ABSTRACT
The introduction of digital technology into image production has changed the way in which some of the older imaging devices work. This chapter looks at the way images are formed by the different imaging devices, concentrating on current approaches and on principles. For all images produced using radionuclides which emit single photons the gamma camera needs to scan completely around the patient. B-mode ultrasonic imaging was in use prior to the introduction of computed tomography (CT) imaging. The success of CT depended largely on the development of a fast and accurate image reconstruction algorithm. Electrical impedance tomography is a fast and inexpensive method of imaging tissue properties. In practice, the resolution of an EIT image, as with all images, is also limited by the number of data points collected. This number does rise as the square of the number of electrodes.
