This article reports on recent research findings into the factors thatinfluence the detectability performance of different systems of computedtomography (CT) scanners. These systems include multidetectorCT (MDCT) of different slice numbers, dual-source CT(DSCT), and cone-beam CT (CBCT). The introduction of more slicesfor MDCT, DSCT, and the new technology of CBCT increasesthe need to optimize the image quality and to examine the potentialreduction of radiation doses to the patient. Low-contrast detail detectabilityis a method that has proven to be an appropriate evaluationmethod for this purpose. However, it is essential to recognizefactors that affect detectability performance and understand howthese factors influence image quality and radiation dose. It is arguedthat deep understanding of the influences of these factors is the keyto image quality optimization in terms of contrast-detail detectabilityand radiation dose reduction. The purpose of this article is, therefore,to specify these factors and to explain their influence on detectabilityperformance and hence on CT image quality. Further low-contrastdetail studies are required to optimize imaging performance of differentCT systems and scanners.