Since its invention in the 1970s, computed tomography technology—commonly known as CT or CAT (computed axial tomography) scanning—has revolution ized the way doctors find and diagnose problems inside the body.

Today’s CT scanners enable doctors to view the internal structures of patients’ bodies by taking very thin (fractions of a millimeter thick) x-ray slices across the head or body. The cross-sectional images provide a greater contrast and better view of internal organs and soft tissues such as the heart, lungs, arteries, and brain, so abnormalities can be more easily detected and diagnosed.

X-rays were discovered in 1895, and for the next several decades, scientists worked to develop ways to produce clearer images. In 1914, the Polish doctor Carol Mayer was able to capture a reasonable image of the heart by blurring out the shadows of the ribs and leaving one remaining plane, or slice, of the heart. This technique soon became known as tomography—tomo being Greek for “section” or “cut”—and primitive tomography machines were developed over the next few decades. The Tufts University professor Allan Cormack (1924–1998) was the first to combine computers and x-ray tomography, which he used to construct three-dimensional images of mannequins in 1963. Like his predecessors, however, he was unable to drum up funding or support from the medical community.

It wasn’t until 1971 that a successful CT scanner was put into use, by London-based Electrical and Musical Industries (EMI) Limited. The EMI scientist Godfrey Hounsfield (1919–2004) performed the first head-only scan—a 15-hour process— on a woman suspected of having a brain tumor. The scanner recorded more than 28,000 readings on magnetic tape, which was sent to a computer across town to be processed. The computer produced a cross-sectional image of the brain, revealing a tumor in the patient’s left frontal lobe.

After the EMI scanner went into production, improvements came rapidly. Newer machines were developed to scan the entire body, and slices got thinner and more accurate while scans got quicker. Spiral CTs, widely used today, rotate the patient at the same time as the x-ray beams, reducing radiation exposure and speeding up the process.

ADDITIONAL FACTS

  1. It’s been suggested that the invention of computed tomography was made possible by the success of the British rock band the Beatles. EMI was the Beatles’ record label, and the company made so much money from their album sales that it was able to donate laboratory space and funding to CT research.
  2. Cormack and Hounsfield won a Nobel Prize in 1979 for their work in developing CT scans.
  3. The number of CT scans performed in the United States tripled between 1995 and 2007, and some researchers fear they are ordered too frequently. In 2009, the American Heart Association urged limits on the use of cardiac CT scans because of cancer risk.