An imaging apparatus, method, and computer readable medium are disclosed, which can detect in a case where a foreign substance such as air and blood other than transparent liquid is present inside a catheter, and can urge a user to perform priming so that an image having higher accuracy can be reconstructed. According to the present disclosure, the imaging apparatus can determined whether or not the foreign substance such as air and blood is present between an imaging core and an inner surface of a catheter sheath, from line data which is generated based on interference light data obtained when the priming is performed or at stages before and after pull-back scanning is performed. In a case where the foreign substance enters, a message urging the user to perform the priming is displayed.
