الفهرس 
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Abstract
Computed tomographic (CT) route has much superior diagnostic accuracy in different clinical circumstances in comparison to other brain radiography. Although argumentative, contemporary data acquiesce that medical radiation exposure increases significantly the risk effects of contrary radiation. A number of CT routines sophisticated to reduce radiation dose, however, preserving image quality. The standard CT reconstruction algorithm filtered back projection techniques (FBP) cannot produce diagnostic quality images combined with a reduction of x-ray tube currents expressed in (mA). The main goal of the presented work is to reduce the effective dose of radiation resulting from (CT) protocols with pediatric cases of age range between a day and 10 years without effecting on the quality or contrast of images. Four different stages were adapted to perform this aim, First Stage:- Stage 1 involve CT brain scan for 14 Children age range (1 day to 10 years) arranged according to their ages. The protocol of measurement based on using tube current 148 mA, applied voltage 120 kV with filtered back projection (FBP). Measurements calculated for 9 different points in 3 different levels with the gray matter and another 9 points in 3 different levels in white matter region. Effective dose (ED), Signal to Noise ratio (SNR), and Contrast to Noise ratio (CNR) were calculated. It was concluded that effective dose is directly depends on age range in pediatric cases that can be interpreted in terms of density and distance travelled by the radiation. Second Stage:- A pilot study on changing current was performed in three different cases to optimize current change and rate of ASIR that must be used to obtain acceptable image with a low effective dose and high Signal to Noise ratio (SNR) and Contrast to Noise ratio (CNR). The process performed with three different currents namely (100, 80, 60 mA) using ASIR (40, 60, 80 %). Third Stage:-Standard protocol was modified and currents (100, 80, 60, and 40 mA) with ASIR (40, 60, 80%) was studied for 7 cases. Calculated parameters (ED, SNR, and CNR) suggests that 60 mA current gives the relatively low effective dose with a good SNR and CNR. With 40 mA, current does not give a remarked decrease in effective dose. In addition, image quality was accepted. Fourth Stage:- Same calculations were performed on different cases with the same (k-factor) age range (5-10 years) to check if age range effects in calculated parameters. Measurements performed using three different currents (100, 80, 60) mA with application of ASIR ratio (40, 60, 80 %) it was noticed that using of 60mA current reduce the effective dose to about 0.85 mSv and SNR reach to 7.39 and CNR reach to 1.85. Above results, recommend using of 60 mA tube current in pediatric cases in every age stages.