Do we really need standards in digital image management?
College of Radiology, Academy of Medicine of Malaysia
Convention dictates that standards are a necessity rather
than a luxury. Standards are supposed to improve the exchange of health and
image data information resulting in improved quality and efficiency of patient
care. True standardisation is some time away yet, as barriers exist with
evolving equipment, storage formats and even the standards themselves. The
explosive growth in the size and complexity of images such as those generated
by multislice computed tomography have driven the need for digital image
management, created problems of storage space and costs, and created a
challenge for increasing or getting an adequate speed for transmitting,
accessing and retrieving the image data. The search for a suitable and
practical format for storing the data without loss of information and medico-legal
implications has become a necessity and a matter of ‘urgency’. Existing
standards are either open or proprietary and must comply with local, regional
or national laws. Currently there are the Picture Archiving and Communications
System (PACS); Digital Imaging and Communications in Medicine (DICOM); Health
Level 7 (HL7) and Integrating the Healthcare Enterprise (IHE). Issues in
digital image management can be categorised as operational, procedural,
technical and administrative. Standards must stay focussed on the ultimate goal
– that is, improved patient care worldwide. © 2008 Biomedical Imaging and
Intervention Journal. All rights reserved.
Keywords: Digital image management, DICOM, PACS, lossy
compression, lossless compression
Does the theory of standardisation translate into truly
useful day-to-day clinical practice that all involved in the digital imaging
era can relate to? What barriers are we facing, and how do we overcome them?
Standard or Standards by definition is the level of
quality where people think is acceptable (Oxford Advanced Learner’s
Dictionary). This may refer to behaviour where the morally acceptable level is
the standard or an official unit of measure. For example, the industry standard
may refer to a specific size and the gold standard is what others are compared
to. Standard could also mean what is normal or average for a person, situation
or even a language. When standards are applied, quite often there are
modifications because there is a need to be ‘different’, to stand out from the
rest, to have better display and to communicate an idea or message better.
In the setting of standards, who should be the
stakeholders? For digital image management, this could include, in no specific
order, the scientists, engineers, inventors, hardware specialists, software
programmers, communications specialists, vendors, marketing personnel, the
users (for example, the radiologists and radiographers) and the government.
Issues in digital image management
The explosive growth in the size and complexity of images
such as those generated by multislice computed tomography (MSCT), dual source
computed tomography (DSCT) and positron emission tomography–computed tomography
(PET-CT) have driven the need for image management, created problems of storage
in terms of space and costs and created a challenge for increasing or getting
an adequate speed for transmitting, accessing and retrieving the image data.
Previously a CT scan would generate 40-60 images, now it easily goes into 900
images. Magnetic resonance imaging (MRI) angiography or cardiac MRI could have
images totalling 15,000 for a larger scan series. With the great improvements
and innovative imaging equipment development, the bottleneck is now in the time
required for reconstruction of complex datasets and the time to process the
images for display and interpretation.
Storage issues include how to compress, how much
compression and the size after compression. Compressing thin slices (as in the
multislice CT at 0.75mm) is more difficult because there will be inherently
more noise on the data, yet with less redundant information.
As in all electronic data storage, backups are imperative
and management includes ensuring reliability and redundancy for breakdowns in
the system. Then there are security and privacy issues, litigation and laws
which may vary from country to country. Other considerations include patient
details, reports and other relevant and related clinical information, the need
to link to other centres and the financial costs.
We can categorise issues in digital image management as
operational, procedural, technical and administrative. We are therefore looking
at compatibility, interchangeability and interoperability.
What should the standards define?
The American College of Radiology (ACR) Technical Standard
for Digital Image Data Management  specifies the following: goals, personnel
qualifications, equipment guidelines, specifications of data manipulation and
management, quality control and quality improvement methods.
Goals of digital image management as expressed in the ACR
Technical Standards for Digital Image Data Management include accurate
labelling and identification of image data in the acquisition, generation and
recording of image data, transmission of images to appropriate storage medium
for retrieval for display and formal interpretation, review and consultation.
Retrieval of available prior imaging studies is essential for comparison with
current studies. Images should also be able to be transmitted to remote sites
for consultation, review or formal interpretation. There should be appropriate
image data compression to facilitate storage or transmission without loss of
clinically significant information. Archived data should contain accurate
patient medical records for timely retrieval, and must meet applicable
facility, state and other regulations while maintaining patient
As compression formats are still being developed and
tested while imaging modalities are improving and enabling more functions,
goals of digital image management will also be evolving. We also need to
integrate advanced image processing into the system (3-dimensional as well as
computer aided detection).
For equipment specifications, compliance with the American College of Radiology (ACR)- National Electrical Manufacturers Association (NEMA)
Digital Imaging and Communications in Medicine (DICOM)  standard is strongly
recommended for all new equipment acquisitions and consideration of periodic
Barriers to true standardisation
These barriers include the fact that goals, image
acquisition, compression formats, storage systems, and communications are all
still evolving. Add to this the legacy systems and the fact that equipment
vendors are competing to develop better imaging equipment and ‘one-up’ each
other in marketing. Then, one must look at the other side of the coin: are
standards going to make the situation rigid and stifling? Will it stem
creativity, innovation, improvements and progress?
Needless to say, since utopia has yet to be attained,
things must continue and need to evolve. So it is with foresight that the ACR
technical standard preamble includes the following – that ‘the technical
standard is just an educational tool to assist practitioners in the provision
of appropriate radiologic care and it is not a set of inflexible rules or
requirements of practice and is also not intended nor should be used to
establish a legal standard of care’ .
Standard or standards already in existence
Standards can be open or proprietary. Currently there are
the Picture Archiving and Communications System (PACS); Digital Imaging and
Communications in Medicine (DICOM); Health Level 7 (HL7) and Integrating the
Healthcare Enterprise (IHE). These shall only be dealt with in brief.
PACS was developed to provide an organised mechanism for
digital image management. There are single modality PACS, minipacs or
multimodality PACS. An image management specialist is needed for the PACS. This
system may become the standard in hospitals within the next decade in North
America and United Kingdom as well as Nordic countries. The increased
utilisation is due to new digital imaging modalities, reduced costs (thanks to web-based
solutions, affordable software licences, reduced costs of flat panel displays
and storage) and government-driven initiatives, for example, Britain’s National Health Service.
As mentioned earlier, the number of images generated has
increased exponentially, such that there is really no choice but to adopt PACS.
In a properly implemented PACS, radiologists can see up to 10% more patients
per day, perform post processing, 3D rendering and surgical planning with PACS,
and access images from home.
DICOM  is also an evolving standard and facilitates
PACS development. It allows creation of diagnostic information databases that
can be accessed by a variety of devices worldwide. The DICOM standard is a
structured multipart document and arose as there was a need to transfer images
and associated information between devices manufactured by various vendors.
These devices produced a variety of digital image formats!
HL7  is a standard for exchanging information between
medical applications and is just a protocol for data exchange. It defines the
format and content of messages to be used when exchanging data in various
circumstances. It promotes the use of such standards within and among the
healthcare organisations to increase the effectiveness and efficiency of
healthcare delivery for the benefit of all.
IHE  is a multi-year initiative that creates the
framework for passing vital health information seamlessly from application to
application, from system to system and from setting to setting across the entire
healthcare enterprise. IHE is under the leadership of the Healthcare
Information and Management Systems Society (HIMSS) and the Radiological Society
of North America (RSNA). It has been around since 1998. Before the IHE, there
was no agreed method for various systems in Radiology to work together – HIS
(Hospital Information System), RIS (Radiology Information System), PACS,
printers, workstations and various imaging equipment. There are at least 16 IHE
Radiology Integration Profiles.
Where to from here?
In a recent report, researchers at the Dana-Farber Cancer
Institute in Boston  developed a solution in the form of a PET/CT database
of all settings of prior imaging procedures to allow consistent imaging of
cancer patients over time. This was necessary as current PACS and HIS/RIS did
not capture this data. This illustrates how and why current digital image
management systems and standards will need to evolve.
Lossy (irreversible compression with some loss of
information) or Lossless (reversible compression with no loss of information) –
that is the question ? How to compress and compression to what size are
questions that are still under study. The litigation potential of missed or
inaccurate diagnosis of irreversibly compressed images is a major factor contributing
to why equipment makers will delay adoption of newer compression formats. Loss
of information, of course, concerns radiologists, patients and other
physicians. The concern with lossy compression is that the reconstructed image
quality may be affected and there may be perceived or actual distortion of
clinically significant image details.
In lossless compression, the decompressed image is
numerically identical to the original. Examples of lossless compression include
run-length encoded (RLE), low ratio JPEG (Joint Photographic Experts Group) and
JPEG-LS (the new JPEG lossless compression standard). Currently the focus of
some groups is determining if lossy image compression can be used in Radiology
without compromising information for interpretation. The DICOM working group 4
in 2002 has already announced the wavelet-based JPEG 2000 compression algorithm
as standard. JPEG 2000 has higher compression with less distortion. No
diagnostic data is discarded during the compression although some data will be
discarded during compression and cannot be recovered.
The ACR Technical Standard for Digital Image Data
Management  does not specify an acceptable compression ratio – and this is
left to the discretion of a qualified physician. The Canadian Association of
Radiologists (CAR) PACS and Teleradiology Committee has accepted lossy
compression for use in primary diagnostic and clinical review. Compression
ratios may differ depending on the imaging modality and for different organ
systems within a single modality. For example, a musculoskeletal image can be
compressed to a greater degree than a chest image. It is also of interest to
note that images compressed with JPEG 2000 at low ratios may actually have
better quality than original images. This was attributed to the first level of
decomposition in wavelet compression, which at low filter eliminates noise and
therefore improves visual quality.
The practice of standards in reality
There is no reason to doubt that everyone wants to support
standards. Standards in general are supported, adopted and may or may not be
used in its entirety. It all depends on the 'local' requirements, available
infrastructure, resources (which include human and financial), the
local/regional laws, and the need for security and privacy. We note the need
for the ‘birth’ of new personnel – the image management specialist . This
person has to assess and provide problem solutions, initiate repair, coordinate
system-wide maintenance, be available in a timely manner for trouble shooting
or malfunction correction, and be directly involved in system expansion to
assure sustainable high image quality and system function.
In reality, standards are actually slow to garner support,
and slow to be adopted. Even more questionable would be to what extent these
standards are used. Technophobia is not uncommon amongst all categories of
users, including the radiologists. The image acquisition vendor may also be
‘lethargic’ as in the case of adopting enhanced DICOM objects. Enhanced DICOM
objects were added to the DICOM standard in 2003. PACS vendors and CT vendors
were slow to support and adopt this, respectively. JPEG2000 shows great promise
in lossy compression of thin section data, yet this fact has not been taken
advantage of mainly because of medico-legal considerations.
Digital image management – An expense or an investment?
Is digital image management an expense or an investment?
Adequate capital is needed for systems such as PACS. If there is still a need
to print on films, then there is increased cost and negates some of the plus
points in using PACS. Training costs are involved and there is a learning curve
for users. If users cannot be motivated to see how it will help them in their
daily routines, learning and acceptance will be uphill tasks. There is also a need
to employ more personnel for technological and technical support.
Investments should support business needs, and proposals
to adopt PACS/digital image management need to be presented in a manner where
the hospital or department management can see returns or benefits. It is more
important to define the value of the project over its entire life rather than
just ‘returns on initial investment’. The payback (how soon the investment will
be recovered) and the opportunity costs (the cost of passing up the next best
choice when making a decision) as well as soft benefits such as qualitative
measures of productivity, image and morale will all assist in the successful
bid for the hospital budget and enable proper implementation.
Challenges in implementation will exist but the
satisfaction comes in a properly implemented and well-thought out digital image
Standards in digital image management are needed. The
various issues, although easily categorised into operational, procedural,
technical and administrative, will entail far more in practical terms. All the
stakeholders – the scientists, engineers, inventors, hardware specialists,
software programmers, communications specialists, vendors, marketing personnel,
the users such as the radiologists and radiographer and governments – need to
cooperate in recognising and evaluating the evolving needs and respond with
flexibility and agility in the development of standards. The ultimate goal is
improved quality and efficiency of patient care worldwide through improved
exchange of health and image data information and improved access in remote
American College of Radiology Technical Standard For Digital Image Management [Online]. 2006; Available at http://www.siimweb.org/assets/6D4AC337-AE70-42A2-AF7D-93A7938013F3.pdf. (Accessed 31 August 2007).
Digital Image and Communications in Medicine (DICOM) Homepage [Online]. 2008; Available at http://medical.nema.org. (Accessed 31 August 2007).
The Health Level 7 Homepage (United States) [Online]. 2008; Available at http://www.hl7.org. (Accessed 31 August 2007).
Integrating the Healthcare Enterprise [Online]. 2008; Available at http://www.ihe.net. (Accessed 31 August 2007).
Syrkin L, de Vries D, Lefever G et al. Development of a PET/CT Database of Patient Information and Scanning Parameters. J Nucl Med 2007; 48 (Supplement 2):199P.
Koff DA, Shulman H. An overview of digital compression of medical images: can we use lossy image compression in radiology? Can Assoc Radiol J 2006; 57(4):211-7.
|Received 11 February 2008; accepted 1 April 2008
Correspondence: College of Radiology, Academy of Medicine of Malaysia and Consultant Clinical Radiologist, Imaging Department, Megah Medical Specialists Group Sdn Bhd, Kuala Lumpur, Malaysia. Tel.: +603-78061384 ; Fax: +603-78038090; E-mail: firstname.lastname@example.org (Evelyn Ho).
Please cite as: Ho ELM,
Do we really need standards in digital image management?, Biomed Imaging Interv J 2008; 4(4):e20