Nuclear magnetic relaxation dispersion (NMRD) profiles are essential tools to evaluate the efficiency and investigate the properties of magnetic compounds used as contrast agents for magnetic resonance imaging (MRI), namely gadolinium chelates and superparamagnetic iron oxide particles. These curves represent the evolution of proton relaxation rates with the magnetic field. NMRD profiles are unparalleled to probe extensively the spectral density function involved in the relaxation of water in the presence of the paramagnetic ion or the magnetic nanoparticles. This makes such profiles an excellent test of the adequacy of a theoretical relaxation model and allow for a predictive approach to the development and optimization of contrast agents. From a practical point of view they also allow to evaluate the efficiency of a contrast agent in a certain range of magnetic fields. Nowadays, these curves are recorded with commercial fast field cycling devices, often limited to a maximum Larmor frequency of 40 MHz (0.94 T). In this article, relaxation data were acquired on a wide range of magnetic fields, from 3.5 × 10−4 to 14 T, for a gadolinium-based contrast agent and for PEGylated iron oxide nanoparticles. We show that the low-field NMRD curves can be completed with high-field data obtained on a shuttle apparatus device using the superconductive magnet of a high-field spectrometer. This allows a better characterization of the contrast agents at relevant magnetic fields for clinical and preclinical MRI, but also refines the experimental data that could be used for the validation of relaxation models.

中文翻译：

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造影剂的样品穿梭弛豫测量：单个设备 1 T 以上的 NMRD 曲线

核磁弛豫色散 (NMRD) 曲线是评估用作磁共振成像 (MRI) 造影剂的磁性化合物（即钆螯合物和超顺磁性氧化铁颗粒）的效率和研究其特性的重要工具。这些曲线代表质子弛豫率随磁场的演变。NMRD 谱在广泛探测顺磁性离子或磁性纳米粒子存在下水弛豫所涉及的谱密度函数方面是无与伦比的。这使得此类轮廓成为理论松弛模型充分性的绝佳测试，并允许采用预测方法来开发和优化造影剂。从实用的角度来看，它们还可以评估造影剂在特定磁场范围内的效率。如今，这些曲线是用商业快速现场循环设备记录的，通常限制在最大拉莫尔频率 40 MHz (0.94 T)。在本文中，针对钆基造影剂和聚乙二醇化氧化铁纳米颗粒，在从 3.5 × 10−4 到 14 T 的广泛磁场中获取了弛豫数据。我们证明，低场 NMRD 曲线可以通过使用高场谱仪的超导磁体在航天飞机装置上获得的高场数据来完成。这样可以在临床和临床前 MRI 的相关磁场下更好地表征造影剂，而且还可以细化可用于验证松弛模型的实验数据。