Historical Development CT scanners are categorized into several generations depending on the type of detectors, scanning method etc

First Generation Scanners Single detector, single x-ray tube, rotate/translate pencil beam system, rotation angle/step 1° Long scan time Poor spatial resolution Best scatter rejection

First generation model of a CT head scanner

Second Generation Scanners Linear array of about 30 detectors, single x-ray tube, rotate/translate motion, narrow angle (10 ° ) fan beam rotation angle/step 10° Shortest scan time was about 18 s per slice

Third Generation Scanners Linear array of about 800 detectors, single x-ray tube, rotate/rotate motion only, wide fan beam to cover the entire patient Scan time of newer scanners is about ½ s per slice Can produce ring artifacts

Fourth Generation Scanners Complete circular array of about 4800 stationary detectors Single x-ray tube rotates with in the circular array of detectors Wide fan beam to cover the entire patient Scan time of newer scanners is about ½ s per slice Designed to address ring artifacts

Fifth Generation Scanners 210° arc array of stationary detectors x-rays are produced from the focal track as high energy electron beam strikes the tungsten target Scan time is about 50 ms per slice Developed for cardiac tomographic imaging

Three major components of EBCT scanner: A – Electron gun B- Tungsten targets C - Detectors