On a third-generation single-row detector scanner, if there are 715 detectors and there are 900 projections in a full rotation how many samples of attenuation data are collected for the raw data of a single slice if the scan calls for an overscan of a 400* rotation?
a. 286,000
b. 648,500
c. 715,000
d. 845,000
c--There are 900 projections in a full rotation of 360*, but the question asks about an overscan of 400*. An overscan is sometimes used to decrease aliasing artifacts. 900 projections in 360* means that there are 900 / 360, or 2.5 projections per degree. There are 400-360, or 40 more degrees than a full scan. Multiplying 40 degrees by 2.5 projections per degree yields an additional 100 projections. Therefore, the total number of projections equals 900 + 100, or 1000 projecitons. The number of samples of attenuation profiles in the raw data equals thenumber of detectors time the number of projections 715 detectors x 1000 projections samples