How safe are CT scans?

Q: Once I had a CT scan of the head done. Is it safe? A lot of people say it leads to tumour or cancer due to exccessive radiations? How would a person know whether excessive radiations have damaged him or not?

A:Radiation exposure is measured over a time period and not by a single investigation only. Radiation risks happen when the total amount of radiation received exceeds the annual permitted exposure dose. A CT scan of the head is well within the permissible dose and is completely safe. One CT scan of the head cannot lead to a tumour.