Skin segmentation in 3D slicer

Hi,

Basically my task is to extract skin surface of infant whole body from CT image, but the limitation is my CT image comes from a dead baby with sunken skin in some areas, as you can see in the figure.
The figure is displayed under the CT_muscle window of the Volume Rendering of 3D slicer.

Does anyone have some suggestions? I hope to get a smoother skin surface as a normal skin.

Best regards,
Chuan