Detection sensitivity of lymph nodes of various sizes using USPIO nanoparticles in magnetic resonance imaging.

Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles-based magnetic resonance imaging (MRI) have offered new promise for early detection of lymph nodes and their metastases. These nanoparticles are taken up by macrophages in normal lymph nodes and produce signal changes based on susceptibility artifact and dipolar relaxation. The effects of MR protocols and their parameters on artifact size and detection sensitivity have been studied before. In this study USPIO nanoparticles were used as MRI contrast agent, and their detection sensitivity in axillary lymph nodes was evaluated using earlier defined pulse sequences. The minimum amount (dose) of USPIO nanoparticles that delineates lymph nodes of various sizes using susceptibility-based gradient echo pulse sequences was also determined. It was found that a dose administration of as low as 0.028 mg iron (Fe)/kg for subcutaneous injection and 0.16 mg Fe/kg for intravenous injection can be used to visualize axillary lymph nodes when a sensitive MR protocol is employed. FROM THE CLINICAL EDITOR: Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are taken up by macrophages and have been shown to be promising negative contrast agents in the early detection of metastases in lymph nodes. In this study, their detection sensitivity in axillary lymph nodes was evaluated using previously defined MRI pulse sequences. The minimum dose of USPIO to delineate lymph nodes using gradient echo-based optimized pulse sequences was 0.028 mgFe/kg for subcutaneous and 0.16 mgFe/kg for intravenous injection.