不同MRI序列在显示颞叶内侧硬化的对照研究

目的比较各序列在颞叶内侧硬化病人显示海马信号强度增加的作用。材料与方法对３０例临床及脑电图或脑地形图诊断为颞叶癫痫的病人采用双回波常规自旋回波（ＳＥ）序列、快速自旋回波（ＦＳＥ）序列和液体衰减反转恢复（ＦＬＡＩＲ）序列进行ＭＲＩ检查，并通过目测观察和信号强度测量等方法对图像进行处理。结果ＳＥ序列质子密度加权像判别海马信号强度增加的准确度最差（４３．３％）；ＦＳＥ序列次之（６２．２％）；ＳＥ序列Ｔ２加权像和ＦＬＡＩＲ序列判别海马信号强度增加的准确度很高，且ＦＬＡＩＲ序列（８８．９％）较ＳＥ序列Ｔ２加权像（７７．８％）更为准确。结论在诊断颞叶内侧硬化方面ＦＬＡＩＲ序列有可能成为常规ＳＥ序列的替代者     

Diffusion MRI findings of cytomegalovirus-associated ventriculitis: a case report

Cytomegalovirus (CMV) ventriculoencephalitis is a rare but serious potential complication of CMV infection in immunocompromised patients. Characteristic diffusion-weighted imaging findings can be helpful for the diagnosis of CMV ventriculitis, as in this case report.     

Comparison of 3D turbo spin-echo SPACE sequences with conventional 2D MRI sequences to assess the shoulder joint

Purpose

To determine the accuracy and reliability of three-dimensional (3D) T1- and proton density (PD)-weighted turbo spin-echo (TSE) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) compared with conventional 2D sequences in assessment of the shoulder-joint.

Materials and methods

Ninety-three subjects were examined on a 3-T MRI system with both conventional 2D-TSE sequences in T1-, T2- and PD-weighting and 3D SPACE sequences in T1- and PD-weighting. All examinations were assessed independently by two reviewers for common pathologies of the shoulder-joint. Agreement between 2D- and 3D-sequences and inter-observer-agreement was evaluated using kappa-statistics.

Results

Using conventional 2D TSE sequences as standard of reference, sensitivity, specificity, and accuracy values of 3D SPACE were 81.8%, 95.1%, and 93.5% for injuries of the supraspinatus-tendon (SSP), 81.3%, 93.5%, and 91.4% for the cartilage layer and 82.4%, 98.5%, and 97.5% for the long biceps tendon. Concordance between 2D and 3D was almost perfect for tendinopathies of the SSP (κ = 0.85), osteoarthritis (κ = 1), luxation of the biceps tendon (κ = 1) and adjacent bone marrow (κ = 0.92). Inter-observer-agreement was generally higher for conventional 2D TSE sequences (κ, 0.23–1.0), when compared to 3D SPACE sequences (κ, −0.33 to 1.0) except for disorders of the long biceps tendon and supraspinatus tendon rupture.

Conclusion

Because of substantial and almost perfect concordance with conventional 2D TSE sequences for common shoulder pathologies, MRI examination-time can be reduced by nearly 40% (up to 11 min) using 3D-SPACE without loss of information.     

不同MRI序列检出聚丙烯酰胺水凝胶注射隆乳患者乳腺病变效能的比较研究

目的 探讨不同MRI序列对聚丙烯酰胺水凝胶（PAHG）注射隆乳后乳腺病变的检出效能。 方法 回顾性分析80例临床怀疑合并乳腺病变的注射隆乳患者的MRI影像资料,扫描序列包括T1加权像、T2加权像、短时间反转恢复（STIR）、弥散加权成像（DWI）、MR水成像（MRH）及肝脏容积超快速（LAVA）三维多期动态增强序列,分析各序列图像中病灶的信号特点、位置、形态、大小和数量,以及时间-信号强度曲线,分别计算不同序列对乳腺病变的总检出率和对乳腺癌的诊断准确率。各序列病灶的总检出率差异采用R×C交叉表卡方检验,组内两两比较采用卡方检验分析。 结果 160个乳腺中共检出86个病灶,其中乳腺癌病灶30个。T1加权像、T2加权像、STIR、DWI、MRH及LAVA增强序列对乳腺病灶的总检出率分别为32.56%（28/86）、61.11%（53/86）、63.88%（55/86）、41.66%（36/86）、89.53%（77/86）、100%（86/86）,其中乳腺癌病灶诊断准确率分别为33.33%（10/30）、66.67%（20/30）、66.67%（20/30）、46.67%（14/30）、100%（30/30）、100%（30/30）。对各序列乳腺病变的总检出率行R×C交叉表卡方检验：χ2=129.428,P < 0.05,差异有统计学意义;对各序列乳腺癌病灶诊断准确率行R×C交叉表卡方检验：χ2=51.843,P < 0.05,差异有统计学意义。对各序列乳腺病变总检出率和乳腺癌病灶诊断准确率行组内两两比较分析,除T1加权像与MRH、T2加权像与STIR对乳腺病变总检出率的差异无统计学意义外（χ2=1.593、0.100,P均>0.05）,其他均有统计学意义（χ2=6.729~87.509,P均 < 0.05）;而MRH与T1加权像、MRH与T2加权像、MRH与STIR、T2加权像与STIR,以及DWI与LAVA增强序列对乳腺癌诊断准确率的差异均无统计学意义（χ2=1.111、2.443、2.443、0.000、0.000,P均>0.05）,其他序列的差异有统计学意义（χ2=12.000~30.000,P均 < 0.05）。 结论 DWI和LAVA增强序列对PAHG注射隆乳后乳腺病变的总检出率最高;合理应用MRI序列,有利于提高乳腺癌病灶的诊断准确率。     

Comparison of echo-planar sequences for perfusion-weighted MRI: which is best?

We compared gradient-echo (GRE), spin-echo (SE) and stimulated-echo (STE) echo-planar imaging sequences for perfusion-weighted imaging at different field strengths. Focal cerebral ischaemia was induced by endovascular occlusion of the middle cerebral artery in eight rats. MR was performed at 4.7 T or 2.35 T. With each sequence, we acquired data sets before, during and after bolus injection of Gd-DTPA with a time resolution of 1.2 s per image. The perfusion-weighted images were assessed with regard to image quality, artefacts, signal-to-noise ratio (SNR), and signal-attenuation-to-noise ratio (ΔSNR) of the non-ischaemic tissue. Visual assessment showed GRE-EPI images acquired at 4.7 T to suffer from distortion due to susceptibility artefacts. Artefacts were less marked with the SE and STE series. The GRE-EPI sequence gave the highest SNR and ΔSNR. At 2.35 T, the SNR of the STE sequences was less than 3 and therefore did not allow construction of reliable signal-time curves. SE-EPI was best suited for perfusion-weighted imaging at high field strength thanks to its minimal distortion artefacts and high SNR. Using lower field strengths (2.35 T and less), susceptibility artefacts are reduced; GRE-EPI sequences are then best suited, because they have the highest SNR and T2^* sensitivity. Received: 19 September 1997 Accepted: 16 October 1997     

Comparison of single-breath-hold fast spin-echo sequences with routine non-breath-hold techniques: Application to MRI of renal masses

In 24 patients presenting with 55 renal lesions (mean size, 20.8 mm), single-breath-hold (SBH) fast spin-echo (FSE) techniques allowing T1 and T2 images to be produced within 20 and 23 sec, respectively, were compared with routine non-breath-hold (NBH) spin-echo (SE) T1 and NBH-FSE T2 sequences. Contrast-to-noise ratios (CNRs) measured from SBH-FSE T1 images were an average of 97% higher than their NBH counterparts (P = .0001) and allowed an improved lesion conspicuity in 80% of the cases (P = .0001). For T2 imaging, SBH-FSE and NBH-FSE sequences were not statistically different with respect to lesion conspicuity (P = .55) and CNR values (P = .19). This was observed despite a 35% average decrease in CNR of SBH-FSE compared to NBH-FSE images. By reducing respiratory motion artifacts while preserving SE-like image contrast, SBH-FSE techniques have the potential to replace routine NBH sequences for an optimal diagnosis of renal masses.     

Comparison of 3T and 7T MRI clinical sequences for ankle imaging

The purpose of this study was to compare 3T and 7T signal-to-noise and contrast-to noise ratios of clinical sequences for imaging of the ankles with optimized sequences and dedicated coils. Ten healthy volunteers were examined consecutively on both systems with three clinical sequences: (1) 3D gradient-echo, T(1)-weighted; (2) 2D fast spin-echo, PD-weighted; and (3) 2D spin-echo, T(1)-weighted. SNR was calculated for six regions: cartilage; bone; muscle; synovial fluid; Achilles tendon; and Kager's fat-pad. CNR was obtained for cartilage/bone, cartilage/fluid, cartilage/muscle, and muscle/fat-pad, and compared by a one-way ANOVA test for repeated measures. Mean SNR significantly increased at 7T compared to 3T for 3D GRE, and 2D TSE was 60.9% and 86.7%, respectively. In contrast, an average SNR decrease of almost 25% was observed in the 2D SE sequence. A CNR increase was observed in 2D TSE images, and in most 3D GRE images. There was a substantial benefit from ultra high-field MR imaging of ankles with routine clinical sequences at 7T compared to 3T. Higher SNR and CNR at ultra-high field MR scanners may be useful in clinical practice for ankle imaging. However, carefully optimized protocols and dedicated extremity coils are necessary to obtain optimal results.     

Comparison of MRI pulse sequences for investigation of lesions of the cervical spinal cord

Small spinal cord lesions, even if clinically significant, can be due to the low sensitivity of some pulse sequences. We compared T2-weighted fast (FSE), and conventional (CSE) spin-echo and short-tau inversion-recovery (STIR)-FSE overlooked on MRI sequences to evaluate their sensitivity to and specificity for lesions of different types. We compared the three sequences in MRI of 57 patients with cervical spinal symptoms. The image sets were assessed by two of us individually for final diagnosis, lesion detectability and image quality. Both readers arrived at the same final diagnoses with all sequences, differentiating four groups of patients. Group 1 (30 patients, 53 %), with a final diagnosis of multiple sclerosis (MS). Demyelinating lesions were better seen on STIR-FSE images, on which the number of lesions was significantly higher than on FSE, while the FSE and CSE images showed approximately equal numbers of lesions; additional lesions were found in 9 patients. The contrast-to-noise ratio (CNR) of 17 demyelinating lesions was significantly higher on STIR-FSE images than with the other sequences. Group 2, 19 patients (33 %) with cervical pain, 15 of whom had disc protrusion or herniation: herniated discs were equally well delineated with all sequences, with better myelographic effect on FSE. In five patients with intrinsic spinal cord abnormalities, the conspicuity and demarcation of the lesions were similar with STIR-FSE and FSE. Group 3, 4 patients (7 %) with acute myelopathy of unknown aetiology. In two patients, STIR-FSE gave better demarcation of lesions and in one a questionable additional lesions. Group 4, 4 patients (7 %) with miscellaneous final diagnoses. STIR-FSE had high sensitivity to demyelinating lesions, can be considered quite specific and should be included in spinal MRI for assessment of suspected demyelinating disease. Received: 21 September 1999/Accepted: 10 December 1999     

Comparison of magnetic resonance imaging sequences with computed tomography to detect low-grade subarachnoid hemorrhage: Role of fluid-attenuated inversion recovery sequence

OBJECTIVES: To compare computed tomography (CT) with magnetic resonance imaging (MRI) for the presumptive diagnosis and localization of acute and subacute low-grade subarachnoid hemorrhage (SAH). METHODS: We consecutively enrolled 45 patients clinically suspected of low-grade SAH, comparing them with a control group. We obtained axial nonenhanced CT scans as well as fluid-attenuated inversion recovery (FLAIR) and T2-weighted gradient echo (T2*) MRI sequences at 1.0 T. Two neuroradiologists scrutinized the presence of blood at 26 different regions in the intracranial subarachnoid space (SAS). RESULTS: Three of 45 patients had normal CT and MRI scans, and SAH was excluded by lumbar puncture. We demonstrated SAH on CT scans in 28 of 42 (66.6%) patients, T2* sequences in 15 of 42 (35.7%) patients, and FLAIR sequences in 42 of 42 (100%) patients. Fluid-attenuated inversion recovery sequences were superior to CT in 16 of the 26 evaluated regions. CONCLUSIONS: The FLAIR sequence was superior for presumptive diagnosis and localization of acute and subacute low-grade SAH, representing a potential tool in this setting.     

Whole-body muscle MRI to detect myopathies in non-extrapyramidal bent spine syndrome

Objective

Bent spine syndrome (BSS), defined as an abnormal forward flexion of the trunk resolving in supine position, is usually related to parkinsonism, but can also be encountered in myopathies. This study evaluates whole-body muscle MRI (WB-mMRI) as a tool for detecting underlying myopathy in non-extrapyramidal BSS.

Materials and methods

Forty-three patients (90 % women; 53–86 years old) with a non-extrapyramidal BSS were prospectively included. All underwent a 1.5-T WB-mMRI and a nerve conduction study. Muscle biopsy was performed if a myopathy could not be eliminated based on clinical examination and all tests. Systematic MRI interpretation focused on peripheral and axial muscle injury; spinal posture and incidental findings were also reported.

Results

WB-mMRI was completed for all patients, with 13 muscle biopsies ultimately needed and myopathy revealed as the final etiological diagnosis in five cases (12 %). All biopsy-proven myopathies were detected by the WB-mMRI. Relevant incidental MRI findings were made in seven patients.

Conclusions

This study supports WB-mMRI as a sensitive and feasible tool for detecting myopathy in BSS patients. Associated with electroneuromyography, it can better indicate when a muscle biopsy is needed and guide it when required. Rigorous radiological interpretation is mandatory, so as not to miss incidental findings of clinical consequence.     

A molecular MRI probe to detect treatment of cardiac apoptosis in vivo

Cell death by apoptosis is critical in myocardial diseases, and noninvasive detection of early, reversible apoptosis might be useful clinically. Exogenous Annexin‐V (ANX) protein binds membrane phosphatidylserine, which is externalized in early apoptosis. A molecular MRI probe was constructed with superparamagnetic iron oxide (SPIO) conjugated to recombinant human ANX (ANX‐SPIO). Apoptosis was induced with doxorubicin, a cardiotoxic cancer drug, in culture in neonatal rat ventricular myocytes, cardiac fibroblasts, and mesenchymal stem cells, and in vivo in the mouse heart. ANX‐SPIO was validated using T2*‐weighted 3T MRI. ANX‐SPIO produced T2* signal loss, reflecting iron content, that correlated highly with independent apoptosis markers; bound with high affinity to apoptotic myocytes by competition assay (Ki 69 nM); detected apoptosis in culture much earlier than did TUNEL stain; and revealed fibroblast resistance to apoptosis. With apoptosis in vivo, ANX‐SPIO produced diffuse myocardial T2* signal loss that correlated with increased iron stain and caspase activity. Treatment with an alpha‐1‐adrenergic agonist in vivo reversed apoptosis and eliminated the ANX‐SPIO MRI signal. It is concluded that cardiac MRI of ANX‐SPIO detects early, nonischemic cardiac apoptosis in culture and in vivo, and can identify reversibly injured cardiac cells in diseased hearts, when treatment is still possible. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

磁共振FLAIR序列在颅脑病变中的应用

目的探讨液体衰减反转恢复（FLAIR）序列在颅内病变诊断中的应用价值。方法对88例患者均行FLAIR序列和FSE—T2WI检查,比较两种序列对病灶的显示能力。结果88例中,透明隔间腔5例,交通性脑积水6例,梗阻性脑积水10例,室管膜瘤2例,转移瘤2例,胶质细胞瘤5例,脑膜瘤5例,亚急性脑室内出血（基底节区出血破入脑室）2例,慢性硬膜下血肿2例,侧脑室内囊肿1例,脑白质脱髓鞘疾病20例,基底节区梗死15例,血管母细胞瘤5例,脑囊虫病3例,脑炎5例。以上疾病的病灶,在FLAIR序列上均能显示,并可清晰显示病灶边界;但在T2WI像上虽可显示病灶,但边界不清晰,难以清晰显示病灶边缘与周围组织关系。结论FLAIR序列能够抑制脑脊液的信号,提高脑室内、脑室旁病灶的对比度,对脑室旁病灶、尤其是脑室内病变的显示较FSE—T2WI清晰。