Optimization of iron oxide nanoparticle detection using ultrashort echo time pulse sequences: comparison of T1, T2*, and synergistic T1- T2* contrast mechanisms.
Optimization of iron oxide nanoparticle detection using ultrashort echo time pulse sequences: comparison of T1, T2*, and synergistic T1- T2* contrast mechanisms.
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DOI：
10.1002/mrm.22755
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发表时间：
2011-06
影响因子：
3.3
通讯作者：
Mattrey RF
中科院分区：
文献类型：
--
作者：
Girard OM;Du J;Agemy L;Sugahara KN;Kotamraju VR;Ruoslahti E;Bydder GM;Mattrey RF
氧化铁纳米颗粒（IONP）在各种MRI应用中用作阴性造影剂。一个主要的挑战是区分由于IONP导致的信号空白区域与由于低信号组织或敏感性伪影导致的区域。为了克服这种限制，已经提出了几种正对比策略。依靠IONP T1缩短效应产生阳性对比度是一种特别有吸引力的策略，因为当与来自T2* 效应的通常阴性对比度相关联时，它应该提供额外的特异性。在本文中，超短TE（UTE）成像是一个强大的技术，可以充分利用这两种对比机制。比较T1和T2* 对比效率的方法进行了描述和一般规则，允许优化IONP检测灵敏度的推导。与传统观点相反，优化T1对比度通常是IONP成像的好策略。在某些条件下，从UTE信号中减去较晚的回波信号不仅通过提供长的T2* 背景抑制来改善IONP特异性，而且还增加检测灵敏度，因为它能够实现通常拮抗剂T1和T2* 对比的协同组合。体外实验支持我们的理论和分子成像的应用证明，在体内使用肿瘤靶向的IONP。
Iron oxide nanoparticles (IONPs) are used in various MRI applications as negative contrast agents. A major challenge is to distinguish regions of signal void due to IONPs from those due to low signal tissues or susceptibility artifacts. To overcome this limitation, several positive contrast strategies have been proposed. Relying on IONP T1 shortening effects to generate positive contrast is a particularly appealing strategy since it should provide additional specificity when associated with the usual negative contrast from T2* effects. In this paper, Ultrashort TE (UTE) imaging is shown to be a powerful technique which can take full advantage of both contrast mechanisms. Methods of comparing T1 and T2* contrast efficiency are described and general rules that allow optimizing IONP detection sensitivity are derived. Contrary to conventional wisdom, optimizing T1 contrast is often a good strategy for imaging IONPs. Under certain conditions, subtraction of a later echo signal from the UTE signal not only improves IONP specificity by providing long T2* background suppression, but also increases detection sensitivity, as it enables a synergistic combination of usually antagonist T1 and T2* contrasts. In vitro experiments support our theory and a molecular imaging application is demonstrated using tumor-targeted IONPs in vivo.
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