A private-equity firm based in New York is buying Minneapolis-based Center for Diagnostic Imaging, a large operator of MRI and CT scanners in the Twin Cities with imaging centers in more than 20 states.

The firm, Wellspring Capital Management, did not disclose financial terms for the deal.

Center for Diagnostic Imaging (CDI) was founded in 1981 and operates imagining centers, surgery centers and mobile imaging units. CDI employs 685 people in Minnesota, including about 315 people in its corporate office.

"We are very pleased that Wellspring has invested in CDI given the firm's history of building successful businesses in the healthcare sector," said Rick Long, president and chief executive of CDI, in a statement.

Wellspring Capital Management has raised more than $4 billion since 1995 of initial capital commitments through six private-equity funds. CDI operates 122 centers in 22 states, including 26 imaging centers in Minnesota.

CDI has about 2,000 employees overall.

Christopher Snowbeck