historical development ct scanners are categorized into several generations depending on the type of...
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Historical DevelopmentHistorical Development
CT scanners are categorized into CT scanners are categorized into several generations depending on the several generations depending on the type of detectors, scanning method type of detectors, scanning method etcetc
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 ScannersSecond Generation ScannersLinear array of about Linear array of about 30 detectors, single x-30 detectors, single x-ray tube, ray tube, rotate/translate rotate/translate motion, narrow angle motion, narrow angle (10 (10 °° ) fan beam ) fan beam
rotation angle/step 10rotation angle/step 10°°
Shortest scan time Shortest scan time was about 18 s per was about 18 s per sliceslice
Third Generation ScannersThird Generation Scanners
Linear array of about Linear array of about 800 detectors, single x-800 detectors, single x-ray tube, rotate/rotate ray tube, rotate/rotate motion only, wide fan motion only, wide fan beam to cover the beam to cover the entire patiententire patient
Scan time of newer Scan time of newer scanners is about ½ s scanners is about ½ s per sliceper slice
Can produce ring Can produce ring artifactsartifacts
Fourth Generation ScannersFourth Generation ScannersComplete circular array of Complete circular array of about 4800 stationary about 4800 stationary detectorsdetectors
Single x-ray tube rotates Single x-ray tube rotates with in the circular array of with in the circular array of detectorsdetectors
Wide fan beam to cover Wide fan beam to cover the entire patientthe entire patient
Scan time of newer Scan time of newer scanners is about ½ s per scanners is about ½ s per sliceslice
Designed to address ring Designed to address ring artifactsartifacts
Fifth Generation ScannersFifth Generation Scanners
210210° arc° arc array of stationary detectors array of stationary detectors
x-rays are produced from the focal track x-rays are produced from the focal track as high energy electron beam strikes the as high energy electron beam strikes the tungsten targettungsten target
Scan time is about 50 ms per sliceScan time is about 50 ms per slice
Developed for cardiac tomographic Developed for cardiac tomographic imagingimaging
Three major components of EBCT scanner:A – Electron gunB- Tungsten targetsC - Detectors