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Background: Radiotherapy is thecrucial treatment for most malignancies, however; it has short and long-term side effects. The occurrence of secondary cancer following radiation-induced genomic instability in stem cells is an important long-term side effect of radiation therapy. The radiation response of human mesenchymal stromal cells (hMSCs) is critical in cancer patients who are treated with radiotherapy for hMSCs lifetime proliferative potential. Evaluation of genomic instability in human mesenchymal stem cells at different radiation doses and times, and examining the relative expression of some effective genes, have been the objectives of this study. Methods: After extraction, characterization, and expansion of hMSCs, they were irradiated for 0, 0.5, 2, and 6 Grays. Nuclear alterations were evaluated at 2, 10, and 15 days after irradiation using the cytokinesis-block micronucleus assay. As well as TP53, Bax, Bcl2, and KRAS gene expressions were analyzed 48 hours post-irradiation for genomic response evaluation. Results: The mean incidence of micronucleus, nucleoplasmic bridges, and nuclear buds incidences were 4.8±1.6, 47.6±6, and 18±2.6, respectively, 48 hours after the fourth passage in the non-irradiated (control) group for one thousand binucleated cells. Micronuclei incidences in 0.5, 2, and 6 grays radiation groups were 14.3±4.9, 32.3±6.5 and 55±9.1 respectively in 48 hours after irradiation and 12.6±1.5, 19±5.5, and 22.3±5.2, respectively ten days post-irradiations. Conclusion: Low levels of nuclear alterations as genomic instability markers were seen in various cell generations of control groups, which must be considered for cell therapy and regenerative medicine applications. In the irradiated groups, chromosomal aberration increased significantly with the dose, 2days post-irradiation due to a disproportionate increase in the Bax/Bcl2 ratio and high expression of the KRAS gene. significant nuclear alterations were seen in the tenth to fifteenth generations of irradiated hMSCs due to radiation-induced genomic instability which may persuade secondary malignancies in the following years after the radiotherapy treatment of patients.

Background: A chest X-ray (CXR) is known as the most common radiography used for adult and pediatric patients worldwide. Improper X-ray field collimation can result in excessive radiation dose on non-thoracic organs in chest radiographs. Objectives: This study was to investigate X-ray field collimation quality in neonatal chest radiography. Methods: A total of 213 chest radiographs of neonates from three hospitals were analyzed for collimation quality assessment in a retrospective study. Accordingly, ideal imaging field (IIF) and current imaging field (CIF) were initially defined. The margins of the IIF included acromioclavicular (AC) level to lower costal margin (i.e. top to bottom) and one centimeter beyond the broadest area of the chest on each side (that is, right to left). The CIF size was also defined as the square borders of collimators. Results: The findings revealed that the area of the CIF was 1.65 ± 0.39 times to the ideal imaging firlddd (IIF) for three hospitals, suggesting that collimation quality in neonatal chest radiographs was not accurate and it had defects. According to the results, acceptable collimation percentage (36.6%) in Hospital A was more than that in two other centers, and the given center also provided the lowest radiation due to the exposure of non-thoracic structures to primary beams. Conclusions: It was concluded that training radiographers and using patient immobilization devices and stabilizers were of important points that could reduce radiation exposure to non-thoracic organs in pediatric CXR.