GE SIGNA 0.5T MR冷头系统故障分析

1故障现象磁共振(MR)液氦蒸发率超标,日消耗液氦大于2%,并不断升高,液氦低温容器压力大于27.579kPa(4psi),液氦渗透流量达到满刻度(10SCFH)。2故障分析SIGNA0.5TMR超导磁体冷却系统是一个复杂的系统,它由磁体中的液氦冷屏、冷头、氦压缩机和冷水机组系统组成。冷屏是磁体的组成     

Siemens impac 1．0MR液氦指示故障检修及原理分析

我院MR为西门子Impact 1．0机型。其超导磁体内的低温环境是靠磁体容器内被镶嵌在液氮容器中的冷头，外面的氦压缩机、热交换器以及冰水机组所组成的制冷系统来维持。液氦处在真空封闭的磁体内，其容量多少是靠液氦监测系统来测量和显示的。具体电路由D80、D83、D88、D89、D90电路板组成。液面指示系统可以了解冷头工作情况以及液氦的余量。我院的MRI每天损耗液氦量约0．15％，观察液氦的损耗数能了解冷头的工作效率，同时提醒在必要时及时补充液氦。     

超导磁共振的日常维护

磁共振 (ＭＲ)是医院的一种大型医疗设备 ,它系统复杂 ,软硬件环节多 ,技术含量高 ,知识覆盖面广。尤其是超导型磁共振 ,它的持续正常运行 ,要靠精心、到位的日常维护来保证。　　 1.制冷系统维护　　超导型磁体是由处于超导状态下的线圈通电后产生的 ,超导状态由超低温的液氦 (氦的沸点温度是- 2 69℃ )来提供。由于液氦的价格很高 ,为减少液氦的消耗 ,ＭＲ磁体在液氦容器外又加了三层绝热层。最外层是真空层 ,它在液氦容器与环境温度之间起绝热作用。中间两层叫冷屏 ,它进一步把氦容器与外界隔离开来 ,使环境温度很难渗入。冷屏里的冷氦气…     

朗润1.5T超导磁共振制冷系统的维护保养

随着医学影像技术的不断发展,超导磁共振由于其磁场更稳定、更均匀以及场强更高的特点,在影像学诊断中发挥着至关重要的作用。超导,是指某些金属导体在温度降到接近绝对零度(-273.15℃)时,表现出的零阻值特性。氦作为所有已知物质中沸点最低的物质,其沸点为4.2 K,利用液氦可获得接近绝对零度的低温,为超导线圈建立和保持超导环境。但是作为超导磁共振理想的制冷介质,受制于氦气资源和制氦工艺,当前用于磁共振的液氦资源大多依赖进口,因此液氦价格昂贵。     

超导MRI磁体无液氦改造探讨

该文从国内超导磁共振成像仪（MRI）使用现状出发,在液氦市场的供求危机中,申述了超导MRI磁体无液氦改造的重要意义,并根据企业的制作流程,提出了无液氦改造操作的若干实践与设想,为国内超导MRI制造与使用提供了重要的价值取向。     

浅淡超导磁共振机器在加充液氦时应注意的几点问题

超导磁共振机器为了能使机器正常工作 ,就要使体线圈处于一个超导状态。所谓超导是指某些金属导体在温度降到接近绝对温度 0即 - 2 73 15℃的时候 ,电阻几乎完全消失。这种现象叫超导现象。为了使线圈长期处于超导环境中 ,就要用液氦来进行降温处理 ,那么随着液氦的不断的消耗蒸发 ,就存在一个定期加充液氦的问题 ,下面就在加充液氦过程中应该注意和可能出现的几个方面的问题 ,就自己在工作中的一点体会简单说明一下。一、液氦在机器内的液面高度当机器工作一段时间后随着液氦的蒸发 ,液面下降到 53%时 ,应进行加充液氦。因为在加充液氦前要…     

超导磁共振设备的安全维护与保养

在超导磁共振设备的使用过程中,由于涉及到强磁场、射频场、液氦等诸多不安全因素,因此,认识磁共振设备的安全和维护保养注意事项十分必要。本文总结了超导磁共振设备的安全维护与保养要点。     

超导磁共振低温系统的维护

超导MRI(磁共振成像)设备必须使用液氦作为制冷介质，为超导线圈建苞和保持环境温度(4．2K)，因此磁体采用多层真空绝热结构，但由于结构支撑等多种因素，不可能完全阻上热传导，所以需用液氦以蒸发的形式带出导入的热量，以维持4-2K的温度。为减少液氦的蒸发，超导磁共振设备上装有制冷系统，用来提供冷量减少液氦蒸发。制冷系统由冷头、压缩机、水冷机组3部分组成；冷头是制冷部件，为超导线圈提供20K、77K两级低温，它是一个膨胀机，经过压     

MR冷头更换应注意的几个问题

MR普遍采用小型制冷机制取低温，冷头是其主要的制冷部件。氦压机循环的高压氦气在冷头中经过膨胀，将冷量贮存于冷头中的蓄冷材料，通过缸套上的铟垫圈将冷量导出，提供给磁体的冷屏，使超导线圈在液氦里保持4．2K（-269℃）的环境温度，降低液氦消耗。     

磁共振冷水机故障维修分析

阿尔西公司的MEDICOOL/CH系列医用冷水机组是一种特制的风冷式冷水机组,用于冷却磁共振设备在运行过程中零部件所产生的热量.目前有两台该系列型号为10P6R407C的冷水机,随磁共振一起安装,一台用于梯度冷却,另一台用于液氦压缩机冷却.使用中由于环境问题,机组保养等问题造成了磁共振冷水机设备的一系列故障.笔者详细分析这两台冷水机在运行过程中曾出现几次故障,并将故障解决的过程梳理成文供同行参考.     

Improving quality: bridging the health sector divide.

ISSUE: All too often, quality assurance looks at just one small part of the complex system that is health care. However, evidently each individual patient has one set of experiences and outcomes, often involving a range of health professionals in a number of settings across multiple sectors. ADDRESSING THE ISSUE: In order to solve the problems of this complexity, we need to establish high-quality electronic recording in each of the settings. In the UK, primary care has been leading the way in adopting information technology and can now use databases for individual clinical care, for quality assurance using significant event and conventional auditing, and for research. BUILDING TOWARDS A SOLUTION: Before we can understand and quality-assure the whole health care system, we need electronic patient records in all settings and good communication to build a summary electronic health record for each patient. Such an electronic health record will be under the control of the patient concerned, will be shared with the explicit consent of the patient, and will form the vehicle for quality assurance across all sectors of the health service.     

Forecasting the number of patients with end-stage renal disease (Model of the system)

The authors are dealing with the renal replacement therapies in Hungary. They are on the opinion that in view fo patient flow renal replacement therapies (such as various methods of dialysis and kidney transplantation) can be considered as one system. With analysing the number of patients in the past years they can establish that end-stage renal disease puts significant burden on the health insurance fund. According to their calculations the number of patients with end-stage renal disease will increase by 14-16% in the next few years if current trends continue. If we want to operate the system efficiently, we can reduce--up to a certain extent--the economic burden of dialysis by increasing the number of kidney transplantations.     

What's new in MR safety: the latest on the safe use of equipment in the magnetic resonance environment

Magnetic resonance (MR) scanners present a unique set of safety risks for the healthcare facility. In the space surrounding an MR scanner, ferromagnetic objects can become deadly projectiles, device cables can become hot enough to cause burns, and medical equipment can cease to function properly. ECRI detailed these risks--and provided recommendations to help healthcare facilities minimize them--in a December 2001 Guidance Article. In this supplement to that article, we detail some recent MR safety developments and offer additional guidance. In particular, we describe changes in the terminology used to characterize the safety of devices in the MR environment, we outline new guidance on MR safe practices published by the American College of Radiology, and we review the safety issues that facilities need to be aware of when implementing 3-tesla (3 T) MR systems. We also present an updated Starter List of medical device models that have been designed for use in the MR environment. In addition, supplementary articles address the use of ferromagnetic detection systems and the selection of a fire extinguisher for use in the MR environment.     

A framework for the investigation of pleiotropy in two‐sample summary data Mendelian randomization

Mendelian randomization (MR) uses genetic data to probe questions of causality in epidemiological research, by invoking the Instrumental Variable (IV) assumptions. In recent years, it has become commonplace to attempt MR analyses by synthesising summary data estimates of genetic association gleaned from large and independent study populations. This is referred to as two‐sample summary data MR. Unfortunately, due to the sheer number of variants that can be easily included into summary data MR analyses, it is increasingly likely that some do not meet the IV assumptions due to pleiotropy. There is a pressing need to develop methods that can both detect and correct for pleiotropy, in order to preserve the validity of the MR approach in this context. In this paper, we aim to clarify how established methods of meta‐regression and random effects modelling from mainstream meta‐analysis are being adapted to perform this task. Specifically, we focus on two contrastin g approaches: the Inverse Variance Weighted (IVW) method which assumes in its simplest form that all genetic variants are valid IVs, and the method of MR‐Egger regression that allows all variants to violate the IV assumptions, albeit in a specific way. We investigate the ability of two popular random effects models to provide robustness to pleiotropy under the IVW approach, and propose statistics to quantify the relative goodness‐of‐fit of the IVW approach over MR‐Egger regression. © 2017 The Authors. Statistics in Medicine Published by JohnWiley & Sons Ltd     

Adipose Tissue Dysfunction in Obesity: Role of Mineralocorticoid Receptor

The mineralocorticoid receptor (MR) acts as an essential regulator of blood pressure, volume status, and electrolyte balance. However, in recent decades, a growing body of evidence has suggested that MR may also have a role in mediating pro-inflammatory, pro-oxidative, and pro-fibrotic changes in several target organs, including the adipose tissue. The finding that MR is overexpressed in the adipose tissue of patients with obesity has led to the hypothesis that this receptor can contribute to adipokine dysregulation and low-grade chronic inflammation, alterations that are linked to the development of obesity-related metabolic and cardiovascular complications. Moreover, several studies in animal models have investigated the role of MR antagonists (MRAs) in preventing the metabolic alterations observed in obesity. In the present review we will focus on the potential mechanisms by which MR activation can contribute to adipose tissue dysfunction in obesity and on the possible beneficial effects of MRAs in this setting.     

A Bayesian approach to Mendelian randomisation with dependent instruments

Mendelian randomisation (MR) is a method for establishing causality between a risk factor and an outcome by using genetic variants as instrumental variables. In practice, the association between individual genetic variants and the risk factor is often weak, which may lead to a lack of precision in the MR and even biased MR estimates. Usually, the most significant variant within a genetic region is selected to represent the association with the risk factor, but there is no guarantee that this variant will be causal or that it will capture all of the genetic association within the region. It may be advantageous to use extra variants selected from the same region in the MR. The problem is to decide which variants to select. Rather than selecting a specific set of variants, we investigate the use of Bayesian model averaging (BMA) to average the MR over all possible combinations of genetic variants. Our simulations demonstrate that the BMA version of MR outperforms classical estimation with many dependent variants and performs much better than an MR based on variants selected by penalised regression. In further simulations, we investigate robustness to violations in the model assumptions and demonstrate sensitivity to the inclusion of invalid instruments. The method is illustrated by applying it to an MR of the effect of body mass index on blood pressure using SNPs in the FTO gene.     

Fostering needs assessment and access to medical rehabilitation for patients with chronic disease and endangered work ability: protocol of a multilevel evaluation on the effectiveness and efficacy of a CME intervention for general practitioners

Background

Studies show that endangered work ability (EWA) can be maintained or restored through medical rehabilitation (MR). For patients, general practitioners (GP) represent an important point of access to MR in outpatient care. However, many different barriers and shortcomings hinder GPs in both timely detection of the need for MR and the recognition of its potentials for their EWA-patients. These are necessary if GPs are to adequately inform patients about MR options and successfully support applications for MR. This study describes the evaluation of a continuing medical education (CME) module designed to improve rehabilitation-related practical performance of GPs regarding a) subjective satisfaction of GPs with the CME module, b) stability of attitudes and knowledge over time regarding rehabilitation, and c) subjective and objective changes in MR-related competencies needed to support MR applications.

Methods

This study is an open, non-randomised, pre-post-intervention study. The intervention involves a CME module for GPs (n = 1365) in the German state of Saxony-Anhalt on the topic of medical rehabilitation in connection with the federal German pension fund (Deutsche Rentenversicherung). The module will be initially held as regularly scheduled meetings in moderated GP quality circles (QC), and then offered as a written self-study unit. At the end it will be evaluated by the GPs. The study’s primary focus is on the organizational practice as measured by the number of approved MR applications supported by medical reports submitted by the participating GPs in the 6 months before and 6 months after the CME module. Other study aims involve measuring self-perceived competencies of GPs, as well as their attitudes towards and knowledge of rehabilitation (both upon completing the CME and 6 months later). In addition, the level of satisfaction with the CME module will be analysed among participating GPs and QC moderators (as CME facilitators).

Discussion

Implementing targeted CME on complex topics such as those involving barriers is possible, even promising, when using QCs and their moderators. Of particular importance is how aware moderating physicians are of the relevance of MR need detection and access.

Ethics and dissemination

The ethics committee of the Martin-Luther-Universität Halle-Wittenberg has registered this study under the number 2014–13. The study will be reported on in peer-reviewed journals and at national and international conferences. The results will be available to current and future initiatives aiming to improve detection of MR need and making MR accessible to EWEC patients needing such support to minimize the effects of chronic disease on their livess.

Trial registration number

German Clinical Trials Register (ID number DRKS00006188) and WHO International Clinical Trials Registry Platform, Universal Trial Number (UTN) U1111–1158-8334.

     

Extending the MR‐Egger method for multivariable Mendelian randomization to correct for both measured and unmeasured pleiotropy

Methods have been developed for Mendelian randomization that can obtain consistent causal estimates while relaxing the instrumental variable assumptions. These include multivariable Mendelian randomization, in which a genetic variant may be associated with multiple risk factors so long as any association with the outcome is via the measured risk factors (measured pleiotropy), and the MR‐Egger (Mendelian randomization‐Egger) method, in which a genetic variant may be directly associated with the outcome not via the risk factor of interest, so long as the direct effects of the variants on the outcome are uncorrelated with their associations with the risk factor (unmeasured pleiotropy). In this paper, we extend the MR‐Egger method to a multivariable setting to correct for both measured and unmeasured pleiotropy. We show, through theoretical arguments and a simulation study, that the multivariable MR‐Egger method has advantages over its univariable counterpart in terms of plausibility of the assumption needed for consistent causal estimation and power to detect a causal effect when this assumption is satisfied. The methods are compared in an applied analysis to investigate the causal effect of high‐density lipoprotein cholesterol on coronary heart disease risk. The multivariable MR‐Egger method will be useful to analyse high‐dimensional data in situations where the risk factors are highly related and it is difficult to find genetic variants specifically associated with the risk factor of interest (multivariable by design), and as a sensitivity analysis when the genetic variants are known to have pleiotropic effects on measured risk factors.     

GE1.5T核磁共振系统水冷机组自动旁路的改造

水冷机组是核磁共振制冷系统的组成之一,若其发生故障而不能及时发现并进行相应处理,会导致磁体压力上升,继而损失液氦。本文介绍如何用一些常用的简单元件组成一个自动旁路装置,对水冷机的水路进行相应改造,通过改造达到尽可能减少因水冷机故障而导致的氦压机停机时间。     

扫描优化对消除高磁场MRI伪影的效果研究

目的:探讨消除MRI伪影的各种手段。方法:原始组选择我院MR扫描仪伪影出现比较频繁的检查患者2000例,改进组为经过工程师和技师多方面分析问题后,采取适当抑制伪影措施后的检查患者2000例。结果:原始组伪影例数比例为18.45%,改进组伪影例数比例为4%,后者明显低于前者。结论:通过对二组病例研究,我们了解了伪影产生的原因及比较有效的消除手段。