Dear Delmon,
I changed the contrast of the image:
This way you can see the hair of the mouse (and maybe some distortion of the CT image ?). Since these regions are not clear black as air should be, their voxel regions are filled with dense material, which leads to dose deposition there.
You may try to edit the material of these lower density regions on the page for voxel generation (See: “Voxel Generation” at Flair manual, but this could lead to changes at some internal organs as well.
Cheers,
David