What is First Generation Of CT scan ?
The original EMI unit was the first generation of CT scan. The first generation of ct scan is rotate/ translate pencil beam and Only one detector per tomography section. Only two x-ray detectors were used, and they measured the transmission of x-rays through the patient for two different slices. A thin x-ray beam passed
linearly over the patient, and a single detector followed on the opposite side of the patient. The tube and detector were then rotated slightly, and the process was repeated until a 180° arc was covered. Scan times were very long. This design is no longer in use. The original EMI scanner was designed specifically for evaluation of the brain. In this unit the head was enclosed in water bath between the x-ray tube above and a pair of detector. A took about 4.5 Minutes per scan with 1.5 minutes to reconstruction a slice.
Advantage
1) Pencil beam allow efficient scatter rejection.
Disadvantage.
1) It take 4.5 min to 5 min for one slice and it take approx 22 min to 25 min total Scan of head.
2) Water bath acted as a bolus
.
3) The NaI detector had a significant amount of after glow.
4) NaI hygroscopic.
5) Complex mechanical motion of translate – rotate.
6) Poor spatial resolution.
