radiology department
Refers to the hospital department specializing in diagnostic imaging and radiation therapy.
He had an X-ray taken at the radiology department.
放射線 means 'radiation' itself, while 放射線科 is the medical department that uses radiation.
内科 is 'internal medicine', a different hospital department.
radiologist
Compound of 放射線 (radiation) + 科 (department, field of study).