Sonic Estimation of Elasticity via Resonance (SEER)

Effective management of clinical bleeding requires rapid diagnosis of its physiological cause. Abundant literature has shown that measurement of the evolving shear modulus of an in vitro clot yields valuable insights into the causes of bleeding. In this paper we describe a novel approach using ultrasound induced shear wave resonance to measure the evolving modulus of a forming clot. Each measurement applies a high-energy ultrasound pulse to induce a shear wave within a rigid walled chamber, and then uses low energy ultrasound pulses to measure displacements associated with the resonance of that shear wave. The modulus is quantified by finding the best match with a library of time-displacements predicted by a Finite Difference Time Domain (FDTD) model. Our current implementation requires 62.4 ms for each measurement. We analyzed experimental data using fixed-viscosity and free-viscosity models. Shear moduli measured with the free-viscosity model showed a precision of 2.5%, while moduli measured with the fixed-viscosity model shoed a precision of 1.8%. The shear moduli of kaolin induced clots varied from 1.4 kPa in refrigerated samples, to 3.3 kPa in fixed samples. These results show the promise of this technique for rapid, point of care assessment of coagulation.