| AVS 58th Annual International Symposium and Exhibition | |
| Nanometer-scale Science and Technology Division | Thursday Sessions |
| Session NS-ThA |
| Session: | Biological Nanomaterials |
| Presenter: | Alexander Liberman, University of California, San Diego |
| Authors: | A. Liberman, University of California, San Diego H.P. Martinez, University of California, San Diego Z. Wu, University of California, San Diego S.L. Blair, University of California, San Diego Y. Kono, University of California, San Diego R.F. Mattrey, University of California, San Diego A.C. Kummel, University of California, San Diego W. Trogler, University of California, San Diego |
| Correspondent: | Click to Email |
The reported positive margin rate from wire localized excisions of breast cancers is approximately 20-50%; however, using radioactive seeds and a radiation detector 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 foci can be localized, and incisions are required to implant the seeds, so it is rarely employed. As a safe alternative, gas-filled hollow boron-doped silica particles have been developed, which can be used for ultrasound-guided surgery for multiple focii. The function of the boron doping is to increase the mechanical strength of the silica shell. The particles are synthesized through a sol-gel method on a polystyrene template, and subsequently calcined to create hollow, rigid microspheres. The boron doped silica shell is derived from tetramethoxy orthosilicate (TMOS) and trimethyl borate (TMB), which forms a rigid, mesoporous shell upon calcination. The microshells are filled with perfluoropentane vapor. The perfluorocarbon vapor is contained within the porous shell due to its extremely low solubility in water. In addition, the high surface tension of water may serve to seal the fluorous phase within the pores of the shell wall as water enters the outer surface of the porous shell by capillary action. Considerable testing of particle functionality, signal persistence and acoustical properties have been performed in various phantoms including ultrasound gel, chicken breast, and excised human mastectomy tissue. Furthermore, preliminary particle injection longevity studies have been performed in a rabbit animal model. In vitro studies have shown that continuous particle imaging time is up to approximately 45 minutes. In vivo studies have shown consistent signal presence even 48 hours post injection in rabbits with an injection volume of 50 μl carrying only 100 μg of particles. As a result these particles may provide a significant improvement over current methods in terms of patient comfort in having a small injection 1-2 days prior to surgery. On going studies are currently aimed at improving the understanding of the mechanism by which these microspheres are capable of producing such robust signal under color doppler ultrasound.