在低磁场强度下全血中增强的 Xe T1 弛豫和 SPIONs 的存在。
Enhanced Xe T relaxation in whole blood and in the presence of SPIONs at low magnetic field strengths.
机构信息
Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
出版信息
Magn Reson Med. 2023 Jul;90(1):21-33. doi: 10.1002/mrm.29619. Epub 2023 Feb 16.
PURPOSE
To compare the effect of superparamagnetic iron oxide nanoparticles (SPIONs) on the T of Xe and H and to measure the relaxation of Xe in blood at low and high magnetic field strengths.
METHODS
Xe and H T relaxometry was performed at low- and high-field strengths in samples containing different SPION concentrations, while imaging was used to compare the contrast obtainable in these two field regimes. In vivo experiments at variable field strengths were performed to determine the depolarization of Xe in blood and the feasibility of in vivo dissolved-phase spectroscopy and imaging at low field.
RESULTS
The SPION relaxivity was substantially greater at low field for H, increasing from 0.92 ± 0.06 mM s at 11.7T to 31.5 ± 1.8 mM s at 0.6 mT, and for Xe, which increased from 0.13 ± 0.03 mM s at 11.7T to 7.32 ± 0.71 mM s at 2.1 mT. The additional MR signal loss increased from 0.7% at 9.4T to 20.6 ± 4.2% at 0.6 mT for H and from -0.7 ± 3.4% at 9.4T to 12.7 ± 3.5% at 2.1 mT for Xe. Blood was found to depolarize Xe below 3T in a manner inversely proportional to the field strength. In vitro studies at 2.1 mT suggest Xe relaxation times below 5 s in blood dilutions as low as 0.4% volume.
CONCLUSION
SPIONs longitudinal relaxivity increases at low field both for H and Xe. The depolarization of xenon in blood, which is found to increase below 3T, effectively prevents in vivo dissolved-phase spectroscopy and imaging at low-field strengths.
目的
比较超顺磁氧化铁纳米粒子（SPIONs）对氙气和氢气 T1 的影响，并测量低磁场和高磁场下血液中氙气的弛豫率。
方法
在低磁场和高磁场下对含有不同 SPION 浓度的样品进行氙气和氢气 T1 弛豫率测量，同时使用成像技术比较这两种场强下获得的对比度。在可变场强下进行体内实验，以确定血液中氙气的去极化情况，并评估在低场进行体内溶解相光谱学和成像的可行性。
结果
低磁场下，氢气的 SPION 弛豫率显著增加，从 11.7T 时的 0.92±0.06mM·s-1增加到 0.6mT 时的 31.5±1.8mM·s-1，氙气的弛豫率也从 11.7T 时的 0.13±0.03mM·s-1增加到 2.1mT 时的 7.32±0.71mM·s-1。对于氢气，额外的 MR 信号损失从 9.4T 时的 0.7%增加到 0.6mT 时的 20.6±4.2%，对于氙气，从 9.4T 时的-0.7±3.4%增加到 2.1mT 时的 12.7±3.5%。研究发现，血液中的氙气在低于 3T 的磁场下发生去极化，这种去极化与磁场强度成反比。在 2.1mT 的体外研究中，血液稀释度低至 0.4%时，血液中的氙气弛豫时间可低于 5s。
结论
SPIONs 对氢气和氙气的纵向弛豫率在低磁场下均增加。血液中氙气的去极化作用，在低于 3T 的磁场下会增加，这有效地阻止了在低场强度下进行体内溶解相光谱学和成像。
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