Introduction:
This study aims to investigate the reduction of radiation dose in cerebral computed tomography (CT) perfusion by lower low-tube current.

Material and methods:
Two hundred patients, who underwent cerebral non-contrast CT and CT perfusion, were randomized to four groups according to tube current and contrast media (CM) concentration: group A (60 mAs, 320 mg I/ml), group B (60 mAs, 370 mg I/ml), group C (100 mAs, 320 mg I/ml), and group D (100 mAs, 370 mg I/ml). Among these four groups, the CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED) were 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).

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

Conclusions:
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.