Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, DNA tests other tests, or medical imaging. The benefits of screening in terms of cancer prevention, early detection, and subsequent treatment must be weighed against any harms. CT angiography (CTA) is a diagnostic tool used to locate tumors in the body, determine whether cancer has spread, and detect abnormal blood vessels that may indicate a health risk. CTA produces multiple X-rays of cross-sections of the body, which are reconstructed through a computer to form a 3-D image.