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

 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 xray 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 xray 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