CT Imaging System: Physics and Mathematical Concepts

CT Imaging System

• Physics and Mathematical Concepts: The physical principles of CT involve physics and mathematical concepts to understand how the image is produced, including data acquisition, image reconstruction, and image display, manipulation, storage, and recording.

Data Acquisition

• Steps: The steps of CT data acquisition include X-ray tube and detectors in perfect alignment, scanning the patient to collect transmission measurements, shaping the beam with a special filter, collimating the beam to pass through the slice of interest, attenuating the beam by the patient, and measuring it with detectors.
• Conversion: The detectors convert X-ray photons into an electrical signal (analog data), which is then converted to digital data by an analog-to-digital converter (ADC) and sent to the computer for image reconstruction.

Scanner Generations

1st Generation Scanner

• Design: Single X-ray source and single X-ray detector cell to collect all data for a single slice.
• Beam: Pencil beam translated across the patient to obtain a set of parallel projection measurements at one angle.
• Source/Detector Rotation: The source and detector rotate slightly, and a subsequent set of measurements is obtained during translation past the patient.
• Translation and Rotation Process: This geometry is referred to as a translate/rotate scanner.
• Scan Time: 4.5 minutes for a single scan.
• Resolution: Very poor resolution.

2nd Generation Scanner

• Design: Multiple detectors (30 detectors) with a small fan beam.
• Translation: Source and array of detectors are translated as in a first-generation system.
• Multiple Projections: Multiple projections are obtained during each traversal past the patient.
• Scan Time: Reducing scan time (two to three minutes).
• Number of Detectors: Up to 53 detectors.
• Comparison: Faster than the 1st generation scanner.

3rd Generation Scanner

• Design: Larger array of detectors (300-700 detectors) with a wide fan beam.
• Rotation: Tube and detector array rotate around the patient.
• Projections: Different projections are obtained during rotation.
• Scan Time: Shorter scanning time (2 seconds).
• Spatial Resolution: High spatial resolution.
• Imaging Process: Significantly faster than 1st or 2nd generation systems.

4th Generation Scanners

• Design: Stationary detector ring and rotating X-ray tube (600 to 4,800 detectors) with a larger fan beam.
• Rotation: Only the X-ray generator and tube rotate at 360°.
• Scan Time: Shorter scanning time.

Fifth-Generation Scanner

• Design: High-speed scanner acquiring scan data in milliseconds.
• Applications: Primary application is cardiac imaging.
• Electron Beam CT Scanner (EBCT): A high-speed scanner capable of producing dynamic three-dimensional (3D) images.
• Dynamic Spatial Reconstruction (DSR): A highly specialized fifth-generation high-speed scanner capable of producing dynamic 3D images.

Sixth-Generation CT Scanners

• Design: Two X-ray tubes and two sets of detectors, resembling the third generation with an additional set of tube and detectors.
• Goal: Reduce scanning time, improving temporal resolution for imaging the heart.

Seventh-Generation CT Scanners

• Design: Flat-panel digital detectors, providing ultra-high spatial resolution, but lower contrast resolution, suitable for applications requiring sharpness, such as angiography.