CT scanners have been categorized into generations based on their detectors and scanning methods. First generation scanners had a single detector and x-ray tube, long scan times, and poor image quality. Second generation scanners used a linear detector array, faster rotation, and improved image quality. Third generation scanners featured larger detector arrays, only rotational motion, faster scans, and the potential for ring artifacts. Fourth generation scanners used a full circular detector array and single rotating x-ray tube to address ring artifacts.

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

2. 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

4. First generation model of a CT head scanner

7. 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

8. 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

9. 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

10. 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

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