Keywords
PACS - teleradiology - digital radiography
Introduction
Twenty years ago, when patient CDs replaced film as the medium for sharing radiology
examination data, the new CD media’s lack of interoperability created significant
challenges for the radiology community.
In response, the German Radiological Society (DRG) launched its Media Exchange Certification
Project [1], which received technical support from the OFFIS Institute, in order to promote
interoperability for media content and standardize import processes. Twenty years
later, a new challenge faces users as virtual media, e.g. download links and QR codes,
are replacing physical data storage devices. Additionally, the interfaces for the
file sharing solutions currently available commercially vary greatly in terms of their
operation and the range of functions provided. Similar to 20 years ago, working with
new media is once again disrupting established processes.
This time, however, DRG has taken a different approach. Together with the Professional
Association of German Radiologists (BDR), the DIN Standards Committee for Radiology [2] founded a working group on QR codes and online availability of image data. The result
is the DIN/TS 19455 DICOM Link Exchange (DLX), which promotes standardized processes
for working successfully with these new media.
Materials & Methods
The DIN working group on QR codes and online availability of image data was launched
officially in 2023 at the German Radiology Congress in Wiesbaden. Under the leadership
of the DIN Standards Committee for Radiology (NAR), it included 17 members representing
industry and users.
At the first meeting, it was agreed that the resulting technical specification (DIN/TS)
should whenever possible be based on existing standards, and the specification must
also provide a solution that allows its users to process transmission data both manually
and automatically.
To further develop the technical specification, the working group first divided itself
into four subcommittees based on the following topics:
Based on each of these topics, the respective subcommittee members reviewed the best
available technology, the legal requirements, and, if relevant, existing standards,
in order to develop solutions for ensuring the online availability of patient CD content.
Moreover, content was not restricted to radiological data.
In addition to accessing the application data via an HTTP link, the basic conditions
that had to be taken into account included that solutions focused, in particular,
on the perceived usability by end users, data security, data privacy, and at the same
time the ease with which the solution could be implemented using commercially available
products. Furthermore, the media structure for the data transmission format had to
be defined by the IHE Portable Data for Imaging (PDI) profile [3]
[4] or, optionally, by the IHE Cross-Enterprise Document Media Interchange (XDM) profile
[4]
[5] in the form of a ZIP container [6]. These basic conditions were unanimously agreed and adopted by the working group
members during the first two meetings.
The subcommittees’ findings were discussed with all members of the working group at
monthly meetings.
The findings adopted by the working group were then gradually incorporated in the
text of the new DIN/TS. The public comment period for this initial draft [7] followed in the summer of 2024 and ended in early October 2024. The feedback obtained
was incorporated in the final version of the standard. The DIN Standards Committee
for Radiology officially approved this version on December 18, 2024, clearing its
way for publication by DIN.
Results
The results essentially consist of the following three definitions:
-
The form and content of the application data media
-
The form and content of the access data transmission media
-
The standardization of access to application data
Application data medium
DLX requires a ZIP container to transfer application data ([Fig. 1] DLX ZIP container structure), where the mandatory internal structure of the ZIP
container corresponds to the IHE PDI definition for the medium [4]. As an option, the media structure can also be combined with the structure described
in the IHE XDM profile and expanded accordingly (4.47.4.1.3.4.1 Grouping with XDM
(IHE ITI Technical Framework)) [8].
Fig. 1 DLX ZIP container structure.
Additional files can also be stored directly at the root level of the DLX ZIP container,
as well as in other subdirectories, provided they do not conflict with the definitions
of both the IHE PDI and XDM profiles. Handling this additional content is not covered
by DLX.
Access data transmission media
Access to the linked application data requires access information on the recipient
side. In practice, the storage media currently available are paper printouts, electronic
transmission methods, such as email or SMS, or verbal transmission. In view of legal
requirements (GDPR, §218 German Criminal Code (StGB), etc.), no confidential content
(such as passwords) may be transported via insecure channels without the explicit
permission of the person concerned. The previously mentioned transmission methods/channels
currently available in practice generally require two media/transmission methods for
legally compliant transmission, e.g. two paper printouts, paper printout and email,
email and SMS. The DIN/TS DLX standard takes this into account. The standard defines
the content required for use in practical applications.
The following boxes 1 and 2 list the most important contents of the access data media,
which allow users to handle the access data in a simple and standardized manner. From
a user perspective, the requirements of particular note are that download links are
as short as possible and characters used are unique, as well as information about
the validity of the access data and how this can be extended, if necessary.
Access data transfer medium with 1st factor
Issuing instance
Identifier to enable the unambiguous assignment of both media when two access data
media are issued
Download link in plain text and in a user-friendly format (variable internet address
(URL) portion < 9 characters) and the use of non-confusable characters, e.g. Base58
Download link in the form of a QR code
Authentication information part 1, e.g. user ID
Validity period of the access data
Notice about an extension of the validity period for the access data
Access data transfer medium with 2nd factor
Identifier for assigning the access data medium of the 1st factor
Authentication information, part 2: 2nd factor, e.g. password or similar in plain
text or reference to the knowledge factor
The use of two access data transmission media is not required. This depends on the
use case. The contents described by DIN/TS can also be transmitted using only one
medium, provided that the legal requirements for data protection and security are
met.
Access to application data
For access to application data, DLX specifies the HTTPS transmission protocol, for
which an interface based on the OpenAPI standard [9]
[10] is additionally specified for automated access. In addition to the introduction
of the private HTTP header tag X-DICOM-LINK-EXCHANGE, the OpenAPI DLX API essentially
defines three endpoints:
In the absence of the X-DICOM-LINK-EXCHANGE tag, the servers respond as before by
accessing the website, where users can manually view or download the shared application
data. As an improvement over the previous behavior of the various program interfaces,
DIN/TS requires that the endpoints defined by the DLX API must also be available directly
at the top program level or immediately after a successful login, even for non-automated
manual access. This means, for example, that the options for downloading radiological
image data are available directly at the program level after the user has logged in.
Discussion
Application data medium
The requirement to build the media structure on the IHE PDI profile derives from its
use worldwide. The vast majority of commercially available DICOM archives (PACS) can
handle such media. The option of adding content to the application data medium in
accordance with the IHE XDM specifications now also makes it possible to transfer
files in other common file formats such as PDF and JPEG in a standardized manner in
the patient context, in addition to pure DICOM files and to import them after receipt.
Access data transmission media
In practice, the content of the media in use today causes problems on a daily basis
due to its handling. Often enough, difficulties arise when scanning QR codes and then
the link needs to be entered manually. Due to the lack of length restrictions and
ambiguous characters, input errors are now commonplace. The length restriction and
the additional requirement for uniqueness of the characters used thus reduce important
sources of error. Without any indication of the validity period, data access is often
denied currently in practice, resulting in time-consuming interruptions in the import
process. By providing the expiration date together with information on how the period
of validity can be extended, these problems should become a thing of the past, even
if, as is common today, the appointments between the radiology examination and the
follow-up treatment appointment lie far apart.
Separating the password information and transmitting it via a separate medium also
makes sense in practice. This ensures that the patient can continue to retain control
over access, while preparations for data import can be made by non-medical staff.
Or, there is the possibility of electronically transmitting the non-confidential part
of the access data via insecure channels, such as email, if this better suits the
processes for the respective use case. Identification of the access data transmission
media also ensures that the information is clearly assigned and enables the risk of
confusion to be minimized even when dealing with large volumes of these access data
transmission media.
Access to application data
Until now, the commercially available solutions have focused on manual access by users.
The lack of standards results in serious problems in everyday use. Each data sharing
solution has a different interface, with the result that it is not transparent for
users where in the program the function for downloading the image data or viewing
the data online is available, or even whether it is available at all. DLX now makes
it clear which functions must be present at which point in the program logic. If users
do not find a feature, they can be sure that the corresponding function does not exist
in the software they are using. If a manufacturer declares conformity with DLX, it
becomes clear to users, for example, that there is a download of shared data or the
import of DICOM objects at least at the examination level, depending on the type of
software (download portal, data importer).
The definition of the DLX API now goes a decisive step further and enables automation
of the import of data linked to a download link. Despite the need to enter a second
factor to access the download data, these functions can now be integrated in the workstation
interfaces – regardless of which provider makes the downloads available. This ensures
that data import processes can also be defined for the virtual media provided via
QR codes, similar to those processes for reading the former patient CD data carriers
– and potentially even more efficiently, because the DLX API also provides targeted
access to individual files.
Outlook
DIN/TS 19455 DLX is one step further in the era of digitalization in healthcare, and
it integrates radiology and its image data in newly emerging processes. In the next
step, the contents of the radiology report should also be made available, together
with the underlying image data, for all treatment processes.
This could be achieved by combining different standards. As part of the digitalization
of the healthcare system, new standardized data structures, or medical information
objects (MIO), are being defined on an ongoing basis for Germany. These objects enable
the interoperable exchange of structured and thus machine-readable data. They have
already been described and published for various application areas, such as vaccination
records, maternity records, and patient summary files.
The electronic format for the radiology report is currently being developed in the
form of the MIO imaging report [11]. This definition is about to be released for public comment. Among other things,
MIOs make it possible to provide a reference (link) to the image data. This meets
the prerequisites for communication between the two definitions of DLX and MIO imaging
report. For the type of targeted communication that is typically required between
two healthcare providers, this step would allow for automated transmission of radiological
data, together with structured content information, without the mandatory need for
a complex infrastructure to map access rights. By further combining it with an established
and secure transmission channel, such as the TI service KIM (Communication in Medicine)
[12], the majority of today’s existing communication needs in patient care, where radiology
is involved, could be solved directly and across Germany.
In order to take the next step of transferring data to practical applications, discussions
are already under way between project managers for the MIO image report (MIO42) and
gematik, the national agency for digital medicine, in conjunction with representatives
from the user community and manufacturers.
