磁共振常规成像及DWI对脑膜瘤的诊断价值

目的:比较磁共振常规成像序列(T1WI、T2WI及FLAIR)与DWI对脑膜瘤的检出率,探讨其鉴别病理亚型及良恶性的价值。方法:回顾性分析70例经手术病理证实的脑膜瘤患者的MRI图像,计算不同序列对脑膜瘤的检出率;测量并比较不同病理亚型、不同病理分级的肿瘤实质的平均ADC值和相对ADC值(rADC值)。结果:在T2WI上出现低信号的多是纤维型、过渡型和砂粒体型,出现高信号的多是脑膜上皮型和血管瘤型。在各个序列中,以DWI对脑膜瘤病变的检出率最高(87.1%),T2WI次之(74.3%),T1WI最低(38.6%)。恶性脑膜瘤的囊变发生率(67%)明显高于良性脑膜瘤(22%)。良性组各亚型间、良恶性两组间平均ADC值及rADC值差异均无统计学意义(P>0.05)。结论:DWI可提高对脑膜瘤的检出率,但单独根据ADC值并不能鉴别脑膜瘤的亚型及良恶性。DWI结合常规MRI表现对脑膜瘤亚型及良恶性的鉴别有一定意义。     

胆囊癌多b值磁共振扩散加权成像的临床应用

目的 评价不同b值磁共振扩散加权成像对胆囊癌的显示能力和最佳b值的选择;并探讨表观扩散系数值与胆囊癌分化程度的关系.方法 对33例胆囊癌患者术前行常规MRI和DWI检查.测量肿瘤的ADC值,计算多b值扩散成像和T2 WI图像中的信噪比、对比噪声比及信号强度比等数据;对经手术病理证实的33例胆囊癌患者进行病理分级,比较不同b值时不同分化程度胆囊腺癌的ADC值;并进行统计学分析.结果 33例胆囊癌病灶均被DWI检出,肿瘤的SNR和肿瘤与正常肝脏的CNR随b值的增加逐渐下降,而肿瘤的SIR随b值增加逐渐升高.b值800s/mm2时DWI图像肿瘤与正常肝脏的CNR、肿瘤的SIR和SNR均高于T2WI,差异有统计学意义（P＜0.05）.胆囊腺癌的ADC值随着b值增高逐渐变小,差异有统计学意义（P＜0.05）.结论 胆囊癌扩散加权成像的最佳b值为800s/mm2,可以得到胆囊癌的良好显示;胆囊腺癌ADC值随着肿瘤分化程度的降低而减小.     

弥散MRI诊断颅内表皮样囊肿的价值

目的:探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)图诊断颅内表皮样囊肿的价值.材料和方法:分析19例表皮样囊肿常规MRI和DWI的信号特征,定量测定表皮样囊肿、正常脑实质和脑脊液的ADC值.结果:17例表皮样囊肿T1WI、T2WI呈等或稍高于脑脊液信号,2例T1WI呈高低混杂信号.肿瘤边缘弧线形增强或不增强.19例肿瘤DWI呈明显高于脑实质和脑脊液信号,肿瘤较脑脊液的平均ADC值显著减低,较脑实质的平均ADC值显著增高.结论:DWI优于常规MRI发现颅内表皮样囊肿,DWI上表皮样囊肿的高信号可能是肿瘤组织的T2余辉效应所致.     

颅内表皮样囊肿的常规T_1WI、T_2WI、FLAIR及DWI对比分析

目的:通过定性分析和定量比较来探讨颅内表皮样囊肿(ECs)的FLAIR和DWI特征。方法:ECs16例,测量其T1WI、T2WI、FLAIR及DWI上病灶信号强度和ADC值,计算组织间对比度(CR)和对比噪声比(CNR)。结果:在FLAIR上ECs平均信号强度高于脑脊液(CSF),低于脑组织。在T1WI上,表皮样囊肿与脑脊液间的CR和CNR分别是0.11±0.06和1.02±1.11;在T2WI上,ECs与CSF间的CR和CNR分别是0.05±0.04和1.05±0.58;而在DWI上,ECs与CSF间的CR是12.56±2.87,CNR是18.23±5.42。16例患者示踪DWI图像上均呈明显高信号。ECs平均ADC值明显低于CSF(P<0.001),而高于脑白质(P=0.002)。结论:FLAIR对颅内表皮样囊肿显示优于常规MRI序列,DWI描述ECs轮廓优于其它MRI序列。     

DWI对颅底脊索瘤与软骨肉瘤鉴别诊断的应用价值

目的 探讨扩散加权成像(DWI)在颅底脊索瘤与颅底软骨肉瘤鉴别诊断中的应用价值.方法 回顾性分析经病理证实的14例经典型颅底脊索瘤、9例未分化型颅底脊索瘤及18例软骨肉瘤的临床及影像学资料.分析瘤体组织的部位、T2WI相对灰质的信号、强化方式及表观扩散系数(ADC).增强扫描未见强化记为0分,不均匀强化为1分,90％以上瘤体均匀强化为2分.采用非参数检验进行统计.结果 3种肿瘤病灶的平均ADC值、最小ADC值、最大ADC值及T2 WI信号强度均存在显著差异(P＜o.05).瘤体的强化方式在病例数量方面存在显著差异(P＜0.05),但强化方式的得分及发病部位无显著差异(P＞0.05).结论 DWI对颅底肿瘤的鉴别诊断具有重要的临床价值,结合T2 WI信号可提高颅底肿瘤的诊断率.     

磁共振扩散加权成像在肝外胆管癌诊断中的应用研究

目的探讨MR扩散加权成像(DWI)及表观扩散系数(apparent diffusion coefficient,ADC)值对肝外胆管癌的诊断价值。资料与方法回顾性分析58例经手术病理证实的肝外胆管癌患者的MRI原始资料,包括不同b值的DWI(b值为100 s/mm2、300 s/mm2、500 s/mm2、800 s/mm2、1000 s/mm2)及常规MRI平扫(T2WI、T1WI)。测量不同b值时肝外胆管癌病灶ADC值,计算病灶与正常肝脏间对比噪声比(CNR),根据HE染色病理图片记录肝外胆管癌细胞密度,并进行分析。结果 DWI对肝外胆管癌病灶的信号显示优于T2WI及T1WI。随着b值的增大,病灶ADC值逐渐降低,病灶与正常肝脏间CNR呈逐渐下降趋势,差异有统计学意义(P<0.05)。不同b值时,肝外胆管癌病灶ADC值与细胞密度之间均呈负相关(P<0.05);b=800 s/mm2时,其相关性最高(r=-0.81,P<0.05)。结论 DWI能较清楚地显示肝外胆管癌病灶,b值为800 s/mm2时最佳,与ADC值测量共同分析,有助于肝外胆管癌病灶的检出。     

DWI在不同肺癌类型中的鉴别诊断

目的探讨扩散加权成像(DWI)在不同肺癌类型中的诊断价值。方法选取2016年3月~2017年3月我院收治的肺癌患者58例,所有患者均行DWI扫描,扩散敏感因子b值取500s/mm^2,比较不同类型肺癌的表观扩散系数(ADC)。结果58例患者中,中央型肺癌19例,周围型肺癌39例;小细胞肺癌(SCLC)11例,非小细胞肺癌(NSCLC)47例,其中NSCLC包括腺癌32例,鳞癌15例;肺癌实性部分在T1WI呈等信号或稍低信号,在T2WI抑脂呈高或不均匀高信号;腺癌及鳞癌在DWI呈等或高信号,ADC呈低或偏低信号;SCLC在DWI呈高信号,ADC呈偏低信号;中央型肺癌ADC值与周围型肺癌比较,差异无统计学意义(P>0.05);NSCLC患者ADC值明显高于SCLC患者(P<0.05),腺癌ADC值明显高于鳞癌(P<0.05);DWI诊断不同病理类型肺癌的AUC为0.848。结论当b值为500s/mm^2时,DWI在腺癌、鳞癌、SCLC鉴别诊断中具有一定价值。     

肝细胞肝癌肿瘤ADC值与病理分级的相关性研究

目的 探讨肝细胞肝癌(HCC)磁共振扩散加权成像(DWI)表观扩散系数(ADC)最小值和平均值与肿瘤病理分级的相关性.方法 回顾性分析241例经手术病理证实为HCC患者的术前MRI图像.所有患者术前均行MRI平扫、增强及DWI成像.根据磁共振增强图像,感兴趣区(ROI)尽量避开瘤内坏死灶及血管,分别测量肿瘤实性部分的平均ADC值和最小ADC值.比较不同病理级别间肿瘤实性部分平均ADC值和最小ADC值的差异及其与病理分级的相关性.采用受试者工作特征(ROC)曲线分析最小ADC值区分低分化与非低分化HCC的最佳临界值及其敏感度和特异度.结果 低、中、高分化HCC肿瘤实性部分平均ADC值依次为0.99×10-3 mm2/s、1.14×10-3mm2/s、1.14×10-3 mm2/s;最小ADC值分别为0.84×10-3mm2/s、0.98×10-3 mm2/s、1.02×10-3 mm2/s.低分化组平均ADC值及最小ADC值均低于中分化组和高分化组(P均＜0.05);肿瘤最小ADC值与肿瘤病理分级呈负相关(rs=-0.118,P ＜0.05),平均ADC值与病理分级无相关性(rs=-0.09,P＞0.05).以最小ADC值≤0.925×10-3mm2/s为阈值,诊断低分化HCC的敏感度为60％,特异度为70％,ROC曲线下面积为0.648.结论 HCC DWI肿瘤最小ADC值有助于术前预测评估肿瘤病理分级.     

3.0T磁共振DWI结合T2加权成像诊断前列腺癌侵犯膀胱

目的 探讨T2WI及DWI 2种成像序列对前列腺癌(PCa)侵犯膀胱的诊断价值.方法 68例经病理证实的PCa患者在行3.0T MR前列腺常规和DWI(b值分别为0、800 s/mm2)扫描后被诊断为PCa侵犯膀胱,所有患者均行膀胱镜检查.分析所有PCa癌灶、受侵膀胱和未受侵膀胱壁的MRI表现,比较其ADC值.采用5分制评分,将所得结果与膀胱镜病理结果对照,用SPSS11.5分别做受试者工作特征曲线(ROC)分析比较各组方法诊断的敏感度和特异度.结果 膀胱镜检查45例(66%)患者病理证实为PCa侵犯膀胱,PCa癌灶、受侵膀胱壁和正常膀胱壁的ADC值分别为(0.931±0.098)×10-3mm2/s,(0.963±0.155)×10-3mm2/s和(1.517±0.103)×10-3mm2/s,受侵膀胱壁的ADC值明显低于正常膀胱壁(P＜0.05),而PCa癌灶和受侵膀胱壁的ADC值之间无明显差异.分别应用T2WI和DWI诊断PCa侵犯膀胱的ROC曲线下面积(AUC)明显低于联合2种成像方法(P＜0.05).结论 PCa侵犯膀胱的ADC值明显低于正常膀胱壁;联合应用DWI和T2WI诊断PCa侵犯膀胱优于单独使用DWI或T2WI.     

儿童幕下髓母细胞瘤的MRI诊断

目的 :分析儿童幕下髓母细胞瘤MRI常规及DWI表现,掌握髓母细胞瘤常见影像学特征,并了解其不常见影像学特征。方法:回顾性分析23例经病理确诊为幕下髓母细胞瘤的MRI资料,扫描图像包括T1WI、T2WI、DWI及增强扫描。由2名放射科医师采用单盲法分析MRI图像。结果:23例中,常见表现为肿块位于小脑蚓部18例,实性为主、散在小囊变15例;16例T1WI呈等、低信号,T2WI呈高、稍高信号,DWI呈高信号,ADC值为(0.68±0.16)×10-3mm2/s,增强扫描病灶中度或明显强化16例。不常见表现为肿瘤位于小脑半球(2例),第四脑室(2例),桥小脑角(1例),大囊变(1例在小脑半球,2例在蚓部),T1WI呈低信号,T2WI呈高信号,DWI呈稍高信号(7例),ADC值为(0.73±0.18)×10-3mm2/s,轻度强化5例,结节样强化1例,环形强化1例。结论:发生于小脑蚓部、实性为主、小囊变、DWI高信号是儿童幕下髓母细胞瘤的MRI常见表现,诊断不难。髓母细胞瘤不常见表现多样,结合病灶DWI信号特点,可与幕下其他肿瘤相鉴别,提高诊断水平。     

DSA功能性参数的提取与利用

本文介绍了在临床实际中利用功能性参数，对冠状动脉ＤＳＡ心肌血流灌注成像、冠状动脉血流量测定、左心室功能测定、肺动脉高压程度的评价等项目研究结果。重点讨论了提取ＤＳＡ功能性参数的一般方法，认为功能性参数在现代影像诊断学中的作用是对疾病做出程度、定量、动态及功能诊断。     

A monitoring,feedback, and triggering system for reproducible breath-hold MR imaging

A technique is described that provides improved reproducibility of breath-holding for MR image acquisition by monitoring the superior-inferior (S/I) position of the diaphragm. The method incorporates detection of the level of inspiration using an MR signal, rapid display to the patient of diaphragm position to enable breath-hold adjustment, and triggering of image data acquisition once appropriate position is attained. The response time of the system is short, approximately 10 ms. Studies in six volunteers using this method demonstrate a considerable decrease in the S/I range of diaphragm position over 10 consecutive periods of suspended respiration. The mean range is 1.3 mm with the system, while it is 8.3 mm without using it is expected that this method will be of assistance in many abdominal and cardiothoracic studies that use breath-hold techniques.     

Fast imaging of phosphocreatine in the normal human myocardium using a three-dimensional RARE pulse sequence at 4 Tesla

PURPOSE: To investigate the use of a three-dimensional rapid acquisition with relaxation enhancement (RARE) pulse sequence for direct acquisition of phosphocreatine (PCr) images of the human myocardium. MATERIALS AND METHODS: A short elliptical birdcage radiofrequency (RF) body coil was constructed to produce a uniform flip angle throughout the chest cavity. In vivo images using a spectrally-selective RARE sequence with a spatial resolution of 1.2 cm x 1.2 cm x 2.5 cm (4 cm(3)) were acquired in nine minutes and 40 seconds. RESULTS: Scans of phantoms demonstrated excellent spectral selectivity. The signal-to-noise ratio in the myocardium ranged from 12.6 in the anterior wall to 5.3 in the mid septum. CONCLUSION: This study demonstrates that PCr data can be acquired using a three-dimensional RARE sequence with greater spatial and temporal resolution than spectroscopic techniques.     

Current Status of Optical Imaging for Evaluating Lymph Nodes and Lymphatic System

Optical imaging techniques use visual and near infrared rays. Despite their considerably poor penetration depth, they are widely used due to their safe and intuitive properties and potential for intraoperative usage. Optical imaging techniques have been actively investigated for clinical imaging of lymph nodes and lymphatic system. This article summarizes a variety of optical tracers and techniques used for lymph node and lymphatic imaging, and reviews their clinical applications. Emerging new optical imaging techniques and their potential are also described.     

Simultaneous multislice (SMS) imaging techniques

Simultaneous multislice imaging (SMS) using parallel image reconstruction has rapidly advanced to become a major imaging technique. The primary benefit is an acceleration in data acquisition that is equal to the number of simultaneously excited slices. Unlike in‐plane parallel imaging this can have only a marginal intrinsic signal‐to‐noise ratio penalty, and the full acceleration is attainable at fixed echo time, as is required for many echo planar imaging applications. Furthermore, for some implementations SMS techniques can reduce radiofrequency (RF) power deposition. In this review the current state of the art of SMS imaging is presented. In the Introduction, a historical overview is given of the history of SMS excitation in MRI. The following section on RF pulses gives both the theoretical background and practical application. The section on encoding and reconstruction shows how the collapsed multislice images can be disentangled by means of the transmitter pulse phase, gradient pulses, and most importantly using multichannel receiver coils. The relationship between classic parallel imaging techniques and SMS reconstruction methods is explored. The subsequent section describes the practical implementation, including the acquisition of reference data, and slice cross‐talk. Published applications of SMS imaging are then reviewed, and the article concludes with an outlook and perspective of SMS imaging. Magn Reson Med 75:63–81, 2016. © 2015 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.     

Echo-Time-Encoded Burst Imaging (EBI): A Novel Technique for Spectroscopic Imaging

A new technique for rapid spectroscopic imaging is presented. The proposed experiment enables a complete mapping of the two-dimensional reciprocal space k_x, k_o, and thus the acquisition of a 1D spectroscopic image in a single scan. The properties of the pulse sequence, based on the use of a burst of low flip angle pulses, are analyzed in the framework of linear response theory, and it is shown that chemical shift information may be introduced into the spatially encoded echoes. First experimental results are presented demonstrating that 32 x 32 proton spectroscopic images may be acquired within less than 1 min with a conventional imaging system.     

RARE spiral T2-weighted imaging

Spiral imaging has a number of advantages for fast imaging, including an efficient use of gradient hardware. However, inhomogeneity-induced blurring is proportional to the data acquisition duration. In this paper, we combine spiral data acquisition with a RARE echo train. This allows a long data acquisition interval per excitation, while limiting the effects of inhomogeneity. Long spiral k-space trajectories are partitioned into smaller, annular ring trajectories. Each of these annular rings is acquired during echoes of a RARE echo train. The RARE refocusing RF pulses periodically refocus off-resonant spins while building a long data acquisition. We describe both T₂-weighted single excitation and interleaved RARE spiral sequences. A typical sequence acquires a complete data set in three excitations (32 cm FOV, 192 × 192 matrix). At a TR = 2000 ms, we can average two acquisitions in an easy breath-hold interval. A multifrequency reconstruction algorithm minimizes the effects of any off-resonant spins. Though this algorithm needs a field map, we demonstrate how signal averaging can provide the necessary phase data while increasing SNR. The field map creation causes no scan time penalty and essentially no loss in SNR efficiency. Multiple slice, 14-s breath-hold scans acquired on a conventional gradient system demonstrate the performance.     

Molecular imaging programs in the United States: results of a national survey

RATIONALE AND OBJECTIVES: We sought to identify and describe the characteristics of molecular imaging (MI) programs in the United States and to determine the factors considered critical for their future. MATERIALS AND METHODS: In a cross-sectional study, a validated survey was sent to members of the Society of Chairmen in Academic Radiology Departments (SCARD) in the United States, and 26 variables were studied. RESULTS: The response rate was 40.3%; 67.9% of the departments surveyed have an MI program. The main focus of 47.4% of departments is oncology. The number of radiologists working for the department was the only variable found to be significantly positively correlated with (1) number of researchers in the MI program, (2) number of MI modalities available, (3) total number of grants, and (4) having ongoing MI clinical trials. These four variables plus the number of federal grants and the space used by MI programs were independent of the geographical region, hospital size (number of beds), and department size (number of radiological examinations per year). All the MI programs received grants during 2005. Only 16.1% have no alliances with industry. Among all the departments, 82% identified staff training and recruitment as the keys for success; 78.57% considered oncology the most important future application of MI and cancer management the hospital service most affected by MI. CONCLUSION: MI programs are starting to be more widespread throughout the United States, and the trend is for more academic radiology departments to become engaged in MI activities; their development is independent of department characteristics. Radiology departments strongly agreed about the key components for success of MI initiatives and the areas that will be most affected by MI applications.     

Partially parallel imaging with phase-sensitive data: Increased temporal resolution for magnetic resonance temperature imaging.

Magnetic resonance temperature imaging can be used to monitor the progress of thermal ablation therapies, increasing treatment efficacy and improving patient safety. High temporal resolution is important when therapies rapidly heat tissue, but many approaches to faster image acquisition compromise image resolution, slice coverage, or phase sensitivity. Partially parallel imaging techniques offer the potential for improved temporal resolution without forcing such concessions. Although these techniques perturb image phase, relative phase changes between dynamically acquired phase-sensitive images, such as those acquired for MR temperature imaging, can be reliably measured through partially parallel imaging techniques using reconstruction filters that remain constant across the series. Partially parallel and non-accelerated phase-difference-sensitive data can be obtained through arrays of surface coils using this method. Average phase differences measured through partially parallel and fully Fourier encoded images are virtually identical, while phase noise increases with g(sqrt)L as in standard partially parallel image acquisitions..