Influence of SENSE on image properties in high-resolution single-shot echo-planar DTI.

Limited spatial resolution is a key obstacle to the study of brain white matter structure with diffusion tensor imaging (DTI). In its frequent implementation with single-excitation spin-echo echo-planar sequences, DTI's ability to resolve small structures is strongly restricted by T2 and T2* decay, B0 inhomogeneity, and limited signal-to-noise ratio (SNR). In this work the influence of sensitivity encoding (SENSE) on diffusion-weighted (DW) image properties is investigated. Computer simulations showed that the PSF becomes narrower with increasing SENSE reduction factors, R, enhancing the intrinsic resolution. After a brief theoretical discussion, we describe the estimation of SNR on a pixel-by-pixel basis as a function of R. The mean image SNR behavior is manifold: SENSE is capable of increasing SNR efficiency by reducing the echo time (TE). Each SNR(R) curve reveals a maximum that depends on the amount of partial Fourier encoding used. The overall best SNR efficiency for an eight-element head coil array and a b-factor of 1000 s/mm2 is achieved at R = 2.1 and partial Fourier encoding of 60%. In vivo tensor maps of volunteers and a patient, with an in-plane resolution of 0.78 x 0.78 mm2, are also presented to demonstrate the practical implementation of the parallel approach.     

膀胱癌的MRI诊断价值

目的:总结膀胱癌的MRI征象,探讨MRI对膀胱癌分期的作用及鉴别诊断要点。方法:对探讨经手术与病理证实23例膀胱癌的MRI回顾性对比分析。其中男性,19例,女性,4例,年龄50~90岁,平均年龄70岁。18例行MRI增强检查。结果:膀胱三角区及膀胱后侧壁是最常见好发部位,表现为膀胱壁突向腔内肿块和(或)膀胱壁局限性不规则增厚;肿瘤平扫T1WI等或略高信号,T2WI呈高信号,Gd-DTPA动态增强早期肿块显著强化。根椐肿瘤生长方式可分为:①小结节型,②广基肿块型,③浸润型。MRI对膀胱癌定位、定性诊断正确率分别为95.7%(22/23)、91.3%(21/23);术前MRI诊断与TNM分期符合率为82.3%(19/23),MRI较病理分期偏高。结论:膀胱癌的MRI表现具有独特性。T1加权主要用于肿瘤的定性诊断,T2加权主要用于肿瘤的术前分期;MRI检查多方位、多序列成像,是显示膀胱癌最理想的检查方法。     

Ventilation imaging of the lung: Comparison of hyperpolarized helium-3 MR imaging with Xe-133 scintigraphy

RATIONALE AND OBJECTIVES: To compare hyperpolarized helium-3 (HHe) magnetic resonance imaging (MRI) of the lung with standard Xe-133 lung ventilation scintigraphy. MATERIALS AND METHODS: We performed a retrospective review of 15 subjects who underwent HHe MRI and Xe-133 lung ventilation imaging. Coronal MRI sections were acquired after a single inhalation of HHe gas, and standard posterior planar lung ventilation scintigraphy was performed during continuous breathing of Xe-133 gas. The first breath scintigram of each patient was compared with a composite MR image composed of the sum of the individual MR images and with the individual helium-3 MR images. Ventilation defects on the two imaging modalities were compared for size, conspicuity, and concordance in presence and location. Assessment was done separately for each of four lung quadrants. RESULTS: Comparing the composite HHe MR images with Xe-133 scintigraphy, ventilation defect size, conspicuity and concordance were the same in 67% (40/60), 63% (38/60), and 62% (37/60) quadrants, respectively. Comparing the individual HHe MR image sections with the Xe-133 ventilation scan, there was concordance between the ventilation defects in 27% (16/60) of quadrants. More defects were identified on the individual HHe MR images in 62% (37/60) of quadrants. CONCLUSION: There was good agreement between composite HHe MR image and first breath Xe-133 scintigraphic images, supporting the widely held assumption that HHe MRI likely depicts first breath lung ventilation.     

颅内黑色素瘤3例

1病例介绍例1男性患者,35岁,因为头痛1月、加重伴左侧肢体活动受限5天入院。体格检查:左上肢肌力Ⅳ级、左下肢肌力Ⅲ级,强握反射阳性,有震颤。CT检查:右侧颞顶部高密度病灶约5.3 cm×4.2 cm,边缘光滑规则,占位效应明显;该病灶内还有一个边界清楚的高密度影,明显强化,诊断为脑膜     

Efficient high-frequency body coil for high-field MRI.

The use of body coils is favored for homogeneous excitation, and such coils are often paired with surface coils or arrays for sensitive reception in many MRI applications. While the body coil's physical size and resultant electrical length make this circuit difficult to design for any field strength, recent efforts to build efficient body coils for applications at 3T and above have been especially challenging. To meet this challenge, we developed an efficient new transverse electromagnetic (TEM) body coil and demonstrated its use in human studies at field strengths up to 4 T. Head, body, and breast images were acquired within peak power constraints of <8 kW. Bench studies indicate that these body coils are feasible to 8 T. RF shimming was used to remove a high-field-related cardiac imaging artifact in these preliminary studies. P41RR13230     

皮层下动脉硬化性脑病的影像学诊断

目的 探讨皮层下动脉硬化性脑病（SAE）的影像学诊断价值。方法 选择经影像学检查结合临床资料确诊的病例，其中单做CT检查84例，单做MRI检查14例，既做MRI检查对照24例进行分析。另又对某一时期内60岁以上（不管什么原因）做头颅CT检查患者，只有2例有痴呆，CT分型Ⅰ型47例，Ⅱ型13例，Ⅲ型为24例；同一时期头颅CT检查患者中，有SAE表现42例，无SAE表现42例；24例CT与MRI检查对照。MRI优于CT。结论 CT与MRI检查可以对SAE作出早期诊断，有助于早期治疗。     

12例Dandy—Walker综合征的临床CT与MRI分析

目的分析Dandy—Walker综合征的临床及cT与MR!影像特征。方法采用cT与MRI常规扫描，对12例Dandy—Walker综合征的临床表现、CT与MRI征象进行回顾性分析；结果12例Dandy—Walker综合征的CT与MRI表现归纳为①小脑蚓部缺失，小脑半球发育不良、完全分离，分离的小脑半球可以不对称；②第四脑室呈囊状、扇形、三角形显著扩张或后颅窝巨大囊状阴影与第四脑室相通；③窦汇异常抬高，越过人字缝／天幕抬高；④幕上脑室对称性扩张，脑积水。结论对Dandy—Walker综合征的诊断，CT扫描能够显示后颅凹及天幕上下脑的形态与结构，其CT表现具特征性；MRI可多平面扫描，无骨质伪影，显示后颅凹优于CT，在矢状面上可显示小脑、第四脑室、导水管、后颅凹囊肿以及与天幕的关系。CT与MRI扫描对Dandy—Walker综合征能够做出定性诊断，是术前诊断的主要依据，检查无痛苦，有重要的诊断和鉴别诊断价值。     

壶腹癌的MRI诊断

目的:探讨MRI诊断壶腹癌的价值。材料和方法:回顾性分析20例壶腹癌的MRCP及MRI影像资料,并与病理学诊断进行对照。结果:20例壶腹癌中显示局部软组织肿块13例、胆总管腔“截断征”17例、肝内胆管软滕样扩张19例、胆囊增大17例和“双管征”14例。结论:MRI,特别是MRCP能显示典型的“双管征”、“软藤征”和较清晰的癌肿范围,对壶腹癌有较高的诊断价值。     

脑原发性淋巴瘤的CT、MRI诊断

目的:探讨脑原发性淋巴瘤的CT、MRI特征,以提高诊断水平。材料和方法:回顾性分析经病理证实的20例脑原发性淋巴瘤的CT和MRI表现。结果:20例共52个病灶,其中脑干4个、基底节14个、丘脑1个、胼胝体8个、枕叶10个、顶叶5个、颞叶5个、额叶4个、硬脑膜1个。位于脑深部近中线区域占78.8%;形态不规则(71.2%),内部发现囊变(15.4%),均未见钙化、出血。CT平扫均呈等或略高密度。T1WI呈低信号(30.7%)等信号(63.5%),T2WI等信号(69.3%),高信号(26.9%),增强后均呈显著增强。周围水肿(84.6%)。结论:脑原发性淋巴瘤的CT、MRI表现有一定特点,熟悉其临床及表现特点有助于对本病作出正确的诊断。     

Quantification of the expression level of integrin receptor alpha(v)beta3 in cell lines and MR imaging with antibody-coated iron oxide particles.

Targeted imaging requires site-specific accumulation of a contrast agent (CA), and the properties of that agent must be selected according to the abundance of the target to obtain a signal above the detection limit of the instrument. However, numerical estimates of receptors per cell are rarely found in the literature. Integrin receptors would be particularly promising targets because of their accessibility from the blood stream and expression on activated neovascular endothelial cells. We systematically estimated the number of integrin receptors of cell lines and primary cells by flow cytometry analysis. Since integrin receptors are heterodimeric molecules, and alpha(v) forms complexes with various beta subunits, the numbers of alpha(v) and beta(3) subunits are therefore dissimilar. The observed values are 3 . 10(3)-1.4 . 10(4)/cell for alpha(v), and 5.3 . 10(2)-1.1 . 10(4)/cell for beta(3). Despite the low number of exposed receptors, we show that up to single-cell MR visualization can be achieved with the use of iron oxide beads complexed with antibodies as CAs.