Challenges in medical image analysis became popular after the organization of the Grand Challenges for Medical Image Analysis at the MICCAI conference in 2007. Hosting challenge events quickly became commonplace it conferences such as MICCAI, ISBI, and SPIE Medical Imaging, amongst others, have hosted challenge events. Leading journals such as IEEE Transactions on Medical Imaging and Medical Image Analysis have welcomed overview papers that described the results of individual challenges.

Grand Challenge was developed in 2010 to make it easy for organizers of challenges to set up a website for a particular challenge and to bring all information on challenges in the domain of biomedical image analysis available at one place. In 2012 we switched to Django web framework. Hence 2012 as the initial year in our copyright statement at the bottom of each page.

Grand Challenge provides key functionality for running challenges, such as user management and role base access control, a discussion forum to communicate with and between participants, the possibility that participants form Teams, support for adding multiple phases to a challenge, each with their own leaderboard, and much more. Over 70,000 user accounts have been created on Grand Challenge from countries all across the globe.

Maintaining a challenge, so that new submissions are quickly processed upon submission, is a lot of work. Typically, a junior researcher at some institution is responsible for maintaining a challenge website, but at some point the researcher moves on and the site is no longer kept up-to-date. We have therefore set up a system where challenge organizers can upload the code that computes the score for a submission in the form of a Docker container. This system has been operational since 2017 and has been used by almost 200 challenges. We now process around 2,000 submissions per month. In total over 50,000 submissions have been evaluated and placed on the leaderboard.

The last few years we have seen that container technology has become more widely used and several challenges have been organized where participants are asked to upload a container with their algorithm. The challenge organizers than run the secret test data through the container. We have developed a principled solution by adding the possibility for any user to create Algorithms, containers that perform computation tasks on uploaded input, typically a scan, and produce output, say a set of detected objects with their location, a classification or a segmentation. There is a flexible and extendible system from input(s) and output(s) to choose from for your Algorithm. You can specify what kind of computational requirements are needed (CPU, RAM, GPU) to run the Algorithm. Algorithms can be submitted as solutions to Challenges. In this way, it is possible to organize challenges where the test data is never released to the participants and, more importantly, where the submitted solutions are directly available to the Grand Challenge community. Physicians or clinical researchers can upload their own data and have Algorithms process these, and download the result. Such usage can be automated using the Grand Challenge API.

We have also extended the platform to support various medical viewers that run in the browser and the possibility to set up Reader Studies. In a Reader Study, a user is presented with images and a set of questions. Questions can include annotations, for example, segment the liver. The organizers of the Reader Study can download the results via the website or using the API. With Reader Studies, researcher can carry our observer studies, or set up annotation efforts that are usually needed to run a challenge. You can even set up training programs for physicians; it is possible to provide immediate feedback after a question has been answered.

The software behind Grand Challenge is open source. It was largely written by research software engineers from the Diagnostic Image Analysis Group at Radboud University Medical Center. Radboud University Medical Center is also the responsible entity for the website https://grand-challenge.org. If you would you like to suggest new features, set up your own server, or contribute to the development, have a look at our developer documentation or leave a message in the Forum. You can find more information in the documentation section and our page on Partners.