generations of computed tomography

1. Generations of Computed Tomography
Muhammad Arif Afridi
Lecturer in Medical Imaging
Medical Imaging Technologist (MIT) - Radiology
Master in Public Health (MPH)
Email: RFafridi@hotmail.com
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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2. Generations Of Computed Tomography
There are four Generations Of Computed Tomography.
1. First-generation imaging system: translate and rotate, pencil beam,
single detector, 5-minute imaging time.
2. Second-generation imaging system: translate and rotate, fan beam,
detector array, 30-second imaging time.
3. Third-generation imaging system: rotate and rotate, fan beam,
detector array, subsecond imaging time.
4. Fourth-generation CT imaging system: rotate and stationary, fan
beam, detector array, subsecond imaging time.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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3. First Generation Imaging System
• The type of scanner built by EMI in 1971 is
called the first-generation CT.
• X-ray tube and single detector are connected.
• Move together by translation and then
rotation.
• X-ray beam has linear (pencil-like) shape.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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4. Second Generation Imaging System
• same type of movement
• multiple detectors arranged in a row
• fan shaped x-ray beam instead of linear
shaped
Difference: Although this was still a translation-rotation
scanner, the number of rotation steps was reduced by
the use of multiple pencil beams.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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5. Third Generation Imaging System
• Full rotation of x ray tube and complex detectors
are installed.
• Third-generation detector assembly allows for
better x-ray beam collimation and reduces the
effect of scatter radiation.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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6. Disadvantage of Third Generation Imaging
System
• the principal disadvantages of third-
generation CT imaging systems is the
occasional appearance of ring artifacts.
• If any single detector or bank of detectors
malfunctions.
• The acquired signal or lack thereof results in
a ring on the reconstructed image
• Now remove such artifacts
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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The malfunction of a single detector can
result in the ring artifact.

7. Fourth Generation Imaging System
• Only x-ray tube rotates
• Detectors are stationary
• Radiation detection is accomplished through a fixed
circular array of detectors, which contains as many as
4000 individual detectors.
• Fourth-generation imaging systems were developed
because they were free of ring artifacts.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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8. Today
• Today essentially all CT imaging systems are third-generation and
have evolved into helical and multi slice imaging.
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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9. Thank you
Muhammad Arif Afridi
Lecturer in Medical Imaging | RFafridi@hotmail.com
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