how to use hounsfeild units for vertibrae in pre processing for a CT data of vertibrae?

Hello. I am using CT data for segmentation of vertebrae with deep learning. I applied an algorithms for feature learning. auto encoder learns the features but a problem in a classification. my dataset is not normalized properly. I think auto encoder can not learn the features very well due to pre processing step. I missed the pre processing. i want to know how to take a hounsfeild units for a vertebrae. and which pre processing step is better for vertebrae? thanks