PUTTING THE BENEFITS
OF DICOM TO WORK: INFORMATION FOR RADIOLOGISTS
In the 1980's, it became clear to radiologists and the manufacturers of medical imaging
equipment that the tremendous growth in image acquisition systems, display workstations,
archiving systems, and hospital-radiology information systems made the connectivity and
interoperability of all pieces of equipment vital. Because different manufacturers use their own
designs, users have had to purchase custom interfaces to enable multi-vendor equipment to
connect.
In order to simplify and improve equipment connectivity, medical professionals joined forces
with medical equipment manufacturers in an international effort to develop DICOM, the Digital
Imaging and Communications in Medicine Standard. When DICOM is built into a medical
imaging device, it can be directly connected to another DICOM-compatible device, eliminating
the need for a custom interface. DICOM defines the interface.
While most radiologists are familiar with the benefits of DICOM and have witnessed its
widespread implementation in the industry, applying it successfully may still present a challenge.
Through the use of practical examples, this brochure has been prepared specifically to assist
radiology department professionals and facility administrators in understanding how DICOM
should be used to assemble medical imaging and information management systems.
DICOM: Knowing When "Plug and Play" Applies
The DICOM Standard is a very thorough specification which a manufacturer uses in the design
of a product. Its major objective is to enhance the ability of devices from multiple manufacturers
to connect - to "plug and play." DICOM is the technology which enables the movement of
medical images and information between systems (e.g., between a CT scanner, a workstation or a
printer).
FIGURE 1
DICOM Connectivity
Figure 1 shows the scope of DICOM connectivity as currently supported by the standard. This
exchange of information facilitates the operation of a wide range of clinical applications.
In order to understand what DICOM can and cannot provide, it is important for radiologists to
distinguish between DICOM connectivity and application interoperability. DICOM connectivity
refers to the DICOM message exchange standard responsible for establishing connections and
exchanging properly structured messages so that an information object sent from one application
will be completely received by the receiving application - in other words, the successful transfer
of information; the successful "plug and exchange" between two pieces of equipment.
On the other hand, application interoperability -- the ability to process and manipulate images -is enabled by DICOM, but "plug and play" at this level cannot in general be guaranteed by
DICOM, although it works in many cases. These distinctions are highlighted in Figure 2.
FIGURE 2
DICOM - Image Objects, Services , Applications
As seen in Figure 2, DICOM has defined a number of image objects for which services can be
applied. These services form the foundation for many applications although DICOM does not
standardize the wide variety of possible acquisition parameters. For example, the CT image
object includes acquisition parameters which include geometric information. This image object
can be sent to a workstation which then uses the object to do the application; e.g. multi-planar
reconstruction (MPR). A particular MPR implementation may require additional optional
attributes which may not be provided by some modality implementations
The DICOM Conformance Statement
Connectivity between two pieces of equipment can be evaluated ahead of time by the use of the
equipments' DICOM conformance statements. For some simple applications (e.g., building a CT
or MR 3D reconstruction), application interoperability can also be determined with the DICOM
conformance statement. This is not always possible to do, particularly for advanced applications
with complex data. The DICOM conformance statement serves as the foundation on which
connectivity and interoperability can be determined.
It is not enough for a vendor simply to claim conformance to DICOM. A radiologist should insist
upon a conformance statement for any device that claims to be DICOM conformant. Since its
inception, DICOM has depended on the voluntary cooperation of medical equipment
manufacturers and the health professionals they serve. There are no "DICOM police" that
enforce compliance. Nor does there exist an officially sanctioned body that certifies a product as
DICOM conformant.
Once the conformance statements are in hand, someone involved in the purchasing decision-
making process must be able to read them. If no one on staff is familiar with reading DICOM
conformance statements, there are a number of experts available to assist. These experts, most of
whom are available on a consulting basis, can be found in academia or through the vendors
themselves.
The DICOM Conformance Statement
The DICOM conformance statement is a formal document which describes how a product
adheres to the DICOM Standard. Comparing the conformance statements of two pieces of
equipment allows customers and vendors to determine whether, and to what extent, the
equipment can connect with each other. By reading a DICOM conformance statement, a
potential purchaser of imaging equipment would, for example, learn which features of a new
piece of equipment would successfully communicate with his or her existing equipment.
If, for example, the receiving piece of equipment is in need of more than the minimum that
DICOM requires, then a receiver may not be able to support a complex application. Reading
the DICOM conformance statements alert both customer and manufacturer ahead of time as
to a potential problem.
Many manufacturers have made their conformance statements available on the Internet.
Successfully Implementing DICOM in the Radiology Department
Utilizing DICOM in a clinical setting takes advance planning. There are a number of steps
radiologists should take when considering the acquisition of additional imaging equipment,
whether it is a single piece of equipment or a complex picture archiving and communications
system (PACS).
Users need to give a great deal of thought to the question: What are the radiology department's
application requirements? Once current needs are established it is a good idea to also consider
future needs as well. Developing a "wish list" of current and future clinical application
requirements will serve a potential purchaser well.
The next question to consider is: Can the clinical application requirements be supported by basic
standardized DICOM communication service classes? Service classes are precise definitions of
how devices establish associations in order to send and receive images and related information.
For two devices to connect, both must support the same service class and corresponding role
(e.g., service class user or service class provider).
DICOM Service Classes
The arrows in Figure 3 indicate the DICOM services (which relate to the DICOM "connectivity
cloud" pictured in Figure 1). These services can be classified in four application areas addressed
by DICOM. These are :
Network Image Transfer: Provides the capability for two devices to communicate by sending
images, querying remote devices, and retrieving images. This is commonly performed between
scanners, workstations, and archives. Network image transfer is currently the most common
connectivity feature supported by DICOM products. The storage service class of various image
objects support this function (e.g., CT, MR, CR, X-Ray Angiography, X-Ray RF, PET, NM, US,
etc.).
On-Line Imaging Study Management: Provides imaging devices with the network capability to
integrate with various information systems (HIS, RIS, archives, etc.). For example, a modality
worklist which downloads patient demographic and procedure information to a scanner.
Network Print Management: Provides the capability to print images on a networked camera. An
example of this is multiple scanners or workstations printing images on a single shared camera.
Open Media Interchange: Provides the capability to manually exchange images and related
information (e.g., reports or filming information). DICOM standardizes a common file format, a
medical directory, and a physical media. Examples include the exchange of images for a
publication and mailing a patient imaging study for remote consultation. For example, DICOM
CD-R is currently used in cardiology to replace cardiology cine films.
FIGURE 3
Service Classes
Conclusion
DICOM has been embraced by the medical professionals using imaging equipment as well as the
companies that manufacture them. DICOM can be used to connect acquisition modalities,
specialized systems, 3D image processing workstations, tele-radiology systems, and hardcopy
devices. DICOM provides connectivity to other information systems (e.g., RIS/HIS) as well. The
DICOM Standard is constantly expanding in order to keep current with industry innovations. For
example, supplements to the original 1993 Standard were completed in 1995 and 1996 allowing
for the exchange of images stored in digital form on media such as optical disks. Recent
supplements to DICOM are extending its usefulness to other medical disciplines such as
radiation therapy, endoscopy, dentistry, cardiology, and pathology.
For further information, please contact:
David Snavely, Industry Manager, NEMA, 1300 North 17th Street, Suite 1847, Rosslyn, VA
22209 USA. Phone: (703) 841-3285; fax (703) 841-3385, dav_snavely@nema.org
Vicki Schofield, Industry Manager, NEMA, 1300 North 17th Street, Suite 1847, Rosslyn, VA
22209 USA. Phone: (703) 841-3281; fax (703) 841-3381, vic_schofield@nema.org
Jim Potter, Associate Director, Government Relations, American College of Radiology, 1891
Preston White Drive, Reston, VA 22091 USA. Phone: (703) 716-7540; fax: (703) 391-0397,
jaesp@acr.org
Support for this brochure comes from the American College of Radiology and the MedPACS
Section of NEMA whose members include:
Acuson
AGFA
ATL
Camtronics Ltd. Medical Systems
Dejarnette Research Systems
E for M Corporation
E-Systems Medical Electronics, Inc.
Eastman Kodak Company
GE Medical Systems
Hewlett-Packard Company
Imation Corporation
InfiMed, Inc.
Life Imaging Systems
Lockheed Martin Communications Systems
Loral Medical Systems
Matsushita Electric Corp. of America
Merge Technologies Inc.
Philips Medical Systems
Picker International, Inc.
Siemens Medical Systems
Sony Medical Systems
Sterling Diagnostic Imaging
Tomtec Imaging Systems
Toshiba America Medical Systems
Mortimore, William and Van Syckle, Donald. "DICOM: State of the Nation -- The 'Plug & Play'
Scenario," Administrative Radiology Journal, Vol. 15, No. 6, June 1996. Van Syckle, Donald E.,
Sippel-Schmidt, Teresa and Parisot, Charles R. "Buying Imaging Products with a DICOM
Interface -- Made Easy," SCAR, 1994.