One CT image of a brain changed science and medicine forever.
Half a century ago, the first CT image of a patient lifted the veil (面纱) of invisibility that. covers the interior of the human body, providing scientists a window on our innards (内脏) unlike any before.
Today, doctors in the United States alone order more than 80 million scans per year. X-ray computed tomography, or CT, is frequently the quickest way of getting a handle on what's causing a mysterious problem. CT scans can find out heart disease, tumors, blood clots, internal bleeding and more. The technique can give surgeons a heads-up about what they will encounter inside a patient, and guide treatment for cancer and other diseases.
"It answers so many questions quickly. That's why it's used," says medical physicist Cynthia McCollough of the Mayo Clinic in Rochester, Minn.
A CT scan involves thousands of X-ray measurements taken from multiple angles. Here's how it works: A source of X-rays moves around the body, sending a beam (光束) of radiation through bone, blood and tissue, while moving detectors measure the beam that makes it through.
Different materials in the body absorb X-rays differently. The calcium (钙) in bone actively absorbs X-rays, for example, while soft tissues absorb less. So when the data collected by the detectors are joined together by a computer, it can form a cross-sectional view of what's inside based on where X-rays are absorbed more or less. Moving the table holding the patient so that the X-ray beam and detectors slide along the body enables 3-D reconstructions of organs and other parts.
Over the years, scientists have continually improved the technology, making it faster and higher resolution (清晰度), and cutting the amount of radiation that patients receive. These improved CT scans have painted ever more detailed landscapes of the human body. It's hard not to be impressed by the beauty of the inner world that the scans bring to the surface.
