title: Quantitative analysis of superparamagnetic contrast agent in sentinel lymph nodes using ex vivo vibrating sample magnetometry.
abstract: As the first step in developing a new clinical technique for the magnetic detection of colorectal sentinel lymph nodes (SLNs), a method is developed to measure the magnetic content in intact, formalin fixated lymph nodes using a vibrating sample magnetometer (VSM). A suspension of superparamagnetic nanoparticles is injected ex vivo around the tumor in the resected colon segments. A selection of three lymph nodes is excised from the region around the tumor and is separately measured in the VSM. The iron content in the lymph nodes is quantified from the magnetic moment curve using the Langevin model for superparamagnetism and a bimodal particle size distribution. Adverse, parasitic movements of the sample were successfully reduced by tight fixation of the soft tissue and using a small vibration amplitude. Iron content in the lymph nodes is detected with 0.5 μg accuracy and ranged from 1 to 51 μg. Histological staining confirmed iron presence. The current method of measuring intact biological tissue in a VSM is suitable to show the feasibility and merit of magnetic detection of SLNs in colorectal cancer. For clinical validation of magnetic SLN selection in colorectal cancer, a new magnetometer with high specificity for superparamagnetic nanoparticles is required.
authors.affiliation: Neuro-Imaging Group, MIRA Institute for Biomedical Engineering and Technical Medicine, University of Twente, 7500 AE Enschede, The Netherlands. m.visscher@utwente.nl
authors.forename: Martijn
authors.initials: M
authors.lastname: Visscher
authors.forename: Joost J
authors.initials: JJ
authors.lastname: Pouw
authors.forename: Joop
authors.initials: J
authors.lastname: van Baarlen
authors.forename: Joost M
authors.initials: JM
authors.lastname: Klaase
authors.forename: Bennie
authors.initials: B
authors.lastname: Ten Haken
mesh_terms: D015179:Colorectal Neoplasms / Q000737:chemistry* / Q000473:pathology; D003287:Contrast Media / Q000032:analysis* / Q000737:chemistry; D006651:Histocytochemistry; D006801:Humans; D008198:Lymph Nodes / Q000737:chemistry* / Q000473:pathology; D008207:Lymphatic Metastasis; D058185:Magnetite Nanoparticles / Q000032:analysis* / Q000737:chemistry; D060306:Magnetometry / Q000379:methods*; D010316:Particle Size; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D014732:Vibration
chemical_list: D003287:Contrast Media; D058185:Magnetite Nanoparticles