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In radiation therapy with high-energy photon beams (E > 10 MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature.

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Creutzfeldt-Jakob Disease (CJD) is a rare rapidly progressive neurodegenerative disease. The diagnosis of CJD is based on magnetic resonance imaging (MRI) findings, electro-encephalography (EEG), or 14-3-3 protein detection. We report a case of a previously-healthy 72 years old woman, with evidence of coronavirus disease 2019 (COVID-19), who complained of behavioral changes and rapidly progressive dementia. While hospitalization, she didn't have orientation to time and place and repeated an irrelevant sentence in response to questions. Also, anomia and impaired comprehension was observed. Myoclonic jerks, abnormal signal intensity at bilateral parieto-occipital cortices in MRI, periodic sharp wave complexes in EEG, and increased lactate dehydrogenase in cerebrospinal fluid (CSF), highly recommended CJD for her. This is the second case of CJD after COVID-19 during this pandemic, which can be an alarm to clinicians about the silent impact of COVID-19 on the central nervous system.

Objectives: Percutaneous and transcutaneous posterior tibial nerve stimulation (PTNS and TTNS) showed a promising effect on overactive bladder (OAB) and interstitial cystitis/painful bladder syndrome. We aimed to give a systematic review and meta-analysis on the efficacy and safety of these therapeutic methods as well. Methods:We searched studies available on PubMed, Embase, Cochrane, Scopus, Web of Science, and ProQuest on March 31, 2021, to find both published and unpublished studies. The retrieved articles were screened by two independent researchers and then the selected studies were critically appraised by Cochrane risk-of-bias tool for randomized trials, and Joanna Briggs Institute's checklist for quasi-experimental studies. Finally, the results of studies were synthesized using Review Manager (RevMan) 5.4 statistical software when the data were homogenous. The meta-analysis was performed by calculating the effect size (mean difference) and their 95% confidence intervals (CIs).