Generations of CT Scanners
Low Voltage Slip Ring
480 AC X-ray controls are transmitted to slip ring by the low voltage brushes (glide into grooves) Power is provided to high voltage transformer, which transmits high voltage to the x-ray tube
First Generation Scanners
1971 Built by EMI Pencil beam with a single detector Source and detector were linearly translated to aquire individual measurements Rotated 1 degree to next angular postition to get next set of images Total scan time about 5 minutes per image (pt motion)
Third Generation Scanners
1975 Systems used today are this type Fan Beam Multiple detectors along an arc Tube and detector rotate around the patient Total scan time faster than 1 second per image Incorperated SLIP RINGS Also called rotate rotate scanners
High Voltage Slip Ring
AC delivers power to the high voltage generator, which provides power to the slip ring Then transfered to the x-ray tube
Brush Designs - Composite
Block of some conductive material as a sliding contact (silver graphite alloy)
Sixth Generation Scanners
Dual Source scanner 2 x-ray tubes 2 sets of detectors offset by 90 degrees Cardiac imaging Has the temporal resolution needed to image moving structures
Fifth Generation Scanners
Electron Beam or Dynamic Spatial Reconstructor 1980 and 1984 Used for cardiac applications Similar to cathode ray tube No mechanical moving parts Because of noise, multiple scans are averaged to produce the final image 20 to 50 ms to get an image
Fourth Generation Scanners
Fan beam Multiple detectors encircles the patient Total scan time is faster than 1 second per image CON-scattered radiation PRO-Spacing between samples is determined by rate at which measurements are taken
Second Generation Scanners
Fan beam geometry 1975 EMI introduced 30 detector scanner (complete scan in 20 seconds) Used Multiple detectors in a straight line Tube/detector moved across the patient then rotated 5 degrees
Advantages of Slip Ring
Faster scan times Minimal interscan delay Capacity for continous aquisition protocols (spiral/helical) Eliminates the start/stop process Removal of the cable wrap around process
Seventh Generation Scanners
Flat panel digital detectors Still a prototype Detector consists of cesium iodide scintillator with an amorphous silicon thin film transisitor array Has excellent spatial resolution
Slip Ring Technology
Made Spiral/helical possible Allows tube to continuously rotate Provides the electrical power to the tube Eliminated the high tension cables Generators are located in the gantry (Transfers the signals from the detector for input into the image reonstruction computer)
Which generation introduced the slip ring?
Third Generation