Fast CT-PRESS-based spiral chemical shift imaging at 3 Tesla.

A new sequence is presented that combines constant-time point-resolved spectroscopy (CT-PRESS) with fast spiral chemical shift imaging. It allows the acquisition of multivoxel spectra without line splitting with a minimum total measurement time of less than 5 min for a field of view of 24 cm and a nominal 1.5x1.5-cm2 in-plane resolution. Measurements were performed with 17 CS encoding steps in t1 (Deltat1=12.8 ms) and an average echo time of 151 ms, which was determined by simulating the CT-PRESS experiment for the spin systems of glutamate (Glu) and myo-inositol (mI). Signals from N-acetyl-aspartate, total creatine, choline-containing compounds (Cho), Glu, and mI were detected in a healthy volunteer with no or only minor baseline distortions within 14 min on a 3 T MR scanner.     

Prediction and Detection of Secondary Hemorrhages after Thrombolytic Therapy in Ischemic Stroke

Abstract It is well established that thrombolytic therapy increases the risk of secondary intracerebral hemorrhage in ischemic stroke patients. However, the term “intracerebral hemorrhage” (ICH) covers a wide spectrum from tiny spots of blood to massive space-occupying hematoma. We will review the etiology and clinical consequences of secondary hemorrhage after thrombolysis in ischemic stroke patients and discuss the ability of magnetic resonance imaging (MRI) to predict this phenomenon. MRI is a highly sensitive tool for detection of hemorrhagic transformation after ischemic stroke. The definitions of a so-called symptomatic hemorrhage after ischemic infarction differ considerably and will also be described. Attributing a causal relationship of a clinical deterioration to a secondary hemorrhage is not easy and should be only addressed when it exceeds at least 30% of the infarct volume. In other patients, secondary hemorrhage might be regarded as side effect of reperfusion within the region with the most severe perfusion deficit. Cerebral microbleeds (CMBs) are a frequent finding in patients with leukoaraiosis and appear to be a general marker of various types of bleeding- prone small vessel disease and a predictor of recurrent vascular events. Current data do not support the hypothesis that the detection of CMBs is a useful diagnostic criterion for the exclusion of patients with CMBs from thrombolytic therapy. However, an increased risk for the rare patients with numerous CMBs can not be ruled out.      

原发性肝癌的彩色多普勒及三维血流能量成像特征及其临床意义

目的:探讨三维血流能量成像(3D-CPA)和彩色多普勒血流成像(CDFI)的临床应用价值。方法:对47例原发性肝癌的病灶进行二维、CDFI及3D-CPA的检查,比较CDFI及3D-CPA显示肿瘤瘤内或瘤周血流多普勒信号丰富程度及血管分布类型,并检测肿瘤的血流参数。结果:3D-CPA显示肿瘤血流分布丰富程度及血管分布类型与CDFI均有显著性差异(均P<0.05),CDFI均可探及肿瘤的搏动性动脉血流,其中,收缩期峰值血流速度(PSV)为43~157cm/s,阻力指数(RI)为0.49~0.82,大于0.65者45例。结论:3D-CPA结合彩色多普勒血流参数的检测可作为临床评价原发性肝癌血供及血管分布的常规检查方法。     

精神分裂症首次发病患者的磁共振弥散张量显像研究

目的探讨从未用过药的精神分裂症首次发病(以下简称首发)患者的重要白质及部分灰质区的磁共振弥散张量显像(DTI)的特点。方法选取9例首发精神分裂症患者(患者组)及9名年龄、性别、受教育程度与患者组相配对的健康者,应用DTI成像技术检测脑额颞交界处、内囊等白质区和颞中回灰质、中央前回、中央后回等灰质区的各向异性(FA)、表观扩散系数(ADC)及双侧海马体积。结果患者组及对照组组内左右两侧兴趣区FA值及ADC值的差异无统计学意义(P>0.05);患者组与对照组各感兴趣区FA值差异无统计学意义(P>0.05),但患者组颞中回灰质(8.655×10-9)、中央前回(7.816×10-9)、中央后回(7.855×10-9)ADC值高于对照组(分别为7.428×10-9,6.921×10-9,7.013×10-9;P=0.049,0.009,0.005);两组内及组间双侧海马体积比较,差异均无统计学意义(P>0.05)。结论首发精神分裂症患者与健康者DTI参数之间没有明显区别。     

Optimizing the efficiency of high-field multivoxel spectroscopic imaging by multiplexing in space and time.

A new strategy to yield information from the maximum number of voxels, each at the optimum signal-to-noise ratio (SNR) per unit time, in MR spectroscopic imaging (MRSI) is introduced. In the past, maximum acquisition duty-cycle was obtained by multiplexing in time several single slices each repetition time (TR), while optimal SNR was achieved by encoding the entire volume of interest (VOI) each TR. We show that optimal SNR and acquisition efficiency can both be achieved simultaneously by multiplexing in space and time several slabs of several slices, each. Since coverage of common VOIs in 3D proton MRSI in the human brain typically requires eight or more slices, at 3 T or higher magnetic fields, two or more slabs can fit into the optimum TR (approximately 1.6 s). Since typically four or less slices would then fit into each slab, Hadamard encoding is favored in that direction for slice profile reasons. It is demonstrated that per fixed examination length, the new method gives, at 3 T, twice as many voxels, each of the same SNR and size, compared with current 3D chemical shift imaging techniques. It is shown that this gain will increase for more extensive spatial coverage or higher fields.     

MR T2加权成像显示胆囊壁增厚点状高信号的意义

目的研究病理组织学证实的胆囊腺肌瘤病、慢性胆囊炎和管壁增厚型胆囊腺癌在MRL加权成像（T2WI）显示病变胆囊壁点状高信号的特征。方法38例患者（胆囊腺肌瘤病16例，慢性胆囊炎13例，管壁增厚型胆囊腺癌9例），每例均进行了MR常规T1WI、常规T2WI和3mm薄层T2WI及MR胰胆管成像（MRCP）。所有患者均接受了胆囊切除手术。2名高年资放射科医生共同分析不同序列MRI，观察胆囊壁增厚及T2WI显示病变胆囊壁点状高信号的不同表现，将观察结果与病理组织学检查所见对照。结果所有患者的胆囊壁均明显增厚，厚度范围5～15mm，平均9mm。T2WI显示病变胆囊壁存在各种各样的点状高信号，在胆囊腺肌瘤病，点状高信号分布于整个增厚的胆囊壁，且数量较多（5～15个／cm^2），较大（直径2～7mm），边界清楚，呈现中等至明显高信号；在慢性胆囊炎，点状高信号主要位于增厚胆囊壁的黏膜侧，数量较少（3～5个／cm^2），较小（直径2～4mm），边界清楚，呈中等至明显高信号；在管壁增厚型胆囊腺癌，点状高信号边界欠清，呈现稍高信号，其数量和大小差异较大，分布范围取决于癌组织浸润胆囊壁的深度。结论胆囊腺肌瘤病、慢性胆囊炎和管壁增厚型胆囊腺癌在T2WI呈现的点状高信号有一定差别，正确识别这些点状高信号的特征有助于鉴别诊断良恶性胆囊壁增厚。     

阿尔茨海默病患者脑白质损害与认知功能的关系

目的用磁共振扩散张量成像(DTI)研究阿尔茨海默病(AD)患者脑白质损害的特点及其与认知功能改变的相关性。方法对16例AD患者和12名年龄及性别相当的健康老年人行DTI、T1液体衰减反转恢复序列(FLAIR)及T2-FLAIR检查,测量胼胝体膝部和压部、内囊前肢和后肢、额颞顶枕叶白质的部分各向异性分数值(FA)和平均弥散度(MD),分析FA、MD值与简易精神状态量表(MMSE)评分之间的相关关系。结果AD患者胼胝体压部、额叶、顶叶、颞叶FA值分别为0.602±0.043、0.270±0.034、0.294±0.043、0.302±0.032,与健康老人组相比显著下降(P<0.05),且与MMSE评分呈正相关关系,而内囊前后肢、枕叶、胼胝体膝部的FA值则无明显变化(P>0.05);胼胝体压部、顶叶白质的MD值分别为(0.918±0.029)、(0.826±0.015)×10-9m2/s,与健康老人组相比显著升高(P<0.01),且与MMSE评分呈负相关,而内囊前后肢、额叶、颞叶、枕叶和胼胝体膝部的MD值则无明显变化(P>0.05)。结论AD患者表现为脑白质的选择性损害,且损害程度与认知功能密切相关;这种选择性损害反映了AD病理机制中皮质-皮质及皮质-皮质下联系的丢失;DTI技术可以用来监测疾病的进展情况及评价AD治疗药物的临床疗效。     

Primary angiitis of the central nervous system: MRI features and clinical presentation

We report the MRI features in a series of four patients with primary angiitis of the central nervous system (PACNS). Based on MRI features, clinical presentation, paraclinical investigations and laboratory tests, including cerebrospinal fluid (CSF) analysis, various differentials were considered. In two patients with MRI findings of cortical, subcortical and deep white matter lesions, lack of mass effect, focal areas of bleed and heterogeneous parenchymal, leptomeningeal or pial enhancement and a normal magnetic resonance angiography, a differential diagnosis of primary angiitis of the CNS was also considered. In all patients, an open brain biopsy was advised to establish a definitive diagnosis of PACNS. Here, we briefly discuss the MRI features, correlation with clinical presentation and paraclinical parameters for the diagnosis of this entity. We also briefly review the literature.     

甲状腺~(99)Tc~mO_4~-显像冷结节的临床诊断价值

目的　探讨甲状腺99TcmO-4 显像冷结节对不同性质甲状腺疾病的诊断价值。方法　采用静脉注射99TcmO-4 185MBq ,2 0min后甲状腺前位静态显像 ,采集总计数 1× 10 6。显像显示甲状腺结节局部放射性分布缺损或低于正常甲状腺组织则定性为冷结节。结果　 34 2例甲状腺99TcmO-4 显像发现冷结节 85例 ,发生率为2 4.9% ,85例冷结节中 ,37例 (4 3.5 % )为甲状腺瘤 ,15例为甲状腺癌 (17.6 % ) ,2 0例 (2 3.5 % )为结节性甲状腺肿 ,8例 (9.4% )为甲状腺炎 ,4例 (4 .7% )为单纯性甲状腺囊肿 ,1例 (1.3% )为甲状腺外肿物。结论　冷结节在甲状腺99Tcm O-4 显像时较为常见 ,且不同性质甲状腺疾病的冷结节及其周围组织有一定的特征性表现 ,因此99TcmO-4显像冷结节对甲状腺腺瘤、甲状腺癌、甲状腺囊肿、甲状腺炎等常见疾病具有较高的临床价值。