CR系统伪影的分析和解决方法

目的：对CR系统图像伪影原因的分析，探讨预防和消除伪影产生的方法。方法：对82例伪影进行回顾性分析。结果：产生伪影的原因有：(1)成像板伪影；(2)系统硬件造成的伪影；(3)后处理造成的伪影；(4)记忆伪影；(5)滤线栅伪影。结论：在工作中，正确使用和维护CR系统，可以减少CR图像的伪影。     

多层螺旋CT冠状动脉造影伪影及其产生因素的研究

目的:探讨多层螺旋CT冠状动脉成像的伪影表现及其产生因素。方法:回顾性分析136例冠状动脉多层螺旋CT成像,分析冠状动脉伪影的表现,评分法判断伪影的程度,产生伪影的原因。结果:以曲面重组为标准重组方式评判。109例见伪影占80.2%,232段冠状动脉发生伪影占23.8%。伪影分为自身因素和技术因素两大类。呼吸运动与心脏运动表现为阶梯状影,冠状动脉错位、中断、模糊;高密度物质表现为局部管腔模糊;邻近结构伪影表现为冠状动脉显影模糊;技术原因表现为冠状动脉不能成像。冠状动脉伪影程度5分3例,4分8例,3分24例,2分33例,1分41例。轻度伪影74例占54.4%(74/136),中度伪影占24例17.6%(24/136),重度伪影11例占8.1%(11/136)。结论:伪影的产生各有其原因,影像学表现各异,通过多种手段的联合应用可降低伪影的发生率及对诊断的影响。     

双源CT冠状动脉成像中影响图像质量的因素分析

目的分析双源CT（doube source computed tomography,DSCT）冠状脉成像中影响图像质量的因素。方法回顾性分析150例临床可疑或确诊冠心病经手术治疗后复查的患者,男性103例,女性47例,平均年龄60．6岁;均经DSCT冠状动脉成像,对其图像质量影响因素进行了回顺性分析。结果扫描技术直接影响冠状动脉成像的质量。影响图像的因素分为呼吸伪影,心律不齐伪影,上腔静脉、右房高密度造影剂产生的伪影,冠状动脉支架产生的伪影,上述各种伪影均具有独特的影像特征。结论优化CT扫捕技术,准确分析冠状动脉成像伪影的CT表现及成因,对保证冠脉成像质量,减少诊断失误有着至关重要的作用。     

磁共振Propeller技术消除伪影的临床应用

目的:探讨Propeller技术在临床的应用价值。方法:日常工作中随机对19例磁共振头颅检查中出现躁动或有固定金属异物患者,应用Propeller技术进行成像,与常规T2FRFSE序列、DWI序列进行对比扫描。其中因躁动产生运动伪影进行PropellerT2加权成像11例,因金属异物产生伪影进行PropellerDWI成像8例,同时进行PropellerT2WI、DWI成像5例。结果:19例应用Propeller技术进行T2WI、DWI成像消除因运动、金属引起的伪影均获得满意图像。结论:应用PropellerT2WI、DWI成像技术明显消除患者因运动或金属异物造成的伪影,可生成高分辨无伪影具有临床诊断意义的理想图像。     

CT能谱成像用于减少锁骨下对比剂伪影的临床研究

目的:寻找CT能谱成像的最佳能量点以减少肺部增强CT扫描锁骨下腋静脉和锁骨下静脉对比剂伪影,并改善图像质量。方法:共66名病人接受能谱CT扫描。一次能谱成像获得12组图像:140kVp混合能量图像和11组单能量图像(40～140keV)。比较混合能量和单能量图像在肺部增强CT动脉期的伪影区噪声、信噪比(SNR)、对比噪声比(CNR)和平均线束硬化伪影指数(BHAs)。BHAs是感兴趣区和背景区噪声平方差的平方根。结果:与常规混合能量组相比,120keV可最大程度地减少硬化伪影(P=0.000),同时SNR、CNR明显减小,导致软组织对比度明显减低。70keV可以减小硬化伪影(P=0.042),且SNR、CNR最高,优于混合能量图像和其他单能量图像,而伪影区噪声减低,图像质量最好。结论:在肺部增强扫描中,120keV去除对比剂硬化伪影的能力优于混合能量图像及其他单能量图像,但是组织对比度较差,可以结合70keV图像共同进行诊断。     

不同场强影响介入性磁共振穿刺针成像因素的初步探讨

目的　探讨 0 .3T、1.5T场强下影响介入性磁共振穿刺针成像的因素。以便提供正确的穿刺方法及成像技术参数 ,确保介入性磁共振操作的安全性及准确性。方法　将MR相容性介入穿刺针置于琼脂模型内 ,在 0 .3T、1.5T场强下 ,采用自旋回波序列、快速自旋回波序列、梯度回波序列 ,将穿刺针平行、垂直于主磁场 ,频率编码方向平行或垂直于穿刺针的方向进行扫描 ,在工作站测量图像上穿刺针的宽度及针尖的位置 ,比较图像上和实际针尖位置的差异 ,并比较不同场强下影响穿刺针伪影的因素。结果　各序列中梯度回波序列产生的伪影较大 ,快速自旋回波序列产生的伪影较小 ,自选回波序列产生的伪影最小 ,但快速自旋回波序列与自旋回波序列产生的伪影无明显差异。快速自旋回波序列与自旋回波序列中 ,当频率编码轴垂直于穿刺针长轴时伪影较大 ;当穿刺针方向逐渐平行于主磁场方向时 ,伪影逐渐减小。所有图像上针尖位置与实际针尖位置的差异在 1cm内。结论　 1.5T场强下伪影宽度大于 0 .3T场强。在 0 .3T、1.5T场强下改变频率编码方向、脉冲序列、成像参数时 ,针尖位置的变化在 1cm内 ,穿刺针平行于主磁场方向时 ,在不同场强下明显降低伪影的宽度     

预饱和技术在3.0T MR抑制流动伪影中的应用

在MRI检查过程中、人体内流动的血液及脑脊液常引起流动伪影,流动伪影是MR成像中一种引起MR图像质量下降的常见原因,尤其是3．0T MR流动伪影更加明显。笔者就3．0T MR在头部、颈部应用预饱和技术抑制流动伪影体会如下。     

宝石CT能谱成像去除脊柱金属植入物伪影的应用研究

目的:探讨宝石CT能谱成像(GSI)在减除脊柱金属植入物伪影的应用价值;同时研究应用能谱曲线寻找最佳keV值的可行性。方法:对6例脊柱金属植入术患者行宝石CT GSI扫描,并以10keV为间隔重建11组单能量(Mono)图像质量的客观指标。通过比较140kVp(QC)和各级别Mono图像的客观指标伪影指数(AI)和对比噪声比(CNR)、软组织和骨质以及金属植入物图像质量的主观评分(4分法,1分图像最优,4分图像最差),寻找GSI去金属伪影最佳成像条件。并以最佳图像为对照,比较利用能谱曲线寻得最佳Mono图像的质量和诊断效能。结果:AI在90~140keV时减低,在100~130keV达最低;CNR在100～120keV时减低且最低。能谱成像技术在90~140keV对软组织、骨质及金属植入物诊断效能提高,在110~130keV对软组织观察最优,在110~140keV对骨质及植入金属观察最优。利用能谱曲线寻得最佳单能量成像条件为100~120keV,范围落在普通方法确定的电压值区间内,其图像均能满足诊断。结论:宝石能谱CT GSI在高电压区可有效减除脊柱金属植入物伪影,最佳成像区间为100~120keV。利用能谱曲线可快速有效获得最佳单能量成像。     

颈胸部连续CT扫描时颈部扫描参数的选择(附30例分析)

目的 :探求颈胸部 CT连扫时颈部较佳扫描参数组合 ,获得满意图像。方法 :30例分三组各 10例 ,按扫描野、扫描角度、图像矩阵等参数不同组合扫描成像并分析。结果 :扫描野大 ,椎骨横突后条纹伪影较严重 ,并可能有辐射状伪影 ,图像分辨率受到影响 ;扫描野小、扫描角度、图像矩阵小时 ,图像分辨率差。结论 :扫描野小、过角度扫描、图像矩阵大的参数组合 ,其扫描可提高图像质量。     

CR成像和照片伪影表现及其原因分析

目的:研究CR成像和照片中伪影的表现特点及其原因,提高CR照片质量。材料和方法:回顾性分析2003-05～2007-01,应用ACR-2000iIP板读出装置,柯达8100干式激光相机,柯达CR激光片,日本岛津500mA UD150高频X线机系统的CR成像和照片伪影的表现特点及其原因。结果:IP板污染伪影59幅(34%),表现为点状/结节状高密度影。激光扫描仪/激光相机污染伪影49幅(28%),表现为横细条状密度增高影。激光扫描仪传动部件磨损/异物贴附扫描仪滚轴转速不匀伪影21幅(12%),表现为限局细波浪黑白相间。激光扫描仪读取系统障碍伪影19幅(11%),表现为部分信息丢失。IP板表层膜破损伪影15幅(9%),表现为弧形/线形高密度影。部分影像叠加伪影10幅(6%),表现为组织影像重叠。结论:熟悉CR成像和照片中伪影的特点及其原因,有助于准确及时的采取措施,消除消除伪影,提高CR成像和照片质量。     

Pictorial essay: pitfalls in magnetic resonance imaging of the shoulder

Numerous imaging pitfalls of normal variants due to imaging technique and artifacts can be seen on routine magnetic resonance imaging of the shoulder. Familiarity with these pitfalls is crucial to avoiding diagnostic errors. Understanding of the common causes of shoulder imaging artifacts will enable the radiologist to make rational changes in imaging technique to eliminate or reduce the effects of artifacts on magnetic resonance images. This pictorial essay highlights possible pitfalls that arise from imaging techniques, imaging artifacts, and normal variations, and how they may be recognized.     

非肺栓塞灌注缺损的双源CT双能量肺灌注成像表现及原因

目的 分析双源CT双能量肺灌注成像(DEPI)中非肺栓塞引起的灌注缺损(PDs)的原因及其影像学表现特征.方法 回顾性分析行DEPI扫描而确诊无肺栓塞的208例患者的影像学资料.由2位影像科医生分析PDs原因,统计不同原因所致PDs的肺段数量、所占比例、形态、灌注表现类型等,分析各种原因引起PDs的影像特征.结果 208例患者中,共有1 118个肺段出现PDs,引起PDs的原因包括4类:肺内病变、血管性病变、伪影类及原因不明者,受累肺段数目分别为752(67.26%)、36(3.22%)、308(27.55%)、22(1.97%).观察肺内病变、血管性病变以及原因不明者所致PDs,将其灌注表现类型分为3种:楔形分布、不均匀分布、区域性均匀分布.上述病变灌注类型以不均匀、区域性均匀分布为主,与非灌注图像所示病变形态基本一致.伪影类包括2大类:对比剂所致局部线束硬化伪影、运动伪影.不同原因伪影所致PDs常有其特点部位及形态.结论 认识非肺栓塞所致PDs的影像特征有助于提高DEPI诊断肺栓塞的准确性.     

Motion artifacts in brain and spine MR

As a result of the effects of cerebrospinal fluid and blood motion, motion artifacts are common in brain and spine MR imaging. These artifacts, which are most common on T2-weighted spin-echo sequences, show up as streaking and ghosting in the phase-encoding (PE) direction (PE artifacts) and as loss of signal from flowing material (flow void). A review of the physical and physiologic causes of these artifacts and a review and explanation of several techniques that are useful in reducing or eliminating them are presented in this article.     

Signal intensity artifacts in clinical MR imaging.

Signal intensity artifacts are often encountered during magnetic resonance (MR) imaging. Occasionally, these artifacts are severe enough to degrade image quality and interfere with interpretation. Signal intensity artifacts inherent in local coil imaging include intensity gradients and local intensity shift artifact. The latter can be minimized but not eliminated with optimal coil design and tuning. Improper coil or patient positioning can produce subtle or, in some cases, severe signal intensity artifacts, and each is easily corrected. Signal intensity artifacts and image degradation can also occur in a perfectly functioning coil if protocols are not optimized. Failure of decoupling mechanisms can produce signal intensity artifacts that will not respond to protocol optimization and will worsen with gradient imaging. Improper coil tuning manifests as a shading artifact that can mimic other findings. Signal-degrading artifacts may be caused by a ferromagnetic foreign body in the imager. Signal intensity artifacts can also result from performing ultrafast imaging with coils that were not designed for this type of imaging or from MR imaging system malfunction. Familiarity with the various causes of signal intensity artifacts is necessary to maintain optimal image quality and should be required as part of any MR imaging quality assurance program.     

Artifacts in body MR imaging: their appearance and how to eliminate them

A wide variety of artifacts can be seen in clinical MR imaging. This review describes the most important and most prevalent of them, including magnetic susceptibility artifacts and motion artifacts, aliasing, chemical-shift, zipper, zebra, central point, and truncation artifacts. Although the elimination of some artifacts may require a service engineer, the radiologist and MR technologist have the responsibility to recognize MR imaging problems. This review shows the typical MR appearance of the described artifacts, explains their physical basis, and shows the way to solve them in daily practice.     

Artifacts and pitfalls in myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is an important imaging modality in the management of patients with cardiovascular disease. MPI plays a key role in diagnosing cardiovascular disease, establishing prognosis, assessing the effectiveness of therapy, and evaluating viability. However, MPI is a complex process, subject to a variety of artifacts and pitfalls, which may limit its clinical utility. These factors may be related to the patient (including unique aspects of the patient's heart), the nuclear medicine equipment, or the actions of the technologist. After reviewing this article, the reader should be familiar with the causes and the effects of these potential artifacts and pitfalls. The reader should develop an understanding of steps to limit these factors, actions to correct them if they do arise and, when necessary, how to incorporate their influence into the interpretation of the study.     

Artifacts in ECG-synchronized MDCT coronary angiography

OBJECTIVE: In MDCT coronary angiography, image artifacts are the major cause of false-positive and false-negative interpretations regarding the presence of coronary artery stenoses. Hence, it is important that observers reporting these investigations are aware of the potential presence of image artifacts and that these artifacts are recognized. CONCLUSION: The article explores the technical causes for various artifacts in MDCT coronary angiography imaging and clinical examples are given.     

Coronary arterial stents: safety and artifacts during MR imaging

PURPOSE: To investigate the safety and imaging artifacts with different coronary arterial stents and magnetic resonance (MR) imaging sequences. MATERIALS AND METHODS: The heating, artifacts, and ferromagnetism with different stents were studied with a 1.5-T MR tomograph with ultrafast gradients by using turbo spin-echo, turbo gradient-echo, and echo-planar imaging sequences. Nineteen stents, which were 8-25 mm in length and 3.0-4.5 mm in diameter, were evaluated. Stent deviation induced by the magnetic field and during MR imaging, migration, and heating caused by the radio-frequency pulses were examined. The size of imaging artifacts was measured with all the stents under standardized conditions and with six stents after their implantation into the coronary arteries of freshly explanted pig hearts. RESULTS: All except two types of stents showed minimal ferromagnetism. No device migration or heating was induced. Turbo spin-echo images had minimal artifacts; larger artifacts were seen on the turbo gradient-echo and echo-planar images. With ultrafast gradients, the artifacts on the echo-planar images were substantially reduced. CONCLUSION: The studied coronary stents were not influenced by heating or motion during 1.5-T MR imaging. Artifact size differed according to the type and size of the stent and the MR imaging sequence used. Thus, patients with these stents can be safely examined.     

PET/CT imaging artifacts

The purpose of this paper is to introduce the principles of PET/CT imaging and describe the artifacts associated with it. PET/CT is a new imaging modality that integrates functional (PET) and structural (CT) information into a single scanning session, allowing excellent fusion of the PET and CT images and thus improving lesion localization and interpretation accuracy. Moreover, the CT data can also be used for attenuation correction, ultimately leading to high patient throughput. These combined advantages have rendered PET/CT a preferred imaging modality over dedicated PET. Although PET/CT imaging offers many advantages, this dual-modality imaging also poses some challenges. CT-based attenuation correction can induce artifacts and quantitative errors that can affect the PET emission images. For instance, the use of contrast medium and the presence of metallic implants can be associated with focal radiotracer uptake. Furthermore, the patient's breathing can introduce mismatches between the CT attenuation map and the PET emission data, and the discrepancy between the CT and PET fields of view can lead to truncation artifacts. After reading this article, the technologist should be able to describe the principles of PET/CT imaging, identify at least 3 types of image artifacts, and describe the differences between PET/CT artifacts of different causes: metallic implants, respiratory motion, contrast medium, and truncation.