Abstract (Invited)

Micro-Alterations and Enhanced Transport in Cellular Tissues Exposed to Therapeutic Ultrasound

E.Kimmel (Agricultural Engineering and Biomedical Engineering, Technion, Haifa, Israel)

e-mail: agreita@tx.technion.ac.il

Could low intensity therapeutic ultrasound (TUS) generate new blood vessels (angiogenesis) by applying mechanical loading on the endothelium - the inner cell layer in contact with the blood? Lately, we found that exposure to TUS induces a shear-like angiogenic response in endothelial cells in-vitro, and causes interesting effects in-vivo in the outermost layer of fish skin - the epidermis. In this study we utilize the physical similarity, in relation to TUS between both living cellular tissues, which are in close contact with liquid, to value possible mechanisms and estimate the angiogenic potential of TUS. Under different modes of TUS fish epidermis exhibits rupture of cells, forming of intercellular spaces primarily between the outermost cell layers, enhanced permeability, enhanced convective mass transport and facilitated transdermal dispersion of nano-particles. In the theoretical study, bubble dynamics near a cellular tissue is analyzed and modes of pulsation are categorized. Steady bubble pulsations and micro streaming are suggested to account for the shear-like response of the cellular tissue, the space formation and the augmented convection. Bubble collapse and jet formation are held responsible for the cell rupture and the enhanced permeability. Enhanced dispersion is explained as resulting from induced vibrations in porous media by shear waves.

Section : 5