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Computed tomography basics
- Maulik R. Shah is a consultant biomedical engineer, medical equipment planner, and hospital project consultant based in India. He has degrees in biomedical engineering and healthcare administration. - The document discusses the five generations of computed tomography (CT) scanners since 1970 and how each generation improved scan time and image quality/resolution. First generation scanners took 5 minutes for a single slice while current scanners can acquire a full scan in under 1 second.
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Computed tomography basics
- 1. Maulik R. Shah B.E. (Inst & Control Engg.) M. S. (Biomed Engg., USA) PGDHA (Apollo Hospital) Consultant Biomedical Engineer Medical Equipment Planner Hospital Project Consultant Mobile : 9824019971 Email : mailtomaulik@gmail.com www.atozforhospital.com
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- 4. Tomo = image// to long axis of the body CT = image is transverse to the body
- 5. Basic C TPrinciples • Computed Tomography has the x- ray tube move across the so the image is called a transverse image or one perpendicular to the long axis of the body.
- 6. Computed Tomography Development • Computedtomography has gone through five major design advancements since 1970 • Each development improved both scan time and resolution or image quality. • Scan time have been reduced from 5 minutes to 50 ms. • First scanner used a very tightly collimated pencil beam.
- 7. Generations • First GenerationScanners – Translation/Rotation – Tube produced a finely collimated beam or pencil beam – 1 to 3 detectors were placed opposite the tube for radiation detection – 4.5 minutes to gather enough information for one slice – Tube was only able to rotate 180 degrees
- 8. First Generation • 1971 •Pencil Thin Beam of Radiation • Translate and Rotate – X-ray source and detector fixed relative position – One degree of rotation possible • Scan Time (Single Image) – 5 min • 128 x 128 images Patient X-ray tube Detector
- 9. First Generation CTScanner • Pencil Beam • Translate-Rotate Design • 180 one degree images or translations. • One or two detectors. • 5 minutes scan time
- 11. Second Generation • Fan-shapedx-ray beam • 30 or more detectors • 20 seconds per slice or 10 minutes for a 40 slice exam • 180 degree rotation • Long data reconstruction time
- 12. Second Generation • 1974 •X-rays – Multiple Pencil – Fan Shaped 3 - 26 degrees • Still Translate and Rotate – X-ray source and detector still fixed relative position – Rotation increased from one to three degrees • Scan time (Single Image) – 3.5 min – Eventually 5.3 sec X-ray tube Detectors
- 13. Second Generation CTScanner • Translate-Rotate • Fan beam collimation so there is more scatter radiation. • 5 to 30 detectors • 10 degrees /translation 18 per scan. • 30 second scan times • Faster scan time
- 15. Third Generation • Fan-shapedx-ray beam • 960 detectors opposite the x-ray tube • Complete 360 degree rotation Rotate/Rotate movement • One rotation = one slice • Second data acquisition could be made as the tube and detectors move in the opposite direction. • Time reduced to 1 sec per slice
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- 17. Third Generation • 1977 •X-ray – Fan Shaped – 21 - 45 degrees • Rotation Only – Array of Detectors • Scan Time (Single Image) – 4.8 sec – Eventually reduced to 2.5 seconds Detectors X-ray tube
- 18. Third Generation CTScanner • Rotate-Rotate • Fan shaped beam of 30 to 60° for full patient coverage. • Constant Source to detector distance due to curvilinear detector array.
- 19. Third Generation CTScanner • If one detector fails, a ring artifact appears. • 1 second scan times • Superior reconstruction and resolution.
- 20. Fourth Generation • Developedin 1980’s • Fixed ring of as many as 4800 detectors, completely surrounding the patient, Rotate only movement • Rotating x-ray tube provides short bursts of radiation • Detectors collect the remnant radiation to reconstruct into an image • 1 minute for multiple slices
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- 22. Fourth Generation • 1980 •X-ray – Wide Fan – 48 - 120 degrees • Rotation Only – Full Ring of Detectors • Scan Time (Single Image) – 5 Sec – Eventually reduced to ~1 sec X-ray tube Ring of Detectors
- 23. Fourth Generation CTScanner • The tube rotates around a stationary ring of detectors. • Fan beam • Variable slice thickness with pre and post patient collimation.
- 24. Fourth Generation CTScanner • As many as 8000 detectors. • 1 second scan time. • Auto-detector calibration so no ring artifact. • High radiation dose compared to earlier scanners.
- 25. Fifth Generation CT Scanner •This is the latest generation of CT. • Allows for continuous rotation of the tube for spiral CT. • 5th Generation also includes two novel designs: