@article {Madru459, author = {Renata Madru and Pontus Kjellman and Fredrik Olsson and Karin Wing{\r a}rdh and Christian Ingvar and Freddy St{\r a}hlberg and Johan Olsrud and Jimmy L{\"a}tt and Sarah Fredriksson and Linda Knutsson and Sven-Erik Strand}, title = {99mTc-Labeled Superparamagnetic Iron Oxide Nanoparticles for Multimodality SPECT/MRI of Sentinel Lymph Nodes}, volume = {53}, number = {3}, pages = {459--463}, year = {2012}, doi = {10.2967/jnumed.111.092437}, publisher = {Society of Nuclear Medicine}, abstract = {The purpose of this study was to develop multimodality SPECT/MRI contrast agents for sentinel lymph node (SLN) mapping in vivo. Methods: Nanoparticles with a solid iron oxide core and a polyethylene glycol coating were labeled with 99mTc. The labeling efficiency was determined with instant thin-layer chromatography and magnetic separation. The stability of the radiolabeled superparamagnetic iron oxide nanoparticles (SPIONs) was verified in both sterile water and human serum at room temperature 6 and 24 h after labeling. Five Wistar rats were injected subcutaneously in the right hind paw with 99mTc-SPIONs (25{\textendash}50 MBq, \~{}0.2 mg of Fe) and sacrificed 4 h after injection. Two animals were imaged with SPECT/MRI. All 5 rats were dissected; the lymph nodes, liver, kidneys, spleen, and hind paw containing the injection site were removed and weighed; and activity in the samples was measured. The microdistribution within the lymph nodes was studied with digital autoradiography. Results: The efficiency of labeling of the SPIONs was 99\% 6 h after labeling in both water and human serum. The labeling yield was 98\% in water and 97\% in human serum 24 h after labeling. The SLN could be identified in vivo with SPECT/MRI. The accumulation of 99mTc-SPIONs (as the percentage injected dose/g [\%ID/g]) in the SLN was 100 \%ID/g, whereas in the liver and spleen it was less than 2 \%ID/g. Digital autoradiography images revealed a nonhomogeneous distribution of 99mTc-SPIONs within the lymph nodes; nanoparticles were found in the cortical, subcapsular, and medullary sinuses. Conclusion: This study revealed the feasibility of labeling SPIONs with 99mTc. The accumulation of 99mTc-SPIONs in lymph nodes after subcutaneous injection in animals, verified by SPECT/MRI, is encouraging for applications in breast cancer and malignant melanoma.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/53/3/459}, eprint = {https://jnm.snmjournals.org/content/53/3/459.full.pdf}, journal = {Journal of Nuclear Medicine} }