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Background: Computed Tomography (CT) is main contributor of popula on dose from diagnos c X-ray examina ons. Children are more radiosensi ve than adults, thus op miza on of CT examina on in these pa ents is essen al. The purpose of this study was to evaluate dose delivered to pediatric pa ents' undergoing CT examina on of the common examina ons and also establishing local Diagnos c Reference Levels (DRLs). Materials and Methods: Ques onnaires were designed for data collec on at seven public hospitals and informa on about pa ent, protocol and CT system were recorded during 2013 and 2014. Dose measurement was performed in four age groups: 0-1, 1-5, 5-10 and 10-15 years old and two CT dose quan ty including CTDIw and DLP were calculated. Results: Values of 40, 48, 59.5, 59.5 mGy; 16.9, 16.9, 17.14, 17.14 mGy;17,17,17, 17 mGy;17,17, 19.2,19.2 mGy in terms of CTDIw and 448, 538, 758, 758 mGy cm; 129, 129, 154, 167 mGy cm; 184, 225, 306, 315 mGy cm; 289, 408, 595, 670 mGy cm in terms of DLP as regional DRL for brain, sinus, chest, abdomen and pelvic examina ons were obtained respec vely. Conclusion: The varia ons in dose of some examina on were considerable. As the role and usage of CT technology con nues to expand, it is important that all prac oners adapt op mized protocols, especially for pediatrics scanning, following proposed reference levels.

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The aim of this study is the calculation of equivalent organ dose and estimation of lifetime attributable risk (LAR) of cancer incidence and mortality related to cardiac computed tomography angiography (CCTA) because the use of CT angiography as a noninvasive diagnostic method has increased. The organ dose has been calculated by ImPACT software based on the volumetric CT dose index (CTDIvol), and LAR of cancer risk incidence and mortality from CCTA has estimated according to the BEIR VII report. The median value of the effective dose was 13.78 ± 6.88 mSv for both genders. In all scanners, the highest median value for LAR of cancer incidence in males and females for lung cancer was 44.20 and 109.17 per 100 000, respectively. And in infants was 5.89 and 12 for lung cancer in males and breast cancer in females, respectively. Also, the median value of LAR of all cancer incidence from single CCTA in adult patients for males and females was 122 and 238 cases, respectively. Maximum LAR of cancer mortality in adults for lung cancer was 40.28 and 91.84 and in pediatrics was 5.69 and 8.50 in males and females, respectively. Despite many benefits of CTA in the heart disease evaluation, according to a high radiation dose in CCTA, to reduce the cancer risk: CCTA should be used cautiously, especially for pediatric and females.

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In recent years, with the introduction of 64-slice CT and dual-source CT technology, coronary CT angiography (CCTA) has emerged as a useful diagnostic imaging modality as a non-invasive assessment of coronary heart disease. CT produces a larger radiation dose than other imaging tests and cardiac CT involves higher radiation dose with the advances in the spatial and temporal resolution. The aims of this study are patient dose assessment and establishment of national diagnostic reference level for CCTA in Iran. A questionnaire was sent to CCTA centers. Data for patient and CT protocols were obtained. The volumetric CT dose index (CTDIvol), dose length product (DLP) and total DLP were considered in the 32 cm standard body phantom. Calculation of estimated effective dose (ED) was obtained by multiplying the DLP by a conversion factor [k = 0.014 mSv (mGy·cm)-1]. Mean value of CTDIvol and DLP for CCTA was 50 mGy and 825 mGy·cm. The third quartile (75th) of the distribution of mean CTDIvol (66.54 mGy) and DLP (1073 mGy·cm) values was expressed as the diagnostic reference level (DRL) for CCTA in Iran. The median of ED was 10.26 mSv and interquartile range of ED was 7.08-15.03 mSv. A large variety in CTDIvol and DLP among CT scanner and different sites due to variability in CT parameter is noted. It seems that training could help to reduce patient's dose.