Calculating volume of CT images

Operating system: Mac OS El Capitan
Slicer version: 4.7

Hello, I am new to Slicer and I am trying to calculate volumes of maxillary sinuses. I have multiple axial slices, 1 mm each. Is there a simple way to calculate the volume of each slice of this irregularly shaped cavity and be able to add them up?

Yes. You can use Segment Editor module to segment the structure and then use Segment statistics module to compute volume.