This is the 2007 version. Click here for the 2017 chapter 02 table of contents.

The CT Scan

The first of the modern brain scanning techniques emerged in the 1970s, as a variation of x-ray technology. It was called the CAT scan. A CAT scan involved rotating an x-ray machine around the axis of a person's body. The series of pictures were like slices through the brain. By combining the information, neuroscientists or physicians can build up a 3-dimensional x-ray of a person's brain. This shows tumors, enlarged ventricles (the fluid-filled cavities of the brain), and other physical deformities in the brain. It does not, however, show which areas are actively processing information.

What is a CAT scan? What does it show? What do the letters stand for? What is it called now, and why?

CAT stands for "computer axial tomography." A tomograph is an x-ray showing a layer of tissue at some specific depth. An axial tomograph is one made by rotating the subject around an axis, which means twirling the subject or twirling the machine. During a CAT scan, the patient lies still and the machine rotates around his or her body. A student who received several CAT scans said they made her feel a bit claustrophobic, because her entire body was inserted into the large machine, which was then rotated around her, taking x-ray images from every angle.

As scanning techniques grew more sophisticated, the machines became less imposing. Now a slender doughnut-shaped structure is used for scanning, and receiving a CT scan (as they are more commonly called now) is not so much like being inserted into a huge machine.

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