医用空气消毒净化机预防医院感染的作用研究

目的解决医院重点部门在进行各种医疗活动中空气再污染的动态消毒问题。方法使用肯格王牌净化机对重点部门的空气进行静、动态消毒,监测消毒灭菌效果;同时对使用该机前、后两年相关医院感染病例进行统计对比。结果静态(臭氧)消毒后的空气细菌总数为零;动态消毒中空气细菌总数符合国家关于Ⅱ、Ⅲ类的标准;与空气因素直接有关的不同种部位医院感染率下降。结论使用肯格王牌YKX/G、YDX/Y型系列空气净化机消毒灭菌效果明显,是预防医院感染新型的消毒方法和采取的重要措施之一。     

动态及延时增强磁共振成像对肝血管瘤诊断的评价

目的:研究动态增强及延迟增强扫描磁共振成像对肝血管瘤的诊断价值。材料和方法:34例肝血管瘤病人行常规MRT1WI、T2WI横断面扫描。经肘静脉手推团注0.1mmol/kg体重Gd-DTPA后,再推入10ml生理盐水冲洗后(推入时间5~6s)行射频毁坏傅立叶采集稳态技术T1WI动态增强扫描及延迟增强扫描,分析病灶及邻近肝实质增强。结果:共发现肝血管瘤病灶67个。动态增强见46个病灶呈边缘不连续样的结节样强化,21个病灶呈周边不规则强化或迅速强化充填;5个病灶动态增强早期见引流静脉强化,14个瘤周肝实质强化。延迟增强扫描见53个病灶完全充填强化,14个病灶显示斑片状或裂隙状的低信号未充填区。结论:在磁共振成像检查中,动态增强扫描能够显示肝血管瘤及邻近实质强化方式,延迟增强显示病灶的充填程度,两者结合更有利于肝血管瘤的诊断。     

Improving model selection by nonconvergent methods

Many techniques for model selection in the field of neural networks correspond to well established statistical methods. For example, architecture modifications based on test variables calculated after convergence of the training process can be viewed as part of a hypothesis testing search, and the use of complexity penalty terms is essentially a type of regularization or biased regression. The method of “stopped” or “cross-validation” training, on the other hand, in which an oversized network is trained until the error on a further validation set of examples deteriorates, then training is stopped, is a true innovation since model selection doesn't require convergence of the training process. Here, the training process is used to perform a directed search of the parameter space for a model which doesn't overfit the data and thus demonstrates superior generalization performance. In this paper we show that this performance can be significantly enhanced by expanding the “nonconvergent method” of stopped training to include dynamic topology modifications (dynamic weight pruning) and modified complexity penalty term methods in which the weighting of the penalty term is adjusted during the training process. On an extensive sequence of simulation examples we demonstrate the general superiority of the “extended” nonconvergent methods compared to classical penalty term methods, simple stopped training, and methods which only vary the number of hidden units.     

The clinical significance of gadolinium enhancement of lumbar disc herniations and nerve roots on preoperative MRI

The clinical significance of preoperative gadolinium DPTA enhancement around disc herniations and in the epidural space on MRI is not clear. The relation of nerve root enhancement to dysfunction also remains controversial. To investigate the clinical significance of contrast enhancement we looked at the symptoms and signs and gadolinium DPTA-enhanced images of 71 consecutive surgical candidates in a standardised fashion. Annular rupture and disc enhancement were found to be closely related, and correlated with sensory loss and paresis, respectively. Nerve root enhancement was found to be related to neurological deficits in general and sensory impairment in particular. Received: 4 June 1997 Accepted: 10 March 1998     

Serial MR observation of cortical laminar necrosis caused by brain infarction

To examine the chronological changes characteristic of cortical laminar necrosis caused by brain infarction, 16 patients were repeatedly examined using T1-, T2-weighted spin-echo, T2^*-weighted gradient echo, fluid attenuated inversion recovery (FLAIR) images, and contrast enhanced T1-weighted images at 1.0 or 1.5 T. High intensity cortical lesions were visible on the T1-weighted images from 2 weeks after ictus and became prominent at 1 to 3 months, then became less apparent, but occasionally remained at high intensity for 2 years. High intensity cortical lesions on FLAIR images became prominent from 1 month, and then became less prominent from 1 year, but occasionally remained at high intensity for 2 years. Subcortical lesions did not display high intensity on T1-weighted images at any stage. On FLAIR images, subcortical lesions initially showed slightly high intensity and then low intensity from 6 months due to encephalomalacia. Cortical lesions showed prominent contrast enhancement from 2 weeks to 3 months, but subcortical lesions were prominent from 2 weeks only up to 1 month. T2*-weighted images disclosed haemosiderin in 3 of 7 patients, but there was no correlation with cortical short T1 lesions. Cortical laminar necrosis showed characteristic chronological signal changes on T1-weighted images and FLAIR images. Cortical short T1 lesions were found not to be caused by haemorrhagic infarction. Received: 27 March 1998 Accepted: 23 July 1998     

Growing Hierarchical Tree SOM: An unsupervised neural network with dynamic topology

In this paper we introduce a tree structured self-organizing network, called the Growing Hierarchical Tree SOM (GHTSOM), that combines unsupervised learning with a dynamic topology for hierarchical classification of unlabelled data sets. The main feature of the proposed model is a SOM-like self-organizing process that allows the network to adapt the topology of each layer of the hierarchy to the characteristics of the training set. In particular the self-organization is obtained in two steps: the first one concerns the learning phase and is finalized with the creation of a tree of SOMs, while the second one is in regard to the clustering phase and provides the formation of classes for each level of the tree (hence self-organization not only for training but also for the creation of topological connections). As a result the network works without the need for user-defined parameters. Experimental results are proposed on both synthetic and real data sets.     

应用动态APACHEII评分指导门静脉高压症外科治疗

目的　应用 APACHE II连续评分判断门静脉高压症合并上消化道出血患者不同手术方式的预后。方法　对本院 2 0 0 2 .1～ 2 0 0 3.1 2间门静脉高压症合并上消化道出血手术的 4 7例患者 ,术前、术后 1、3、5、7d APACHE II连续评分 ,比较死亡组和非死亡组、断流手术组与断流加分流手术组 (联合组 )预后、死亡率与评分值关系。结果　 4 7例患者中断流手术 33例 ,分流手术 1 4例。死亡组术后 APACHE II连续评分逐日上升或居高不下且与生存组有显著差异 ;断流组术前评分低于联合手术组但无显著差异 ,而术后 1、3d断流组评分显著低于联合手术组 ,术后第 5、7d两组评分无显著性差异表现 ;断流组的死亡率小于联合手术组 ,但无显著性差异 ;利用 APACHE II术后死亡危险性 R公式对患者术前、术后 1、3、5和 7d APACHEII死亡危险系数评估 ,提示断流和联合手术两组不同时段的 APACHE II死亡危险性预测数中术后 7d的数值与实际发生数最为接近。结论　动态 APACHE II评分适用于门静脉高压合并上消化道手术预后的评估 ;断流术与联合手术早期评分有差异 ,5 d后无显著差异 ,且两者死亡率无显著差异 ;术后第 7d APACHE II死亡危险性预测数值与实际发生数最为接近     

动力髋螺钉治疗股骨粗隆间骨折35例分析

目的 :探讨动力髋螺钉 ( DHS)在股骨粗隆间骨折治疗中的应用价值。方法 :对35例股骨粗隆间骨折病例应用 DHS进行治疗 ,并评价其疗效。结果 :平均随访 1 5个月 ,所有病例均在 8～ 1 4周骨折愈合 ,优良率 94.3%。结论 :DHS手术操作容易掌握 ,固定牢靠 ,患者可早期活动 ,并发症少 ,是治疗股骨粗隆间骨折的理想方法。     

薄荷醇和氮酮对水杨酸体外透皮吸收的促进作用

目的 研究薄荷醇和氮酮单独使用及合用时对水杨酸的促透作用。方法 采用离体鼠皮作透皮吸收试验。结果 薄荷醇对水杨酸的促透作用强于氮酮,而两药合用时的促透作用并不比分别使用时的促透效果好,在合用浓度较高时,甚至表现促透作用降低。     

肾综合征出血热发病率的ANN预测模型

目的 :探讨ANN时间序列预测模型在疾病发病率或死亡率预测上的应用前景。方法 :利用动态学习比率BP算法以双曲正切函数为功能函数的非线性时间序列预测方法。结果 :建立HFRS发病率的ANN预测模型 ,其预测精度高。结论 :BP人工神经网络可以用于疾病发病率或死亡率的预测