Intra‐operative ex vivo photoacoustic nodal staging in a rat model using a clinical superparamagnetic iron oxide nanoparticle dispersion

Abstract

The ability to accurately detect tumor metastases in lymph nodes is essential for intra-operative staging of various malignancies. Histopathological assessment of nodes has the drawback of a time delay before results are available to the surgeon and a likelihood of missing metastases. Photoacoustic (PA) imaging has been shown to possess the potential to detect melanoma metastases in resected in toto lymph nodes based on intrinsic contrast. To extend application of the method to other malignancies, extrinsic contrast for lymphatic mapping is important. We investigate in a metastatic animal model whether clinically approved superparamagnetic iron oxide (SPIO) nanoparticles, applied for MRI, can help PA imaging for staging in an intra-operative ex vivo setting. Imaging results are compared with 14 Tesla MR images and histology. We observe that irregularities in SPIO distribution in PA images of the nodes and a decrease in contrast correlate with metastatic involvement as seen in MR images and histology. The results show that a PA based imaging technique may be valuable for nodal staging in the field of surgical oncology.

Structural and functional photoacoustic molecular tomography aided by emerging contrast agents

“…157 In recent studies, the potentials of SPIO as PAT contrast agent were investigated for nodal staging. 158,159 Lymph nodes in tumor environment usually exhibit responsive lymphadenopathy which could be mimicked by Incomplete Freund adjuvant (IFA) injection. 160 Thus, 0.1 mL IFA (consisting of water in oil emulsion) was injected on both hind footpads to create induced lymph node swelling.…”

Light In and Sound Out: Emerging Translational Strategies for Photoacoustic Imaging

“…Grootendorst et al have shown in healthy rats that superparamagnetic iron oxide nanoparticles (Endorem(®)) can be used as a photoacoustic imaging agent for lymph node visualization (87). More recently, they have shown promising results using the same nanoparticles in an ex vivo intraoperative setting in a metastatic prostate cancer model in rats (181). …”

Nanomaterial-based activatable imaging probes: from design to biological applications

“…14A). 191 Carbon nanoparticles, 192 copper sulfide nanoparticles (CuS NPs), 18,193,194 nano-graphene, 195 iron oxide NPs, 196 or even QDs 197 have also been successfully used as PA contrast agents. 185 Except for these endogenous optical absorbers, the emergence of exogenous contrast agents accelerated PA imaging applications in signal sensing, functional imaging, biomarker labeling and therapy monitoring greatly.…”