Having several brain CTs is generally not associated with a decrease in white blood cells. 1. The radiation of brain CT will have an effect on the white blood cells, but the effect is very mild, and it is generally safe to do a few brain CTs, which generally will not cause a decrease in white blood cells. If the CT is done repeatedly, it may cause leukopenia, and it is not necessary to do CT examination frequently. 2. Leukopenia can be seen in severe infections, radiation damage, aplastic anemia, leukemia, systemic lupus erythematosus and so on. After a few brain CT, white blood cell reduction should be timely to the regular hospital, by the doctor according to the symptoms, signs and auxiliary examination results to determine the cause of the disease, for the cause of the correct treatment.