The reported positive margin rate from wire localized excisions of breast cancers is approximately 20-50%; however, by preoperatively injecting a radioactive seed into the tumor under CT guidance, the excision rate is halved because the surgeon can constantly reorient the dissection to place the seed in the center of the specimen. Unfortunately, radioactive seed localization has several safety challenges, only single focus can be localized, and incisions are required to implant the seeds, so it is rarely employed. As a safe alternative, perfluoropentane-filled Fe-SiO2 particles have been developed, which can be used for ultrasound-guided surgery even for multiple foci. The particles are synthesized through a sol-gel method with tetratmeyl orthosilicate and iron ethoxide on a polystyrene template, and calcined to create hollow, rigid nanoshells. In vitro studies have shown that continuous particle imaging time is up to approximately 45 minutes. In vivo particle injection longevity studies have been performed in tumor bearing mouse models show signal presence up to ten days post injection. To study biodistribution, nanoshells were functionalized with DTPA and radiolabeled with Indium-111 and then imaged by gamma scintigraphy over 72 hours. Scintigraphic imaging and gamma counting confirm that particles undergoing IV delivery to tumor bearing mice will passively accumulate in the tumors.Perfluorocarbon filled silica shells break under acoustic excitation to increase acoustic energy absorption and reduce acoustic cavitation threshold. Therefore they may also be employed as a sensitizing agent in high intensity focused ultrasound (HIFU) therapy. It was found that nanoshells systemically adminstered to breast tumor bearing mice could be cavitated by HIFU 24 hours after administration. This mechanical cavitation caused liquification within the focal volume of the HIFU which contained the nanoshells within seconds of the HIFU application. This may potentially allow for a larger area to be ablated in less time with less power.

Ultrasound imaging, gamma scintigraphy and HIFU therapy with perfluorocarbon loaded iron-silica nanoshells

247th National Meeting (2014)

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