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1.
The use of radiation for primary liver cancers has historically been limited because of the risk of radiation-induced liver disease. Treatment fields have become more conformal because of several technical advances, and this has allowed for dose escalation. Stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiotherapy, is now able to safely treat liver tumors to ablative doses while sparing functional liver parenchyma by using highly conformal therapy. Several retrospective and small prospective studies have examined the use of SBRT for liver cancers; however, there is a lack of well-powered randomized studies to definitively guide management in these settings. Recent advances in systemic therapy for primary liver cancers have improved outcomes; however, the optimal selection criteria for SBRT as a local therapy remain unclear among other liver-directed options such as radiofrequency ablation, transarterial chemoembolization, and radioembolization.  相似文献   
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目的 观察基于蒙特卡罗模拟的小动物质子CT (PCT)的最优射束能量。方法 采用蒙特卡罗模拟建立PCT系统,分别以不同能量质子束对体模1、2进行扫描,并以滤波反投影法重建图像,观察其中不同材料质子的相对阻止本领(RSP)值、重建误差、空间分辨率、信号噪声比(SNR)及对比噪声比(CNR),评估图像质量,筛选最优质子射束能量。结果 重建图像中,特氟龙、聚丙烯及骨骼等效材料的RSP的相对误差均随质子能量增高而先降后升,于质子能量为130 MeV时最小,分别为0.76%、0.08%及0.05%。体模1内4种插件的SNR和CNR均随质子能量增高而降低。重建图基本无法分辨体模2内直径0.2 mm铝插件,质子能量较低时可分辨直径0.4 mm铝插件;不同质子能量下均可分辨直径0.8 mm铝插件,且空间分辨率随质子能量增高而提升,质子能量大于130 MeV后变化趋缓。结论 以蒙特卡罗模拟的小动物PCT平台的最优成像质子射束能量为130 MeV。  相似文献   
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Ionising radiation causes secondary tumours and/or enduring cognitive deficits, especially in children. Proton radiotherapy reduces exposure of the developing brain in children but may still cause some lasting effects. Recent observations show that ultra-high dose rate radiation treatment (≥40 Gy/s), called the FLASH effect, is equally effective at tumour control but less damaging to surrounding tissue compared with conventional dose rate protons (0.03–3 Gy/s). Most studies on the FLASH effect in brain and other tissues with different radiation modalities (electron and photon radiation), show FLASH benefits in these preclinical rodent models, but the data are limited, especially for proton FLASH, including for dose, dose rate and neurochemical and neurobehavioural outcomes. Tests of neurocognitive outcomes have been limited despite clinical evidence that this is the area of greatest concern. The FLASH effect in the context of proton exposure is promising, but a more systematic and comprehensive approach to outcomes is needed.  相似文献   
4.
Proton therapy is a form of particle therapy with physical properties that provide a superior dose distribution compared to photons. The ability to spare healthy, developing tissues from low dose radiation with proton therapy is well known. The capability to decrease radiation exposure for children has been lauded as an important advance in pediatric cancer care, particularly for central nervous system (CNS) tumors. Favorable clinical outcomes have been reported and justify the increased cost and burden of this therapy. In this review, we summarize the current literature for proton therapy for pediatric CNS malignancies, with a focus on clinical outcomes to date.  相似文献   
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Extracellular pH changes may constitute significant signals for neuronal communication. During synaptic transmission, changes in pH in the synaptic cleft take place. Its role in the regulation of presynaptic Ca2+ currents through multivesicular release in ribbon‐type synapses is a proven phenomenon. In recent years, protons have been recognized as neurotransmitters that participate in neuronal communication in synapses of several regions of the CNS such as amygdala, nucleus accumbens, and brainstem. Protons are released by nerve stimulation and activate postsynaptic acid‐sensing ion channels (ASICs). Several types of ASIC channels are expressed in the peripheral and central nervous system. The influx of Ca2+ through some subtypes of ASICs, as a result of synaptic transmission, agrees with the participation of ASICs in synaptic plasticity. Pharmacological and genetical inhibition of ASIC1a results in alterations in learning, memory, and phenomena like fear and cocaine‐seeking behavior. The recognition of endogenous molecules, such as arachidonic acid, cytokines, histamine, spermine, lactate, and neuropeptides, capable of inhibiting or potentiating ASICs suggests the existence of mechanisms of synaptic modulation that have not yet been fully identified and that could be tuned by new emerging pharmacological compounds with potential therapeutic benefits.  相似文献   
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Chemical exchange saturation transfer (CEST) is an MRI technique that allows mapping of biomolecules (small metabolites, proteins) with nearly the sensitivity of conventional water proton MRI. In living organisms, several tissue‐specific CEST effects have been observed and successfully applied to diagnostic imaging. In these studies, particularly the signals of proteins showed a distinct correlation with pathological changes. However, as CEST effects depend on various properties that determine and affect the chemical exchange processes, the origins of the observed signal changes remain to be understood. In this study, protein aggregation was identified as an additional process that is encoded in the CEST signals of proteins. Investigation of distinct proteins that are involved in pathological disorders, namely amyloid beta and huntingtin, revealed a significant decrease of all protein CEST signals upon controlled aggregation. This finding is of particular interest with regard to diagnostic imaging of patients with neurodegenerative diseases that involve amyloidogenesis, such as Alzheimer's or Huntington's disease. To investigate whether the observed CEST signal decrease also occurs in heterogeneous mixtures of aggregated cellular proteins, and thus prospectively in tissue, heat‐shocked yeast cell lysates were employed. Additionally, investigation of different cell compartments verified the assignment of the protein CEST signals to the soluble part of the proteome. The results of in vitro experiments demonstrate that aggregation affects the CEST signals of proteins. This observation can enable hypotheses for CEST imaging as a non‐invasive diagnostic tool for monitoring pathological alterations of the proteome in vivo.  相似文献   
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Summary

The mechanism of the radioprotective action of cyanide has been investigated with rat-thymocyte suspensions, cultured human-kidney cells and with mice.

Cyanide does not protect cells in vitro. In the thymocyte system, cyanide has instead a slight radiosensitizing action. The presence of cyanide after the irradiation causes an inhibition of the development of eosin permeability.

In mice, cyanide produces a hypoxia of the spleen and bone-marrow. This hypoxia explains the protection against a lethal dose of x-rays.  相似文献   
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