* 10 pages, 13 figures, submitted to IEEE Transactions on Medical
Imaging. v2: wadded funders acknowledgements to preprint Access Paper or Ask Questions
* 10 pages, 2 figures, 3 algorithms - v2: Fixed typos / grammatical
errors and mathematical errors in the primal/dual formulation. Extended
methods for weighted DAGs rather than DAGs with edge multiplicity Access Paper or Ask Questions