CT - Computed Tomography (also known as CAT - Computed Axial Tomography). This is a type of scan which provides good images of problems but also gives a radiation dose. The National Academy of Sciences has said there is no safe level of radiation dose and further their researchers said their results indicate that 1 in every 1000 people would develop cancer from a radiation dose of 10 millisievert (mSv), the average radiation dose in a single whole-body CT scan.