The investigations of nuclear magnetic resonance (NMR) relaxation of protons in aqueous solution and 2% agar–agar gel in the presence of magnetic nanoparticles were performed. To identify the effect of magnetic nanoparticles on the contrast of magnetic resonance images, the dependences of the MR signal intensity on the parameters of the two pulse radio-frequency (RF) sequences ( spin - echo , gradient - echo ) most commonly used in MRI for different values of the magnetic nanoparticle (MNP) concentration were simulated and analyzed. Recommendations for choosing the optimal values of pulse RF sequence parameters for MR imaging (MRI) in the presence of MNPs are formulated. MRI studies of phantom samples with 2% agar–agar gel containing MNPs have been performed for choosing the fast pulse RF sequence which shows the greatest contrast effect on MR images. A program for modeling magnetic resonance tomograms and determination of optimal values of pulse RF sequence parameters to achieve the best contrast of magnetic resonance images is developed. This program allows to reduce the time of MRI studies, to assess the possibility of using MNPs for contrast of MR images and to simulate the MR image in the presence of magnetic nanoparticles at the planning stage of procedures in MR-guided theranostics.

中文翻译：

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磁性纳米粒子对 MR 图像对比度影响的研究和建模

在磁性纳米粒子的存在下进行了水溶液和 2% 琼脂凝胶中质子的核磁共振 (NMR) 弛豫的研究。为了确定磁性纳米粒子对磁共振图像对比度的影响，MR信号强度对MRI中最常用的两种脉冲射频（RF）序列（自旋回波、梯度回波）参数的依赖性。对不同值的磁性纳米颗粒 (MNP) 浓度进行了模拟和分析。制定了在 MNP 存在的情况下为 MR 成像 (MRI) 选择脉冲射频序列参数的最佳值的建议。已对含有 MNP 的 2% 琼脂凝胶的体模样品进行 MRI 研究，以选择对 MR 图像显示最大对比度效果的快速脉冲 RF 序列。开发了一种用于对磁共振断层图进行建模并确定脉冲射频序列参数的最佳值以实现磁共振图像的最佳对比度的程序。该程序允许减少 MRI 研究的时间，评估使用 MNP 进行 MR 图像对比度的可能性，并在 MR 引导的治疗诊断程序的计划阶段模拟存在磁性纳米粒子的 MR 图像。