Rotate the patient between the x-ray tube and the image receptor to see how every projection and position gets its name.
Right posterior oblique (RPO)position
The right posterior aspect of the body is closest to the image receptor. This may also be described as an AP oblique projection, because the central ray still enters anteriorly and exits posteriorly.
Source: Bontrager, Radiographic Positioning & Related Anatomy, 10e, Ch. 1