5.2 CT: image quality and artifacts

Question 1

how many generations of CT scanners are there?

Answer 1

4
(pencil beam 1790, partial fan beam 1972, fan beam 1976, fan beam 1978)

Question 2

which generation of CT scanners started using multiple detectors instead of just one?

Answer 2

2nd generation

Question 3

which generation of CT scanners did we observe a significant improvement in duration of scan?

Answer 3

2nd generation

Question 4

what was the “number of detectors” for each generation of CT scanners?

Answer 4

1st: one
2nd: multiple, up to 30
3rd: multiple, 288-700
4th: multiple, more than 2000

Question 5

what was the “type of beam” for each generation of CT scanners?

Answer 5

1st: pencil-like x-ray beam
2nd: fan-shaped x-ray beam
3rd: fan-shaped
4th: fan-shaped

Question 6

what were the “tube-detector movements” for each generation of CT scanners?

Answer 6

1st: translate-rotate
2nd: translate-rotate
3rd: rotate-rotate
4th: rotate-fixed

Question 7

what is the “average duration of scan” for each generation of CT scanners?

Answer 7

1st: 25-30 mins
2nd: less than 90 sec
3rd: 5 sec
4th: few secs

Question 8

describe the difference of tube-detector movements between the 3rd and 4th generation of CT scanners

Answer 8

3rd gen: detectors rotate together with the x-ray tube
4th gen: fixed detectors, rotation of only the x-ray tube

Question 9

does a higher generation of CT scanners mean it is more advanced?

Answer 9

no, the 3rd gen is still used to today in some cases rather than 4th gen

Question 10

what is a characteristic of ALL CT systems when it comes to x-ray tubes and detectors

Answer 10

in all systems, there is only ONE x-ray tube, and many detectors

Question 11

what are the 2 types of beam?

Answer 11

• multiple pencil beams
• small fan beams