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generations of ct scanners - computed tomography learning
CT scanners were first introduced in 1971 with a single detector for brain study under the leadership of Godfrey Hounsfield, an electrical engineer at EMI (Electric and Musical Industries Ltd). Thereafter, it has undergone several changes with an increase in the number of detectors and decrease in the scan time.
First generation
detectors: one
type of beam: pencil-like X-ray beam
tube-detector movements: translate-rotate
duration of scan (average): 25-30 mins
Second generation
detectors: multiple (up to 30)
type of beam: fan-shaped x-ray beam
tube-detector movements: translate-rotate
duration of scan (average): less than 90 sec
Third generation
detectors: multiple, originally 288; newer ones use over 700 arranged in an arc
type of beam: fan-shaped x-ray beam
tube-detector movements: rotate-rotate
duration of scan (average): approximately 5 sec
Fourth generation
detectors: multiple (more than 2000) arranged in an outer ring which is fixed
type of beam: fan-shaped x-ray beam
tube-detector movements: rotate-fixed
duration of scan (average): few seconds
Other technologies
Other CT technologies have been adapted to third and fourth generation scanners, including:
helical ("spiral") image acquisition
used in all modern CT machines
slip-ring technology made helical acquisition possible
dual energy CT scanning
Practical points
third and fourth generation scanner technologies are both used in many health care settings
the fourth generation is a fundamentally different acquisition method, but the resulting image quality is similar to the third generation for most applications
GENERATIONS OF CT SCANNERS
The different generations of CT scanner was developed over the years to increase scan time and efficiency of scanning. The changes were majorly on the X-ray tube and detector arrangements.
Major adjustment in the technology of CT scanners were manifested in
Tube orientation and shape of beam (from pencil beam through narrow beam to fan beam)
Number of detectors (from single detectors to multiple detectors).
Detector arrangement.
Slip ring technology.
This primarily led to decrease in scan time and increase in efficiency of the scanners.
