DUO & LTB – What are they, and how can you use them?

Ever since the introduction of digital imaging in radiology, we in the Netherlands (and beyond) have been searching for solutions to share these images across departmental and hospital boundaries. If you are active in this domain in the Netherlands, then terms such as LTB, TLB, DUO, XDS, DVDExit, Twiin, etc. will certainly not be new to you. All of them relate to the pursuit of a form of Nationwide Image Availability. In this article, I attempt to explain what these terms mean and how they relate to the realization of a Landelijke Tijdlijn voor Beeldbeschikbaarheid (National Timeline for Image Availability).

History

After the first digital PACS systems were rolled out, the "DICOM CD” quickly made its appearance, and local “networks” emerged in which images were sent based on the “push principle.” Around 2008, the first solutions appeared that were no longer based on “push,” but on “pull.”

With pull, it is not the sender who determines what a receiver gets; instead, the receiver determines which information, made available by a “source”, is requested.

The challenge that quickly emerged was that the legal context between sending (push) and requesting (pull) is so fundamentally different that the latter is only permitted when strict privacy and security requirements are met. Although these requirements are entirely logical, in practice they posed a challenge to exchanging patient information and/or images on a regional and/or national scale.

Between 2010 and 2022, the exchange of images therefore largely remained limited to the regional level. Because not all regions were equipped to the same extent, success was not guaranteed everywhere, and nationwide exchange was not feasible. This increasingly came to be seen as a problem, as healthcare during the same period was moving toward network-based care. Oncology networks are a good example of this.

Challenges

The inability to scale both regional and national exchange became painfully clear during the COVID period. While COVID patients were transported across the entire country in search of an intensive care bed, exchanging essential patient information proved to be far less straightforward. Temporary solutions such as the COVID Portal offered a solution during the crisis but were dismantled afterward. For a short time, the idea prevailed that the crisis had taught us how it could be done. To the frustration of many, that idea turned out not to be sustainable.

Within the radiology domain, this “frustration” was channeled into the vision of the Nederlandse Vereniging voor Radiologie (NvvR) on “image availability.” Quite rightly, the NvvR places the importance of “nationwide image availability” at the center of the radiologist’s workflow and actively advocates for achieving it.

The start of DUO

It is therefore no surprise that DUO and the NvvR vision of “Landelijke tijdlijn beeldbeschikbaarheid” are closely aligned. At the beginning of 2024, a decision point arose when the Digitaal Transitie Orgaan (DTO) of the Ministerie van Volksgezondheid, Welzijn en Sport (VWS) asked how a national timeline could be concretely realized.

At that time (and still today), there were two dominant image exchange infrastructures in use. One was based on the “push” principle (Twiin Portal), and the other on the “pull” principle (XDS networks). Each had its own advantages and disadvantages, and each had its own supporters and opponents. An impasse loomed on the horizon.

From both “sides,” proposals were made to realize a national timeline. One involved converting the Twiin Portal into a pull-based solution, at the time referred to as TPP (Twiin Portal Plus). The other involved connecting existing (regional) XDS networks, including building a bridge to the yet-to-be-developed TTP system. The elaboration of this “bridge” was introduced under the name “DUO.”

The DTO decided on a two-track approach. On the one hand, a pilot with Twiin Portal Plus was launched, focusing not only on technical feasibility but especially on legal feasibility. On the other hand, the “DUO feasibility study” was initiated to determine whether building such a bridge—using internationally proven and accepted standards—would be possible and practically feasible.

Testing DUO

In March 2025, the results of the DUO feasibility study were discussed within the DTO. In line with expectations, the conclusion was that connecting different exchange infrastructures in the proposed manner is not only feasible but also better aligned with other developments at the national (Wegiz) and European (EHDS) level. In addition, DUO offers healthcare institutions freedom of choice to select a solution that best suits their needs.

The DTO therefore decided to carry out a Proof of Concept (PoC), allowing three vendors—Founda Health, Enovation, and Alphatron—to validate these conclusions. The prospect was that, if successful, DUO would form the basis of a “national timeline (for) image availability” that is vendor- and application-independent. An additional requirement was that Mitz be used both for checking “patient consent” and for “targeted querying,” in order to guarantee the aforementioned legal feasibility.

Through two joint test sessions in June and December 2025, the mentioned vendors demonstrated that they could successfully exchange radiological images and reports among themselves and feed each other’s applications with information relevant to realizing a timeline. At the end of December, a cooperation agreement was concluded between the three vendors, Zorgverzekeraars Nederland, and VZVZ to implement the Landelijke Tijdlijn Beeldbeschikbaarheid (LTB) based on DUO.

2026 and beyond

What does this mean for the period ahead? First of all, it is important to know that the “national timeline for image availability” is already a reality for a large part of Dutch healthcare institutions. Institutions that use XDS and have signed the national “Knoop” covenant are part of a nationwide XDS network that connects more than 50 healthcare institutions.

Institutions that have not yet signed the covenant but do have an XDS connection can easily join this network. Institutions that do not yet have an XDS connection can still consider acquiring one.

DUO makes nationwide image availability and image exchange possible by linking existing infrastructures, creating a vendor- and application-independent solution that builds on what already works.

To become part of a national network that can also reach institutions without an XDS connection, a “DUO extension” is a prerequisite. DUO is not the end goal, but a fundamental stepping stone toward making medical images available and exchangeable as envisioned within EHDS.

Financing

The good news is that the Ministry of VWS and Zorgverzekeraars Nederland are offering a financial reimbursement to healthcare institutions that actively engage with DUO in combination with XDS. This funding is part of an agreement to create a level playing field, giving hospitals the freedom to choose the solution that suits them best.

This reimbursement helps institutions that already have an XDS connection to make it suitable for the required linkage with Mitz. It also enables them to connect their PACS system to XDS, so that the “timeline” is accessible to radiologists via their own PACS workstation. Institutions that do not yet have XDS can also use this reimbursement to acquire an XDS connection.

A combination of DUO and XDS offers a wide range of additional benefits. In addition to radiological images and reports, imaging studies from other disciplines can also be made available and exchanged. Non-image information such as laboratory results, referral letters, and medical correspondence can easily be shared via the national XDS network. Integrations are also possible with, for example, PGOs, the MDO Portal, and general practitioner information systems. XDS also provides a solid foundation for future IHE profiles (XC-WADO and MADO), which form the basis for EHDS-driven image exchange.

Moving forward

A national timeline for image availability has never been this close. Healthcare institutions are therefore advised to consider how they can become part of the national timeline, with or without their XDS connection. Contact your XDS vendor for more information, and have them explain how easy it is to make an existing XDS connection “DUO-ready,” or how your institution can still obtain an XDS connection (including the DUO linkage).

If you use an XDS solution from Founda Health BV (formerly Forcare), please contact Tom van Duin, Andries Hamster, or leave your contact details at https://www.foundahealth.com/contact