الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The standard head and body phantom in combination with longitudinal ionization chamber dedicated for CT dose were used to measure the computed tomography dose index (CTDI) and dose length product (DLP) for selected protocols at different scan parameters .
Fifteen computed tomography scanners were chosen to involve in this study. The x-ray tube potential range is from 80 to 120 kVp, time - current tube range is from 50 to 250 mAs and the scan mode utilized for the Multi-slice helical scan at two CT examination (Routine Head and Routine Abdomen).
Evaluation of the volume C T dose index (CTDIVOL) and the Dose – Length product (DLP) at different physical parameters (kVp – mAs) and perform quality control tests for CT scanners. Compare between the values of CTDLVOL which measured by electrometer and recorded by operator’s console.
Comparison step between our measured verification data which is taken by ionization chamber and data obtained from the CT scanner, within the range from 4 % to 11 %. For head scan, the average effective dose was ranged from 0.11mSv to 0.96 mSv with an average 0.46 mSv, and the corresponding attributable risk of cancer was 0.0026 cancers per 10,000 patients (ranged from 0.0006 to 0.005 cancers per 10,000 patients). For body scan, the effective dose was ranged from 0.43 mSv to 3.85 mSv with an average 1.81 mSv, and the corresponding attributable risk of cancer was 0.01 cancers per 1000 patients (ranged from 0.00243 to 0.021 cancers per 1000 patients). If the tube voltage decreased from 120 to 100 kVp at constant tube current, the dose reduced by factor 20% to 50% with acceptable image quality
The radiation exposure associated with CT has increased substantially over the past two decades, and efforts need to be undertaken to minimize radiation exposure from CT, including reducing unnecessary examinations, reducing the dose per study, and reducing the variation in dose across patients and facilities. Patient outcomes studies are needed to highlight the benefits expected from the examinations and reducing or preventing the associated health risk. Understanding exposures to medical radiation delivered through actual clinical studies is a crucial first step toward developing reasonable strategies to minimize unnecessary exposures.