How do you get an aerial image (ecw or jpeg) as a background image into Navisworks? My company has both Review and Manage 2009, going to 2010 shortly.

I am attempting to place our 3D design surface with a partial transparancy on top of the image so that we can view our civil design (railway track and design surface) in relation to property boundaries, buildings and existing structures when reviewed.

Can a raster image be taken in directly? Is there a plug-in? Or do I have to use one of the other Autodesk products to bring this raster image in?