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CT Scanner Detection system

Explore high-frequency CT scanner systems with fast scanning, gas or solid state detectors, and advanced image processing capabilities for accurate diagnostics. Learn about detector efficiency, MTF factors, system design, and reconstruction techniques.

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CT Scanner Detection system

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  1. CT Scanner Detection system

  2. CT Scanner • Generator • High frequency, 30 - 70 kW • X-ray tube • Rotating anode, high thermal capacity: 3-7 MHU • Dual focal spot sizes: about 0.8 and 1.4 • Gantry • Aperture: > 70 cm of diameter • Detectors: gas or solid state; > 600 detectors • Scanning time: <1 s, 1 - 4 s • Slice thickness: 0.5 - 10 mm • Spiral scanning: up to 1400 mm

  3. Gas detector (xenon) • Fast detection response • High Sensitivity • Stability against Radiation damage • Stability against Temperature & Humidity • Higher Dynamic range • But less Quantum efficiency • Inherent collimation • Total DQE(Detective Quantum Efficiency) • = 60 percent

  4. Solid detectors • (Ultra Fast Ceramics) UFC • Godalinium OxiSulphade has uniform sensitivity and fast response time • Need collimation so: • Less Geometric Detection Efficiency (GDE) • Total DQE(Detective Quantum Efficiency) • = 80 percent

  5. MTF of CT detectors • MTF depends on Geometric characteristics and size of detector • Also depends on time response of the detectors: • It may be effected by Cross Talk from adjacent projections or Slices due to long Decay time • In new systems Decay time is about 3 s • Afterglow is about 10-4 after 3mS • Design type and construction of detector arrays, detector separation and distance is also important for MTF

  6. number=1000×(mpixel-mwater)/mwaterDetector Calibration CT CT Projections and Reconstruction

  7. Window width & window level

  8. CT scanner Image processing: • Reconstruction time: • 0.5 - 5 s/slice • Reconstruction matrix: 256x256 – 1024x1024 • Reconstruction algorithms: • Bone, Standard, High resolution, etc • Special image processing software: • 3D reconstruction • Angio CT with MIP • Virtual endoscopy • CT fluoroscopy

  9. Introduction to Reconstruction

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