Eastern Maine Healthcare Systems announced on Wednesday that it has signed a clinical affiliation agreement with Massachusetts General Hospital in Boston. The agreement means Mainers in the northern half of the state will have access to Mass General’s clinical resources, providing high-level medical expertise not readily available in the Bangor area to patients of Eastern Maine Medical Center. “Massachusetts General Hospital is a world-class teaching and research hospital,” Matt Weed, senior vice president for strategy and marketing at EMMC, said.