Abstract： Objective:To evaluate image quality and radiation dosage of CT cerebral perfusion (CTP) imaging of 70 kV with different tube current and scanning passes and its diagnostic value for hyperacute cerebral infarction.Methods:A total of 190 patients with suspected hyperacute cerebral infarction in Lishui Central Hospital of Zhejiang Province from December 2017 to February 2019 were selected prospectively, and all patients were divided into 4 groups according to random number table and received non-contrast CT examination and dual-source CT cerebral perfusion imaging with 70 kV protocol simultaneously within 6 hours after the onset of symptoms: group A, 120 mA, 21 scanning time points; group B, 100 mA, 21 scanning time points; group C, 100 mA, 17 scanning time points; group D, 80 mA, 21 scanning time points. The values of perfusion parameters such as cerebral blood flow (CBF), crerbral blood volume (CBV), mean transit time (MTT), time to peak (TTP) were acquired. Image quality was evaluated and effective dose (ED) was recorded. The quantitative variables of image quality and radiation dosage were compared between four groups using one-way analysis of variance test.Results:There was no differences between groups on the CBF, CBV, MTT, TTP maps for all CTP values ( P>0.05), and all images could meet the diagnostic requirements. The subjective image quality score of vessel sharpness and overall image quality of both internal carotid artery and middle cerebral artery and the degree of noise of internal carotid in artery in group A was higher than that in group D ( P<0.05). The score of vessel sharpness of internal carotid in artery ingroup A was higher than those in both groups B and C ( P<0.05). The scores of vessel sharpness of both internal carotid artery and middle cerebral artery internal carotid in artery ingroups B and C were higher than that in group A ( P<0.05). The mean EDs of non-contrast CT in group A, B, C, D were 1.10, 2.11, 1.76, 1.42, 1.40 mSv; compared to group A, ED was reduced approximately 16.6% (0.35/2.11), 32.7% (0.69/2.11) and 33.6% (0.71/2.11), respectively ( P<0.05). The diagnostic accuracy of low dose dual source CTP for detecting hyperacute cerebral infarction was 93.5% (172/184), while that of non-contrast CT was 52.2% (96/184);for detecting hyperacutelacunar cerebral infarction, it was 72.1% (31/43) and 16.3% (7/43) respectively ( P<0.05). Conclusion:Appropriate reduction of tube current (100 mA) and scanning passes (17 scanning time points) can reduce the radiation dosage and acquire comparable image quality for 70 kV protocol CTP. Compared with non-contrast CT, low dose dual-source CTP is more sensitive to hyperacute cerebral infarction, especially hyperacute lacunar cerebral infarction.