DPI of a linked image, illustrator - extendscript

Hi,

I am creating a script that needs to be able to find the DPI of a linked image. I presume there must be some way of getting to this data as it is in the links window in illustrator.

I do also need to get other information in that window (colour space & scale), but the DPI is the one im struggling with at the moment.

Mac 10.9, illustrator CS6, extendscript

Has anyone got any ideas?

Thanks in advance,

Tom