VisEn Medical Inc. of Woburn, Mass., has announced a research collaboration with Merck & Co. Inc. of Whitehouse Station, N.J. Under the terms of the agreement, the partners will develop biomarkers for Merck to use in its drug discovery programs to study disease progression and therapeutic response. Fluorescence molecular tomography systems from VisEn will be used for analysis. The Massachusetts company also will commercialize technologies resulting from the partnership.