Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
J Magn Reson Imaging. 2010 Nov;32(5):1172-83. doi: 10.1002/jmri.22349.
To develop novel magnetic resonance (MR) imaging methods to monitor accumulation of macrophages in inflammation and infection. Positive-contrast MR imaging provides an alternative to negative-contrast MRI, exploiting the chemical shift induced by ultra-small superparamagnetic iron-oxide (USPIO) nanoparticles to nearby water molecules. We introduce a novel combination of off-resonance (ORI) positive-contrast MRI and T(2ρ) relaxation in the rotating frame (ORI-T(2ρ)) for positive-contrast MR imaging of USPIO.
We tested ORI-T(2ρ) in phantoms and imaged in vivo the accumulation of USPIO-labeled macrophages at the infection site in a mouse model of burn trauma and infection with Pseudomonas aeruginosa (PA). PA infection is clinically important. The USPIO nanoparticles were injected directly in the animals in solution, and macrophage labeling occurred in vivo in the animal model.
We observed a significant difference between ORI-T(2ρ) and ORI, which leads us to suggest that ORI-T(2ρ) is more sensitive in detecting USPIO signal. To this end, the ORI-T(2ρ) positive contrast method may prove to be of higher utility in future research.
Our results may have direct implications in the longitudinal monitoring of infection, and open perspectives for testing novel anti-infective compounds.
开发新的磁共振（MR）成像方法来监测炎症和感染中巨噬细胞的积累。正对比磁共振成像提供了一种替代负对比 MRI 的方法，利用超顺磁氧化铁（USPIO）纳米粒子对附近水分子的化学位移来实现。我们引入了一种新的离共振（ORI）正对比磁共振成像和旋转框架中的 T（2ρ）弛豫（ORI-T（2ρ））组合，用于 USPIO 的正对比 MR 成像。
我们在体模中测试了 ORI-T（2ρ），并在烧伤创伤和铜绿假单胞菌（PA）感染的小鼠模型中，对感染部位 USPIO 标记的巨噬细胞的积累进行了体内成像。PA 感染在临床上很重要。USPIO 纳米粒子直接注射到动物体内的溶液中，在动物模型中体内发生巨噬细胞标记。
我们观察到 ORI-T（2ρ）和 ORI 之间存在显著差异，这使我们认为 ORI-T（2ρ）在检测 USPIO 信号方面更敏感。为此，ORI-T（2ρ）阳性对比方法在未来的研究中可能具有更高的实用性。
我们的结果可能对感染的纵向监测具有直接影响，并为测试新型抗感染化合物开辟了前景。
