原发性肝癌MnDPDP增强MRI两种T1W成像序列的比较研究

目的 :比较研究原发性肝癌MnDPDP增强MRI两种T1W成像序列的价值。材料和方法 :对36例原发性肝细胞癌(HCC)进行MnDPDP增强MRI前瞻性研究。平扫序列为SET1WI、FSET2W和FMPSPGRT1WI。静脉滴注MnDPDP后5min开始行FMPSPGRT1WI和SET1WI ,每隔5min成像一次直至40min ;并进行延迟24h成像。三位资深MRI诊断医师以盲法分别比较两种T1W图像(SET1WI和FMPSPGRT1WI)的信噪比(S/N)、对比度噪声比(C/N)、病灶的显示率和定性诊断率 ,以及两种T1W图像上HCC的信号强度差异。结果 :(1)MnDPDP增强后不同延迟时间的两种T1W图像之间的S/N±SD均无显著差异(p>0.05) ,而C/N±SD于延迟5min至40minFMPSPGRT1W图像优于SET1W(p<0.01) ;但延迟24hSET1W图像的C/N±SD优于FMPSPGRT1W(p<0.01)。(2)SET1W图像上HCC呈高信号的概率明显高于FMPSPGRT1W(5～40min :58.8 %对21.6 % ;24h :80.4 %对43.3 %)(p<0.005)。(3)SET1W和FMPSPGRT1W的HCC检出率均为92.7 % ;两者的定性率分别为92.7 %(SE)和87.3 %(FMPSPGR)。结论 :MnDPDP增强两种T1WMR图像对HCC的检出率相当 ,定性以SET1W稍优。作者推荐的HCC检查方案为 :(1)10～40min之间成像一次 ,序列为SET1W或(和)FMPSPGRT1W ;(2)延迟24h成像一次 ,序列为SET1W。     

MR对比剂增强扫描长时间延迟技术在肝脏炎性假瘤特异性诊断中的价值

目的 探讨MR对比剂增强扫描长时间延迟技术在肝脏炎性假瘤(inflammatory pseudotumors in liver, IPT)特异性诊断中的价值.方法 对经病理及随访证实的26例IPT进行MR平扫、DWI和动态增强扫描,增强扫描延迟时间均＞20 min,分析病变的MR表现特征.结果 1例为肝脏弥漫性病变,其余25例共发现29个病灶.所有病灶T1WI为低或等信号,T2WI为等、略高或高信号,部分病灶出现"环征".29个病灶中,DWI显示19个中心为高信号;动态增强扫描时,动 脉期、静脉期、3 min、5 min、10 min、15 min、20 min延迟时分别有5、11、25、26、26、28、28个病灶出现边缘强化.延迟期＞20 min(20 min～ 4 h之间)时,所有病灶均显示典型的环形、花边样或多囊样边缘强化,强化边缘厚度一致,内壁光滑;延迟期＞5 min时21个病灶出现纤维间隔.结论 动态对比剂增强扫描长时间延迟(＞20 min)有助于IPT特异性表现的显示.     

口服静脉用钆喷酸葡胺稀释液改善MRCP质量的研究

目的　口服静脉用钆喷酸葡胺 (Gd DTPA)稀释液作为胃、十二指肠阴性对比剂 ,改善磁共振胰胆管成像(MRCP)质量。资料与方法　实验部分 :取Gd DTPA静脉注射液 1、2、3、4、5、6和 7ml分别加温开水配制成浓度分别为 4 .6 4、9.2 7、13.91、18.5 4、2 3.19、2 7.82和 32 .4 6mg/ml稀释液各 80ml,并依次分组。设立 80ml温开水对照组。行T1WI(SE)和重T2 WI(IR EXPRESS )成像 ,测量各组在不同成像序列的信号强度 ,并计算增强率。临床应用 :对 2 1例经多方位MRCP不能避开胃、十二指肠内高信号背景干扰者 ,行口服稀释液前和后立即、5和 10min放射状多角度MRCP ,然后对各解剖结构显示情况加以判定。结果　浓度为 2 3.19、2 7.82和 32 .4 6mg/ml稀释液在重T2 WI(IR EXPRESS)成像序列中信号强度和增强率最小 ,且无明显差别。口服稀释液前与后 5、10minMRCP图像对胆总管、胰管、胆囊结构的显示具有显著性差异 (P <0 .0 5 ) ;而口服稀释液后 5与 10minMRCP图像对上述结构的显示无明显差异 (P >0 .0 5 )。结论　可选用浓度为 2 3.19mg/mlGd DTPA稀释液 80ml,作为胃、十二指肠阴性对比剂抑制高信号背景 ;口服稀释液后 5min成像可获得较为理想的MRCP图像。     

MnDPDP在临床上的应用状况

MnDPDP是磷酸吡多醛的锰络合物,在体内主要被肝细胞吸收,由胆道排泄.它有明显缩短T1的作用,故在T1WI上呈明显的高信号.与Gd比,其增强时间窗长,毒副作用小,图像S/N和C/N较高,有利于病灶显示.由于其细胞特异性和代谢特点,可用于鉴别诊断和对肝功能的观测.作为MR的一种新型肝细胞特异性对比剂,MnDPDP在欧洲已进入第三期临床试验,国内尚未见报道.     

多层动态增强MRI技术对肝血管瘤诊断的评价

目的:研究射频毁坏傅立叶采集稳态技术(RFFAST)的动态增强及延迟增强扫描MRI对肝血管瘤的诊断价值。方法:34例肝血管瘤患者行常规MRT1WI和T2WI横断面扫描。经肘静脉团注GdDTPA0.1mmol/kg,后推入10ml生理盐水冲洗(推入时间5～6s),再行射频毁坏傅立叶采集稳态技术T1WI动态增强扫描及延迟增强扫描,分析病灶及邻近肝实质增强。结果:共发现肝血管瘤病灶67个,T1WI上呈低信号,T2WI上呈高信号;动态增强显示46个病灶呈边缘不连续的结节样强化,21个病灶呈周边不规则强化或迅速强化充填;5个病灶动态增强早期见引流静脉较早强化,14个瘤周肝实质强化。结论:磁共振成像检查中,射频毁坏傅立叶采集稳态技术T1WI动态增强扫描能够显示肝血管瘤及邻近实质强化方式,与其他成像序列结合更有利于肝血管瘤的诊断。     

肝细胞特异性对比剂泰乐影与腹部屏气扫描技术的研究

目的:探讨肝细胞特异性对比剂泰乐影增强扫描时最优的T1WI序列及成像参数。方法:对13例病例20个病灶行MR SE T1WI序列、FFE T1WI in phase序列、FFE T1WI out phase序列扫描,测量各序列肝脏病变及正常肝实质的平均信号强度,计算并比较各序列信噪比(signal/noise, S/N)、对比噪声比(contrast/noise, C/N)及对比伪影比(con trast/artifact,C/A)。结果:out phase和in phase序列图像的呼吸运动伪影最小,20个病灶中仅有2个(10%)有呼吸运动伪影,而SE序列则有8例(90%)有呼吸运动伪影。out phase序列显示肝内门静脉及肝静脉优于SE序列,显示病变比SE序列清楚。结论:FFE T1WI out phase序列为肝细胞特异性对比剂泰乐影T1WI成像的最优序列,TR 25 ms、TE 6.9 ms、翻转角20°为其最优成像参数。     

排泄性磁共振尿路成像在泌尿系疾病诊断中的价值

目的:探讨对比增强磁共振尿路成像(排泄性MRU)在诊断泌尿系疾病方面的价值.方法:选择经手术病理和影像学检查证实的泌尿系结石20例、肾盂旁囊肿6例、肾盏憩室1例、膀胱憩室3例和输尿管移行细胞癌4例,均先行磁共振尿路成像(常规MRU),然后增强扫描后延迟至5、10和20 min行排泄性MRU,显示不良者4 h后再扫描一次.将两者源图像分别进行最大强度投影(MIP)重组,并分别独立诊断,对两者结果进行对比分析.结果:排泄性MRU尿路显示清楚 5 min 5例,10 min 25例,4 h 4例.两者定位诊断符合率均为100%.排泄性MRU均能作出准确定性诊断,常规MRU准确定性诊断分别为泌尿系结石17例(17/20)、肾盂旁囊肿2例(2/6)、膀胱憩室3例(3/3)、输尿管移行细胞癌2例(2/4).结论:排泄性MRU能清楚显示尿路形态变化及、排泄功能,有利于尿路疾病的诊断.     

MnDPDP在临床上的应用状况

MnDPDP是磷酸吡多醛的锰络合物,在体内主要被肝细胞吸收,由胆道排泄,它有明显缩短Ti的作用,故在T1WI上呈明显的高信号,与Gd比,其增强时间窗长,毒副作用小,图像S／N和C／N较高,有利于病灶显示,由于其细胞特异性和代谢特点,柯用于鉴别诊断和对肝功能的观测,作为MR的一种新型肝细胞特异性对比剂,MnDPDP在欧洲已进入第三期临床试验,国内尚未见报道。     

动态及延时增强磁共振成像对肝血管瘤诊断的评价

目的:研究动态增强及延迟增强扫描磁共振成像对肝血管瘤的诊断价值。材料和方法:34例肝血管瘤病人行常规MRT1WI、T2WI横断面扫描。经肘静脉手推团注0.1mmol/kg体重Gd-DTPA后,再推入10ml生理盐水冲洗后(推入时间5~6s)行射频毁坏傅立叶采集稳态技术T1WI动态增强扫描及延迟增强扫描,分析病灶及邻近肝实质增强。结果:共发现肝血管瘤病灶67个。动态增强见46个病灶呈边缘不连续样的结节样强化,21个病灶呈周边不规则强化或迅速强化充填;5个病灶动态增强早期见引流静脉强化,14个瘤周肝实质强化。延迟增强扫描见53个病灶完全充填强化,14个病灶显示斑片状或裂隙状的低信号未充填区。结论:在磁共振成像检查中,动态增强扫描能够显示肝血管瘤及邻近实质强化方式,延迟增强显示病灶的充填程度,两者结合更有利于肝血管瘤的诊断。     

3.0T MR LAVA序列在上腹部检查的优势

目的 探讨3.0T MR LAVA序列多期动态增强扫描对上腹部病变检出率的优势.方法 对42例临床怀疑肝脏占位患者行MR检查,15例无肝脏病变患者作对照.常规MR T_1WI和T_2WI扫描,包括T1WI 2D和3D FSPGR序列,增强采用LAVA屏气动态多期扫描.分别对2D和3D及LAVA序列图像对病灶检出率进行比较分析,并测量肝、脾的信噪比等情况.结果 LAVA序列对42例肝脏病变患者做多期增强扫描后发现68个病灶,其显示率达100%,对病灶定性诊断准确率达95.6%(65/68).3D T_1WI FSPGR序列增强扫描对病灶显示率为91.2%(62/68),对病灶定性准确率为76.5%(52/68).2D T_1WI FSPGR序列病灶显示率为89.7%(61/68),对病灶定性准确率为70.6%(48/68).15例正常肝、脾组织,使用不同序列测量所得信噪比为:平扫LAVA肝29.68±2.31,脾36.21±3.67,2D肝46.21±5.32,脾58.75±4.68,3D肝19.79±2.23,脾23.36±2.14.增强LAVA肝41.75±5.13,脾57.96±6.13,2D肝56.33±5.63,脾63.21±5.32,3D肝29.05±4.68,脾46.37±5.17.结论 LAVA序列多期动态增强扫描对肝脏病灶的显示及肝血管显示方面较常规2D和3D序列优越.     

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。     

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.     

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.     

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.     

Dynamic bioluminescence imaging for quantitative tumour burden assessment using IV or IP administration of <Emphasis Type="SmallCaps">d</Emphasis>-luciferin: effect on intensity,time kinetics and repeatability of photon emission

Introduction In vivo bioluminescence imaging (BLI) is a promising technique for non-invasive tumour imaging. d-luciferin can be administrated intraperitonealy or intravenously. This will influence its availability and, therefore, the bioluminescent signal. The aim of this study is to compare the repeatability of BLI measurement after IV versus IP administration of d-luciferin and assess the correlation between photon emission and histological cell count both in vitro and in vivo. Materials and methods Fluc-positive R1M cells were subcutaneously inoculated in nu/nu mice. Dynamic BLI was performed after IV or IP administration of d-luciferin. Maximal photon emission (PE_max) was calculated. For repeatability assessment, every acquisition was repeated after 4 h and analysed using Bland–Altman method. A second group of animals was serially imaged, alternating IV and IP administration up to 21 days. When mice were killed, PE_max after IV administration was correlated with histological cell number. Results The coefficients of repeatability were 80.2% (IV) versus 95.0% (IP). Time-to-peak is shorter, and its variance lower for IV (p < 0.0001). PE_max was 5.6 times higher for IV. A trend was observed towards lower photon emission per cell in larger tumours. Conclusion IV administration offers better repeatability and better sensitivity when compared to IP. In larger tumours, multiple factors may contribute to underestimation of tumour burden. It might, therefore, be beneficial to test novel therapeutics on small tumours to enable an accurate evaluation of tumour burden. Marleen Keyaerts is a Ph. D. fellow of the Research Foundation—Flanders (Belgium; FWO).     

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.