Assessment of image quality of a standard and three dose-reducing protocols in adult cranial CT.

The purpose of this study was to analyze the effect of various tube current settings (mAs) and optimize the image quality and dose for adult cranial CT protocol. Sixty adult patients who underwent a cranial CT scanning for different indications were subdivided into three subgroups. Subjective image and noise quality scores and quantitative noise measurements were selectively studied on three reference levels (cerebellar, basal ganglia and centrum semiovale levels). For each subgroup, only one level was studied. Head circumference (HC) and the maximum anteroposterior diameter (MAPD) of each patient were measured. At 50% decreased dose protocol, there was no poor quality score at any level. At nearly 60% decreased dose protocol, the incidence of poor quality scores was much higher at the cerebellar level than at the other two levels. For the same protocol number, quantitative noise measurements were higher at the cerebellar level than the other two supratentorial levels. The correlation was found to be significant between HC, MAPD and quantitative noise measurements, and there was a non-significant correlation between HC and subjective noise scores. In adult cranial CT, depending on the level, a dose reduction of up to 60% may be possible while maintaining image quality.