity among capture, diagnostic, and clinical displays.
Applications will also be able to control some aspects of softcopy display such as
luminance and choice of display function used. With standardized communications
between applications and displays, the new service class will facilitate multi-vendor
image quality and quality control for institutions of all sizes.
Although DICOM currently supports setting and retrieving a number of parameters for
DICOM printing, the proposed factors will enable additional quality control functions for
hardcopy devices.
Description of Proposal
The proposed Display Performance Service Class would provide a mechanism for
applications to communicate with display systems to both set display parameters, and
also to return performance information to applications. Such data would include the
number of displays attached to a workstation, as well as the physical characteristics of
each monitor. Through DPSC, a Service Class User (DPSCU) would query the
display/print capabilities of a Display Performance Service Class Provider (DPSCP).
Some configurable parameters of displays could be set by a DPSCU, including the
luminance range and the particular display function to be used.
Information that could be queried includes the number of displays, the matrix and
physical size of each display, the display function installed, the number of grayscale and
color levels available, minimum and maximum luminance values, time of last calibration,
ambient light conditions, and, if available, the display system’s characteristic luminance
curve. Additional information should include spatial characteristics such as MTF and
luminance uniformity, including results automatically measured and others evaluated by
a human observer, for example the score of the test patterns for evaluating image
sharpness or artifact.
The new class includes functionality similar to the existing Printer Configuration
Retrieval SOP Class, as defined in DICOM Part 4. The Display Performance IOD will
be an abstraction of the softcopy display system and will be the basic Information Entity
to retrieve key imaging characteristics of the display system.
The Display Performance SOP Instance is created by the SCP during start-up of the
display system and has a well-known SOP Instance UID. The DIMSE Services N-Get
and N-Set are applicable to the IOD for retrieving performance information and setting
key characteristics of the display system, respectively.
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The work proposed for the DICOM standard would include defining appropriate data
elements to be retrieved and set by applications, setting up new query behavior, and
defining the detailed actions of appropriate SCUs and SCPs for this new service.
We further propose additions of retrievable parameters to the Printer Configuration
Retrieval SOP, including descriptions of media quality (e.g., freedom from visible
coating variations), printer quality (e.g., freedom from visible variations in exposure or
processing), the number of true monotonically increasing gray levels, the printable matrix
size, degree of artifacts, spatial frequency response, and quality of viewing conditions.
Each of these image quality factors can be methodically quantified using appropriate test
patterns and measuring tools. Capturing such values may be done manually or
automatically.
Parts of Standard Affected
The proposed new service class will require changes in the following parts of the DICOM
standard:
 Part 3 will require a new IOD and modules for defining the data to be exchanged
by the proposed Display Performance Service Class
 Part 4 will require a new SOP class for Display Performance Services as well as
new DIMSE service definitions. The behavior should be similar to that of
corresponding DICOM print entities. New items will be added to extend the
Printer Configuration Retrieval SOP Class (H.4.11)
 Part 6 will require new dictionary items and UIDs for the attributes and identifiers
required.
Workload
DICOM Working Group Eleven is the most appropriate entity to create this supplement.
The expected workload to define the new supplement is modest since the scope of the
work is well defined. Current work items of the Working Group include Hanging
Protocols (Supplement 60) and a new General Presentation State that will incorporate
color support and color calibration (Supplement number to be assigned). Supplement 60
recently completed its Public Comment period, and the General Presentation State work
is in its initial phase. Working Group Eleven may also consider a presentation state for
N-Dimensional data being defined in Working Group Seventeen.
The proposed work item will have a small effect on Working Group Eleven’s schedule
since work on Supplement 60 is expected to be largely complete by the end of 2003. The
proposed item complements the General Presentation State effort, although it will involve
the same people. It is anticipated, however, that additional people will join WG-11 to
support this effort, particularly display system vendors and researchers interested in
image quality and PACS quality control.
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It is expected that 16 to 20 hours of Working Group Eleven time would be needed to
create the supplement. We expect that Working Group Six will spend no more than 4
hours on the subject during mid- to late-2004 for the review and approval of public
comment and letter ballot versions.
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