Multimodal detection of iron oxide nanoparticles in rat lymph nodes using magnetomotive ultrasound imaging and magnetic resonance imaging

Abstract

Detection and removal of sentinel lymph nodes (SLN) is important in the diagnosis and treatment of cancer. The SLN is the first regional lymph node draining the primary tumor, and if the cancer has spread, it is most likely to find metastases in the SLN. In this study, we have for the first time been able to image the very same contrast agent, superparamagnetic iron oxide nanoparticles (SPIO-NPs), in rat SLNs by using both our frequency- and phase-gated magnetomotive ultrasound (MMUS) algorithm and conventional magnetic resonance imaging (MRI); MMUS post mortem, MRI in vivo. For both higher NP-concentration and smaller NPs, we found that the MMUS data showed a larger magnetomotive displacement (1.56 ± 0.43 and 1.94 ± 0.54 times larger, respectively) and that the MR-images were affected to a higher degree. The MMUS displacement also increased with lower excitation frequency (1.95 ± 0.64 times larger for 5 Hz compared with 15 Hz) and higher excitation voltage (2.95 ± 1.44 times larger for 30 V compared with 10 V). The results show that MMUS has potential to be used as bedside guidance during SLN surgery, imaging the same particles that were used in prior staging with other imaging techniques.

In vivo magnetomotive ultrasound imaging of rat lymph nodes - a pilot study

“…The color bar was adjusted to accommodate displacements up to 0.8 μm, while pixels showing a larger displacement were set to 0.8 μm (white). As expected and seen previously, higher voltages resulted in larger magnetomotive displacement [4,5].…”

“…As in previous reports [4,5] a positive relationship between an increased magnetic field excitation voltage and a larger magnetomotive displacement can be seen. The result of this is illustrated in both in Fig.…”

“…We have previously developed a motion artefact robust algorithm which is able to detect this movement [4] and most recently we have proven it to successfully image SPIO-laden sentinel lymph nodes (SLN) in rats in situ [5]. The SLN is the first lymph node which drains a primary tumor region, and it is of special therapeutic interest, particularly in cases of breast cancer and malignant melanoma.…”

Combined Magnetomotive ultrasound, PET/CT, and MR imaging of 68Ga-labelled superparamagnetic iron oxide nanoparticles in rat sentinel lymph nodes in vivo

“…It can be argued that this is a result of the particles not having enough time to migrate to the SLN. However, from previous studies we have established that the period between injection and imaging in this study should be more than sufficient for SLN uptake 23, 29, 30, 32 . The reason for the variability within this group is instead most probably a result of animal 4 receiving the lowest concentration of SPIONs and a liver uptake of SPIONs in animal 6, likely due to the particles partly being injected into the bloodstream.…”

Magnetomotive Optical Coherence Elastography for Magnetic Hyperthermia Dosimetry Based on Dynamic Tissue Biomechanics

“…Supplied with both MNPs and fluorescent dyes, MM-OCT can be complemented with fluorescence imaging [37]. The magnetomotive principle has also been applied in ultrasound and demonstrated with multimodal imaging [41]. …”