Reported January 2011

HOW CT SCANS WORK: CT scans use X-rays to image the body. X-rays can pass through most materials. It all depends on the size of the atoms that make up the material; larger atoms absorb X-ray photons, while smaller atoms do not, and the X-rays pass right through. For instance, the soft tissue in the body is composed of smaller atoms, so it doesn't absorb X-rays very well. But calcium atoms in the bones are much larger and do absorb X-rays. A camera on the other side of the patient records the patterns of X-ray light passing through the patient's body. In a CT scan, a series of X-ray beams is directed through the body from different angles. This creates cross-sections so scientists can get a better view of the body. The images are put together by a computer into a stack of pictures that can be viewed rapidly, like flipping through a deck of cards.

WHAT DO PHYSICISTS HAVE TO DO WITH MEDICINE? Commonly known as medical physicists these are the people who work within medicine to design and ensure the safety of modern medical tools. Harnessing the power of light and subatomic particles makes advanced imaging techniques and radiation therapies possible. Medical physicists also work to ensure that these powerful devices deliver radiation accurately and safely.

If you would like more information, please contact:

Karen Tong
Public Affairs, Johns Hopkins Bayview Medical Center
Baltimore, Maryland
ktong4@jhmi.edu