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。     

宝石能谱CT的功能特点及心血管检查的临床应用

宝石能谱CT拥有一系列独特的技术,包括宝石探测器、高压发射器、ASIR重组技术、能谱栅技术等,使其具有低剂量高清成像、能谱成像和动态500排成像特点,实现了全身0.23mm的极限空间分辨率和类MRI的软组织低密度分辨率,为心脏能量成像、斑块性质的鉴别及金属伪影的消除提供了全新有效的手段。其特有的高纯度和高通透性的物理学特性,再加上影像链中采样率的增高,专有的高清算法,使得宝石能谱CT能够在更低的剂量下,获得更为清晰的图像质量,达到目前业内最高的空间分辨率和密度分辨率;同时,其独有的能谱栅成像技术,将CT诊断从形态学带入功能学领域,因此也被称为"显微CT,病理CT,绿色CT",宝石能谱CT代表了目前CT发展的趋势,它用准确的绝对CT值的单能量成像(keV)诊断和基物质成像诊断来取代传统的相对CT值的混合能量(kVp)成像诊断,用多参数CT成像诊断来代替传统的单参数CT成像诊断,而"三同"(同时、同源、同向)的物理基础保证了其能谱成像的准确性,使CT能谱成像真正走入了临床诊断的第一线,从而提高了心血管疾病诊断的准确性和安全性。为CT在心脏疾病的诊断方面开拓了新领域和新方法。     

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。     

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.     

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。     

爱克发ADC Compact CR系统常见图像伪影分析

本文以爱克发ADC Compact CR系统为例,分析CR系统常见图像伪影的产生原因。并结合CR系统的工作原理和本人工作经验,介绍各种伪影的处理过程及方法,供大家参考。     

宝石能谱CT GSI成像和常规成像在上腹部应用价值的对比研究

目的:探讨宝石能谱CT GSI扫描模式在上腹部检查中降低辐射剂量和优化图像质量的可行性及应用价值。方法:选择2016年9月至2016年12月期间我院40例拟行上腹部三期增强的患者,根据扫描模式将患者分为A组和B组,每组20例。A组患者采用宝石能谱CT常规扫描模式行螺旋扫描,管电压120 Kvp及自动毫安管电流,确定NI值为10。B组患者采用GSI模式行三期增强扫描收集门脉期图像。回顾性自适应统计迭代重建(ASIR)70kev单能量图像,应用ASIR Review工具收集0到100%ASIR的CT值、噪声值,计算图像信号噪声比(SNR)。记录各组剂量报告中CT剂量容积指数(CTDI vol)及剂量长度乘积(DLP),并计算有效剂量(ED),采用图像质量主观评分对图像进行评价。结果:B组CT值、噪声值及SNR均高于A组(P0.05),B组CTDIvol、DLP和ED均显著低于A组(P0.05);随着ASIR升高,SNR升高,但是图像质量主观评分先升高后降低。当ASIR为50%时,图像质量最高,不同ASIR的CT值、噪声值之间的差异无统计学意义(P0.05)。结论:宝石能谱CT GSI扫描模式的效果明显优于螺旋扫描,同时在降低图像噪声的前提下选择50%ASIR,可保障图像质量。     

能谱CT优化胃肿瘤扫描辐射剂量对肾上腺嗜铬细胞瘤的诊断价值

目的:探讨能谱CT优化胃肿瘤扫描辐射剂量对肾上腺嗜铬细胞瘤的诊断价值。方法:采用回顾性、抽样、随机研究方法选择2012年9月到2017年2月在我院诊治的肾上腺嗜铬细胞瘤患者59例作为研究对象,所有患者都给予常规CT扫描与能谱CT优化胃肿瘤扫描,记录和比较辐射剂量与图像质量。结果:所有病例包膜均完整,边缘清楚,肿瘤内见单发或多发低密度区,肿瘤实质区呈不均匀显著强化。常规CT与能谱CT的图像质量主观评分分别为3.89±0.45分和4.54±0.34分;常规CT与能谱CT图像的胃肿瘤CT值分别为31.94±6.39HU和35.29±5.19HU,对比都有显著差异(P0.05)。能谱CT图像的膀胱和皮下脂肪图像噪声值都显著低于常规CT图像,对比差异都有统计学意义(P0.05);能谱CT扫描的CTDIvol和DLP分别为12.39±3.48mGy和624.10±39.19mGy.cm,都显著低于常规CT扫描的14.09±4.13mGy和653.92±56.29mGy.cm(P0.05)。结论:能谱CT优化胃肿瘤扫描在肾上腺嗜铬细胞瘤诊断中的应用能有效减少辐射剂量与图像噪声,提高图像CT值与主观质量,临床应用价值更高。     

肝脏能谱CT虚拟平扫成像替代传统CT平扫成像可行性研究

目的:探讨肝脏能谱CT虚拟平扫成像替代传统CT平扫成像可行性,以供参考。方法:随机选取2013年6月至2014年6月我院已确诊的肝脏疾病患者49例作为研究对象,将2种不同的扫描成像方法分为2组,对照组:对49例患者采用传统CT平扫成像的方式进行肝脏扫描成像分析;实验组:对49例患者采用肝脏能谱CT虚拟平扫成像的方式进行肝脏扫描成像分析。2组成像结果出来之后统一交给经验丰富的影像诊断小组,并由诊断小组对2种影像进行噪声、伪影、病灶检测能力三方面进行主观对比评价、分析。结果:肝脏能谱CT虚拟平扫成像的平均噪声为2.18±0.58,平均伪影为1.57±0.38,而患者的平均吸收剂量为10.16±2.57;传统CT平扫成像的平均噪声为1.68±0.37,平均伪影为1.44±0.24,而患者的平均吸收剂量为20.06±4.47。且2组差异具有统计学意义(p0.05)。结论:肝脏能谱CT虚拟平扫成像可以代替传统CT平扫成像进行肝脏检查,且具有良好的诊断价值。     

智能期相联合SSF技术改善冠状动脉CTA图像运动伪影

目的:评价智能期相选择(Smart phase)和自动追踪冻结(Snap-Shot-Freeze, SSF)技术联合应用在前门控冠状动脉CT血管成像(Coronary CT angiography, CCTA)改善图像运动伪影中的价值。方法:94例疑似心血管疾病的患者行CCTA检查。所有患者图像均采用smart phase、SSF及smart phase+SSF两种技术联合进行后处理。将原始图像(A组)、smart phase图像(B组)、SSF图像(C组)和smart phase+SSF图像(D组)导入GE AW4.6工作站。对四组患者冠状动脉三大分支(右冠状动脉、左前降支及左旋支)图像质量进行主观评价(5分法)和测量每组图像主动脉根部及前胸壁肌肉CT值和标准差,并计算图像的噪声(Noise,N)、信噪比(Signal-to-noise ratio,SNR)和对比噪声比(Contrast-to-noise ratio,CNR)和比较。结果:经smart phase处理后,A组冠状动脉三大分支图像评分均得到了明显提高(P<0.05)。经SSF矫正的A组和B组冠状动脉三大分支图像质量评分均得到明显提高(P<0.05)。Smart Phase联合SSF技术得到的图像评分在所有组中评分最高,与其他组均存在显著差异(P<0.05)。结论:Smart phase联合SSF技术可明显改善前门控CCTA图像运动伪影,值得临床推广应用。     

全身一体化成像技术在恒河猴动物实验中的应用

目的探讨并比较CT与核磁共振成像（magnetic resonance imaging,MRI）在恒河猴全身成像研究中的应用范围,以及全身一体化技术（total imaging Matrix,TIM）配合增强扫描对恒河猴骨骼、循环、神经系统成像,总结其影像学表现中与人相应系统解剖的差异。方法应用64层螺旋CT的表面遮盖成像重建技术（3D-SSD）对恒河猴全身骨骼系统进行全身平扫及重建,3．0TMRI的TIM技术与最大密度投影重建（MIP）对恒河猴循环系统、神经系统进行全身平扫及增强扫描并重建。结果64层螺旋CT骨骼系统成像显示恒河猴腰椎骨6块、骶椎骨8块、尾椎骨11块、真肋骨9根,数量多于人类;颈椎棘突未见分叉,与人类不同。MRI动态增强技术与一体化成像技术联用显示恒河猴的动脉系统与人类相近,端脑矢状位最长径与冠状位最长径比值比人类略低,脊髓膨大位置比人类略低。结论多层螺旋CT与MRI的TIM技术可应用于对大型实验动物进行无创性的解剖学分析,是一种无创、快速、可以在体研究并动态连续观察其结构的科学有效方法。     

DR全脊柱成像技术应用探讨

目的探讨DR全脊柱成像技术在脊柱侧弯畸形诊断及测量中的价值,研究不同检查方法对成像质量及测量精度的影响。方法利用PHIIAPS公司Digital Diagnost DR系统和具有全脊柱拼接功能的SUN后处理工作站,对分次所摄的脊柱正位、侧位、左、右侧屈位影像进行拼接处理后作必要的测量,并打印成像。结果经上述处理后的全脊柱正位、侧位及左、右侧屈位均能将颈、胸、腰、骶椎完整联接,显示在1张14＋17的X光片上,其测量的数据真实可靠。结论DR全脊柱成像技术克服了以往颈、胸、腰、骶椎单独成像后测量上的误差,为临床手术提供了更精确的数据。     

Artifacts in magnetic resonance imaging and computed tomography caused by dental materials

Background

Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a common problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the artifacts produced by different dental restoration materials in CT and MRI images.

Methods

Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and embedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples and evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software.

Results

In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts produced in both MRI and CT images were categorized according to the size of the artifact.

Significance

Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth elements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings would help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and CT images.     

Elimination of biological and physical artifacts in abdomen and brain computed tomography procedures using filtering techniques

IntroductionMedical images are usually affected by biological and physical artifacts or noise, which reduces image quality and hence poses difficulties in visual analysis, interpretation and thus requires higher doses and increased radiographs repetition rate.ObjectivesThis study aims at assessing image quality during CT abdomen and brain examinations using filtering techniques as well as estimating the radiogenic risk associated with CT abdomen and brain examinations.Materials and MethodsThe data were collected from the Radiology Department at Royal Care International (RCI) Hospital, Khartoum, Sudan. The study included 100 abdominal CT images and 100 brain CT images selected from adult patients. Filters applied are namely: Mean filter, Gaussian filter, Median filter and Minimum filter. In this study, image quality after denoising is measured based on the Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and the Structural Similarity Index Metric (SSIM).ResultsThe results show that the images quality parameters become higher after applications of filters. Median filter showed improved image quality as interpreted by the measured parameters: PSNR and SSIM, and it is thus considered as a better filter for removing the noise from all other applied filters.DiscussionThe noise removed by the different filters applied to the CT images resulted in enhancing high quality images thereby effectively revealing the important details of the images without increasing the patients’ risks from higher doses.ConclusionsFiltering and image reconstruction techniques not only reduce the dose and thus the radiation risks, but also enhances high quality imaging which allows better diagnosis.     

A detection method for streak artifacts and radiological noise in a non-uniform region in a CT image

By using the CT images obtained by subtracting two CT images acquired under the same conditions and slice locations, we have devised a method for detecting streak artifacts in non-uniform regions and only radiological noise components in CT images. A chest phantom was scanned using 16- and 64-multidetector row helical CT scanners with various mAs values at 120 kVp. The upper lung slice image was employed as a target image for evaluating the streak artifacts and radiological noise. One hundred parallel line segments with a length of 80 pixels were placed on the subtracted CT image, and the largest CT value in each CT value profile was employed as a feature variable of the streak artifacts; these feature variables were analyzed with the extreme value theory (Gumbel distribution). To detect only the radiological noise, all CT values contained in the 100 line profile were plotted on normal probability paper and the standard deviation was estimated from the inclination of its fitted line for the CT value plots. The two detection methods devised in this study were able to evaluate the streak artifacts and radiological noise in the CT images with high accuracy.     

Statistical learning methods as a preprocessing step for survival analysis: evaluation of concept using lung cancer data

Background

Despite its superb lateral resolution, flat-panel-detector (FPD) based tomosynthesis suffers from low contrast and inter-plane artifacts caused by incomplete cancellation of the projection components stemming from outside the focal plane. The incomplete cancellation of the projection components, mostly due to the limited scan angle in the conventional tomosynthesis scan geometry, often makes the image contrast too low to differentiate the malignant tissues from the background tissues with confidence.

Methods

In this paper, we propose a new method to suppress the inter-plane artifacts in FPD-based tomosynthesis. If 3D whole volume CT images are available before the tomosynthesis scan, the CT image data can be incorporated into the tomosynthesis image reconstruction to suppress the inter-plane artifacts, hence, improving the image contrast. In the proposed technique, the projection components stemming from outside the region-of-interest (ROI) are subtracted from the measured tomosynthesis projection data to suppress the inter-plane artifacts. The projection components stemming from outside the ROI are calculated from the 3D whole volume CT images which usually have lower lateral resolution than the tomosynthesis images. The tomosynthesis images are reconstructed from the subtracted projection data which account for the x-ray attenuation through the ROI. After verifying the proposed method by simulation, we have performed both CT scan and tomosynthesis scan on a phantom and a sacrificed rat using a FPD-based micro-CT.

Results

We have measured contrast-to-noise ratio (CNR) from the tomosynthesis images which is an indicator of the residual inter-plane artifacts on the focal-plane image. In both cases of the simulation and experimental imaging studies of the contrast evaluating phantom, CNRs have been significantly improved by the proposed method. In the rat imaging also, we have observed better visual contrast from the tomosynthesis images reconstructed by the proposed method.

Conclusions

The proposed tomosynthesis technique can improve image contrast with aids of 3D whole volume CT images. Even though local tomosynthesis needs extra 3D CT scanning, it may find clinical applications in special situations in which extra 3D CT scan is already available or allowed.     

Utility of fast non-local means (FNLM) filter for detection of pulmonary nodules in chest CT for pediatric patient

PurposeThis study was aimed to evaluate the utility based on imaging quality of the fast non-local means (FNLM) filter in diagnosing lung nodules in pediatric chest computed tomography (CT).MethodsWe retrospectively reviewed the chest CT reconstructed with both filtered back projection (FBP) and iterative reconstruction (IR) in pediatric patients with metastatic lung nodules. After applying FNLM filter with six h values (0.0001, 0.001, 0.01, 0.1, 1, and 10) to the FBP images, eight sets of images including FBP, IR, and FNLM were analyzed. The image quality of the lung nodules was evaluated objectively for coefficient of variation (COV), contrast to noise ratio (CNR), and point spread function (PSF), and subjectively for noise, sharpness, artifacts, and diagnostic acceptability.ResultsThe COV was lowest in IR images and decreased according to increasing h values and highest with FBP images (P < 0.001). The CNR was highest with IR images, increased according to increasing h values and lowest with FBP images (P < 0.001). The PSF was lower only in FNLM filter with h value of 0.0001 or 0.001 than in IR images (P < 0.001). In subjective analysis, only images of FNLM filter with h value of 0.0001 or 0.001 rarely showed unacceptable quality and had comparable results with IR images. There were less artifacts in FNLM images with h value of 0.0001 compared with IR images (p < 0.001).ConclusionFNLM filter with h values of 0.0001 allows comparable image quality with less artifacts compared with IR in diagnosing metastatic lung nodules in pediatric chest CT.     

腰椎骨折患者伤椎置钉与不置钉临床疗效对比分析

目的:探讨腰椎骨折伤椎置钉和不置钉对疗效的影响,以期选择最佳治疗方法。方法:选取2011年6月-2015年6月80例腰椎骨折患者为研究对象,随机分为对照组39例,伤椎不置钉治疗,观察组41例,伤椎置钉治疗,观察治疗后临床效果和相关指标变化。结果:两组在切口长度、手术时间、出血量、住院时间上比较比较无统计学意义(P0.05);两组术后在后凸Cobb角、椎管侵占率上较术前明显下降,椎体高度恢复较术前明显升高,手术前后比较差异显著(P0.05),观察组在手术后6个月、术后12个月、拆除内固定时后凸Cobb角、椎管侵占率明显低于对照组,椎体高度恢复上明显高于对照组,两组比较差异均显著(P0.05),而手术后1周比较差异不显著(P0.05)。结论:腰椎骨折患者伤椎置钉临床疗效满意。     

能谱CT鉴别肺癌成骨性转移瘤与骨岛

目的:探讨能谱CT成像在鉴别诊断肺癌成骨性转移瘤(Osteoblastic metastases,OBMs)与骨岛(Bone island,BIs)的临床应用价值。方法:回顾性分析经病理证实的16例肺癌患者诊断为成骨性转移瘤36个病灶及临床诊断21例骨岛患者21个病灶,所有患者均行能谱CT扫描,测量各病灶40-140 ke V区间单能量水平CT值及钙(水)基物质浓度,最后计算出能谱曲线斜率k。采用独立样本t检验对两组各参数进行差异性比较分析。结果:OBMs的各水平单能量CT值、k值、钙(水)浓度均低于BIs,两组差异均有统计学意义(P0.05)。结论:能谱CT有助于鉴别诊断肺癌成骨性转移瘤与骨岛。