MemorialCare Health Services and RadNet Inc. have founded a joint venture to operate what they say will be the largest outpatient medical imaging network in Los Angeles and Orange counties, the companies announced Monday.

The Fountain Valley–based MemorialCare, which owns three hospitals in Long Beach and two in Orange County, will contribute 10 existing clinics and retain 40 percent ownership of the unnamed venture. RadNet , a national diagnostic imaging services company based in Sawtelle, will contribute 24 clinics and retain 60 percent. The combined venture expects to conduct 500,000 X-rays, MRIs, CT scans and other imaging procedures a year.

The nonprofit Memorial Care also said it intends to purchase five breast imaging centers from the joint venture next year, adding to its current five. Terms of the deals were not disclosed.

Health business reporter Dana Bartholomew can be reached at [email protected]. Follow him on Twitter @_DanaBart.