视神经萎缩的磁共振扩散张量成像研究

目的 探讨视神经萎缩的磁共振扩散张量成像特点.方法 对20例视神经萎缩患者进行视神经磁共振扩散张量成像,并与20例正常健康者作对照.结果 ①萎缩视神经均明显变细,在各向异性(FA)图和方向编码彩色(DEC)图上萎缩的视神经信号强度较对照组明显降低;②萎缩视神经的FA值(0.277±0.078)和λ∥值(1.808±0.307)较正常对照组明显降低,萎缩视神经的平均扩散率(MD)值(1.442±0.264)和λ⊥值(1.231±0.225)较正常对照组明显升高,比较均有明显显著性差异(P均＜0.001).结论 磁共振扩散张量成像对视神经萎缩的信号变化非常敏感,并且可以定量反映视神经萎缩后轴索和髓鞘的病理变化.     

健康成人视神经MR扩散张量成像研究

目的:探索成人视神经MR扩散张量成像的特点.方法:采用单次激发ZOOM自旋回波平面成像序列,对30例成人健康志愿者的视神经行MR扩散张量成像(DTI)研究.将DTI原始数据输入个人计算机,应用Volume-one1.72软件进行后处理.结果:双侧视神经在部分各向异性图(FA图)呈高信号,在方向编码彩色图(DEC图)为绿色高信号,图像清晰,无明显伪影和扭曲变形,视神经周围脑脊液及眶内脂肪被抑制,呈无信号.本研究初步获得了成人视神经的部分各向异性和平均扩散率的参数值.测得视神经的部分各向异性(FA)值分别为左侧0.595±0.067、右侧0.589±0.066,平均扩散率(MD)值分别为左侧(0.948±0.112)×10-3 mm2/s,右侧(0.932±0.088)×10-3mm2/s,双侧视神经的FA值及MD值差异均无显著性意义(P＞0.05).结论:MR-DTI检测视神经非常敏感.     

原发性慢性闭角型青光眼视神经MR扩散张量成像的研究

目的 探讨视神经MR DTI在研究原发性慢性闭角型青光眼所致视神经改变的临床应用价值.方法 对25例原发性慢性闭角型青光眼患者(病变组,4例为单眼发病,其余为双眼发病,共46只眼,其中右眼24只,左眼22只)和20名正常人(对照组)分别行3.0T视神经MRI和DTI检查,对比两组间各向异性(FA)、平行扩散率(λ∥)、垂直扩散率(λ⊥)、平均扩散率(MD)值差别.病变组与对照组同侧视神经比较、病变组内左与右侧视神经间比较,分别采用两独立样本t检验和配对t检验.结果 病变组6例患者8条视神经MRI表现为轻微变细,视神经鞘膜腔轻微增宽.病变组24条右眼视神经DTI的FA、λ∥、λ⊥、MD值分别为(0.27 ±0.09)×10-3、(2.30 ±0.26) ×10-3、(1.55 ±0.35)×10-3、(1.80±0.31) ×10-3mm2/s,22条左眼视神经分别为(0.24 ±0.09)×10-3、(2.25 ±0.41) ×10-3、(1.61 ±0.46) ×10-3、(1.82±0.47)×10-3 mm2/s;对照组20条右眼视神经DTI的FA、λ∥、λ⊥、MD值分别为(0.57±0.04) ×10-3、(1.78 ±0.24) ×10-3、(0.68±0.11) ×10-3、(1.01 ±0.08)×10 -3mm2/s,20条左眼视神经分别为(0.59 ±0.03) ×10-3、(1.76 ±0.13)×10-3、(0.63 ±0.07)×10-3、( 1.04±0.15)×10-3 mm2/s.与对照组比较,病变组FA值降低、λ∥、λ⊥、MD值升高,差异均有统计学意义(P值均＜0.05);病变组内左、右侧视神经相互比较,差异无统计学意义(P＞0.05).结论 DTI可以发现原发性慢性闭角型青光眼视神经扩散异常,并可定量推测视神经病理变化.     

顺行性或逆行性改变:肌萎缩性侧索硬化的磁共振研究

目的 结合磁共振波谱成像(MRSI)、扩散张量成像技术(DTI)及MRI对肌萎缩性侧索硬化(ALS)进行对照研究,观察ALS皮质脊髓束(CST)走行区的代谢以及水分子运动的变化规律,探讨CST是否有顺、逆行性变化.资料与方法 采用MRI、MRSI及DTI技术对12例ALS患者和12名正常志愿者进行扫描,观察测量中央前回皮层下白质(SWM)、半卵圆中心(CS)、内囊后肢(PIC)、侧脑室体旁白质(PV)和大脑脚(CP)等5个CST不同解剖平面的氮-乙酰天门冬氨酸(NAA)与肌酸(Cr)比值,各向异性比(FA值)以及平均扩散率(MD值),分析比较ALS 患者和正常对照组以及不同侧别FA值、MD值以及NAA/Cr值的变化.结果 ALS的FA值较正常对照组明显降低(P＜0.001),在CST走行区的SWM、CS、PV 和 PIC平面,ALS组的FA值较正常组明显降低(P＜0.05或P＜0.01), MD值在ALS组有升高的趋势,但无统计学意义.在SWM和PV平面,ALS的NAA/Cr值较正常组降低明显(P＜0.05).FA值和MD值分别在PV和CP有左高右低的变化(P＜0.05).结论 MRSI与DTI相结合能够早期定量探测ALS患者CST的改变,左侧SWM可能为最先发生改变的区域,CST的改变可能为顺行性改变,在不同的平面改变不对称.     

足月新生儿缺氧缺血性脑病的磁共振扩散张量成像研究

目的 评价3.0TMR扩散张量成像(DTI)在足月新生儿缺氧缺血性脑病(HIE)中的应用价值.方法 以19名无窒息史的正常足月新生儿做为对照,对24例HIE患儿(轻度19例、中重度5例)进行常规MRI及DTI检查.选取双侧大脑脚、豆状核、内囊后肢前后部、丘脑、半卵圆中心层面额叶前后部、顶叶以及胼胝体膝部、压部为感兴趣区(ROI),分别测得分数各向异性(FA)、平均扩散系数(MD)、轴向扩散张量(λ/／)、垂直扩散张量(λ⊥).采用ANOVA分析三组间不同部位各参数的变化.结果 轻度组胼胝体压部FA值及左侧大脑脚MD、λ/／值较对照组降低(P＜0.05).中重度组皮质脊髓束走行区、胼胝体膝部及压部的FA、λ/／较对照组明显降低(P＜0.001).另外,中重度组左侧大脑脚λ⊥较对照组降低,而左侧内囊后肢前部、双侧内囊后肢后部λ⊥较对照组升高(p＜0.01).结论 DTI更能反映不同程度HIE损伤后脑组织轴索、髓鞘细微结构的改变.     

3.0T磁共振DTI和DTT技术对病毒性脑炎的应用研究

目的 探讨磁共振扩散张量成像(DTI)及白质纤维束成像(DTT)技术对病毒性脑炎的临床应用价值. 方法 对25例临床确诊为病毒性脑炎患者(脑炎组)和25例常规MRI检查显示正常的检查者(对照组)行DTI扫描.将DTI扫描数据后处理获得扩散系数(ADC)图、各向异性(FA)图和DTT图,采用ROI测量脑炎组病变区与对照组正常脑组织的ADC值、FA值并对测值进行统计学分析.结果 在病程早期,脑炎组病变区的平均ADC值较对照组明显减低且差异具有显著统计学意义(P＜0.01),而平均FA值较对照组略升高但差异无统计学意义(P＞0.05).在病程中期及晚期,脑炎组病变区平均ADC值较对照组明显升高且差异有显著统计学意义(P＜0.01),平均FA值较对照组明显降低且差异具有统计学意义(P＜0.05).DTT白质纤维示踪成像显示白质纤维主呈浸润性改变,部分纤维中断、缺失,而无推压移位等改变. 结论 DTI与DTT技术能够为病毒性脑炎的诊断及鉴别诊断提供有价值信息.     

正常椎间盘纤维环的MR扩散张量成像及病理对照研究

目的:评价扩散张量成像显示正常椎间盘纤维环的能力.方法:对15例健康志愿者的L3～S1椎间盘和1例新鲜尸体椎间盘离体标本分别行DTI扫描,图像在工作站后处理成纤维环示踪图(FT图)和DCavg图、FA图.观察FT图上纤维环的形态和完整性并与病理相对照,测量正常纤维环和髓核的DCavg值和FA值.结果:所有被检椎间盘均可得到椎间盘纤维环的DCavg图,FA图和FT图.正常纤维环在DCavg图和FA图上呈一DCavg值和FA值连续均匀的环形,FT图示纤维环呈连续完整的环形结构,其纤维板层走行与病理观察一致.正常纤维环的DCavg值比髓核低,而FA值则较髓核高.结论:扩散张量成像能够无创地显示椎间盘纤维环的形态,评价其完整性,为在活体内显示纤维环是否断裂提供了一种新的影像学诊断方法.     

局灶性脑皮质发育不良的扩散张量成像初步研究

目的 探讨DTI技术诊断局灶性脑皮质发育不良(FCD)的价值.方法 回顾性分析12例FCD患者的临床、MRI及DTI等资料.DTI经过图像后处理,获得平均扩散系数(MD)和部分各向异性分数(FA)图及彩色编码张量图,于FCD的皮质下白质区及对侧相应皮质下白质区设置椭圆形ROI,测量每个ROI的MD及FA值.病灶侧与对侧MD、FA值的比较采用配对t检验.扩散张量纤维束示踪成像(DTT)以T_2 WI图像为参照,ROI设置同DTI,以ROI中的任一点作为种子点,获得通过该ROI区域的所有白质纤维束示踪图像.结果 12例患者MR平扫均显示局灶性脑皮质增厚及灰白质界限不清,其中7例显示皮质下白质稍长T_1、稍长T_2信号,2例皮质下白质萎缩,3例皮质下白质无明显异常.DTI分析显示FCD邻近皮质下白质与对侧比较FA值明显下降(患侧0.31±0.05,对侧0.42±0.08,t=-3.995,P<0.01),MD值明显上升[患侧(1.02±0.16)×10~(-3)mm~2/s,对侧(0.86±0.13)×10~(-3) mm~2/s,t=2.655,P<0.05],差异均有统计学意义.DTT显示10例FCD患者皮质下白质纤维束较对侧明确减少,2例较对侧可能减少,主要表现为皮质下白质纤维稀疏,与深部白质纤维间联系减少.结论 FCD除了导致脑皮质结构异常外,也影响局部皮质下白质纤维的发育,DTI是常规MR检查的重要补充.     

正常肾脏扩散张量成像的初步研究

目的 探讨正常成人肾脏扩散张量成像(DTI)的特性及其临床意义.方法 21例志愿者行肾脏DTI检查.分析肾脏皮质、髓质的表观扩散系数(ADC)、分数各向异性(FA值),并行髓质纤维束成像.结果 肾皮质和肾髓质ADC值分别为(2.34±0.16)×10-3 mm2/s和(2.10±0.17)×10-3 mm2/s,两者间具有显著性差异(t=2.45,P<0.05).髓质扩散张量示踪图显示肾髓质内放射状指向皮质的放射束.结论 DTI 可显示正常肾脏超微结构变化.肾髓质中水分子扩散具有高各向异性,肾皮质各向异性较弱.肾髓质的高FA值与肾小管、集合管的放射性走行有关.     

轻度认知障碍患者背外侧前额叶白质的DTI研究

目的用扩散张量成像(DTI)方法研究轻度认知障碍(MCI)患者背外侧前额叶白质的扩散特性,并探讨该区域可能的病理改变及DTI的临床诊断价值。资料与方法对17例MCI患者和18名年龄、性别和受教育程度相匹配的正常老年人进行全脑DTI扫描,测量其双侧背外侧前额叶白质的各向异性分数(FA)值、平均扩散率(MD)值和本征向量值(λ1、λ23),对两组数据进行统计学分析。结果MCI组两侧大脑半球背外侧前额叶白质的FA值较正常对照组减低而λ23值升高,且有显著的组间差异,而MD值和λ1值没有显著差异。结论MCI患者背外侧前额叶白质的FA值显著减低和λ23值升高,反映了MCI患者特定认知相关脑区白质微结构的早期病理改变,在MCI的诊断中具有较好的应用价值。     

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.     

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.     

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.     

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.     

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..