Adzamli K, Periasamy M P, Spiller M, Koenig S H
Department of Medical Information Sciences, University of Illinois, Urbana, USA.
Invest Radiol. 1999 Jun;34(6):410-4. doi: 10.1097/00004424-199906000-00004.
Gd-DTPA-BMEA, a nonionic bis(methoxyethylamide) derivative of Gd-DTPA, is the active ingredient of OptiMARK, now awaiting FDA approval. In this study, we compare the relaxivities of Gd-DTPA-BMEA (OptiMARK) with those of the commercially available DTPA-based agents Gd-DTPA2- (Magnevist) and Gd-DTPA-BMA (Omniscan) at different field strengths (1/T1 nuclear magnetic relaxation dispersion (NMRD) profiles). In addition, we study how changes in structural attributes of small paramagnetic chelate complexes of Gd3+ ions influence 1/T1 NMRD profiles.
1/T1 NMRD profiles of Gd-DTPA-BMEA (OptiMARK) were measured at 5 degrees and 35 degrees C and a set of values for the parameters that describe relaxation by Gd(3+)-proton magnetic dipolar interactions was obtained. The rotational (tau R) and the diffusional (tau D) correlation times for Gd-DTPA-BMA were adjusted for the 15% greater molecular weight of Gd-DTPA-BMEA. tau M (the resident lifetime of Gd(3+)-bound water) was obtained from available 17O NMR relaxation data. For tau S0 and tau V (the low-field relaxation time of the Gd3+ moment and its correlation time), Gd-DTPA-BMA values were taken as initial values and tau S0 refined as needed.
Although, at 35 degrees C, tau M is comparable for the two neutral agents and an order of magnitude longer than that for Gd-DTPA2-, the 1/T1 NMRD profiles of Gd-DTPA-BMEA are indistinguishable from those of Gd-DTPA2- and Gd-DTPA-BMA. A 40% increase in the value of tau S0 from Gd-DTPA2- is required for agreement of data and theory for Gd-DTPA-BMEA.
Based on their 1/T1 NMRD profiles, the efficacy of the three agents should be identical in typical clinical MRI applications. The data can be fit reliably to theory, and differences in the fit parameters (and structure) have no effect on the three profiles at 35 degrees C. The relatively long values of tau M for the two neutral agents would only be of importance at low temperatures.
钆喷酸双甲胺（Gd-DTPA-BMEA）是钆喷酸（Gd-DTPA）的一种非离子双（甲氧基乙酰胺）衍生物，是OptiMARK的活性成分，目前正在等待美国食品药品监督管理局（FDA）的批准。在本研究中，我们比较了钆喷酸双甲胺（OptiMARK）与市售的基于二乙三胺五乙酸（DTPA）的造影剂钆喷酸葡胺（Gd-DTPA2-，马根维显）和钆布醇（Gd-DTPA-BMA，欧乃影）在不同场强下的弛豫率（1/T1核磁共振弛豫色散（NMRD）曲线）。此外，我们研究了钆离子（Gd3+）的小顺磁性螯合物结构属性的变化如何影响1/T1 NMRD曲线。
在5℃和35℃下测量钆喷酸双甲胺（OptiMARK）的1/T1 NMRD曲线，并获得一组描述Gd(3+)-质子磁偶极相互作用弛豫的参数值。考虑到钆喷酸双甲胺的分子量比钆布醇大15%，对钆布醇的旋转相关时间（τR）和扩散相关时间（τD）进行了调整。τM（Gd(3+)-结合水的驻留寿命）从现有的17O NMR弛豫数据中获得。对于τS0和τV（Gd3+矩的低场弛豫时间及其相关时间），以钆布醇的值作为初始值，并根据需要对τS0进行优化。
尽管在35℃时，两种中性造影剂的τM相当，且比钆喷酸葡胺的τM长一个数量级，但钆喷酸双甲胺的1/T1 NMRD曲线与钆喷酸葡胺和钆布醇的曲线无法区分。为了使钆喷酸双甲胺的数据与理论相符，需要将τS0的值比钆喷酸葡胺增加40%。
基于它们的1/T1 NMRD曲线，在典型的临床磁共振成像（MRI）应用中，这三种造影剂的效能应该是相同的。数据可以可靠地拟合理论，并且拟合参数（和结构）的差异在35℃时对三条曲线没有影响。两种中性造影剂相对较长的τM值仅在低温下才重要。
