口腔内金属材料对磁共振检查的影响

检测口腔内常用金属材料在磁共振检查时是否有伪影和伪影的严重程度。对２１种口腔内常用金属材料做了磁共振成像测试,磁共振仪磁场强度为１．５Ｔ,所用序列是梯度回波。铸金片、银汞合金、银尖等９种材料无伪影;钛合金和金属烤瓷成品有轻度伪影;牙用固位钉、椿钉等１０种材料有严重伪影。部分口腔内金属材料会引起严重伪影,影响图象质量,所以在做口腔颌面部和服部磁共振成像时,须引起重视。     

BLADE技术在3.0T磁共振克服关节扫描中运动伪影上的临床应用

目的:探讨在3.0T磁共振成像过程中,刀锋伪影较正(BLADE)技术在克服关节扫描中运动伪影方面的的的临床应用.方法:20例行四肢关节MR扫描检查的患者(肩关节10例,腕关节10例),在常规行T2WI常规扫描中出现不同程度的运动伪影,然后引入BLADE技术,扫描T2WI.,以能否清晰显示韧带肌腱而无重影为标准,对比常规序列扫描来评价BLADE技术在消除关节扫描过程中图像运动伪影方面的价值.结果:常规T2扫描出现运动伪影,用BLADE技术序列扫描出来的图像运动伪影消失,对比度明显提高.结论:应用BLADE技术进行扫描可以有效消除病人细微运动造成的运动伪影,获得高分辨率无伪影具有临床诊断价值的理想的图像.     

乳腺MR检查的常见伪影及解决方案

目的:分析乳腺MR检查中的常见伪影,探讨合理的解决方案,以提高乳腺MR图像质量及诊断准确性。方法:随机抽取我院100例行乳腺MR检查的图像资料,观察图像中出现的各种伪影及其表现,分析其产生的原因和影响因素。结果:乳腺MR图像的影像细节显示能力较强,图像质量与扫描技术关系密切,影响图像质量的常见伪影有:硬件相关伪影、图像处理相关伪影、运动相关伪影。结论:加强MR设备的使用管理,选择合理的扫描序列及参数,做好乳腺MR扫描的检查前准备及扫描,有助于提高乳腺病变的检出率。     

DSA图像中运动伪影的消除方法

由于病人存在着各种运动(如呼吸、肌肉运动、心脏运动、设备噪声),在成像过程中常会造成图像上出现伪影,干扰医生的正常诊断,为消除这种伪影,本文提出一种基于图像配准思想的全自动消除伪影的方法,该方法能够自动消除DSA图像中的大部分运动伪影,使DSA图像得到较好的增强,并为后面的血管分割和三维重建提供便利,是一种快速有效的方法。     

并行采集技术在老年人肝脏MR检查中的应用价值

目的探讨并行采集PAT技术（Parallel acquisition technique）对改善老年人肝脏磁共振扫描中出现的运动伪影的应用价值。方法对63例常规肝脏MRI检查出现呼吸运动伪影的老年患者（其中TrueFisp序列未出现明显伪影）,行iPAT技术扫描（TrueFisp冠状位、T1 Flash轴位）,对比常规序列扫描并评价iPAT技术对肝脏呼吸运动伪影消除的作用。三位磁共振专家对所得两组图像质量进行独立观察及评价,并进行对比分析。结果常规序列磁共振扫描63例肝脏呼吸运动伪影,其中Ⅰ、Ⅱ、Ⅲ和Ⅳ分别为0、15、33和15例,Ⅲ级以上影响诊断的病例共48例,占76%。采用iPAT技术扫描后,Ⅰ、Ⅱ、Ⅲ和Ⅳ分别为53、5、3和2例,Ⅲ级以下符合诊断要求的病例共58例,占92.1%,两者比较有显著差异（P〈0.05）。结论 iPAT技术可以明显缩短扫描的时间,在克服常规肝脏扫描中产生的呼吸运动伪影有明显的作用,可广泛应用于老年人肝脏常规检查产生的呼吸运动伪影校正中。     

能谱CT在去除腰椎术后金属伪影中的应用进展

多层计算机断层扫描(Multi-slice computed tomography,MSCT)具有时间及空间分辨率高的特点已经被广泛应用于脊柱术后评价,然而,因为术中植入金属植入物,CT图像由于其成像原理的限制,其图像质量受到金属植入物的严重影响,金属伪影大多来源于量子噪声、散射线和射束硬化效应,降低图像的对比度,使细微解剖结构显示不清,从而使得感兴趣区域的检测能力降低,其图像质量明显下降,甚至使临床医师做出错误的诊断,因此,为了做出更准确的腰椎术后并发症诊断和术后评估,使金属伪影最小化成为关键。能谱CT及其扫描及重建技术可以有效的去除腰椎术后产生的金属伪影,改善图像质量,本文能谱CT在腰椎术后金属伪影去除方面的应用进行综述。     

MRI典型和特殊故障排除方法

介绍了GE公司的磁共振机（Signa Mri 1．OT）的主机显示器、磁体监视器故障排除方法,以及解决伪影干扰的经验。     

金属植入物和磁共振检查

本文从金属材料的运动和移位,金属材料引起的伪影以及金属材料产生电流和发热三个方面阐述金属材料对磁共振检查的影响。     

英国公司在世界生物技术中的领先地位

两家英国公司,Amersham International plc 及 Celltech Biologics plc,在开发检测直肠结肠癌及卵巢癌的单克隆抗体中占世界领先地位。由 Cytogen Corporation(Princeton,New Jersey)开发的 Onco Scint CR/OV,是首例以单克隆抗体为基础的活体照影技术。该药将与由 Amercham Inte-rnational plc 制造的放射性照影剂 Indiclor 合用。     

MRI在腹部常见疾病的应用

随着MRI设备和技术的不断进展,为MRI诊断腹部实质脏器的疾病开辟了美好的前景。一般常用自旋回波程序,短TR和短TE,如TR=0.25s,TE=15ms,并增加采录数量,如激发8次,然后用平均信号的方法,可减少移动性伪影和噪声。亦可用部分翻转程序,作快速扫描,可在数秒至十余秒时间内完成成像程序,以减少移动性伪影。现将几种常见疾病的MRI表现叙述如下。     

Techniques et activités des hommes du Paléolithique supérieur sur le site de Wangfujing - Oriental Plaza, Pékin, Chine

More than 2000 pieces of cultural relics were unearthed from the Oriental Plaza site, including stone artifacts, bone artifacts, fossils, hematite powder, fire use remains and plant root and foliage. By analyzing these remains in refitting stone and bone artifacts, in experimentally producing some artifacts, and comparing with ethnologic data, it is concluded that the Oriental Plaza site is a seasonal human activity site, that humans had been making a life of hunting and collecting food, can make stone artifacts, bone artifacts to kill their quarries, use fire to cook their food, and at the same time they also conducted some religion activities.     

Phantom based qualitative and quantitative evaluation of artifacts in MR images of metallic hip prostheses

PurposeTo develop methods for qualitative and quantitative evaluation of MRI artifacts near metallic prostheses, and to compare the efficiency of different artifact suppression techniques with different types of hip prostheses.MethodsThree hip prostheses of cobalt-chromium, stainless steel, and titanium were embedded in agarose gel together with a rectilinear grid. Coronal MR images of the prostheses were acquired on a 1.5T scanner. Three pulse sequences were evaluated; TSE: a high-bandwidth turbo spin echo; VAT: TSE with view angle tilting, SEMAC: TSE with both VAT and slice distortion correction (6, 10 or 16 z-phase-encoding steps). Through-plane distortions were assessed as the length of visible gridlines, in-plane artifacts as the artifact area, and total artifacts by subtraction of an ideal, undistorted image from the actual image.ResultsVAT reduced in-plane artifacts by up to 50% compared to TSE, but did not reduce through-plane artifacts. SEMAC reduced through-plane artifacts by 60–80% compared to TSE and VAT. SEMAC in-plane artifacts were from 20% higher (6 encoding steps) to 50% lower (16 steps) than VAT. Total artifacts were reduced by 60–80% in the best sequence (SEMAC, 16 steps) compared to the worst (TSE). The titanium prosthesis produced 3–4 times lower artifact scores than the other prostheses.ConclusionsA rectilinear grid phantom is useful for qualitative and quantitative evaluation of artifacts provoked by different MRI protocols and prosthesis models. VAT and SEMAC were superior to TSE with high bandwidth. A proper number of z-encoding steps in SEMAC was critical. The titanium prosthesis caused least artifacts.     

Cine 4DCT imaging artifacts: Quantification and correlations with scanning parameters and target kinetics

To study temporal resolved computed tomography imaging (4-Dimensional Computed Tomography: 4DCT) artifacts correlations with scanning parameters and target kinetics and to assess uncertainty introduced by 4DCT in radiotherapy treatment planning.In this work we classified 4DCT artifacts as finite gantry rotation speed related (FGS) and finite sampling frequency related (FSF). We studied FGS artifacts using a respiratory phantom and FSF artifacts using a Monte Carlo simulation of acquisition timing.From our analysis FGS localization error is comparable with image resolution determined by voxel dimensions. Remaining FGS artifacts are correlated with gantry rotation time (Trot), target velocity (v) and their interaction.FSF artifacts occurrence is correlated with sampling ratio (SR), i.e. the ratio of patient respiratory period (Tresp) and sampling time (Ts).In the studied velocity range (0–2 cm/s), using a Trot of 0,5s and a SR higher than 15, FGS and FSF artifacts became comparable with other sources of uncertainty.Our considerations are valid for “ideal” breathing pattern only. When variations from periodical breathing, high target velocity (more than 2 cm/s) or high peak to peak amplitude (more than 2 cm) are present, patient specific images artifacts analysis is recommended.     

洛阳北窑黄土旧石器遗址1998年发掘报告

本文报道了洛阳北窑黄土旧石器遗址1998年发掘出土的771件石制品。石制品出自黄土地层S2到L1底部, 相当于200ka BP to 70—80 ka BP, 属于旧石器时代早中期。以S2和S1中最为丰富, 而L1底部和L2中较少; 石制品类型包括石核、石片、断块和断片, 石器数量很少, 仅尖状器和刮削器两类; 和中国北方小石片-刮削器传统有更多的相似之处; 从早到晚,石制品的性质没有明显变化。本文认为北窑遗址属于一处古人类临时加工石器的场所。     

Technical artifacts in magnetic resonance imaging

Various artifacts of Magnetic Resonance Imaging (MRI) typically associated with currently available imaging techniques such as projection reconstruction and two-dimensional fourier transform (2D-FT) are described and illustrated. Examples of MRI artifacts were obtained with an imaging unit with a super conducting magnet operated at .15 Tesla and .27 Tesla with corresponding proton resonance frequency of 6.4 MHz and 11.25 MHz. The .15 Tesla images were obtained using projection reconstruction and the .27 Tesla using the 2D-FT method. Instrument related artifacts include those due to direct current (DC), projection, gradient offset, active shimming, phase encoding, and pulse sequencing. Other often encountered artifacts are related to the patient. These include those due to motion, ferromagnetic effect, and tissue contents. The cause of these artifacts and how (if possible) they may be eliminated or minimized is discussed.     

Detection of cerebral embolism using transcranial Doppler sonography: can artifacts be reliably recognized?]

A requirement for the use of TCD for the detection of emboli in the field of cardiac and vascular surgery is the reliable differentiation between true emboli and artifacts. In ten healthy volunteers we carried out a study to establish the method with which artefacts can most reliably be identified. Automatic detection of increasing signal intensity misinterpreted 14% of all artifacts as emboli; 1.7% of all artifacts sounded suspicious for embolism, and 0.6% met the classical criteria of an embolus. Using simultaneous recording of the flow signal in two sections of the middle cerebral artery, all artifacts were identified on the basis of their simultaneous manifestation. Reliable intra-operative differentiation of emboli from artifacts requires attentive, continuous acoustic and visual analysis of signals by an experienced investigator familiar with the surgical procedure. The introduction of a multiple-depth algorithm might significantly improve the automatic detection program.     

黄河中游晋陕峡谷延安段新发现的石制品

2018年6月,我们在黄河中游晋陕峡谷陕西一侧延安段新发现5处旷野石器地点,采集石制品556件,部分石制品暴露于黄土地层的剖面上。古人类加工石制品的原料来自于黄河河床和阶地的砾石层,岩性以石英岩为主,其次为石英。除上述两种原料之外,燧石、硅质岩、硅质灰岩、石英砂岩、细砂岩、蛋白石、玛瑙、火成岩等也有少量使用。石制品类型包括石锤、石核、石片、工具、断块和碎片屑,尺寸以小型为主。石核和石片以自然砾石台面者居多。剥片主要采用锤击法直接剥片,少量使用砸击法,可能偶而使用碰砧法和锐棱砸击法。工具多为以石片为毛坯加工而成的中小型刮削器,有少量以砾石为毛坯加工而成的砍砸器。伏羲村、苏亚河、高家畔、延水关4个地点发现的石制品原生埋藏地层为黄河第二级阶地上覆的马兰黄土堆积,该套地层形成于晚更新世晚期,石制品属简单的石核-石片工业,可能属于旧石器时代晚期。衣锦滩地点的石制品分别埋藏于黄河第二级阶地上覆的马兰黄土堆积和黄河第一级阶地上覆的土状堆积中,时代分属于旧石器时代晚期和新石器时代。本次新发现的旧石器地点进一步扩大了黄河晋陕峡谷地区旧石器遗存的分布范围,丰富了该地区旧石器文化的内涵,为未来的研究工作提供了新线索。     

河北迁安县爪村地点发现的旧石器

本文记述了河北迁安县爪村旧石器时代文化地点发现的21件石制品。通过对1958年发现的标本的研究和1973年的野外工作,对1958年发现的7件石质标本提出了自己的看法,肯定其人工性质;在1973年,在该地点还找到一些新的石制品。其时代为旧石器时代晚期,依陈铁梅等用同层出土的牛化石(1973年采)做铀系法年代测定,其年代为距今4.8±0.2万年或4.4土0.2万年。