兔肝脏3.OT MR多模态定量成像扫描技术探讨

目的 探讨3.0T MR在兔肝脏多模态定量扫描时的技术要求.方法 选择新西兰大白兔8只,应用3.0T MR成像系统,行肝脏T1 mapping、T2 mapping、MT序列及Gd-EOB-DTPA(0.025 mmol/kg)动态增强扫描,后者采用不同的速率(1.5 mL/s和2 mL/s)和生理盐水用量(6 mL和8 mL)进行匹配.判断各种技术的图像质量是否符合要求.结果 全部扫描时间约为20～25 min.T1mapping、T2 mapping、MT序列均获得满意的扫描图像.Gd-EOB-DTPA动态增强扫描时,各组间图像质量无明显差异(P＞0.05),但采用2 mL/s和8 mL的条件时,2只动物死亡.结论 选取合适的扫描参数时,可以成功进行3.0T MR多模态兔肝脏定量成像.     

评估HBV相关HCC病人的肝脏功能:Gd-EOB-DTPA增强T_1 mapping与DWI的比较

<正>摘要目的比较钆塞酸二钠(Gd-EOB-DTPA)增强MRI T1mapping与扩散加权成像(DWI)评估乙肝病毒(HBV)相关肝细胞癌(HCC)病人肝脏功能的可行性。方法 100例连续的     

用钆塞酸二钠增强MRI弛豫率评估基于体积的肝功能

正摘要目的探讨钆塞酸二钠(Gd-EOB-DTPA)肝脏MRI弛豫率是否能定量评估用吲哚氰绿(ICG)清除率确定的肝功能。方法 107例病人进行了ICG检测及Gd-EOB-DTPA增强MRI,包括行3 T MR弛豫成像。在Gd-EOB-DTPA注入前及注入后20 min后行内置T1值计算程序的3D VIBE序列横断面扫描。计算对比剂注入前后T1的减少率(rr T1)及基于肝     

3.0T MRI T_2~* mapping评估儿童血友病性关节病膝关节软骨的价值

目的探讨磁共振T_2~* mapping成像技术在儿童血友病性关节病(hemophilic arthropathy, HA)膝关节软骨损伤的诊断价值。方法采用西门子Skyra 3.0T MRI对19例HA患儿组、15例正常组儿童膝关节行MRI扫描,行T_2~* mapping序列扫描,并测量T_2~*值。比较患儿组T_2~* mapping、T_1WI-SE、T_2WI-TSE-FS序列所测量的关节内含铁血黄素沉积。T_2~* mapping序列扫描后在工作站分别测量膝关节研究髌骨、股骨远端内侧髁(承重区、后部非承重区)、股骨远端外侧髁(承重区、前后部非承重区)、胫骨内、外侧平台面8处软骨T_2~* mapping成像的T_2~*值,比较两组膝关节T_2~*值的差异。另对关节内含铁血黄素在T_2~* mapping、T_1WI-SE、T_2WI-TSE-FS三个序列中分别测量最大截面,比较这三个序列在评估血友病性关节病含铁血黄素沉积显示结果的差异,P0.05具有统计学意义。结果血友病性关节病患者膝关节髌骨软骨平均T_2~*值(31.6±12.5)ms,股骨远端内侧髁承重区、后部非承重区软骨平均T_2~*值分别为(29.4±10.0)ms、(34.1±9.7)ms,股骨远端外侧髁承重区、前部、后部非承重区软骨平均T_2~*值分别为(33.7±9.8)ms、(35.6±12.2)ms、(37.2±11.2)ms,内、外侧胫骨平台面软骨平均T_2~*值(30.2±7.9)ms、(28.0±8.7)ms。股骨外侧髁、股骨内侧髁后部非承重区、胫骨平台内外侧与健康组T_2~*平均值比较,差异具有统计学意义(P0.05)。股骨内侧髁承重区、髌骨软骨与健康组T_2~*平均值比较无统计学意义(P0.05)。T_2~* mapping、T_1WI-SE、T_2WI-TSE-FS三个序列最大截面显示含铁血黄素沉积分别是(142.0±137.9)mm~2、(114.8±111.4)mm~2、(115.6±115.3)mm~2,差异不具有统计学意义。结论磁共振T_2~* mapping序列通过T_2~*值的测量,能定量的反应膝关节血友病性关节病早期的损伤、变性。     

磁共振成象评价放射性肝损害:肝细胞造影剂与网状内皮系统造影剂的比较

作者用啮齿动物放射性肝损害模型比较了主要随胆汁排泌的亲肝细胞磁共振造影剂Gd-EOB-DTPA和由网状内皮系统清除的亲Kupffer细胞造影剂SPIO(超顺磁性氧化铁颗粒)的肝脏摄取与强化。18只SD大鼠肝脏的一侧接受了一次性X线照射(50Gy 9只,60Gy 5只,70Gy4只)。X线照射3天后对同一鼠先后注射两种造影剂并作SE序列T_1加权(200/6)和质子加权(850/25)磁共振成象。另外,对接受全肝照射(50Gy)的5只鼠及对照组的4只鼠的胆道和泌尿道的Gd-EOB-DTPA的排泄率进行了定量分析。结果表明,注入0.1mmol/kg的Gd-EOB-DTPA后,肝的信号强度对称性增强,接受三种剂量的照射区与未照射区之间增强幅度无显著性差异。注入10μmol/kg     

基于3.0T磁共振的同龄健康人群心肌原始T_1和T_2 mapping研究

目的本研究目的是初次探究同龄健康人群组心肌原始T_1和T_2 mapping的均质性和性别差异。方法本研究纳入30例使用3.0T磁共振行心脏成像的25岁健康志愿者,左室心底、中部和心尖3层短轴层面(short-axis slice,SAX)的原始T_1、T_2 mapping用于图像分析。使用修正的11次单脉冲SSFP稳态反转恢复序列、3次不同T_2 准备时间的单脉冲SSFP分别获得T_1及T_2 mapping图像并定量获得每层面、每部分心肌的T_1和T_2 弛豫时间。结果心底、中部、心尖的T_1、T_2 弛豫时间分别是:1274.1ms/36.5ms,1273.2ms/37.4ms,1297.8ms/38.2ms;变异系数(%)(T_1/T_2 )分别是2.9/4.2,2.7/4.3,3.6/5.5。总体和每个层面的T_1和T_2 mapping均有明显的性别差异(P0.01)。结论根据年龄和性别建立一组心肌T_1和T_2 mapping的正常参照,给临床提供更精确的参考、更有效地区分病灶与正常心肌组织。考虑到未来心肌T_1和T_2 mapping技术的研究进展,对照组(健康人群)年龄分布和性别差异均需考虑。     

比较Gd-EOB-DTPA增强MRI与扩散加权成像对肝内小转移灶的检出

目的比较Gd-EOB-DTPA增强MRI与扩散加权成像(DWI)检出肝内小转移灶(2cm或更小)的准确性。方法 45例病人行腹部3TMRI检查,所用序列包括T1加权     

肝脏的单次屏气MR T_2WI:单次激发快速自旋回波(SSFSE)和多次激发自旋回波(MSFSE)EPI的价值

在肝脏MR成像中T_2WI具有重要作用。常规自旋回波序列(CSE)T_2WI对于肝局灶性病变的检出和定性非常有用,但该序列成像时间长,且由于运动伪影较大造成图像质量差。为减少由呼吸运动造成的图像质量下降,在T_2WI中应用呼吸触发快速自旋回波(RTFSE)或屏气快速自旋回波(BHFSE)。 作者的目的是评价单次屏气T_2WI对局灶性肝病变的诊断价值。共研究了51例病人,其中男性36     

肝胆特异性对比剂Gd-EOB-DTPA对正常肝脏及其肿瘤ADC值的影响

目的探讨肝胆特异性对比剂钆塞酸二钠(Gd-EOB-DTPA)对正常肝实质及肿瘤组织的表观扩散系数(ap-parent diffusion coefficient,ADC)值的影响。方法 20例患者共检出肝脏肿瘤性病变灶21个,在静脉注射Gd-EOB-DTPA前、后20 min分别行肝脏容积加速快速成像(liver acquisition with volume acceleration,LAVA))和扩散加权成像(diffusionweighted imaging,DWI)扫描(b值=0及800 s/mm2),分别测量增强前后T1WI图像的信噪比(signal-to-noise ratio,SNR)、肝脏及肿瘤的对比噪声比(contrast-to-noise ratio,CNR)、正常肝实质及肿瘤组织的ADC值,应用配对t检验比较增强前、后SNR、CNR、ADC值的变化。结果静脉注射Gd-EOB-DTPA 20 min后T1WI图像的SNR(186.67±59.64)显著高于增强前(102.79±26.95),差异有统计学意义(t=6.841,P<0.01);增强后CNR(84.86±46.2)显著高于增强前(33.09±21.79),差异有统计学意义(t=5.758,P<0.01);增强前、后肿瘤的ADC值分别为(1.45±0.57)×10-3mm/s和(1.37±0.48)×10-3mm/s,差异无统计学意义(t=1.320,P=0.202);增强后正常肝实质的ADC值(1.27±0.23)×10-3mm/s较增强前(1.34±0.25)×10-3mm/s降低,差异有统计学意义(t=2.189,P=0.033)。结论静脉注射Gd-EOB-DTPA 20 min后肝脏T1WI的SNR和CNR均显著高于增强前,故有利于病变的显示及检出;增强前、后肝脏肿瘤的ADC值未见显著差异,而正常肝实质的ADC值较增强前降低,静脉注射Gd-EOB-DTPA20 min后会影响正常肝实质的ADC值的测量。     

Study of clinical application of hepatic-biliary specific MR contrast agent (Gd-EOB-DTPA) in the diagnosis of focal hepatic lesions

目的:探讨Gd-EOB-DTPA MRI增强扫描时肝局灶性病变的表现及此新型对比剂的诊断效能,提高对肝脏局灶性病变的诊断准确性.方法:已知或怀疑为肝脏局灶性病变的34例患者共90个病灶,病灶性质依次为肝囊肿20个、肝细胞肝癌16个、胆管细胞癌1个、肝脏转移性肿瘤37个、肝血管瘤9个、退变结节1个、肝脏局灶性结节增生1个、肝细胞腺瘤1个、肝脏炎性病变3个及肝脏淋巴上皮瘤样癌1个.所有患者依次行MRI平扫(抑脂TSE T2 WI、抑脂3DVIBE、2D GRE T1 WI)、Gd-EOB-DTPA三期(动脉期、门脉期和平衡期)增强扫描(抑脂3D VIBE)及延迟20min肝实质期扫描(抑脂2D GRET1WI、抑脂TSE T2 WI、抑脂3D VIBE).测量并分析Gd-EOB-DTPA增强前后肝脏和病灶信号变化、病灶-肝脏对比噪声比绝对值(|CNR|)变化情况;并观察病灶Gd-EOB-DTPA增强扫描表现和特征.结果:Gd-EOB-DTPA增强后各期肝实质信号及病灶肝脏|CNR|均显著增加(P＜0.001).动脉期、门脉期和平衡期所有病灶符合应用常规含钆(Gd)对比剂时的强化表现和特征;延迟20min肝实质期扫描时,肝脏局灶性结节增生呈等信号—高信号.1个肝细胞肝癌呈相对高信号,其余肝囊肿、肝细胞肝癌、胆管细胞癌、肝脏转移性肿瘤、淋巴上皮瘤样癌、退变结节、肝细胞腺瘤、肝血管瘤和肝脏炎性假瘤等均呈相对低信号.结论:Gd-EOB-DTPA动态增强扫描与延迟肝实质期扫描联合应用,可以提供病变形态、血供、细胞来源及功能等更多相关信息,从而提高诊断信心及诊断准确性.     

Potential of Liver T1 Mapping for the Detection of Fontan-associated Liver Disease in Adults

Purpose:The native T₁ value at 3T MRI is a sensitive marker for diffuse fibrosis or damage in various organs including the heart, liver, and pancreas. Despite the fact that Fontan-associated liver disease (FALD) is a crucial issue in adults with Fontan circulation, there are only a few studies with liver T₁ mapping in children and adolescents. We investigated the potential of the liver native T₁ mapping in detecting FALD in adult patients.Methods:We prospectively enrolled 16 consecutive adults with Fontan circulation (age 31.3 ± 8.5 years), who were in New York Heart Association Functional class II–IV. Twenty with tetralogy of Fallot (TOF), and 20 age-matched controls also underwent cardiac magnetic resonance (CMR) imaging at 3T. Myocardial T₁ mapping with a Modified Look-Locker Inversion recovery sequence was applied to liver T₁ mapping. Patients in the Fontan group underwent the right heart catheter and liver function tests, including those for fibrotic markers.Results:Liver native T₁ values in the Fontan group were significantly higher than that in TOF and controls (P < 0.001). In the Fontan group, the liver native T₁ value was significantly correlated with age, γ -glutamyltransferase, model for end-stage liver disease XI score, and albumin-bilirubin score (P = 0.01, 0.01, 0.044, 0.001). However, it demonstrated no correlation with central venous pressure, pulmonary vessel resistance, or fibrotic markers.Conclusion:Liver native T₁ value derived from CMR may be a non-invasive adjunctive and/or screening marker to detect FALD.     

Myocardial T1 mapping: application to patients with acute and chronic myocardial infarction.

T(1) maps obtained with modified Look-Locker inversion recovery (MOLLI) can be used to measure myocardial T(1). We aimed to evaluate the potential of MOLLI T(1) mapping for the assessment of acute and chronic myocardial infarction (MI). A total of 24 patients with a first MI underwent MRI within 8 days and after 6 months. T(1) mapping was performed at baseline and at selected intervals between 2-20 min following administration of gadopentetate dimeglumine (Gd-DTPA). Delayed-enhancement (DE) imaging served as the reference standard for delineation of the infarct zone. On T(1) maps the myocardial T(1) relaxation time was assessed in hyperenhanced areas, hypoenhanced infarct cores, and remote myocardium. The planimetric size of myocardial areas with standardized T(1) threshold values was measured. Acute and chronic MI exhibited different T(1) changes. Precontrast threshold T(1) maps detected segmental abnormalities caused by acute MI with 96% sensitivity and 91% specificity. Agreement between measurements of infarct size from T(1) mapping and DE imaging was higher in chronic than in acute infarcts. Precontrast T(1) maps enable the detection of acute MI. Acute and chronic MI show different patterns of T(1) changes. Standardized T(1) thresholds provide the potential to dichotomously identify areas of infarction.     

Flexible cardiac T1 mapping using a modified Look-Locker acquisition with saturation recovery

A modified Look-Locker acquisition using saturation recovery (MLLSR) for breath-held myocardial T(1) mapping is presented. Despite its reduced dynamic range, saturation recovery enables substantially higher imaging efficiency than conventional inversion recovery T(1) mapping because it does not require time for magnetization to relax to equilibrium. Therefore, MLLSR enables segmented readouts, shorter data acquisition windows, and shorter breath holds compared with inversion recovery. T(1) measurements in phantoms using MLLSR showed a high correlation with conventional single-point inversion recovery spin echo. In vivo T(1) measurements from normal and infarcted myocardium in 41 volunteers and patients were consistent with previously reported values. Twenty subjects were also scanned with MLLSR using an accelerated sampling scheme that required half the scan time (eight vs. 16 heartbeats) but yielded equivalent results. The flexibility afforded by the improved imaging efficiency of MLLSR allows the acquisition to be tailored to particular clinical needs and to individual patient's breath-holding abilities.     

Simultaneous T1 measurements and proton resonance frequency shift based thermometry using variable flip angles

A method is presented which allows precise temperature and longitudinal (T(1)) relaxation time measurements with high spatial and temporal resolution. This is achieved by combining dynamic variable flip angle based T(1) relaxation mapping with proton resonance frequency shift based thermometry. Herein, dynamic T(1) mapping is either used as a complementary measure of temperature or for the detection of T(1) contrast agent release. For the first application, the temperature evolution during a high-intensity focused ultrasound tissue ablation experiment was measured in both, porcine fat and muscle, simultaneously. In this application, temperature accuracies of 2.5 K for T(1)-based thermometry in fat and 1.2 K for proton resonance frequency shift-based thermometry in muscle were observed. The second application relates to MR-guidance of high-intensity focused ultrasound-induced local drug delivery by means of thermo-sensitive liposomes labeled with a T(1) contrast agent (Gd-HPDO3A). When the measured temperature exceeded the phase transition temperature of the liposomes, T(1) was observed to decrease with a good temporal and spatial correlation due to the release of Gd-HPDO3A. The presented results demonstrate the feasibility of the proposed method for two important applications in MR-guided noninvasive therapy. It offers a high temporal resolution when compared with interleaved Look-Locker based T(1) mapping techniques and thus represents an interesting candidate for simultaneous real-time monitoring of T(1) and temperature changes.     

Modified Look-Locker inversion recovery (MOLLI) for high-resolution T1 mapping of the heart.

A novel pulse sequence scheme is presented that allows the measurement and mapping of myocardial T1 in vivo on a 1.5 Tesla MR system within a single breath-hold. Two major modifications of conventional Look-Locker (LL) imaging are introduced: 1) selective data acquisition, and 2) merging of data from multiple LL experiments into one data set. Each modified LL inversion recovery (MOLLI) study consisted of three successive LL inversion recovery (IR) experiments with different inversion times. We acquired images in late diastole using a single-shot steady-state free-precession (SSFP) technique, combined with sensitivity encoding to achieve a data acquisition window of < 200 ms duration. We calculated T1 using signal intensities from regions of interest and pixel by pixel. T1 accuracy at different heart rates derived from simulated ECG signals was tested in phantoms. T1 estimates showed small systematic error for T1 values from 191 to 1196 ms. In vivo T1 mapping was performed in two healthy volunteers and in one patient with acute myocardial infarction before and after administration of Gd-DTPA. T1 values for myocardium and noncardiac structures were in good agreement with values available from the literature. The region of infarction was clearly visualized. MOLLI provides high-resolution T1 maps of human myocardium in native and post-contrast situations within a single breath-hold.     

Optimization and validation of a fully-integrated pulse sequence for modified look-locker inversion-recovery (MOLLI) T1 mapping of the heart

PURPOSE: To optimize and validate a fully-integrated version of modified Look-Locker inversion-recovery (MOLLI) for clinical single-breathhold cardiac T1 mapping. MATERIALS AND METHODS: A MOLLI variant allowing direct access to all pulse sequence parameters was implemented on a 1.5T MR system. Varying four critical sequence parameters, MOLLI was performed in eight gadolinium-doped agarose gel phantoms at different simulated heart rates. T1 values were derived for each variant and compared to nominal T1 values. Based on the results, MOLLI was performed in midcavity short-axis views of 20 healthy volunteers pre- and post-Gd-DTPA. RESULTS: In phantoms, a readout flip angle of 35 degrees , minimum TI of 100 msec, TI increment of 80 msec, and use of three pausing heart cycles allowed for most accurate and least heart rate-dependent T1 measurements. Using this pulse sequence scheme in humans, T1 relaxation times in normal myocardium were comparable to data from previous studies, and showed narrow ranges both pre- and postcontrast without heart rate dependency. CONCLUSION: We present an optimized implementation of MOLLI for fast T1 mapping with high spatial resolution, which can be integrated into routine imaging protocols. T1 accuracy is superior to the original set of pulse sequence parameters and heart rate dependency is avoided.     

Motion correction for myocardial T1 mapping using image registration with synthetic image estimation

Quantification of myocardial T1 relaxation has potential value in the diagnosis of both ischemic and nonischemic cardiomyopathies. Image acquisition using the modified Look-Locker inversion recovery technique is clinically feasible for T1 mapping. However, respiratory motion limits its applicability and degrades the accuracy of T1 estimation. The robust registration of acquired inversion recovery images is particularly challenging due to the large changes in image contrast, especially for those images acquired near the signal null point of the inversion recovery and other inversion times for which there is little tissue contrast. In this article, we propose a novel motion correction algorithm. This approach is based on estimating synthetic images presenting contrast changes similar to the acquired images. The estimation of synthetic images is formulated as a variational energy minimization problem. Validation on a consecutive patient data cohort shows that this strategy can perform robust nonrigid registration to align inversion recovery images experiencing significant motion and lead to suppression of motion induced artifacts in the T1 map.     

Human myocardium: single-breath-hold MR T1 mapping with high spatial resolution--reproducibility study

A prospective study approved by the local ethics committee was performed to establish the normal range and reproducibility of myocardial T1 values as assessed with single-breath-hold T1 mapping with high spatial resolution. With a 1.5-T magnetic resonance (MR) imaging system, baseline and contrast material-enhanced modified Look-Locker inversion recovery, or MOLLI, imaging was performed in 15 healthy volunteers who had given written informed consent. Image quality scores and myocardial T1 values were derived for standard short-axis segments and sections. Results were compared with those from a second MR imaging study performed on the same day (baseline only) and those from a third study performed on a different day (baseline and contrast enhanced; eight volunteers). Intra- and interobserver agreement were determined. Myocardial T1 maps were obtained rapidly in a reproducible fashion. A normal range for baseline and postcontrast myocardial T1 was established (baseline mean T1 in short-axis sections, 980 msec +/- 53 [standard deviation]; 95% confidence interval: 964, 997; number of sections, 43). This technique could enable direct quantification of changes in tissue characteristics in ischemic and inflammatory myocardial diseases.     

Accuracy of T1 measurement with 3-D Look-Locker technique for dGEMRIC

PURPOSE: To validate the accuracy of T1 measurement by three-dimensional Look-Locker method (3D LL) for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of human subjects with and without osteoarthritis (OA), as compared with two-dimensional inversion recovery fast spin-echo (2D IR-FSE) technique. MATERIALS AND METHODS: MR sagittal images of the knees were acquired for T1 mapping in 29 subjects with standard 2D IR-FSE and 3D LL sequences 90-135 min following administration of 0.2 mmol/kg Gd-DTPA(2-). T1 maps of femoral and tibial cartilage were generated using custom software. Comparisons in T1 values between the two techniques were performed using regression analysis. RESULTS: Good agreement in T1 values between 2D IR-FSE and 3D LL was observed (R values of 0.90, and 0.85, and 0.86 for all, OA, and control subjects, respectively) when acquired within 15 min. CONCLUSION: The 3D LL sequence provides accurate T1 estimates of articular cartilage with advantages of entire joint coverage, shorter acquisition time, and a wide range of inversion times sampled within a single acquisition.     

Fast T(1) mapping with volume coverage.

Four different sequences which enable high-resolution, multislice T(1) relaxation-time mapping are presented. All these sequences are based on the Look-Locker method with differences arising from the use of either a saturation-recovery or inversion-recovery module prior to data acquisition with a full k-space or banded k-space acquisition scheme. The methods were implemented on a standard clinical scanner and the accuracy of the T(1) results was evaluated against spectroscopic measurements. The accuracy of the T(1) maps validated by phantom imaging measurements is around 1% for species which relax with T(1) times that mimic gray/white matter (T(1) < or = 1000 ms). Additionally, the inherent multislice, multipoint capability of the methods is demonstrated. Finally, in vivo results of the human brain obtained using the faster method are presented. The fastest data acquisition was achieved with a saturation-recovery, banded k-space method where k-space was divided into three segments; an overall acquisition time of around 5 min (for species with T(1) < or = 1 sec) was achieved for a T(1) map which can, in principle, provide whole-brain coverage with a matrix size of 256 x 256 at multiple time-points. Magn Reson Med 46:131-140, 2001.