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51.
Gemma  G.  Kenter  Marij  J.P.  Welters  Rob  P.M.  Valentijn  梁伟 《中国处方药》2009,(12):61-61
背景及目的:最近,关于叶酸的安全性引起了广泛的关注,尤其是其与肿瘤风险的关系。本研究是通过两项随机对照试验评价叶酸和维生素B治疗对肿瘤发生率和全因死亡率的影响。  相似文献   
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OBJECTIVE: Determination of the impact of inaccuracies in the determination and setup of the target point in stereotactic radiosurgery (SRS) on the expectable complication and control probabilities. METHODS: Two randomized samples of patients with arteriovenous malformation (AVM) (n=20) and with brain metastases (n=20) treated with SRS were formed, and the probability for complete obliteration (COP) or complete remission (CRP), the size of the 10 Gy-volume in the brain tissue (VOI10), and the probability for radiation necrosis (NTCP) were calculated. The dose-effect relations for COP and CRP were fitted to clinical data. Target point deviations were simulated through random vectors and the resulting probabilities and volumes were calculated and compared with the values of the treatment plan. RESULTS: The decrease of the relative value of the control probabilities at 1mm target point deviation was up to 4% for AVMs and up to 10% for metastases. At 2 mm the median decrease was 5% for AVMs and 9% for metastases. The value for the target point deviation, at which COP and CRP decreased about 0.05 in 90% of the cases, was 1.3 mm. The increase of NTCP was maximally 0.0025 per mm target point deviation for AVMs and 0.0035/mm for metastases. The maximal increase of VOI10 was 0.7 cm(3)/mm target point deviation in both patient groups. CONCLUSIONS: The upper limit for tolerable target point deviations is at 1.3mm. If this value cannot be achieved during the system test, a supplementary safety margin should be applied for the definition of the target volume. A better accuracy level is desirable, in order to ensure optimal chances for the success of the treatment. The target point precision is less important for the minimization of the probability of radiation necroses.  相似文献   
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OBJECTIVES: The purpose of this retrospective study was to determine whether objective assessment of cardiac shifting on two-dimensional ultrasonography can predict postnatal outcome in fetuses with isolated left-sided congenital diaphragmatic hernia (CDH). MATERIALS AND METHODS: Still images at the level of the four-chamber view were obtained in 23 fetuses with left-sided CDH. A group of 12 fetuses (3 non-survivors and 9 survivors) were examined at two periods, between 20 and 30 weeks and between 31 and 40 weeks. A further 11 fetuses (2 non-survivors and 9 survivors) were examined between 31 and 40 weeks. Fetal heart axis and position were determined manually and associated with postnatal outcome. RESULTS: The cardiac axis remained constant in the 9 survivors (15.5 +/- 3.2 versus 17.2 +/- 3.3, p = 0.71) and 3 non-survivors (19.0 +/- 11.5 versus 18.5 +/- 11.8, p = 0.97). There was no statistical difference between the 9 survivors and 3 non-survivors at the two periods. Cardiac displacement remained constant in the 9 survivors (0.2 +/- 0.02 versus 0.2 +/- 0.02, p = 0.32) but increased significantly in the 3 non-survivors (0.2 +/- 0.04 versus 0.4 +/- 0.02, p = 0.015). The difference between survivors and non-survivors was statistically significant between the18 survivors and 5 non-survivors examined between 31 and 40 weeks of gestation (0.2 +/- 0.02 versus 0.4 +/- 0.02, p = 0.037). CONCLUSION: This study does not support the hypothesis that objective assessment of mediastinal shift in fetuses with left-sided CDH has a role in predicting postnatal outcome before fetal viability, which is when it would be more useful for counseling patients regarding whether to continue with the pregnancy or to opt for termination.  相似文献   
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