Objective: This study aims to investigate the reduction of radiation dose in cerebral CT perfusion by lower low-tube current.

Material and methods:
Two hundred patients, who underwent cerebral non-contrast computed tomography (CT) and CT perfusion, were randomized into four groups according to tube current and contrast media (CM) concentration: group A (60 mAs, 320 mgI/ml), group B (60 mAs, 370 mgI/ml), group C (100 mAs, 320 mgI/ml), and group D (100 mAs, 370 mgI/ml). Among these four groups, the CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED) was calculated. The quantitative image comparison included maximum enhancement, noise, signal-to-noise ratio (SNR), cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) from five regions of interests (ROIs).

Ranging from 100 mAs to 60 mAs, groups A and B achieved 40% lower CTDIvol, DLP and ED, when compared with groups C and D. Both the maximum enhancement and noise of all ROIs were higher in groups A and B, when compared to groups C and D (P<0.05). The CBV values were higher in groups B and D, when compared to groups A and C (P<0.05). The image quality (IQ) of each group of perfusion maps met the requirements for imaging diagnosis.

The reduction in tube current from 100 mAs to 60 mAs for cerebral CT perfusion led to a 40% reduction in radiation dose without sacrificing image quality.