Boston Medical Center chief Elaine Ullian has announced that she will retire, amid what could be the hospital's worst financial crisis in years. Earlier this month, Boston Medical Center sued Massachusetts officials, accusing them of illegally cutting payments for treating thousands of poor patients and plunging the hospital into fiscal uncertainty. The hospital estimates that it will lose $175 million in the fiscal year starting Oct. 1 and $38 million by the end of this fiscal year.