الفهرس 
ContentsOnly 14 pages are availabe for public view
 |  | from | 121 |  |  |
| | | from | 121 | | |
Abstract
Computed tomography (CT) is a special X-ray imaging modality that plays an important role in medical diagnosis. CT uses the X-ray attenuation properties in human body to detect abnormalities like cancer, and trauma. Concerns about (CT) radiation risks began in the 2000, initially focused on pediatric CT after that concerns were raised for potential carcinogenesis from medical imaging. The benefits of CT outweigh the relatively small increase cancer risk, and patient management should not be altered on the basis of radiation risk. Clinicians and medical physicist can play a role in minimizing radiation risks to the patients by minimizing the radiation dose. In this study, we investigated the radiation dose associated with the most common CT examination used in the Urology and Nephrology Center, Mansoura University (UNC) and decreased the radiation dose as much as possible while getting an image sufficient for diagnosis in order to avoid the radiation high dose risks.First, we made a survey to find out the most common CT examinations performed over 2014-2015 in the Urology and Nephrology Center, Mansoura University. The non-contrast spiral CT abdomen and pelvis (NCCT) was found as the most frequent CT examination representing 81.5℅ of total examinations. In order to estimate the effective dose range, the patients usually exposed to during the CT examination, 362 patients’ detailed parameters were recorded including the patient’s BMI, and dose parameters CTDIvol , and DLP. The effective dose (E) was calculated for each patient, and the range was 1.1 to 16.5 mSv according to the recommendations of the international commission of radiological protection (ICRP 103). Median value of frequent CT examinations for the same patient was 2 (min 1 scan/year & max 11 scan / year). Results showed CT dose variation associated with NCCT abdomen and pelvis among all patients as highly significant (p value <0.01) depending on the high variation in mAs (r=0.98), and moderate depending on the BMI (r= 0.55). In the second part of this work, for minimizing the CT radiation risks we proposed a low dose protocol (30mAs) to be used at the same time with the UNC protocol (200mAs) for another group of 122 adult patients . The effective dose (E) was calculated, and the image quality was evaluated using ACR phantom for both protocols. For 200 mAs protocol the calculated effective dose range was (6.9 to 9.39 mSv) using the recommendations of ICRP 103. ACR phantom Contrast to Noise was 1.19. For 30mAs protocol the calculated effective dose range was (1.03 to 1.41mSv) using recommendation of ICRP 103. ACR phantom Contrast to Noise was 0.51. Results obtained in this work, adopting the low dose protocol of 30 mAs decreased the effective dose by 85%.but the contrast to noise ratio decreased by 57.1% that was enough to produce accepted image quality to diagnose the urinary tract disorders.