This article explains how to use a ‘dd’ image as the disk for a VirtualBox guest machine. The process is one step; convert the ‘dd’ image to ‘VDI’ format as i’ve done in the example below:
VBoxManage convertdd dd-image.raw sda.vdi --format VDI --variant Fixed
The above command will leave the original image file intact. Now go into VirtualBox and specify the ‘sda.vdi’ file as the disk.