Tomograms taken by a CT scanner are

Tomograms taken by a CT scanner are made of pixels, each of which is given a CT number. A line printer or an electrostatic printer is employed in order to obtain patterns sxpressed by these CT numbers. A line printer can print on entire line at a time at a speed of about 600-1200 lines per minute. These line printers can print alphabets, numbers, and symbols.
Some drawbacks of the line printer are related to its mechanical design, resulting in limited printing speeds and excessive noise. Electronic printers, however, have solved the above problems. There are two types of electronic printers; the electronic type and electrostatic type. The latter converts characters into a pattern of electrostatic charges using many recording needles, and prints directly on recording paper. Since it can record gray level images, electrostatic type printers are now widely used.