Relaxivity Optimization of a PEGylated Iron-Oxide-Based Negative Magnetic Resonance Contrast Agent for T2-Weighted Spin鈥揈cho Imaging

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• 作者：Elmar P枚selt ; Hauke Kloust ; Ulrich Tromsdorf ; Marcus Janschel ; Christoph Hahn ; Christoph Ma脽lo ; Horst Weller
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：February 28, 2012
• 年：2012
• 卷：6
• 期：2
• 页码：1619-1624
• 全文大小：826K
• 年卷期：v.6,no.2(February 28, 2012)
• ISSN：1936-086X

文摘

Concerning the outer sphere relaxation theory, the sensitivity of a T₂ MRI contrast agent, expressed by the transverse relaxivity r₂, depends on the diffusion length of water molecules relative to the particle size. For T₂-weighted spin鈥揺cho imaging, theoretical concepts reveal three regimes regarding the r₂ relaxivity depending on the nanocrystal size: the motional averaging regime (MAR), the static dephasing regime (SDR), and the echo-limiting regime (ELR). The r₂ maximum corresponds to the SDR, which represents a small size regime. To verify the theoretical concepts and to adjust the SDR, tailor-made T₂ contrast agents were synthesized by controlled self-assembly of superparamagnetic iron oxide nanocrystals (SPIOs) into raspberry-like nanoclusters with diameters of 30鈥?00 nm using a PEG-based ligand. The results highlight an opportunity to optimize the relaxivity of T₂ contrast agents by tuning the cluster size of SPIO nanocrystals.

Keywords:

MRI; contrast agent; relaxivity; nanocrystal; SPIO; cluster