What Is Third Generation of CT Scan?
The third generation CT scanner is also rotate / rotate system with wide fan beam and the angle of fan beam was 50° . Both the x-ray tube and detectors rotate around the patient. The original rotate – rotate scanner used 288 detector but newer version of some units use 700 detectors. In third generation the fan beam and detector array formed into arc view entire patient at all time. The curvilinear detector array results in constant source to detector path length which Is advantage of good image reconstruction. Xenon and scientillation crystal were used because the detector and x-ray tube are in precise alignment through entire scan motion. It take at 1 sec or slightly less scan time of per slice. The third generation scanners lead to a situation in which each detector is responsible for the data corresponding to a ring in the image. Any drift in the signal levels of the detector over time affects the µt values that are back projected to produce the CT image, Causing ring artifacts.
Advantage:-
1) In third generation CT scanner produce an image in 1 sec.
2) Xenon detector was used which is highly directinal and efficient reject scattered radiation.
3) The patient dose was less.
Disadvantage:-
1) More expensive as compared to First and second generation of CT scan.
2) More scatter radiation recorded by a fan beam unit than first and second generation scanners.
3) It produce ring artifacts.
