The reasonable adjustment and protective value of spiral CT scan dose in brain

Objective:To investigate the optimal technical parameters which can meet the needs of clinical diagnosis and image quality standards so as to reduce the radiation dose.Methods:① The water phantom simulating adult skull was scanned with 260,200,150,100 and 80 mAs.The standard deviation(SD)of CT value was measured and recorded in same region of interest(ROI)in every image.The level of image noise was evaluated by the SD of CT value in ROI.The mean and SD of CT value were statistically analyzed in different dose groups;② 10 cases with intracranial lesions were randomly selected after the conventional dose of 260 mAs scan,1 slice in lesion center was scanned by 200 mAs with the patient's consent.The image quality was blindly evaluated in two groups and was divided into four levels interms of poor,general,good and better.The evaluation criteria were accorded by spatial resolution,noise and artifacts.Results:① Following the reduction of scan dose,the weighted CT dose index(CTDIw)was evidently reduced,the 200 mAs group reduced 13.34 mGy compared with the 260 mAs group in water phantom scan;② Following the reduction of scan dose,the image noise increased,but there was no difference between the 200 mAs group and the 260 mAs group(P0.05);③ There was no statistical difference in image quality of the 200 mAs group and the 260 mAs group(χ2=0.313,P=0.576).Conclusion:The image quality in 200 mAs is not affected by the reduction of scan dose,but it can reduce the radiation dose and has positive significance on radiation protection.