Detection of Tissue Reaction to Foreign Bodies

Human body normally reacts to the presence of foreign bodies by inflammation, fibrosis, and infection. Such reactions may negatively affect the function of implant or may harm the host. Body reactions lead to alterations in the mechanical properties, such as increase in the stiffness of the tissue. Here we develop a noninvasive method for studying changes in the mechanical properties of tissue near a foreign body. For this purpose, we use modulated focused ultrasound to generate a harmonic radiation force on the object and we use an ultrasound Doppler system or an accelerometer to detect object motion. The frequency response of the object is determined by recording object motion at a range of vibration frequencies and is used to determine changes in the mechanical properties of the tissue at the site of the foreign body. Potential applications of this method include non-invasive monitoring of tissue reaction to foreign bodies.