颅内动脉瘤流动伪影在不同MRI序列上的表现差异

目的 探讨颅内动脉瘤流动伪影在不同MRI序列上的表现.方法 对经DSA或手术证实同时合并有流动伪影的19例颅内动脉瘤的MRI资料进行回顾分析.使用GE Signa 1.0T超导型MRI扫描仪.全部患者均行脑SE序列T1WI和T2WI、GRE序列、FLAIR序列、对比增强T1WI及3D TOF MRA扫描.结果 颅内动脉瘤流动伪影在所有MRI序列图像上均表现为动脉瘤残腔水平的不规则条带状影,且均位于相位编码方向.19例颅内动脉瘤在FLAIR序列上均可显示流动伪影,GRE序列上显示18例,T2WI上显示17例,T1WI上显示9例.行Gd-DTPA增强的7例病人T1WI图像均显示相位编码方向上的流动伪影.GRE序列及FLAIR序列图像上的流动伪影强度大于SE序列;T2WI上的流动伪影强度大于T1WI;对比剂注入后T1WI增强图像上的流动伪影强度明显大于增强前图像.结论 不同MRI序列上颅内动脉瘤流动伪影的强度不同.     

3.0TMR胃癌扩散加权成像——单序列分次屏气与分序列单次屏气比较研究

目的 比较3.0 T MR单序列分次屏气与分序列单次屏气在胃癌扩散加权成像(diffusion weighted imaging,DWI)的信噪比(SNR)、对比噪声比(CNR)、表观扩散系数(ADC)值和伪影等方面的差异.资料与方法 对经胃镜病理证实的18例胃癌患者行术前MR DWI检查,均行单序列分次屏气与分序列单次屏气两次扫描,比较两种检查方法的SNR、CNR、ADC值及伪影等影响图像质量的因素,以及胃癌与正常胃壁ADC值之间的差异.结果 18例胃癌DWI图像上均显示为高信号,两种检查方法间正常胃壁及癌肿ADC测量差异无统计学意义(P＞0.05),而单次屏气DWI的SNR、CNR明显高于分次屏气扫描,单次屏气胃腔内自由水以及背景噪声信号强度明显低于分次屏气扫描,差异均有统计学意义(P＜0.05);单次屏气法DWI图像的呼吸运动及并行采集空间敏感性编码技术(ASSET)伪影明显减轻;胃癌ADC值与正常胃壁ADC值间比较差异有统计学意义(t=- 10.167,P＜0.001),胃癌组明显低于正常胃壁组ADC值.结论 3.0 T MR胃癌DWI中单次屏气图像质量明显优于分次屏气扫描,胃癌ADC值明显低于正常胃壁ADC值,具有很好的临床应用价值.     

PROPELLER技术在颅脑MR成像中的临床应用价值

目的:探讨PROPELLER(螺旋浆)技术对改善颅脑MRI检查时运动伪影的临床应用价值.方法:6例健康志愿者进行静止状态、摇头和点状动作时的MRI检查,以及50例临床受检者,均行PROPELLER-T2WI和FSE-T2WI横轴面扫描.使用GE Signa HD 1.5T双梯度磁共振扫描仪.选取受检者同一层面的FSE-T2WI和PROPELLER-T2WI图像,由3位高年资的影像科医师,对其图像质量进行评价,分析图像的运动伪影和优质片率状况,采用统计学x2检验.结果:正常健康志愿者6例,选取136个层面的272幅图像进行比较,使用PROPELLER-T2WI扫描序列比采用常规FSET2WI扫描序列所获得的图像运动伪影明显减少(χ2=1012.829,P＜0.001),优质图像的显示率明显提高(x2=187.049,P＜0.001);临床受检者50例,选取320个层面的640幅图像进行比较,使用PROPELLER-T2WI扫描序列比采用常规FSE-T2WI扫描序列所获得的图像运动伪影明显减少(χ2=318.418,P＜0.001),优质图像的显示率明显提高(x2=1047.273,P＜0.001),对颅内病变的显示能力,PROPELLER-T2WI优于FSE-T2WI,PROPELLER-T2WI对小病灶显示有较好的清晰度.结论:PROPELLER-MRI解决了显著头动患者进行MRI检查提供一种可能,避免对躁动患者实施药物镇静或进行全身麻醉,PROPELLER MRI具有较高临床实用价值.     

MRI在胃癌诊断及pT分期（TNM）中的运用

目的：探讨MRI对胃癌诊断与pT分期的价值。材料和方法。收集本院1998－2001年间43例经病理证实的胃癌病例,Borrman'sⅠ型胃癌5例,Ⅱ型16例,Ⅲ型14例,Ⅳ型8例。MRI检查采用仰卧横断面SE T1WI平扫及增强扫描;SE重T2WI及FIR脂肪抑制图像;矢状面FSE重T2WI。根据所得到MR的图像进行胃癌的分期诊断,并与手术后病理诊断结果对照。结果：正常胃壁各层结构在MR SE T1WI、FSE重T2WI及FIR脂肪抑制图像不能很好显示,仅浆膜层在各序列上要表现为低信号影。癌块在SE T1WI增强及FSE重T2WI上表现为胃壁不规则增厚、边缘毛糙的稍高信号影;FSE重T2WI及FIR脂肪抑制图像对胃癌的周围浸润范围和腹膜后转移性淋巴结的显示较好,可对肿瘤进行较正确分期。运用后处理技术行胃腔MR仿真内镜成像,可观察腔内病变情况。本组43例胃癌中,除3例较早期（pT1,pT2)胃癌MRI不能区分及4例pT2由于呼吸伪影过度诊断为pT3外,余36例pT分期诊断与病理基本附合。结论：MRI技术对胃癌Ⅱ-Ⅳ期术前诊断及分期有一定价值。     

3.0TMRI螺旋桨技术在女性盆腔中的应用

目的探讨螺旋桨技术(PROPELLER)在3.0T MRI上减轻女性盆腔成像伪影和提高其整体成像质量中的价值。资料与方法 38例女性盆腔患者行矢状面PROPELLER T2WI和常规快速自旋回波(FSE)T2WI扫描,采用相同的成像矩阵、视野、层数、层厚和层间距,评价与呼吸运动和肠管蠕动相关的运动伪影程度、结合带等盆腔结构的显示以及图像整体的成像质量。结果 PROPELLER T2WI在运动伪影程度和女性盆腔结构显示方面的平均得分均高于常规FSE T2WI,且在抑制运动伪影方面差异有统计学意义(P<0.001),其中1名医师在评价盆腔结构显示方面差异无统计学意义(P>0.05)。最后2名医师对两组序列的整体图像质量评分结果差异有统计学意义(P<0.05、P<0.001)。结论 PROPELLER T2WI在显示结合带等解剖结构、矫正肠管蠕动和呼吸运动伪影及提高图像的整体质量方面均优于常规FSE T2WI,在3.0T MRI上进行女性盆腔检查时,可以考虑用PROPELLER T2WI代替常规FSE T2WI。     

流动伪影在颅内动脉瘤MRI诊断中的价值

目的 评价流动伪影对颅内动脉瘤的诊断价值。资料与方法 搜集经DSA(10例)或手术(5例)证实的15例同时合并有流动伪影的颅内动脉瘤的MRI和MRA资料进行回顾分析。使用Siemens Impact1．0T超导型MR扫描仪。全部患者均行脑MRSE序列扫描，13例行3D TOF MRA动脉期扫描。结果 15例颅内动脉瘤共显示29个流动伪影，在所有MR序列图像上均表现为动脉瘤残腔水平的不规则条带状影，且均位于相位编码方向上。T2WI较T1WI上所显示的伪影更为粗大、明显。结论 合理地应用流动伪影有助于颅内动脉瘤的诊断和鉴别诊断。     

探讨PROPELLER和SSFSE扫描技术在颅脑MR成像中应用价值

目的:比较螺旋浆(PROPELLER)扫描技术和单次激发快速自旋回波(SSFSE)扫描技术颅脑磁共振成像的图像质量,揭示PROPELLER这一独特的成像技术在未镇静不配合受检者颅脑磁共振成像中临床应用价值。方法:25例疑颅内病变的临床受检者,采用PROP-T2WI和SSFSE-T2WI扫描所获得的T2WI磁共振图像,由影像科医师,未告知采用扫描方法的前提下,对其图像质量进行评价,分析图像的运动伪影、病灶显示和图像优质片率状况,将影像科医师判读两种扫描技术所获得的颅脑MR图像结果供分析,采用统计学Ridit分析和χ2检验。结果:使用PROP-T2WI和SSFSE-T2WI扫描方法所获得的图像运动伪影均明显减少,颅内病灶均可以显示(Ridit分析,P=0.6664);但PROP-T2WI图像的清晰度、对比度明显优于SSFSE-T2WI图像(χ2检验,P<0.001)。结论:PROPELLER和SSFSE扫描技术具有同等消除磁共振图像运动伪影的能力,但使用PROPELLER技术所得到T2WI对脑实质的显示更为理想,显示病灶较清晰,具有较高临床实用价值。     

MR螺旋桨技术消除颅脑各种伪影的临床应用价值

目的:比较MR螺旋桨技术T2WI序列与常规FSE T2WI序列减少运动伪影效果,评价其临床应用价值。材料和方法:随机对82例行头部常规检查者,同时行螺旋桨技术T2WI序列扫描。由2名高职MR室医师分别评价其血管搏动、眼球运动、脑脊液波动、头部运动伪影。结果:82例中,常规T2WI扫描产生血管搏动伪影56例计106条、眼球运动伪影59例(1例因金属伪影无意义)、脑脊液波动伪影29例32条;头运动伪影35例(5例因金属伪影影响观察)。螺旋桨技术T2WI扫描未产生血管搏动和眼球运动伪影、脑脊液搏动伪影4例、头运动伪影2例。结论:螺旋桨技术在消除常规头颅扫描中产生伪影有显著效果,对疾病的确诊具有临床意义,有较好的应用前景。     

BLADE技术在消除MRI膝关节运动伪影方面的应用

目的 探讨刀锋伪影校正(BLADE)技术在消除MRI膝关节运动伪影的应用价值.方法 32例膝关节常规MRI检查中出现运动伪影的患者,改用BLADE技术扫描(PD矢状位、T2矢状位),以是否能够清晰显示膝关节结构、半月板及交叉韧带为标准,与常规序列对比评估BLADE技术对消除膝关节运动伪影的应用价值.结果 膝关节常规序列扫描中出现运动伪影,改用BLADE技术扫描后,图像运动伪影消除,图像质量明显改善.结论 BLADE技术对膝关节常规扫描中产生的运动伪影有明显的校正作用,可广泛用于产生运动伪影的膝关节MRI检查中.     

磁共振Propeller技术消除头部伪影的临床应用

目的探讨Propeller技术在头部伪影消除的应用价值。方法对21例磁共振头颅日常检查中出现躁动或不能自控患者，用Propeller技术进行T2WI扫描，与常规T2FRFSE序列进行对比；5例DWI序列磁敏感伪影明显者进行Propeller DWI扫描，与常规DWI进行对比。结果21例应用Propeller技术进行T2VI扫描明显减少或消除了运动伪影，5例Propeller DWI明显消除磁敏感效应引起的伪影，均生成较满意图像。结论应用PropellerT2WI及DWI成像技术可以明显减少或消除患者因运动及磁敏感效应造成的伪影，显著提高图像质量，获得具有临床诊断价值的理想图像。     

Highly accelerated real‐time cardiac cine MRI using k–t SPARSE‐SENSE

For patients with impaired breath‐hold capacity and/or arrhythmias, real‐time cine MRI may be more clinically useful than breath‐hold cine MRI. However, commercially available real‐time cine MRI methods using parallel imaging typically yield relatively poor spatio‐temporal resolution due to their low image acquisition speed. We sought to achieve relatively high spatial resolution (～2.5 × 2.5 mm²) and temporal resolution (～40 ms), to produce high‐quality real‐time cine MR images that could be applied clinically for wall motion assessment and measurement of left ventricular function. In this work, we present an eightfold accelerated real‐time cardiac cine MRI pulse sequence using a combination of compressed sensing and parallel imaging (k‐t SPARSE‐SENSE). Compared with reference, breath‐hold cine MRI, our eightfold accelerated real‐time cine MRI produced significantly worse qualitative grades (1–5 scale), but its image quality and temporal fidelity scores were above 3.0 (adequate) and artifacts and noise scores were below 3.0 (moderate), suggesting that acceptable diagnostic image quality can be achieved. Additionally, both eightfold accelerated real‐time cine and breath‐hold cine MRI yielded comparable left ventricular function measurements, with coefficient of variation <10% for left ventricular volumes. Our proposed eightfold accelerated real‐time cine MRI with k–t SPARSE‐SENSE is a promising modality for rapid imaging of myocardial function. J. Magn. Reson. Imaging 2013. © 2012 Wiley Periodicals, Inc.     

八次激发SE-EPI在肝脏MRI的应用

目的；比较八次激发SE－EPI与呼吸门控FSE及SSFSE T2WI在肝脏的应用。方法：对14例志愿者及21例肝病患者行上腹部呼吸门控FSE及SSFSE和屏气八次激发SE－EPI扫描。所有T2WI序列均运用脂肪抑制技术。定量分析肝脏、病灶的信噪比及肝脏－病灶的对比噪声比，评价各序列的图像质量及伪影。结果：八次激发SE－EPI与SSFSE及FSE在肝脏及病灶信噪比，肝脏－病灶对比度噪声比和图像质量方面无明显差异（P＞0．05）。其磁敏感伪影较FSE及SSFSE重（P＜0．01），SE－EPI化学位移伪影与SSFSE及FSE相比无明显差别（P＞0．05）。SE－EPI及FSE运动伪影明显比SSFSE重（P＜0．01），但SE－EPI运动伪影与FSE相比无明显差别（P＞0．05）。SE－EPI与FSE及SSFSE的图像质量无明显差别（P＞0．05）。结论：八次激发SE－EPI能够在较短时间里提供较高质量的上腹部T2WI。被检查者在扫描时可自由平静呼吸或屏气，可作为肝脏T2WI的补充序列。     

Shortening MR image acquisition time for volumetric interpolated breath-hold examination with a recently developed parallel imaging reconstruction technique: clinical feasibility

A recently developed parallel magnetic resonance (MR) imaging technique, parallel imaging with an augmented radius in k space, was used to accelerate the volumetric interpolated breath-hold examination (VIBE) performed in 20 patients referred for clinical liver imaging. Nonaccelerated MR images were also acquired in these patients. A five-point scale was used to score the quality of the images. The acceleration resulted in reduced image quality: The nonaccelerated images had a significantly higher (P <.05) mean score--3.8 +/- 0.3 (SD), indicating good quality--than the accelerated images--3.0 +/- 0.3, indicating acceptable quality. However, for three patients who could not hold their breath for the duration necessary for nonaccelerated imaging, less severe breathing artifacts on the accelerated images resulted in improved quality compared with the quality of the nonaccelerated images. Parallel MR imaging-accelerated VIBE may be beneficial for patients who have difficulty sustaining a breath hold for the duration necessary to perform nonaccelerated imaging.     

Ultra-high-speed MR imaging

Conventional magnetic resonance imaging (MRI) has been shown to provide excellent morphological images of the body organs, particularly structures undergoing little physiologic motion. Nevertheless, the clinical usefulness of MRI has been hampered by long acquisition times, high cost of scanning because of limited patient throughput, and image artifacts due to patient motion. With recent technical developments, several ultrafast scanning techniques capable of acquiring images in a breath-hold now find their introduction into clinical use. The system improvements are potentially useful for a vast range of applications hitherto not accessible to MR imaging. Among these are functional brain imaging, realtime imaging of cardiac motion and perfusion, fast abdominal imaging, improved MR angiography, and potentially real-time monitoring of interventional procedures. Whereas some ultrafast techniques can be performed on conventional scanners, echo-planar imaging, the fastest currently available data acquisition strategy, requires specially designed hardware. This article provides on overview of the technical advances in the ultrafast MRI and discusses potential applications and the possible future impact on body scanning.Correspondence to: G. K. von Schulthess     

Forty-millisecond MR imaging of the abdomen at 2.0 T

The ability of an ultrafast magnetic resonance (MR) imaging technique to provide abdominal MR images free of motion artifacts was studied. Individual T2-weighted transverse MR images were acquired in as little as 40 msec on a whole-body system operating at 2.0 T. Clinical evaluation was undertaken with fat-suppressed images in which only protons of water molecules contributed to image signal intensity. The ultrafast MR images were compared with conventional MR images obtained at 0.6 T. In 22 patients and two healthy volunteers, ultrafast MR images were of diagnostic quality and free of motion artifacts. Images obtained at an echo time (TE) of 30 msec (imaging time, 40 msec) had liver signal-to-noise ratios of 56.3 +/- 22.6 (n = 19). Because of a smaller data matrix, ultrafast MR images had soft-tissue interfaces that were less sharp than those of the highest-quality conventional MR images in which no motion artifacts were present. However, ultrafast MR images demonstrated high T2-dependent soft-tissue contrast, and pathologic and normal anatomies were readily detected with both imaging techniques. This ultrafast imaging technique has significant promise in whole-body MR imaging, in which motion artifacts often degrade image quality.     

Free‐breathing myocardial perfusion MRI using SW‐CG‐HYPR and motion correction

First‐pass perfusion MRI is a promising technique to detect ischemic heart disease. Sliding window (SW) conjugate‐gradient (CG) highly constrained back‐projection reconstruction (HYPR) (SW‐CG‐HYPR) has been proposed to increase spatial coverage, spatial resolution, and SNR. However, this method is sensitive to respiratory motion and thus requires breath‐hold. This work presents a non‐model‐based motion correction method combined with SW‐CG‐HYPR to perform free‐breathing myocardial MR imaging. Simulation studies were first performed to show the effectiveness of the proposed motion correction method and its independence from the pattern of the respiratory motion. After that, in vivo studies were performed in six healthy volunteers. From all of the volunteer studies, the image quality score of free breathing perfusion images with motion correction (3.11 ± 0.34) is improved compared with that of images without motion correction (2.27 ± 0.32), and is comparable with that of successful breath‐hold images (3.12 ± 0.38). This result was further validated by a quantitative sharpness analysis. The left ventricle and myocardium signal changes in motion corrected free‐breathing perfusion images were closely correlated to those observed in breath‐hold images. The correlation coefficient is 0.9764 for myocardial signals. Bland–Altman analysis confirmed the agreement between the free‐breathing SW‐CG‐HYPR method with motion correction and the breath‐hold SW‐CG‐HYPR. This technique may allow myocardial perfusion MRI during free breathing. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Sliding multislice MRI for abdominal staging of patients with pelvic malignancies: a pilot study

PURPOSE: To integrate SMS (sliding multislice imaging technique for acquiring axial images during continuous table motion) into a high-resolution pelvic MRI protocol for additional staging of the entire abdomen within one examination. MATERIALS AND METHODS: Axial two-dimensional images were acquired during continuous table motion using a fat-saturated contrast-enhanced T1-weighted gradient echo sequence. Patients held their breath during the first 20 s of the examination and breathed normally afterward while data acquisition continued. Measurement parameters were adjusted to optimize image quality throughout the total field of view. The method was investigated in 22 patients with pelvic malignancies. Two readers independently compared SMS image quality to conventional abdominal MR images, generated by a stationary multi-breath-hold gradient echo sequence. RESULTS: Qualitative evaluation yielded high diagnostic value of SMS data in body regions with no or minor breathing motion, and in those acquired during the initial breath-hold. Image quality in the upper abdomen, retroperitoneum, and pelvis is reproducible and equivalent to stationary MRI. Interfering artifacts are related to the intestine in the mid-abdomen. CONCLUSION: SMS is a promising technique that may have the potential for a first-line abdominal staging tool in patients with pelvic malignancies.     

心肌灌注显像中位移伪影的辨析

目的 探讨心肌灌注显像时位移伪影的影像学特征、不同轴向、发生位移起始点和帧数与伪影的相关性。方法 在心肌显像过程中依次沿x,y和z轴方向,分别在不同起始点,对不同帧数作一定距离的位移。其图像与正常对照比较判断有无伪影。结果作多因素分析。结果 轻度位移伪影的特征为：x轴位移表现为下壁突出的结节状热区;y轴位移表现为间隔和侧壁呈对称分布的热区;z轴位移表现为前壁的局部热区;这些表现仅见于短轴像上。重度伪影表现为“三角形”分布的壁内热区以及典型的“双三角形”改变。位移距离相同,方向相反,伪影的“冷”“热”分布的壁内热区以及典型的“双三角形”改变。位移距离相同,方向相反,伪影的“冷”“热”区位置相反。伪影与位移帧数和轴向有关,与起始点无关。结论 不同轴向位移伪影各有特征。移动帧数和y轴位移对伪影产生的影响最大。     

MR enteroclysis protocol optimization: comparison between 3D FLASH with fat saturation after intravenous gadolinium injection and true FISP sequences

The aim of this study was to introduce the true fast imaging with steady-state precession (FISP) sequence for MR enteroclysis and compare it with the already used T1-weighted fast low-angle shot (FLASH) sequence. Twenty-one patients underwent both MR and conventional enteroclysis. The MR enteroclysis examination was performed after administration of an iso-osmotic water solution through a nasojejunal catheter and the following sequences were included: (a) true FISP; and (b) 3D FLASH with fat saturation after intravenous injection of 20 mg Buscopan or 1 mg glucagon and 0.1 mmol/kg gadolinium chelates. The true FISP sequence provided images with significantly fewer motion artifacts, whereas 3D FLASH was less sensitive to susceptibility and chemical shift artifacts. The homogeneity of endoluminal opacification, wall conspicuity, and distention of the small bowel were very good to excellent and the two sequences presented no statistically significant differences here. True FISP provided significantly better overall image quality than did 3D FLASH. The true FISP sequence can provide good anatomic demonstration of the small bowel on T2-like images and could be combined with T1-weighted FLASH images for an integrated protocol of MR enteroclysis.     

MR imaging of the small bowel with a true-FISP sequence after enteroclysis with water solution

RATIONALE AND OBJECTIVES: To evaluate a novel MR enteroclysis technique for small-bowel imaging. METHODS: Twenty-one patients with suspected small-bowel disease underwent both MR and conventional enteroclysis. MR enteroclysis was performed by injecting an iso-osmotic water solution through a nasojejunal catheter with a flow rate of 80 to 150 mL/min. A maximum of 2 L of water solution was administered. A dynamic heavily T2-weighted single-shot turbo spin-echo sequence was applied in coronal orientation to monitor the bowel filling and adequate distention. Twelve 4-mm-thick slices were acquired by using a true fast imaging with steady-state precession (true-FISP) sequence during an 18-second breath-hold interval. Small-bowel distention, wall conspicuity, homogeneity of opacification, and the presence of artifacts were subjectively evaluated by two reviewers using five-point scales. RESULTS: Chemical shift artifacts were low and ghost artifacts were absent. Susceptibility artifacts were more prominent in the ileum; motion artifacts were low in the jejunum, ileum, and ileocecal area. Homogeneity of opacification was very good in the jejunum, good to very good in the ileum, and good in the ileocecal area. Distention was very good to excellent in the jejunum and ileum and very good in the ileocecal area. Wall conspicuity was very good to excellent in the jejunum and ileum. CONCLUSIONS: MR enteroclysis with the true-FISP sequence produced high-quality images of the small bowel. Further clinical studies are required to determine the clinical efficacy of the new technique compared with conventional enteroclysis.