General rule
(a) General rule. Except as provided in paragraph (b) of this section, Medicare Part B does not pay for any item or service that is furnished to a hospital outpatient (as defined in 410.2) during an encounter (as defined in 410.2) by an entity other than the hospital unless the hospital has an arrangement (as defined in 409.3 of this chapter) with that entity to furnish that particular service to its patients. As used in this paragraph, the term hospital includes a CAH.