فهرست مطالب e. razavi

This study aimed to assess the risks of exposure-induced death (REID) in patients and embryos during CT examinations in Yazd province (Iran).

Data on the exposure parameters were retrospectively collected from six imaging institutions. In total, 932 patients were included in this study and for each patient, organ doses were then estimated using ImpactDose software. The REIDs were calculated by BEIR VII risk model and using PCXMC software. In the case of gestational irradiation, excess cancer risk of 0.006% per mSv was taken into account in terms of the ICRP 84 recommendations, to calculate the excess childhood cancer risk imposed on the embryo.

The highest estimated organ doses for abdomen-pelvis, routine chest, chest HRCT, brain, and sinus examinations were obtained as 12.82 mSv for kidneys, 12.09 mSv for thymus, 13.16 mSv for thymus, 29.71 mSv for brain, and 11.70 mSv for oral mucosa, respectively. Across all procedures, abdomen-pelvis CT scan induced the highest excess REID to the patients (240 deaths per million). The highest delivered dose to the fetus was roughly 35 mSv, which was lower than the threshold dose proposed by ICRP (100 mSv) for the induction of malformations. However, the associated excess fatal childhood cancer risk of 2122 incidence per million scans can be a subject of concern for public health experts.

Based on the results, although death risks related to induced cancer from CT scans were negligible, this risk can be relatively significant for children exposed during the fetal period.

Renal artery stenosis is a major cause of death and permanent harm to the body. The rigidness of the wall of the arteries is the main cause of atherosclerosis and renal artery stenosis. Therefore, the purpose of this study was to evaluate the effect of vessel wall thickening and renal artery stenosis on the entrance of blood flow through the arterioles of the kidney by using physical modeling, second goal of this study was to evaluate the effect of renal artery stenosis on the characteristics of the flow in the downstream and also to identify areas prone to congestion in the presence of renal artery stenosis. Actual geometry and boundary conditions was used for modeling. In this study, Newtonian and non-Newtonian models was assumed for the viscosity of blood and the results were compared to each other. The effect of mild (30%), moderate (50%) and severe (70%) occlusions was studied on the flow parameters. The areas which were prone to congestion were identified in occluded and non-occluded geometries and the results were compared. The results show that not much difference between Newtonian and non-Newtonian models for blood viscosity is noticed in the present geometry and blood can be considered as a Newtonian fluid. Investigation showed that the congestion-prone areas are located before and also in the first branch of bifurcation because in these areas the shear stress is maximum. The congestions haven’t influenced areas which were prone to occlusion, but the more percentage of stenosis the more there is possibility for occlusion.