P2G-6 High Intensity Focused Ultrasound Induced Transgene Activation in a Cell-Embedded Tissue Mimicking Phantom

A cell-embedded transparent tissue-mimicking phantom was developed to study high intensity focused ultrasound (HIFU) induced gene activation in vitro. The phantom was constructed by using agarose hydro-gel dispersed with rat mammary carcinoma (Mac) cells that were stably transfected with GFP plasmid under the control of hsp70B promoter. Thermally sensitive bovine serum albumin (BSA) proteins were also incorporated in the phantom so that both lesion formation and gene activation could be quantified simultaneously following HIFU exposure. Both acoustic (sound speed, attenuation, acoustic impedance, nonlinear parameter B/A) and thermal properties (thermal conductivity and thermal diffusivity) of the phantom were characterized in a temperature dependant manner. With a 10s HIFU exposure at 3.3-MHz, the inducible GFP gene expression patterns across the focal plane were analyzed and compared with the corresponding temperature distribution quantified by thermocouple measurements. Overall, the cell-embedded tissue-mimicking phantom was found to be a versatile tool for investigating HIFU-induced gene activation and it may also be used for general ultrasound bio-effect studies