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