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2. generations of computed tomography
There are four generations of computed tomography (CT) imaging systems. The first generation used a single detector and pencil beam, taking 5 minutes per scan. The second generation used an array of detectors and fan beam, reducing scan time to 30 seconds. The third generation rotated the x-ray tube and array of detectors, achieving subsecond scan times but risked ring artifacts from detector failures. The fourth generation kept detectors stationary and only rotated the x-ray tube, eliminating ring artifacts. Today, third generation CT systems with helical and multi-slice capabilities are most common.
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2. generations of computed tomography
- 1. Generations of ComputedTomography 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 1
- 2. Generations Of ComputedTomography 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 2
- 3. First Generation ImagingSystem • 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 3
- 4. Second Generation ImagingSystem • 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 4
- 5. Third Generation ImagingSystem • 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 5
- 6. Disadvantage of ThirdGeneration 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 6 The malfunction of a single detector can result in the ring artifact.
- 7. Fourth Generation ImagingSystem • 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 7
- 8. Today • Today essentiallyall 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 8
- 9. Thank you Muhammad ArifAfridi Lecturer in Medical Imaging | RFafridi@hotmail.com 9