海绵窦影像检查方法比较研究

目的对正常CS的CT和MRI序列比较研究,探讨CS实用影像检查方法.方法60例鞍区及CS正常的病人分为三组①20例行SET1WI、FSET2WI、脂肪抑制SET1WI、GRET1WI和SET1WI增强扫描;②20例行3DSPGR和高分辨FSET2WI;③另20例行冠状CT增强扫描.采用双盲法评价并比较(秩和检验)8种检查方法对CS区正常解剖结构的显示能力和伪影程度.结果(1)显示CS内第Ⅲ、Ⅴ1和Ⅵ对颅神经SET1WI增强扫描和CT增强扫描优于其他6种序列(Ρ＜0.05);(2)显示CS边缘GRET1WI和3DSPGR不如其他6种方法(Ρ＜0.05);(3)显示CS间隙GRET1WI、3DSPGR和高分辨FSET2WI不如其他5种方法(Ρ＜0.05);(4)显示ICAGRET1WI、3DSPGR、高分辨FSET2WI和CT增强扫描不如其他4种方法(Ρ＜0.05);(5)显示骨结构CT优于MRI各序列(Ρ＜0.05);(6)磁敏感伪影GRET1WI、3DSPGR和高分辨FSET2WI多于其他序列(Ρ＜0.05);(7)ICA相位方向伪影GRET1WI和3DSPGR多于其他序列(Ρ＜0.05).结论CS区首选检查为冠状位SET1WI和FSET2WI;脂肪抑制SET1WI和SET1WI增强扫描可在必要时使用;疑有骨结构改变时,需使用CT或CT增强扫描;GRET1WI和3DSPGR不适于CS区检查.     

脑弥漫性轴索损伤的MRI表现

目的　分析脑弥漫性轴索损伤 (DAI)的MRI表现 ,评价MRI对脑弥漫性轴索损伤的诊断价值。　方法　回顾性分析 30例CT检查阴性的脑弥漫性轴索损伤的MRI表现。MRI分别采用自旋回波T1WI、T2WI序列、液体衰减反转恢复序列 (FLAIR)及弥散加权成像 (DWI)。所有扫描在伤后 1周内进行。　结果　轴索积聚区多发的小灶性损伤 ,多数病灶为非出血性 (<2cm) ,除 3例超急性期外 ,所有病灶T2WI均显示为高信号 ,中线结构无明显移位。在超急性期患者 ,仅DWI上显示出高信号病灶。　结论　MRI对脑弥漫性轴索损伤敏感性较高 ,其影像学表现与DAI的严重程度有较好的对应关系。采用MRI检查CT表现阴性的临床疑诊患者 ,对脑弥漫性轴索损伤的临床诊断及治疗具有重要意义     

联合SWI与DWI在急性脑弥漫性轴索损伤中的应用价值

目的：评价联合磁敏感成像（SWI）与扩散加权成像（DWI）在急性期脑弥漫性轴索损伤中的应用价值。方法：32例脑弥漫性轴索损伤急性期患者,所有患者行常规MRI序列、DWI及SWI序列全脑扫描。结果：共检出病灶313个,T1WI 78个,T2WI 207个,FLAIR 292个,DWI 286个,SWI 297个。SWI显示245个病灶内分布斑片状、点状出血灶,其它序列共显示43个内分布出血灶。SWI、DWI病灶检出率高于常规T2WI（χ2=82.465,χ2=59.584;P〈0.01）,SWI、FLAIR及DWI病灶检出率无明显差异（χ2=3.052;P〉0.05）。结论：联合SWI与DWI有利于提高急性脑弥漫性轴索损伤的检出率,有助于准确评价病变的严重程度,SWI与DWI应作为急性脑弥漫性轴索损伤的常规扫描序列组合。     

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。     

脑弥漫性轴索损伤的MRI诊断价值与序列优化

目的比较MR各序列成像诊断脑弥漫性轴索损伤(DAI)的价值,优化MRI显示DAI的最佳序列组合.材料和方法对23例DAI患者行常规快速自旋回波(FSE)T1WI、T2WI 、液体衰减反转恢复序列(FLAIR)和场回波序列(FE)T2*WI、快速场回波-平面回波(FFE-EPI)T2*WI扫描,比较各种序列对DAI的显示率,分析其信号特征.结果82个病灶中47个为非出血性病灶,FLAIR显示47个,常规序列显示42个,FLAIR序列对非出血性DAI病灶显示多于常规序列.35个为出血性病灶,FE显示35个,常规序列显示21个,FE和FFE-EPI序列对出血性DAI的检出率、对比度明显高于常规序列.结论FLAIR FE或FFE-EPI序列组合可以准确诊断不同类型的DAI.     

磁敏感加权成像对胼胝体损伤的诊断

目的 探讨磁敏感加权成像(susceptibility weighted imaging,SWI)对胼胝体损伤的诊断价值.方法 回顾性分析15例CT检查阴性而MRI检查阳性的胼胝体损伤的MRI图像,所有患者均行高场强1.5T磁共振T1WI、T2WI、FLAIR、SWI横断位及T2WI矢状位扫描,分析各序列胼胝体损伤的信号特征及显示率.结果 胼胝体损伤T1WI为低、略低、稍高信号6例,T2WI、FLAIR为高信号10例,15例SWI均表现为明显低信号,5例患者CT、T1WI、T2WI、FLAIR均未见异常,其中4例SWI诊断为弥漫性轴索损伤,1例诊断为胼胝体等处多发损伤.脑内其他损伤区SWI表现为低信号影.结论 SWI对显示和诊断胼胝体损伤有较高的敏感性和准确性,并能显示常规MRI序列不能显示的微小损伤.     

原发性肝癌MnDPDP增强MRI两种T1W成像序列的比较研究

目的 :比较研究原发性肝癌MnDPDP增强MRI两种T1W成像序列的价值。材料和方法 :对36例原发性肝细胞癌(HCC)进行MnDPDP增强MRI前瞻性研究。平扫序列为SET1WI、FSET2W和FMPSPGRT1WI。静脉滴注MnDPDP后5min开始行FMPSPGRT1WI和SET1WI ,每隔5min成像一次直至40min ;并进行延迟24h成像。三位资深MRI诊断医师以盲法分别比较两种T1W图像(SET1WI和FMPSPGRT1WI)的信噪比(S/N)、对比度噪声比(C/N)、病灶的显示率和定性诊断率 ,以及两种T1W图像上HCC的信号强度差异。结果 :(1)MnDPDP增强后不同延迟时间的两种T1W图像之间的S/N±SD均无显著差异(p>0.05) ,而C/N±SD于延迟5min至40minFMPSPGRT1W图像优于SET1W(p<0.01) ;但延迟24hSET1W图像的C/N±SD优于FMPSPGRT1W(p<0.01)。(2)SET1W图像上HCC呈高信号的概率明显高于FMPSPGRT1W(5～40min :58.8 %对21.6 % ;24h :80.4 %对43.3 %)(p<0.005)。(3)SET1W和FMPSPGRT1W的HCC检出率均为92.7 % ;两者的定性率分别为92.7 %(SE)和87.3 %(FMPSPGR)。结论 :MnDPDP增强两种T1WMR图像对HCC的检出率相当 ,定性以SET1W稍优。作者推荐的HCC检查方案为 :(1)10～40min之间成像一次 ,序列为SET1W或(和)FMPSPGRT1W ;(2)延迟24h成像一次 ,序列为SET1W。     

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.     

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.     

PROPELLER FSE磁共振扩散加权技术在诊断超急性和急性脑梗死中的价值

目的比较螺旋桨扫描技术(PROPELLER FSE)和平面回波成像(EPI)两种扩散加权成像(DWI)序列,探讨PROPELLER技术在DWI的应用价值。资料与方法选取67例临床疑诊急性脑梗死的患者分别行PROPEL-LER FSE DWI、EPI DWI和常规T1WI、T2WI、T2WI液体衰减反转恢复序列(FLAIR)检查,比较两种不同的DWI序列的图像质量,病灶检出率和对病变的显示程度。结果67例EPI DWI图像均不同程度地存在磁化率伪影,67例PROPELLER FSE DWI图像未见明显伪影及变形。67例中共发现并确诊46个急性脑梗死灶(4例为颅内多发病灶),其中病灶位于颅底区域12个,非颅底区域34个。PROPELLER FSE DWI和EPI DWI均可分辩出所有非颅底区域梗死灶。对12个颅底病灶PROPELLER FSE DWI检出率达100%,而EPI DWI可以明确诊断的7个,检出率达58.3%,病灶形态显示不充分或变形者3个,占25%,漏诊2个,漏诊率为16.7%。所有颅底区域病灶EPI DWI上信噪比(SNR)低于相应PROPELLER FSE DWI的SNR(t=-2.874,P<0.05)。结论PROPELLER FSE DWI能提高图像SNR,有效消除颅底磁化率伪影,改善图像质量,提高颅底病变的检出率。     

Fast spin echo vs conventional spin echo in cervical spine imaging

The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15–66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20 %) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE. Received 6 May 1996; Revision received 19 July 1996; Accepted 26 February 1997     

Radial turbo spin echo imaging

Fast MR imaging methods should provide a familiar contrast behavior at a reduced scan time. The multi-spin echo approach (TSE) is one of the most promising techniques satisfying this condition. Although the data acquisition time is significantly reduced, image quality may still suffer from artifacts due to patient motion and flow. The radial turbo spin echo (rTSE) approach combines TSE methods and projection reconstruction (PR) techniques. In PR images, artifacts induced by patient motion or flow are known to have a different appearance with lower level of intensity. The contrast and artifact behavior of the rTSE approach has been investigated. The new technique has been applied to abdominal imaging with acquisition times shorter than 30 s and to heart imaging in combination with cardiac triggering.     

CINE turbo spin echo imaging

High‐resolution turbo spin echo (TSE) images have demonstrated important details of carotid artery morphology; however, it is evident that pulsatile blood and wall motion related to the cardiac cycle are still significant sources of image degradation. Although ECG gating can reduce artifacts due to cardiac‐induced pulsations, gating is rarely used because it lengthens the acquisition time and can cause image degradation due to nonconstant repetition time. This work introduces a relatively simple method of converting a conventional TSE acquisition into a retrospectively ECG‐correlated cineTSE sequence. The cineTSE sequence generates a full sequence of ECG‐correlated images at each slice location throughout the cardiac cycle in the same scan time that is conventionally used by standard TSE sequences to produce a single image at each slice location. The cineTSE images exhibit reduced pulsatile artifacts associated with a gated sequence but without the increased scan time or associated nonconstant repetition time effects. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.     

Density weighted turbo spin echo imaging

Purpose

To optimize the spatial response function (SRF) while maintaining optimal signal to noise ratio (SNR) in T₂ weighted turbo spin echo (TSE) imaging by prospective density weighting.

Materials and Methods

Density weighting optimizes the SRF by sampling the k‐space with variable density without the need of retrospective filtering, which would typically result in nonoptimal SNR. For TSE, the T₂ decay needs to be considered when calculating an optimized sampling pattern. Simulations were carried out and T₂ weighted in vivo TSE measurements were performed on a 3 Tesla MRI system. To evaluate the SNR, reversed centric density weighted and retrospectively filtered Cartesian acquisitions with identical measurement parameters and SRFs were compared with TE_eff = 90 ms and a density weighted k‐space sampling optimized to yield a Kaiser function for SRF side lobe suppression for white matter.

Results

Density weighting of a reversed centric reordering scheme resulted in an SNR increase of (43 ± 13)% compared with the Cartesian acquisition with retrospective filtering while maintaining comparable contrast behavior.

Conclusion

Density weighting is applicable to TSE imaging and results in significantly increased SNR. The gain can be used to shorten the measurement time, which suggests applying density weighting in both time and SNR constrained MRI. J. Magn. Reson. Imaging 2013;37:965–973. © 2013 Wiley Periodicals, Inc.     

MRI changes in myocarditis--evaluation with spin echo, cine MR angiography and contrast enhanced spin echo imaging

AIM: Myocarditis is probably under-diagnosed with clinical criteria generally used for diagnosis. Magnetic resonance imaging (MRI) has shown promise in detecting heart muscle disorders and we set out to assess the role of cine magnetic resonance angiography (MRA) and contrast enhancement in myocarditis, as there is a need for a non-invasive tool that can aid prognosis and follow-up. MATERIALS AND METHODS: Twenty patients were evaluated with T1 SE pre- and post-gadolinium enhancement and cine MRA. Four patients were histologically proven to have myocarditis, eight others were diagnosed as having myocarditis by clinical criteria and eight did not have myocarditis. Images were evaluated in a blinded fashion for regional wall motion abnormality and contrast enhancement pattern. Analysis of contrast enhancement by signal intensity measurement was also performed. RESULTS: Focal myocardial enhancement with associated regional wall motion abnormality correlated with myocarditis in 10 out of 12 patients, two patients with abnormal focal enhancement alone also clinically had myocarditis. None of the non-myocarditis patients showed abnormal focal enhancement. Enhancement analysis suggests that focal corrected myocardial enhancement of > 40% is abnormal. CONCLUSION: In the correct clinical context, focal myocardial enhancement on spin echo MRI strongly supports a diagnosis of myocarditis, especially when associated with regional wall motion abnormality.Roditi, G. H. (2000). Clinical Radiology55, 752-758.     

A spin echo chemical shift MR imaging technique

A new method is described that produces images of either the fat or water component in tissues in magnetic resonance imaging. Only a single scan is required, with scan times of a few minutes. Chemical shift selectivity is achieved in the spin echo process by controlling the spectral content of the 180 degree pulse that induces the spin echoes. A theoretical analysis of the selective spin echo process for the case of a radio frequency pulse of constant amplitude shows that spin echoes will be suppressed for certain values of offset frequency that are similar to, but different from, the frequencies at which the Fourier spectrum of the pulse vanishes. The theory was confirmed by experiment on a water phantom. The imaging technique was tested on both a phantom of oil and water and on a human forearm. Excellent suppression of the water signal was found in the fat images, and the small fat component seen in the water images is attributable to components of the triglyceride molecule for which spectral lines overlap those of water. The forearm images also showed blood flow effects in the water image that were not visible in the fat image. The relationship of this method to other proposed methods of chemical shift imaging is discussed.     

Intuitive design guidelines for fast spin echo imaging with variable flip angle echo trains.

We present a simple and intuitive means for determining the flip angles (FAs) required for smooth transitions between static pseudo steady states (SPSSs) in fast spin echo (FSE) imaging with variable FA (VFA) echo trains. We demonstrate the effectiveness of single and multiple transition pulses to successfully vary refocusing FAs while retaining high signal levels. The graphical interpretation presented here is consistent with previous analytical techniques and permits accurate signal-intensity predictions along the echo train.     

Multiple spin echo magnetic resonance imaging of the brain

Advantages of 3D multiecho: 1. High signal to noise ratio which is useful for: a) Long TE b) Short TR c) Thin slices 2. Reduced paradoxical enhancement of blood vessels 3. Contiguous slices 4. Number of slices per scan is not reduced by short TR or long TE 5. Thin slices easily generated 6. A short TR multiecho sequence can produce a spectrum of images reflecting a range of both T1 and T2 weighting in the same scan. This information can often improve specificity. Disadvantages of 3D multiecho: 1. Increased motion sensitivity of 3D acquisitions 2. Scan times increase with TR.