This Challenge will be run as a collaboration between researchers, rather than a competition. There will be no “winner” and comparative results will be presented without rankings. We encourage participation by a wide range of researchers using a range of methods, both complex to simple. Groups are encouraged to provide results of algorithms in preliminary stages of development. Each participant commits to submitting a manuscript to the STACOM’11 workshop summarizing the method used and results of the test dataset, and to upload the results to the Cardiac Atlas Project for collation using STAPLE algorithm and for use by other researchers. Comparison results from STAPLE in the form of sensitivity and specificity of each method will be presented at the STACOM’11 workshop. A journal paper summarizing the collaboration will be prepared after the workshop for submission to a journal such as MedIA or IEEE-TMI. Although 200 cases will be made available, participants can choose not to process all the cases if they prefer.