Detection Sensitivity of Lymph Nodes of Various Sizes Using USPIO Nanoparticles in MRI

Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles based magnetic resonance imaging (MRI) has made a 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 effect of MR protocols and their parameters on artifact size and detection sensitivity has been studied before.

In this study, USPIO nanoparticles were used as MRI contrast agent and their detection sensitivity in axillary lymph nodes were evaluated using previous defined pulse sequences. The minimum amount (dose) of USPIO which delineate lymph nodes of various sizes using susceptibility based gradient echo (GRE) pulse sequences was also determined. It was found that a dose administration of as low as 0.028 mgFe/kg for subcutaneous injection and 0.16 mgFe/kg for intravenous injection can be used to visualize axillary lymph nodes when a sensitive MR protocol is employed.