磁共振扩散加权成像在胃肠道良、恶性病变诊断中的应用价值

目的探讨MR扩散加权成像（DWI）在胃肠道良、恶性病变诊断中的价值。资料与方法对69例胃肠道病变进行常规MR平扫和DWI，扩散敏感梯度（b值）分别为0和700s／mm^2，测量病变的表观扩散系数（ADC）值，其中29例同时续行增强扫描。结果59例恶性病变的平均ADC值为（0．96±0．11）×10^-3mm^2／s，10例良性病变的平均ADC值为（1．49±0．12）×10^-3mm^2／s，两组病变之间比较差异有统计学意义（P〈0．01）。将恶性病变ADC值95％可信区间上界1．16×100mm^2／s定位为良、恶性病变鉴别的界值，诊断敏感性为86．6％，特异性为95．8％。结论DWI有助于对胃肠道良、恶性病变的诊断和鉴别。     

DWI在鉴别诊断脑脓肿和坏死、囊变脑肿瘤中的影像学价值

目的研究扩散加权成像（DWI）在鉴别脑脓肿和坏死、囊变脑肿瘤中的诊断价值。资料与方法对17例脑脓肿和23例脑肿瘤（胶质瘤和转移瘤）行常规MR和DWI检查。DWI采用b=1000s/mm^2,b=0s/mm^2时进行采集,测量感兴趣区（ROI）的表观扩散系数（ADC）值,两个独立样本间行秩和检验,与常规MR比较,计算敏感性、特异性、阳性预测值、阴性预测值。结果大部分脑脓肿在DWI上为高信号,ADC值为（0.33±0.11）×10^-3mm/s,除2例外其余脑肿瘤的坏死、囊变部分在DWI上为低信号,ADC值为（2.46±0.49）×10^-3mm/s。结论DWI在鉴别脑脓肿和坏死、囊变脑肿瘤方面是十分有意义的,比常规MR有更大的优越性。     

MR扩散加权成像鉴别颅内囊性病变的价值

目的探讨MR扩散加权成像（DWI）在颅内囊性病变中的鉴别诊断价值。方法对76例经临床及手术病理证实的颅内囊性病变患者，行常规MR、DWI及增强MR检查，其中脑脓肿19例，原发性脑胶质瘤20例，小脑血管母细胞瘤4例，脑转移瘤10例，蛛网膜囊肿7例，表皮样囊肿16例。回顾性分析颅内囊性病变的DWI信号特征，定量测定囊性变区表观扩散系数（ADC）值。结果DWI上19例脑脓肿呈高信号；34例脑肿瘤患者中，除3例脑胶质瘤呈高信号、1例呈等信号，1例脑转移瘤呈高信号外，其余29例均呈低信号。各种病变ADC值分别为：脑脓肿（0．62±0．15）×10^-3 mm^2／s、脑胶质瘤（2．39±0．78）×10^-3 mm^2／s、脑血管母细胞瘤（2．68±0．40）×10^-3 mm^2／s、脑转移瘤（2．79±0．79）×10^-3 mm^2／s。脑脓肿与脑胶质瘤、脑血管母细胞瘤、脑转移瘤的囊变坏死区ADC值比较，差异均有统计学意义（P〈0．01）；脑胶质瘤与脑血管母细胞瘤、脑转移瘤的囊变坏死区ADC值比较，差异均无统计学意义（P〉0．05）。7例颅内蛛网膜囊肿的DWI呈低信号；16例表皮样囊肿DWI呈明显高信号。颅内蛛网膜囊肿和表皮样囊肿的ADC值分别为（2．96±0．36）×10^-3 mm^2／s和（0．94±0．13）×10^-3 mm^2／s，二者之间差异有统计学意义（P〈0．01）。结论DWI及ADC值对鉴别脑脓肿和囊性或坏死性脑肿瘤具有重要的价值，DWI表现为低信号的颅内囊性病变可除外脑脓肿。     

3.0T MR多b值DWI对鼻咽癌患者颈部良恶性淋巴结的鉴别诊断价值

目的探讨3.0T磁共振多b值扩散加权成像(DWI)对鼻咽癌患者颈部良恶性淋巴结的鉴别和诊断价值。方法收集本院66例鼻咽癌患者的临床资料,并以35例良性淋巴结肿大患者为对照。所有患者均行MR常规平扫、增强和多b值DWI影像学检查,比较不同b值下鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结与良性淋巴结肿大患者表观扩散系数(ADC)值的差异。通过绘制受试者工作特征(ROC)曲线计算诊断阈值、ROC曲线下面积、敏感度和特异度,评价不同b值下ADC值对鼻咽癌颈部良恶性淋巴结的鉴别和诊断价值。结果随着b值的增加,鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结与良性淋巴结肿大患者ADC值呈现减少的趋势;鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结之间ADC值的比较,差异均无统计学意义(P>0.05);鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结ADC值均显著低于良性淋巴结肿大患者(P<0.05)。在b值分别取400、600、800、1000s/mm^2时,其对应的ROC曲线下面积分别为0.77、0.82、0.91、0.87。当b=800s/mm^2时,其鉴别和诊断淋巴结良恶性的价值最高,此时ADC值诊断鼻咽癌颈部转移性小淋巴结的阈值为0.945×10^-3mm^2/s,诊断敏感度为98.49%,特异度为79.63%,约登指数为0.78。结论3.0T MR多b值DWI检查可有效区分良恶性淋巴结的性质,并且在b值为800s/mm^2时,其鉴别和诊断不同淋巴结性质的能力最强,可用于临床鉴别和诊断鼻咽癌患者颈部淋巴结转移瘤。     

改良敏感编码技术在肝脏MR扩散加权成像中对肝细胞癌小病灶的影响

目的评价在肝脏MR扩散加权成像（DWI）中应用改良敏感编码（mSENSE）技术是否有助于提高图像质量及对肝细胞癌（HCC）小病灶的表观扩散系数（ADC）值测量有无影响。方法分别用常规DWI和mSENSE-DWI对32例47个HCC小病灶行单次屏气自旋回波-平面回波（SE-EPI）DWI，扩散梯度因子（b）值为300、500、800s／mm^2。对图像质量、对比噪声比（CNR）、病灶的ADC值进行观测和比较，运用配对Wilcoxon signed rank和Friedman检验进行统计学分析。结果图像质量DWI组b=300s／mm^2时图像评分2级5例、3级24例、4级3例，b=500s／mm^2时2级9例、3级22例、4级1例，b=800s／mm^2时1级2例、2级24例、3级6例；mSENSE-DWI组b=300s／mm^2时3级4例、4级25例、5级3例，b=500s／mm^2时3级10例、4级20例、5级2例，b=800s／mm^2时2级7例、3级23例、4级2例。同一b值条件下，mSENSE-DWI组的图像质量均优于常规DWI组（3个不同b值组的Z分别为-5．578、-5．488、-4．796，P值均〈0．01）。DWI组病灶的中位ADC值在b=300、500、800s／mm^2时分别为（1．578×10^-3）、（1．390×10^-3）、（1．173×10^-3）mm^2／s．mSENSE-DWI组病灶的中位ADC值在3个b值下分别为（1．381×10^-3）、（1．242×10^-3）、（1．136×10^-3）mm^2／s，在大b值条件下（500、800s／mm^2），2组所测得的病灶ADC值差异无统计学意义（Z值分别为-0．873、-0．862，P值分别为0．383、0．388）。结论在肝脏DWI中应用mSENSE技术可获得高质量的图像，同时对HCC小病灶的ADC值测量没有影响。     

MR扩散加权成像评估前列腺癌细胞密度的应用价值

目的探讨磁共振扩散加权成像（DWI）及表观扩散系数（ADC）评价前列腺癌（PCa）细胞密度的价值。方法使用Siemens Sonata 1．5T高场强超导MR成像设备和腹部相控阵线圈，采用EPI序列对38例资料完整的前列腺癌病人行DWI检查。根据常规HE染色病理图片记录前列腺癌细胞密度。ADC与细胞密度相关性分析用Pearson相关分析。结果PCa、前列腺增生区和正常外周带的平均ADC值分别为（49．32&#177;12．68）&#215;10^-5mm^2／s，（86．73&#177;26．75）&#215;10^-5mm^2／s，（126.25&#177;27．21）&#215;10^-5mm^2／s，差异有统计学意义（P〈0．05）。PCa细胞密度平均值为12．9％，ADC值与细胞密度存在负相关性（r=-0．646，P〈0．05）。结论细胞密度是影响组织扩散特性的重要因素，ADC值能较好反映组织微观结构特点。     

头颈部病变MR扩散成像的初步研究

目的探讨MR扩散加权成像（DWI）在头颈部病变中的诊断价值。方法回顾性分析57例头颈部病变共85个病灶，其中恶性肿瘤22个（22例），良性肿瘤13个（13例），囊性或液性病灶13例共17个病灶，包括囊肿12个（8例），肿瘤坏死4个（4例），脓肿1个（1例）；淋巴结病灶33个。所有患者均经临床追踪或手术病理证实。分析各病灶在扩散敏感因子（b值）为0、500和1000s·mm^-2时DWI特点及其表观扩散系数（ADC）值。结果良、恶性肿瘤在DWI表现有所不同，13个良性肿瘤与脊髓（或脑干）的信号比值随b值增加迅速下降；22个恶性肿瘤与脊髓（或脑干）信号比值随b值增加变化不明显。恶性肿瘤的平均ADC值[（0．78±0．24）×10^-3mm^2·s^-1]低于良性肿瘤[（1．48±0．20）×10^-3mm^2·s^-1]，差异有统计学意义（t=8．9，P〈0．01）；良、恶性肿瘤的ADC值受试者特异性曲线（ROC）下面积Az值为0．971±0．030，当ADC值取1.13×10^-3mm^2·s^-1时，判断良、恶性肿瘤的敏感度为100％，特异度为90．5％，准确度90．5％。鳞状细胞癌的ADC值与分化程度相关，分化好者其ADC值高。囊性或液性病变（12个）、肿瘤坏死（4个）和脓肿（1个）在DWI上的信号强度与其组织病理成分相关，具有一定的信号特征和ADC值。淋巴结转移瘤的平均ADC值[（0．81±0．11）×10^-3mm^2·s^-1]高于良性淋巴结病变[（0．69±0．04）×10^-3mm^2·s^-1]，差异有统计学意义（t=3．48，P〈0．01），但是两者之间有较大的重叠，且在DWI上表现相仿。结论DWI和ADC值在头颈部病变的鉴别诊断中具有重要价值。     

不同类型正常乳腺表观扩散系数值差异的研究

目的 研究不同类型正常乳腺表观扩散系数（ADC）值的差异，探讨ADC值与组织学分型之间的关系。方法 采用单次激发平面回波（EPI）技术，扩散敏感因子（b）值分别为0、500、1000s／mm^2，对62个正常乳腺（包括42例乳腺病变患者的对侧正常乳腺及10名健康志愿者20个乳腺）进行MR扫描及MR扩散加权成像（DWI）检查，计算62个正常乳腺分别在不同b值时的ADC值。将62个正常乳腺分为3型，比较3型之间ADC值的差异及不同b值时ADC值的差异。结果 42例乳腺病变患者对侧正常乳腺的DWI及ADC图与组织切片对比，不同类型乳腺组织学结构不同，其DWI及ADC图表现亦有差异。62个正常乳腺分为致密型10个，分叶斑点型42个及退化型10个。致密型和分叶斑点型乳腺随b值降低ADC值升高，而退化型乳腺随b值降低ADC值变化不明显。b=1000—0s／mm^2时，致密型、分叶斑点型、退化型乳腺ADC值分别为（1．70±0．37）、（1．93±0．46）、（1．18±0．65）×10^-3mm^2／s，3组间比较差异有统计学意义（F=12．998，P=0．000）。不同b值时每2种类型间进行单因素方差分析，致密型和分叶斑点型之间差异无统计学意义（F=2．167，P=0．147）；致密型和退化型之间、分叶斑点型和退化型之间差异均有统计学意义（F值分别为5．593、19．128，P值分别为0．029、0．000）。结论 3型正常乳腺ADC值受乳腺组织学结构的影响，致密型和分叶斑点型乳腺ADC值受b值高低的影响。     

扩散敏感因子800时乳腺良恶性病变ADC界值的确定

目的：确定扩散敏感因子为800s/mm^2时乳腺良恶性病变的ADC界值,评价MR扩散加权成像（DWI）对乳腺良恶性病变鉴别诊断的价值。方法：回顾性分析经手术病理证实的70例（78个病灶）乳腺病变的DWI图像,其中良性病变26例（31个病灶）,恶性病变44例（47个病灶）。测量DWI图像上显示的病变表观扩散系数（ADC）值。通过ROC曲线确定ADC值的诊断阈值,并以此值进行鉴别诊断,同时计算ROC曲线下面积。结果：良恶性病变的ADC值均符合正态性分布,良恶性病变的ADC平均值分别为（1.46±0.26）×10^-3mm^2/s和（1.02±0.19）×10^-3mm^2/s,恶性病变的ADC值明显低于良性病变（P〈0.05）。约登指数最大法确定的ADC诊断阈值为1.28×10^-3mm^2/s,以此值进行鉴别诊断时的敏感度、特异度和诊断符合率分别为93.6%,75.9%,86.8%;阳性似然比最大法确定的ADC诊断阈值为1.035×103mm^2/s,以此值进行鉴别诊断时的敏感度、特异度和诊断符合率分别为46.8%,96.6%,65.8%;ROC曲线下面积为0.905（95%可信区间为0.836-0.975）。结论：扩散敏感因子为800s/mm^2时乳腺良恶性病变的ADC界值确定为1.28×10^-3mm^2/s,DWI的ADC值测定有助于乳腺良恶性病变的鉴别诊断。     

肾上腺肿瘤MR扩散加权成像表现与细胞密度相关性的初步研究

目的探讨肾上腺肿瘤MR扩散加权成像（DWI）表现，分析良、恶性肿瘤表观扩散系数（ADC）值之间的差异及ADC值与肿瘤细胞密度的相关性。资料与方法采用屏气单次激发自旋回波-回波平面成像．扩散加权成像（SE-EPI-DWI）技术，分别选取3个不同b值检查4｜D例47个肾上腺肿瘤，其中恶性肿瘤18个，良性肿瘤29个；观察DWI表现，比较ADC值差异，并进行受试者工作特征曲线（ROC）分析，以选取肾上腺肿瘤DWI最佳成像b值和ADC值诊断阈值；对其中27个手术切除的肿瘤，在光镜下计数肿瘤细胞密度，并分析其与ADC值相关性。结果b值的大小影响DWI上肿瘤显示及其信号强度；肾上腺良、恶性肿瘤均可表现为均匀的高信号或不均匀高信号，并与肿瘤的类型及囊变、坏死程度有关，其间ADC值差异有统计学意义。经ROC曲线分析，肾上腺肿瘤DWI最佳成像b值为800s／mm^2，以ADC≥1．21×10^-3mm^2／s为阚值，诊断肾上腺良性肿瘤的敏感性为79％、特异性为72％。肾上腺肿瘤ADC值与其细胞密度负相关，以b值取800s／mm^2时相关性最强（r=-0．723，P〈0．01）。结论DWI对肾上腺肿瘤性质鉴别具有价值，是对常规MR检查的有益补充；测量肿瘤ADC值有可能为在体鉴别肾上腺肿瘤性质和病理分级提供新方法。     

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.     

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。     

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.     

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.     

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.     

Temporal resolution improvement in dynamic imaging

In some dynamic imaging applications, only a fraction, 1/n, of the field of view (FOV) may show considerable change during the motion cycle. A method is presented that improves the temporal resolution for a dynamic region by a factor, n, while maintaining spatial resolution at a cost of √n in signal-to-noise ratio (SNR). Temporal resolution is improved, or alternatively, total imaging time is reduced by reducing the number of phase encodes acquired for each temporal frame by 1/n. To eliminate aliasing, a representation of the signal from the static outer portion of the FOV is constructed using all the raw data. The k-space data derived from this representation is subtracted from the original data sets, and the differences correspond to the dynamic portion of the FOV. Improved resolution results are presented in phantom studies, and in vivo phase contrast quantitative flow imaging.     

Phase insensitive preparation of single-shot RARE: Application to diffusion imaging in humans

Although RARE and GRASE can produce single-shot images of excellent quality, their utility has been restricted because preparation of the magnetization with interesting contrast before imaging can cause severe artifacts. These artifacts relate to the strong sensitivity of multiple spin echo sequences to the phase of the prepared magnetization. Modifications of the RARE sequence to eliminate these artifacts are discussed, and an approach that eliminates the artifact producing signals from the very first echo is presented. The approach is applied to diffusion imaging of the human brain in normal volunteers and one patient.