西门子磁共振射频系统原理与故障分析

射频系统由调制器Modulator、射频功率放大器RF Power Amplifier、阻抗匹配网络Impedance Matching也可称为调谐单元Tuning Unit、发射线圈Transmit coil和接收线圈Receive coil等组成。射频子系统(RF system)是MRI系统中实施射频激励并接收和处理RF信号的功能单元,射频系统不仅要根据扫描序列的要求发射各种翻转角的射频波,还要接收成像区域内氢质子的共振信号。因此,射频系统是磁共振成像仪中最关键的部分之一。文章详细介绍了西门子磁共振射频系统的原理、结构和组成,分析了射频系统故障和排除的方法。希望通过对磁共振射频系统的介绍和射频系统故障分析和排除的举例,有助于从事磁共振安装、调试和维修保养的工程技术人员对磁共振成像仪有更深入的了解。     

MR-5002型射频功率放大器几例故障的维修

射频功率放大器是每台MRI系统所必配的重要部件,它的作用是产生足够大的射频脉冲并将其送到发射线圈以产生射频磁场,使得被检体的氢原子核在磁体内产生核磁共振.MR-5002型射频功率放大器由美国EMI公司生产制造,它的最大峰值输出功率为5000W.由飞利浦公司生产的部分MRI设备就配备该型射频功率放大器.笔者在工作中遇到几次因该放大器故障而使整个MRI设备无法工作的情况,经过努力,均将故障排除,为医院节约了支出和缩短了停机时间.     

GE/Elscint 2T磁共振射频系统组成及常见故障分析

射频系统是磁共振设备中最基本的部分，包括发射和接收2部分，当射频系统中任一环节出现问题时，都会使整个设备完全瘫痪。此外，由于该部分电路都是由硬件完成，部件多、功率大、易损坏，出现故障的几率相对大一些，因此研究分析排除这方面的故障就有较大的现实意义。本文就GE／E1scint2T磁共振射频系统组成做一详细说明，并进一步说明射频系统发生故障时的分析思路。     

磁共振常见射频系统发射通道故障分析

本文论述了磁共振射频系统的组成，射频系统常见通道故障的分析以及排除方法。     

关于核磁共振谱仪系统检修的探讨

ＡＳＭ－０１６Ｐ核磁共振成像系统中的谱仪是ＡＮ９１０１型，它是ＡＳＭ－０１６Ｐ核磁共振成像系统的实时控制单元。ＡＮ９１０１对成像系统获取核磁共振信号的整个过程进行实时控制，而且可以接受外部的触发信号，使脉冲序列和外部事件实现同步，亦可向外界发送同步信号，完成与外部设备的同步操作。谱仪是ＭＲ成像系统中最基本的部分，当谱仪系统中任一环节出现问题时都会使整个设备完全瘫痪，连最基本、最简单的任务也不能完成，因此研究如何分析、排除这方面的故障就有较大的现实意义。最近，我们在排除ＡＳＭ－０１６Ｐ核磁共振谱仪…     

核磁共振仪射频系统故障分析

本文主要介绍核磁共振仪射频系统原理和故障分析，通过一个故障的维修过程来探讨核磁共振仪射频系统的最佳维修方法。     

MRI主要子系统可排除故障中文文献的分析

MRI系统由数个功能相对独立的子系统组成，其中射频、梯度、线圈、磁体子系统是MRI中最主要和最复杂的子系统。各子系统又分别由不同的构件组成，通过对1995-2006年期间CBMDisc（中国生物医学文献数据库1中MRI系统可排除故障中文文献的分析，从预防和排除MRI故障的角度，阐述了MRI各主要子系统的可排除故障的类型和发生频率，为MRI的研发和临床应用提供可信的参考数据。     

MR-5002型射频功率放大器故障维修2例

0引言 美国ENI公司生产的MR-5002型射频功率放大器，在20世纪初广泛应用于磁共振系统，我院飞利浦T5-NT磁共振系统配置的射频放大器即是MR-5002射频放大器。随着T5-NT磁共振系统服役期的延长，其射频放大器故障发生率也相应升高，笔者在近10a的临床应用中，总结了该射频功率放大器的一些维修方法和技巧，现介绍其2例故障的排除过程，供参考。     

ECG-6511型心电图机故障检修一例

故障现象：接通电源后开机，记录笔偏向一边，调整基线调节钮不起作用，既无定标信号，又无心电信号。其他键控功能正常。 分析与检修：记录笔单偏是一种比较复杂的故障现象，排除这类故障，首先要确定故障发生的部位，然后再逐级进行检查。可以利用机器面板上的各种功能按键开关和调节器来压缩故障部位。接通电源开关，将等待／工作开关置于工作位置，工作方式选择开关设定在STOP位置，这时记录笔偏向一边，而且调整基线移位钮不起作用。这种故障的原因通常发生在主放大器电路。     

T2000MRI特殊故障的检修

故障现象　我院Ｔ2 0 0 0型ＭＲＩ是深圳九天联谊公司生产的 ,作常规扫描时 ,各个功能指令未见异常 ,但扫描结果没有图像显示 ,只出现几个亮点。故障原因分析　根据核磁共振成像原理及信号形成过程 ,出现上述故障的原因初步判断为射频及梯度有故障。使机器在扫描状态 ,用示波器检查ＲＦ口正常 ,用钳流表测量梯度功放输出线 ,发现梯度功放输出时有时无 ;再用示波器检测梯度发生器输出口 ,结果也是一样。故障原因确定在梯度发生器 (即 30 40板 )上。由于此线路板是厂家从英国购进的 ,英国没有提供任何图纸资料。如更换此线路板需要 2 9.5万元…     

Workplace measurement of respirator effects using respiratory inductive plethysmography

A useful system to study the cardiopulmonary effects of respirators in the workplace would be reliable, portable, and lightweight and would not encumber the nose or mouth or require modification to the respirator. Twenty men using such a system (which measured ventilatory parameters by respiratory inductive plethysmography [RIP]) were studied. The subjects all performed their usual jobs which involved some work with and some without a respirator. Twelve subjects used airline respirators and eight used air-purifying respirators. The RIP equipment measurements included respiratory frequency, tidal volume (VT), minute ventilation (V), and heart rate (HR). The RIP data from 20 other subjects was lost because of equipment malfunction, primarily lead separation in those whose jobs involved climbing around large workpieces. In general, the workers' cardiopulmonary parameters increased during respirator wear, probably because of a combination of factors, including the increased exercise of most respirator-requiring tasks and the weight and heat stress associated with the respirator and protective clothing. When the ventilatory parameters with and without a respirator were compared at the same heart rates, no significant differences were noted in VT for the entire group. Respiratory frequency, however, and V increased with respirator wear. The effects of respirators alone were found to be commonly confounded in the workplace by changes in protective clothing, exercise requirements, and ambient heat stress. Further improvements in the portable RIP system are needed before it can be accepted as a reliable ventilatory measurement device in the workplace.     

芬兰PLANMED乳腺机特殊故障分析

通过对芬兰PLANMED乳腺机的维修保障工作进行分析和探讨,掌握芬兰PLANMED乳腺机特殊故障（Err20）的出现原因及处理方法。对步进电机控制芯片UDN2916LB进行详细的分析,查明了Err20故障原因,对解决设备故障有积极的指导作用。综合分析及合理运用故障处理方法,准确判断了故障原因,为更换UDN2916LB芯片提供了技术支持。     

Stereotactic radiosurgery planning with ictal SPECT images

This paper is motivated by a clinical requirement to utilise ictal SPECT images for target localisation in stereotactic radiosurgery treatment planning using the xknife system which only supports CT and MRI images. To achieve this, the SPECT images were converted from raw (pixel data only) format into a part 10 compliant DICOM CT fileset. The minimum requirements for the recasting of a raw format image as DICOM CT or MRI data set are described in detail. The method can be applied to the importation of raw format images into any radiotherapy treatment planning system that supports CT or MRI import. It is demonstrated that the combination of the low spatial resolution SPECT images, depicting functional information, with high spatial resolution MRI images, which show the structural information, is suitable for stereotactic radiosurgery treatment planning.     

PRIMUS高能加速器MODULATOR INCOMPLATE故障

西门子PRI MUS加速器是一种全数字化机器,具有故障自动诊断报警系统,它所显示的30#MODULATOR I N-COMPLATE联锁故障,并非都是由调制器和速调管故障所发生,它们的外围电路发生故障而引发该联锁的几率也相当高。因此,分析和弄清故障发生的现象和机理,在工作中具有实际作用。     

超声联合磁共振成像在胎儿疾病诊断中的应用

目的: 探讨超声联合核磁共振成像（magnetic resonance imaging,MRI）在临床胎儿疾病诊断中的应用。方法: 回顾性分析2015年1月—2019年7月177例超声检测胎儿胸腔或腹腔异常的患者,并通过MRI进一步检测,排除失访和未复查的病例,按照MRI诊断结果进行分组,并根据随访所获得的妊娠结局分析超声诊断准确率。结果: 超声和MRI检测胎儿呼吸系统、泌尿系统异常的结果较一致,超声和MRI完全符合的比例分别45.9%和53.8%;在胎儿消化系统异常和卵巢囊肿方面,MRI多补充超声结果,MRI补充超声诊断的比例分别为57.7%和80%。MRI诊断胎儿消化系统疾病时,其准确率高于超声（P<0.05）;MRI与超声检测结构异常和回声增强的准确率之间差异无统计学意义（均P>0.05）。结论: 超声检测胎儿呼吸系统和泌尿系统疾病诊断信息不充分时可选择MRI诊断;超声检测胎儿消化系统异常和卵巢囊肿时,无论结构异常还是回声增强,建议MRI检测。     

Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging

Recently, the contraceptive implant Implanon has been introduced in several European countries. In comparison to the six-capsule preparation Norplant, the removal of this single-rod system should be associated with less complications. However, the removal of nonpalpable Implanon rods can be difficult because the implant is not always visible with ultrasound. The aim of this study was to find a radiologic method for the localization of Implanon implants that are nonpalpable and can not be detected by ultrasound. X-ray, ultrasound, computed tomography, and magnetic resonance imaging (MRI) were investigated as methods to localize Implanon in a pig chest preparation and in a woman with a nonpalpable implant. The implant in the woman could be localized unequivocally only by MRI. We conclude that MRI is the best method for the unequivocal localization of nonpalpable, ultrasonographically not detectable Implanon rods. To avoid unnecessary scar tissue formation, it may be appropriate to defer surgery for the removal until definitive localization.     

Central nervous system lesions in Malawian children: identifying the treatable

In Malawi, children with central nervous system (CNS) tumours are seldom able to be treated with curative intent. A study was undertaken of 29 children who underwent CNS MRI during a two year period. A combination of neoplastic and non-neoplastic diagnoses were noted, seven of which were revised on review. As a result an effective system has been set up for remote urgent review to guide prognosis and treatment. The opinion of a paediatric neuro-radiologist greatly assists in differentiating infectious and non infectious causes of CNS lesions and can enable the local team to effectively triage patients.     

BD FACSAriaIII流式细胞仪在血液学中的使用分析研究

目的：对BD FACSAriaIII流式细胞仪在应用中出现的故障原因进行分析、研究,为在科研工作中正确使用该仪器提供依据。方法：通过对2012-2013年实验血液学国家重点实验室技术平台BD FACSAriaIII流式细胞仪的使用情况进行统计,对使用过程中出现的常见故障和需要由厂商工程师现场解决的故障进行统计,总结出高发故障的原因及解决方法。结果：通过对BD FACSAriaIII流式细胞仪的故障进行分析,为高通量流式细胞分选仪的正确使用提供指导,提高仪器运行的稳定性。结论：正确的使用和良好的维护有助于保证BD FACSAriaIII流式细胞仪的正常运行,从而确保科研工作的顺利进行。     

Feasibility of a telemedicine framework for collaborative pacemaker follow-up

We propose a telemedicine framework for remote and manufacturer independent pacemaker (PM) follow-up. The main goal is to provide the caregiver at the point-of-care with an efficient screening method to identify possible malfunction of the pacing system in collaboration with the specialist at the PM clinic. The concept was evaluated in a clinical trial on 44 patients (mean age 76 years). A total of 62 electrocardiogram (ECG) recordings were transmitted using a mobile PM follow-up unit. Using the automatic classification algorithm, 32 PMs were classified as 'OK' and eight PMs were classified as 'not OK'. In four cases a prediction regarding the working status of the PM was not possible. The signal processing classification was confirmed by expert classification (manual review of the ECG). The results indicate that the proposed PM follow-up concept has the potential to work as an efficient screening method and may spare a significant number of patients the burden of having to travel to specialized PM clinics.     

基于外部基准框架的SPECT与MRI／CT的刚性配准及融合

设计了一种简便、有效的基于外部基框架的SPECT（单光子发射型计算机断层）与MRI／CT的刚性配准及融合的方法。在对图像进行一值化分割的基础上,运用侵蚀,扩张等图像处理算法确定图像中用于配准的相应点的坐标、然后利用这些对应点最小化代价函数并获得一个最佳刚性变换,实现图像的精确配准及融合显示。通过对作为外部基准框架的N型支架的设计及成像过程中对其与病人相对位置的严重限制,最大程度地减少成像中的误差,实验表明该方法能有效地实现SPECT与MRI／CT的配准及配合。