Fusion Imaging

Taking advantage of the DICOM standard used in all medical imaging, ultrasound fusion imaging (sometimes called hybrid imaging) overlays the live ultrasound image simultaneously with a series of images on the same patient from another modality, such as CT, MRI or PET. 

Fusion imaging allows direct comparison of volumetric data from prior imaging (CT/PET/MRI) with real-time US images to evaluate specific areas of interest.

Fusion imaging permits superior evaluation of a target area of interest seen on prior studies.  It also dramatically aids in interventional procedures.

The adjacent short video will give you a good introduction to fusion imaging.

Reference: https://www.sciencedirect.com/science/article/pii/S2211968X12001064