Is orbital CT scan and CT scan sinus the same?

Not quite. The CT of the sinuses focuses in on the sinuses (though the radiation goes through the entire skull) and generally covers the entire set of sinuses (sphenoid, maxillary, frontal, ethmoid). The orbital CT will cover the eye sockets (and those pictures are zoomed in). While the sinuses lies behind the eyes (& so they overlap), the focus & coverage of these scans are slightly different.
no. Orbital ct is tailored to look specifically at the eyes. Sinus ct is tailored to look at the paranasal sinuses.