The radiation doses per CT is very low and hence nothing to be afraid of. You are safe. If it is medically required then get them done

The radiation that you get from an HRCT, is so small less than 1mSv, which is way below any sort of danger levels. Also the effect, of radiation on body is so minimal from an HRCT, than the benefit that you get by doing a test like that. I So absolutely nothing to worry about, also this is a one off procedure, and you won't be doing it frequently. Only thing is repeat the test only when indicated and suggested my a qualified medical practitioner. Mammogram is not done - because it is of less use in female less than 40 since their breast is more dense - not because of radiation exposure problem .