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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 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