CT scanners Generations (1st, 2nd, 3rd, 4th, 5th)

CT scanners Generations (1st, 2nd, 3rd, 4th, 5th)

CT scanners were first introduced in 1971 with a single detector for brain study under the leadership of Sir Godfrey Hounsfield, an electrical engineer at EMI (Electric and Musical Industries Ltd). Thereafter, it has undergone multiple improvements with an increase in the number of detectors and decrease in the scan time.

First generation: CT Bench Top

• Detectors: one
• Type of beam: pencil-like x-ray beam
• Tube-detector movements: translate-rotate
• Number of slice per rotation: 1
• Duration of scan (average): 25-30 minutes

Second generation

• Detectors: multiple (up to 30)
• Type of beam: fan-shaped x-ray beam
• Tube-detector movements: translate-rotate
• Number of slice per rotation: 1
• Duration of scan (average): less than 90 sec

Third generation

• Detectors: multiple, originally 288; newer ones use over 1000 arranged in an arc
• Type of beam: fan-shaped x-ray beam
• Tube-detector movements: rotate-rotate
• New concept: Helical ("spiral") image acquisition due to Slip-ring technology.
• New concept: Dual energy CT scanning
• Number of slice per rotation: multiple due the parallel detectors array configuration, include x-ray detectors large enough to cover an entire organ in a single rotation.
• Duration of scan (average): approximately 5 sec
• This geometry configuration of the 3rd Generation won, due the cost and benefits.

Fourth generation

• Detectors: multiple (more than 2000) arranged in an outer ring which is fixed (360 degrees)
• Type of beam: fan-shaped x-ray beam
• Tube-detector movements: rotate-fixed
• Number of slice per rotation: 2 or more due the parallel detector array
• Duration of scan (average): few seconds

Fifth generation

• Detectors: multiple (more than 2000) arranged in an outer 1/2 ring which is fixed (180 degrees)
• Type of beam: The x-tube in this design is a scanning x-ray tube, where the electrons are steered magnetically (like in old TVs) rather than physically moving the x-ray tube. This method allows for very fast acquisitions and is ideal for cardiac scanning (with a temporal resolution of a given slice as low as 17ms).
• Tube-detector movements: fixed-fixed. In 5th?generation CT both the x-ray source material and the detector are stationary.
• Number of slice per rotation: 2 or more due the parallel detector array
• Duration of scan (average): few seconds

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