Changing the Hounsfield unit in a DICOM CT image

Hi everyone
I have a CT image in DICOM format that I exported it from Brachytherapy treatment planning system. I want to remove the Brachy applicators from the CT image. In other words, I want to change its Hounsfield unit to a desired value of zero. I have no idea about this. Can you guide me?
Thanks a lot

You can use the Masking effect in the Segment Editor for that.