The Range of Protons in Human Skullbone

Abstract
This experiment shows that, if the thickness of skull-bone to be penetrated by a beam of protons can be estimated to [plus or minus] 0.5 mm, the range correction required by the presence of bone can be predicted within [plus or minus]0.5 mm in about 2/3 of the cases. Accuracy can be improved substantially only if the local density of bone as well as its thickness is determined. An empirical relationship between the average density and thickness for bone is given, and the stopping power of bone relative to water has been determined. Good agreement is found between theoretical and experimental values of the mass stopping power of bone.