Probing elasticity in diseased tissue

The unusual stiffness or sponginess of dead and decaying biological tissue is readily apparent to the human touch. However, early detection of such mechanical property changes in a tissue’s extracellular matrix could signal the onset of disease. To measure the elasticity of tissue in living patients, needle-based indentation methods are more direct and less expensive alternatives to MRI, ultrasound, and electrical impedance. Such a probe has recently been developed by University of California, Santa Barbara, physicist Paul Hansma and his collaborators. The handheld tissue diagnostic instrument (TDI) consists of a stainless steel probe—175 µm to 1 mm in diameter depending on the tissue sample—that longitudinally oscillates at 4 Hz in a needle-thin stationary sheath. The force from the magnetically controlled oscillation of the probe produces a corresponding displacement in the tissue. The tissue’s elastic modulus, or stiffness, is proportional to the slope of the force-displacement curve, and energy dissipation in...