There are over 70 million CT scans performed in the United States every year. The FDA is investigating problems with overexposure to radiation by CT scans. This is an ongoing problem everywhere but is complicated by significant overexposure of special types of CT scans (called perfusion CTs) at two hospitals.
First, some background: CT scans (also called CAT scans, or computerized tomography) is an x-ray that uses radiation to visualize internal structures of the body through a cross-section of images (unlike the flat images of normal x-rays). One CT scan is equivalent to about 100 chest x-rays. One perfusion CT scan (used to examine blood vessels and often used to diagnose stroke or aneurysm) is equivalent to several hundred chest x-rays.
Sample Perfusion CT