磁共振对比剂不良反应的处理

磁共振成像(MRI)增强用的造影剂gadolinium-die-thylenetriamine Pentaacetic acid(简称Gd- DTPA),商品名为马根维显(德国先灵公司)、磁显葡胺(北京北陆公司)、维影钆铵(广州军大),是一类顺磁性造影剂[1],早在1976年用于动物实验,以后逐渐用于临床,于1987年经美国FDA批准后广泛使用[2].我院自1996年8月磁共振开机以来,使用Gd-DTPA增强扫描3 840人次,现将护理配合中应用Gd-DTPA的安全性、注射剂量、速度及进展等综述如下.     

头颈部肿瘤的磁共振成像

磁共振成像(KST)越来越多地用于肿瘤分级和拟订治疗计划。除可作多个层面扫描外,其组织对比度高,因而特别适用于判断肿瘤的扩展、浸润和转移。技术参数头颈部肿瘤的诊断与选用适宜的检查序列有关,首先应行T_1或T_2加权序列检查。静脉注射造影剂(Gd-DTPA.0.1mmol/kg)后,在T_1加权序列图像及返转回波(IE)序列图     

脊髓亚急性联合变性的MRI诊断价值及临床特点

目的:探讨MRI对脊髓亚急性联合变性(SCD)的诊断价值及其临床表现。方法:维生素B_(12)缺乏及临床诊断为SDC患者9例,行MRI检查,扫描序列包括矢状面SE T_1WI、FSE T_2WI、T_2-FLAIR及横轴面T_2WI,其中6例行Gd- DTPA增强扫描。结果:MR图像上所有病例均显示颈髓或胸髓侧索或后索对称性病变,T_1WI上显示为等或稍低信号,T_2WI上为高信号,T_2-FLAIR上为高信号,病灶范围显示清晰,Gd-DTPA增强扫描病灶无明显强化。结论:MRI有助于SCD的诊断和随访观察,尤其是T_2-FLAIR序列,能准确显示病变范围。     

磁共振分子成像脂质体探针的制备与表征

目的:制备一种磁共振分子成像探针-钆结合空间稳定脂质体(Gd-SLs),并评价其物理属性.方法:利用挤出法制备空间稳定脂质体,表征脂质体粒径、稳定性、钆含量、弛豫率以及体外MR成像特点.结果:所制备之钆结合空间稳定脂质体经高压均质仪过膜后粒径控制于117.4±31.8nm;脂质体Gd载药率达87％～100％;常温下(26℃)Gd-SLs磁共振弛豫率为Gd-DTPA的1.16倍,37℃为1.25倍;体外MR成像显示Gd-SLs与Gd-DTPA两对比剂磁共振T1加权成像作用接近.结论:顺磁性空间稳定脂质体能有效提高磁共振分子探针体内成像信号,制备方法简单,实验操作可控性好,在一定温度范围内性质稳定,具有较高的磁共振弛豫作用,是理想的磁共振分子影像学对比剂载体.     

中枢神经系统肿瘤的MRI评价:Gd-DTPA和Gd-Hp-D03A剂量的对比研究

Gadoteridol(Gd-HP-D03A)是一种新型非离子型低渗造影剂。作者与Gd-DTPA对照研究了Gadoteridol的浓度对颅内肿瘤评价的影响。作者对40例颅内肿瘤病人用Gd-Hp-D03A的试验性剂量(标准剂量的1/2至3倍,即0.05-0.3mmol/kg)行MRI,其中15例也用过标准剂量(0.1mmol/kg)的Gd-DTPA检查。两次检查相隔2～60天,在此期间病人未经手术、化疗或放疗。在给造影剂前获取T_1加权(583～750/20)和T_2加权(2000/100)象,     

SPIO与Gd-DTPA增强对裸鼠肾癌移植瘤显影价值对照研究

目的:比较SPIO与Gd-DTPA增强对裸鼠肾癌移植瘤显影价值.方法:种植人肾癌Ketr-3细胞的雄性裸鼠14只,随机分为2组:SPIO组7只,Gd-DTPA组7只.SPIO组先行T_2 WI平扫,后快速注入Reso-vist,注药后即时、10min重复T_2WI序列.Gd-DTPA组先行T_1WI平扫,后快速注入Gd-DTPA,注药后即时、10rain重复T_1WI序列.扫描结束分别测量两组移植瘤增强前后的信号强度及计算相对增强率.结果:SPIO组注入Resovist后,即时移植瘤T_2信号强度(SI)开始下降,10min后T_2SI逐渐回复.Gd-DTPA组注入Gd-DTPA后,即时移植瘤T_1SI明显增加,10min后T_1SI亦维持于较高水平.结论:Gd-DTPA对于肾癌移植瘤的诊断有着较长的强化时间窗,且强化效果较SPIO更明显.     

不同粒径脂质体包裹顺磁性对比剂的体外R1弛豫率及MR增强成像研究

目的 通过制备不同粒径脂质体包裹顺磁性Gd-DTPA,观察其理化特性及对大鼠肝脏的强化作用.材料与方法 采用薄膜蒸发法制备不同粒径脂质体包裹顺磁性Gd-DTPA,观察其理化特性.动物实验选择雄性健康SD大鼠18只(平均分为3组),静脉注射不同粒径的顺磁性对比剂脂质体,于注射对比剂前、15 min后对实验动物进行MRI.测定增强扫描前后肝脏、背景组织的信号强度,计算强化率、对比噪声比(CNR).结果 制备出粒径分别为400 nm、200 nm、78 nm以下的顺磁性脂质体,其平均R1弛豫率分别为0.64、1.05、1.60 min-1·s-1,随着脂质体粒径减小,其包封率下降,体外R1弛豫率增高.静脉注射3种粒径的顺磁性脂质体后,肝脏的强化存在差异,表现为400 nm粒径的脂质体对肝脏的强化作用高于其他2种粒径脂质体,测量肝脏的强化率和CNR较200 nm、78nm脂质体差异有显著统计学意义(P<0.001).结论 脂质体包裹Gd-DTPA对肝脏具有强化作用,粒径大小对其弛豫率和强化作用有影响.     

呼吸导航与心电触发对兔肝脏磁共振成像应用比较

目的 比较1.5T磁共振扫描仪(Avanto)在呼吸导航技术和心电触发技术配合下对兔肝脏扫描成像质量的优劣.方法 分别应用呼吸导航技术和心电触发技术配合1.5T磁共振扫描仪对10只新西兰大白兔进行肝脏扫描,在保证图像平均信噪比(SNR)在1±0.1状态下,比较每种检查图像的优劣.扫描序列分别为TSE序列T_1加权、脂肪抑制T_1加权平扫及增强、T_2加权和脂肪抑制质子加权.结果 在心电触发配合下各个序列扫描图像质量均优于在呼吸导航下扫描所得图像,主要表现为前者受运动伪影干扰明显少于后者.结论 在SNR为1±0.1状态下.1.5T磁共振采用心电触发技术扫描兔肝脏所得图像质量优于采用呼吸导航时相同序列扫描所得图像,原因可能和兔的生理特点及2种不同门控方法的敏感度差异有关.     

顺磁性对比剂Gd-DTPA对短暂性脑缺血发作1H MRS的影响

目的:分析短暂性脑缺血发作(TIA)患者MR脑灌注成像(PWI)后顺磁性对比剂钆喷酸葡甲胺(Gd DTPA)对质子磁共振波谱(1H MRS)的影响,探讨用PWI检查指导1H MRS定位的可行性.方法:对20例临床诊断为TIA的患者行PWI检查,分别在PWI检查前后于双侧半卵圆中心行1H MRS检查,扫描参数及兴趣区(VOI)均相同.对比分析注射Gd-DTPA前后两次1H MRS主要代谢产物氮-乙酰天门冬氨酸(NAA)、胆碱复合物(Cho)和肌酸复合物(Cr)谱线的形态(峰高和半高宽)及相对浓度值(峰下面积比值).结果:注射Gd-DTPA前后两次1H MRS检查NAA、Cho和Cr谱线的形态未发现明显改变,同一区域代谢物谱线的各项参数差异均无显著性意义(P＞0.05).结论:TIA患者PWI检查注射顺磁性对比剂Gd-DTPA对1H MRS没有明显影响,可以通过PWI显示的灌注异常,指导TIA患者的1H MRS定位.     

椎管内微小占位性病变的MRI诊断

目的:研究椎管内微小占位性病变的MRI特征及其对病变定性、定位诊断的意义。材料与方法:24例椎管内微小占位性病变患者(男12例,女12例,年龄23～67岁,平均29.1岁)均经PHILIPS 1.0NT型MR仪行常规T_1WI、T_2WI磁共振成像,其中6例又经Gd-DTPA增强扫描。全部病例的椎管内占位病变均经病理证实,并对其MRI表现进行了回顾性分析。结果:24例的病变经病理证实,18例为胚胎源性肿瘤(10例表皮样囊肿,4例皮样囊肿,4例畸胎瘤),4例为神经源性肿瘤(3例神经鞘瘤,1例神经纤维瘤),以及脊膜瘤与脂肪瘤各1例。各种占位性病变的MRI表现随其不同的组织学来源而有很大差别。表皮样囊肿多为均质长T_1长T_2信号。皮样囊肿以短T_1,长T_2信号为主。畸胎瘤呈混杂信号。神经鞘瘤为T_1WI低信号、T_2WI高信号,Gd-DTPA增强扫描后,囊壁均匀强化,偶见强化附壁结节。神经纤维瘤呈均质长T_1、长T_2信号,Gd-DTPA增强扫描后,病灶呈异常对比增强。脊膜瘤呈长T_1、稍长T_2信号,Gd-DTPA增强扫描后,病灶呈异常对比强化,并见局部硬脊膜增厚强化而形成的硬膜尾征。结论:各种病变的MRI表现随其组织学来源不同而有明显差异,它们在椎管内微小占位性病变的定性、定位诊断中起着重要作用,其诊断准确性优于X线椎管造影与CT。     

Magnetic field dependence of longitudinal relaxation rates of solutions of various protein-gadolinium3+ chelate conjugates

Bovine serum albumin (BSA) and porcine serum fibrinogen (FIB) were multiply labeled with gadolinium3+ by using three different ligands: DTPA dianhydride, isothio-cyanato-benzyl-DTPA (ITCB-DTPA), in which none of the five coordinating carboxylates is employed for macromolecular linkage, and isothiocyanatobenzyl-TRITA, a macrocyclic ligand. The nuclear magnetic resonance dispersion (NMRD) profiles of the protein-(Gd chelate) conjugates were characteristic to each chelate involved, possessing, as expected, greater longitudinal relaxivities than the corresponding Gd chelates alone and exhibiting prominent peaks at the proton Larmor frequency range of 10 to 40 MHz. Particularly favorable relaxation enhancement was measured in the solutions of BSA-(ITCB-DTPA-Gd) at this field range. When the number of chelates conjugated with protein increased, up to 163 Gd chelates per one fibrinogen, a progressive decrease in relaxivity was observed. This study demonstrates the relaxation properties of novel macromolecular contrast agents designed for magnetic resonance imaging.     

Gadolinium cryptelates as MR contrast agents

Gadolinium cryptelates are complexes of a lanthanide metal ion with amino acids of macrocyclic polyamines. These compounds are water soluble and possess reduced relaxation properties similar to Gd diethylene triamine pentaacetic acid (DTPA). Three Gd cryptelates (Gd NOTA, DOTA, TETA) were evaluated. Gadolinium DOTA is the most stable Gd complex with a dissociation constant of 10(-28) and appears to have a greater serum stability than Gd DTPA. Gadolinium NOTA and Gd TETA have lower dissociation constants than Gd DTPA at 10(-17) and 10(-19). Gadolinium DOTA has tissue distribution properties similar to Gd DTPA, is rapidly excreted by the kidneys, and provides a high degree of contrast enhancement on magnetic resonance (MR) images, both systemically and within the CNS. Hence, Gd DOTA is an alternative water-soluble MR contrast agent to Gd DTPA.     

Tissue relaxation enhancement after intravenous administration of (ITCB-DTPA)-gadolinum conjugated albumin, an intravascular magnetic resonance imaging contrast agent

Gadolinium-isothiocyanato-benzyl-diethylenetriamine pentaacetic acid (ITCB-DTPA-Gd), a derivative of Gd-DTPA, was multiply conjugated to bovine serum albumin (BSA). In the synthesis of BSA-(ITCB-DTPA-Gd) conjugate, none of the five carboxylate groups of DTPA is functionalized for protein-chelate linkage. The rationale for this modification is to improve the affinity for Gd3+. We obtained a high-stability constant for the complex, comparable to unbound Gd-DTPA. Also, the complex had a T1 relaxivity as high as 30.3 seconds-1mmol-1 at 29 MHz (at 24 degrees C). At this field strength, and T1 of rat blood declined 91% after injection of 300 mg/kg of BSA-(ITCB-DTPA-Gd), corresponding to a Gd dose of 0.02 mmol/kg, while at 0.86 MHz it declined 64%. The shortening of T1 in vitro of blood, as well as spleen, lungs, and kidneys, persisted for 60 minutes. Better enhancement on post-contrast magnetic resonance images of rats was obtained at 1.0 T than at 0.04 T. Tissues with rich vascularization and large venous structures were well displayed at the higher field.     

Use of gadolinium-DTPA as a myocardial perfusion agent: potential applications and limitations for magnetic resonance imaging

To establish the effect of the paramagnetic contrast agent gadolinium diethylenetriaminepentaacetic acid ([Gd]DTPA) on myocardial magnetic resonance relaxation parameters T1 and T2, and its relationship to myocardial perfusion, we administered [Gd] DTPA 0.2 mM/kg to two groups of dogs. Group I had severe, resting myocardial ischemia induced by coronary occlusion, followed in 2 min by [Gd]DTPA infusion and heart excision 1 min later. Group II had a variable reduction in blood flow. In Group II the coronary vasodilator dipyridamole was infused to enhance blood flow to the normal myocardium before [Gd]DTPA was given. In Group I [Gd]DTPA caused a significant difference in T1 between the normal and severely ischemic zones; changes in T1 correlated with the severity of myocardial ischemia. Although vasodilatation delivered more Gd-DTPA to the normal myocardium in Group II, the lack of further decrease in T1 suggested that it was cleared more rapidly. Thus, [Gd]DTPA permits the detection and characterization of severe, resting myocardial ischemia by magnetic resonance techniques. Using the experimental techniques described in this study, less severe flow differences caused by vasodilatation and resultant hyperemia are not detected.     

Delayed contrast‐enhanced MRI of cartilage: Comparison of nonionic and ionic contrast agents

The objective of this study was to evaluate if cartilage fixed charge density is the only factor determining the distribution of the measured delayed gadolinium‐enhanced magnetic resonance imaging of cartilage index, T₁(Gd‐DTPA^2?), across cartilage in the clinical delayed gadolinium‐enhanced magnetic resonance imaging of cartilage protocol. Nineteen subjects with osteoarthritis and 14 controls were included. Cartilage T₁(Gd) was measured following administration of 0.2 mmol kg^?1 of nonionic (Gd‐DTPA‐BMA) and, at a different date, anionic (Gd‐DTPA^2?). T₁(Gd‐DTPA‐BMA) was plotted against T₁(Gd‐DTPA^2?); a slope of 0 would indicate domination by charge effects; a nonzero slope would suggest that other factors influence T₁(Gd‐DTPA‐BMA), and hence potentially T₁(Gd‐DTPA^2?). The low slope of the curve found in osteoarthritis subjects (0.31) indicates that Gd‐DTPA‐BMA penetrated most osteoarthritis cartilage to the same extent, and T₁(Gd‐DTPA‐BMA) did not differentiate cartilages, which were differentiated by T₁(Gd‐DTPA^2?). The higher slopes in control subjects (0.88) are possibly due to inhibited transport of contrast agent into healthier cartilage, potentially exaggerated by the fast body clearance of the nonionic contrast agent. Overall, the use of anionic Gd‐DTPA^2? for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage is indicated for better discrimination of the health status of cartilage. Future studies could be designed to use contrast‐enhanced dynamics to understand the transport properties of tissues in the joint and to evaluate the concentration of tissue constituents. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Relaxation of solvent protons by solute Gd3+-chelates,revisited

The magnetic field dependence (NMRD profile) of 1/T₁, of solvent protons in an aqueous solution of Gd(DTPA)^2? was remeasured at 5,15,25,30, and 35°C. The data were reanalyzed with the usual low-field theory, using recently published values for T_M, the residence lifetime of the single inner-coordinated waters of solute Gd(DTPA)^2?. (These T_M values are significantly longer than earlier estimates). Values were obtained for three dynamic parameters: T_R, the rotational relaxation time of solute ions, and T_SO and T_V, the low-field relaxation time of the Gd³⁺ magnetic moment and the related correlation time. These Gd(DTPA)²⁺ values, together with recent results for T_M for Gd(DTPA-BMA) — a nonionic structural analog of Gd(DTPA)^2? with an unusually long T_M — were used to calculate NMRD profiles at 5 and 35°C. These profiles agree very well with new data given here for a solution of Gd(DTPA-BMA). This reaffirms the importance of knowing the temperaturedependent values of T_M a priori in order to obtain unambiguous quantitative theoretical analyses of NMRD profiles of chelates of known structure. Additionally, the theory of inner sphere relaxation is extended to high fields, at which the magnetic energy of a solute moment is greater than its thermal energy.     

Gd-DTPA在MRI中的诊断作用

目的:探讨Gd-DTPA在MRI中的诊断作用。材料与方法:总结分析了被确诊的378例(402人次)患者应用Gd-DTPA增强检查后的效果。对肿瘤、感染、梗塞等病变的强化特点进行了讨论。结果:使用Gd-DTPA后,有23例平扫时误诊的病例得到了纠正,并发现了MRI平扫时未能发现的一些病变,诸如管内型听神经瘤、脑膜炎、脑(脊)膜的转移性病变等。但是,作者还同时发现即使在用了Gd-DTPA之后,仍有多种病变存在鉴别诊断上的困难。结论:合理使用增强检查,将有助于提高诊断的符合率。     

Low molecular weight lanthanide contrast agents: In vitro studies of mechanisms of action

The MR contrast properties of a series of structurally dissimilar low molecular weight (LMW) gadolinium (Gd) and dysprosium (Dy) chelates have been investigated under controlled experimental conditions in various in vitro test systems. Relaxation analysis (water, pH = 5.8, 37°C, .47 T) demonstrated the high dipolar relaxation efficacy of the tested Gd chelates. The T1 and T2 relaxivities of both metal chelate series decreased with decreasing hydration number, confirming the strong correlation between metal chelate structure and dipolar relaxivity. Susceptibility-induced T2 relaxation, commonly known as the susceptibility effect, is modulated primarily by the magnetic susceptibility and compartmentalization of the contrast agent. The influence of these parameters on the susceptibility effect of Dy diethylenetriamine pentaacetic acid bis-methylamide (DTPA-BMA) and GdDTPA-BMA was investigated in two-compartment in vitro models. In red blood cell suspensions (45% hematocrit, 37°C, .47 T, 2 and 3 mM metal ion concentration), the T2 relaxation efficacy of DyDTPA-BMA was markedly improved due to susceptibility effects that were shown to depend on compartmentalization. As the relaxation ability of GdDTPA-BMA was modulated by the dipolar interactions, compartmentalization was not a prerequisite for its T2 relaxation efficacy. In a coaxial glass system with no intercompartmental water exchange, which eliminated the dipolar relaxation mechanism, DyDTPABMA was shown to be the most efficient susceptibility agent because of its higher magnetic susceptibility. The reported one- and two-compartment model studies have demonstrated the different mechanism of action of LMW Gd- and Dy-based contrast agents. Gd chelates are predominantly dipolar relaxation enhancers, whereas Dy chelates are efficient susceptibility agents only in compartmentalized systems.     

Relaxivity and diffusion of gadolinium agents in cartilage.

Prior work indicates that the distribution of Gd(DTPA)(2-) (as measured by T(1)) is a good surrogate measure of the distribution of gycosaminoglycan (GAG) in cartilage. In addition to the measured T(1) in the presence of Gd(DTPA)(2-), the precision of the measurement of Gd(DTPA)(2-) concentration depends on the T(1) without Gd(DTPA)(2-) (T(o)(1)), and the relaxivity (r) of Gd(DTPA)(2-) in cartilage, parameters that are influenced by cartilage composition. These parameters were measured in native and GAG-depleted cartilage in order to estimate the bounds on the values one might expect for cartilage in arbitrary states of degeneration. The range of T(o)(1) was 0.3 sec; the range of r was 0.6 (mM*s)(-1) at 8.5 T and 1.4 (mM*s)(-1) at 2 T. These data suggest that Gd(DTPA)(2-) will be underestimated (and GAG overestimated) if the values for T(o)(1) and r are assumed to be those of native cartilage. (For example, in a severe case a 90% loss of GAG would be underestimated as a 70% loss.) Gd(HPDO3A) was investigated as a nonionic "control agent" and found to have relaxivity and diffusion properties that were comparable to Gd(DTPA)(2-) (r(Gd(HPDO3A))/r(Gd(DTPA)) approximately 1; D(Gd(HPDO3A))/D(Gd(DTPA)) approximately 0.85). Since Gd(HPDO3A) distributes uniformly through cartilage (independent of GAG), the distribution of T(1) with Gd(HPDO3A) can be used as a surrogate measure of variations in T(o)(1) and r, if present. From the perspective of transport, if Gd(HPDO3A) has fully penetrated the cartilage, Gd(DTPA)(2-) would have in the same time frame. Therefore, the data confirm the efficacy of using Gd(HPDO3A) as a "control agent" for dGEMRIC.