Gamma radiation-induced impairment of hippocampal neurogenesis, comparison of single and fractionated dose regimens Deterioro de la neurogénesis en el hipocampo inducida por radiación gamma, comparación de los regímenes de dosis única y fraccionada

Radiation therapy of the brain is associated with many consequences, including cognitive disorders. Pathogenesis of radiation induced cognitive disorder is not clear, but reduction of neurogenesis in hippocampus may be an underlying reason. 24 adult male rats entered to study. Radiation absorbed dose to midbrain was 10 Gy, delivered by routine cobalt radiotherapy machine which its output was measured 115.24 cGy/min. The rats were divided in four groups of sixes, including groups of control, single fraction 10 Gy, fractionated 10 Gy and finally anaesthesia sham group. Number of pyramidal nerve cells was counted in two regions of hippocampus formation (CA1 and CA3). The radiation could reduce the number of cells in two regions of hippocampus significantly (p=0.000). It seems fractionated 10 Gy irradiation to more efficient than single fraction, while role of anaesthesia drug should be cautiously assessed. Moreover the rate of neurogenesis reduction was determined the same in these regions of hippocampus meaning the same radiosensitivity of cells

Quality assurance program for prototype stereotactic system developed for Neptun 10 PC linac

Background: A prototype stereotactic radiosurgery set was designed and constructed for a Neptun 10 PC linac that is currently being used at Imam Reza hospital in Mashhad. Materials and Methods: A complete qualit y assurance program was designed and performed for the constructed system including isocentric accuracy test, localization accuracy test, dose delivery accuracy test and leakage radiation test. Target simulator, control alignment device and plexiglass phantom which were parts of the developed hardware were used to fulfill quality assurance program. Results: The average isocentric shift resulted from the gantry rotation and couch turning were respectively obtained to be 1.4 and 2 mm. The average localization error in the three coordinates was found to be 2.2 mm. The total treatment uncertainty due to all of the probable errors in the system was equal to 4.32 mm. The dose delivery accuracy test was carried out, the result indicated a 3-7% difference between the given and measured dose. Conclusion: The quality assurance tests showed consistent performance of the constructed system within the accepted limits; however, some inconsistency might exist in certain cases. The safety of SRS method is increased when the overall uncertainty is minimized and the treatment of the lesions adjacent to critical organs is avoided

Assessment of cumulative radiation dose of neonate hospitalized in intensive care units

BACKGROUND AND OBJECTIVE: Newborns admitted to the neonatal intensive care unit (NICU), would be undergo a large number of X-ray imaging due to their involvement with various diseases The most important complication of receiving too much X-rays is an increased risk of various cancers. The aim of this study was to determine the average cumulative dose received by neonates admitted to the neonatal intensive care unit. METHODS: This cross-sectional study was performed on 20 neonates admitted to the intensive care unit of Taleghani Children's Hospital who were randomly selected. Infant information registrated including time of birth, arrival time, duration of hospitalization, age, sex, weight and number of radiographs performed on the infant and radiographic information including tube-to-patient distance, tube voltage (kVp) and milliamperes (mAs). The amount of skin absorption dose of each patient was evaluated using MTS700 thermoluminescence dosimeter and the number of imaging was examined. FINDINGS: The amount of entrance skin dose of the studied neonates with an average of 78 micrograys varied from 42 to 121 micrograys (78±19.6). The mean number of imaging and cumulative dose were 6 (6±7.71) and 521 micrograys (521±547.99), respectively. The highest cumulative dose (2106 μg) was related to a neonate who underwent 27 imaging. CONCLUSION: According to the results of this study, the need for multiple imaging of these infants can significantly increase their absorption dose, especially in infants with very low weight. © 2020, Babol University of Medical Sciences. All rights reserved