Apparatus and method for characterization of a ductile membrane, surface and sub-surface properties

Inventors

Moehring, Mark A. • Gates, George A. • Chesavage, Jay • Singh, Rahul

Assignees

Otonexus Medical Technologies Inc

Abstract

An ultrasound signal processor uses an excitation generator to cause displacement of a membrane or surface while a series of ultrasound pulses are applied to the membrane or surface. Phase differences between a transmitted signal and received signal are examined to determine the movement of the membrane or surface in response to the applied excitation. An examination of the phase response of the membrane or surface provides a determination as to whether the fluid type behind the membrane or surface is one of: no fluid, serum fluid, or purulent fluid.

Core Innovation

The invention is a non-contact material characterization system that uses an excitation generator to generate a non-contact displacement force directed to an elastic surface or to a volume of material adjacent to the elastic surface, with the force directed along a direction to move the elastic surface or the volume in that direction. An ultrasound transducer directs a transmit ultrasound signal to the elastic surface or the volume and receives a reflected ultrasound signal from the elastic surface or the volume. A processor coupled to the ultrasound transducer determines a movement characteristic of the elastic surface or the volume based at least in part on the reflected ultrasound signal.

The system distinguishes movement in the direction from movement opposite the direction. In some embodiments, the reflected ultrasound signal includes a Doppler-based reflected signal, and the processor uses phase and optionally amplitude comparisons between transmitted and reflected ultrasound to estimate temporal displacement and derive elasticity/viscosity metrics. Additional analysis includes phase unwrapping and processing of movement characteristics from rise time, fall time, template comparison, and ringdown characteristic analysis such as exponential decay or ring cycle interval/ring cycle frequency.

The disclosed characterization also includes determining whether the fluid behind a membrane is air/no fluid versus serum versus purulent fluid by using reflected ultrasound measurements during non-contact displacement of the membrane or elastic surface. The approach is used in contexts including membrane-over-fluid measurements and in evaluation of animal or human organ elasticity, including eye tonometry and glaucoma-related indicators, as well as characterization of food items such as yogurt, cheese, and fermented items.

Claims Coverage

Independent claims cover a non-contact material characterization system and a non-contact measurement method, each with the core inventive requirement to determine a movement characteristic from reflected ultrasound while distinguishing movement in a specified force direction versus movement opposite that direction. Across the independent claims, the inventive features primarily include: (i) generation of a non-contact displacement force, (ii) ultrasound transmission and reflected signal reception, and (iii) movement-characteristic determination with directional distinction; dependent features further specify signal comparison basis, Doppler reflected signals, excitation waveforms, and quantized frequency/transducer/modalities.

The independent claim set is anchored on determining a movement characteristic from reflected ultrasound signals during non-contact displacement of an elastic surface or adjacent volume, with explicit directional discrimination between movement toward and movement opposite the displacement-force direction. Dependent coverage further refines the movement determination using amplitude and/or phase comparisons (including series phase comparisons), optionally uses a reflected Doppler ultrasound signal, specifies excitation as periodic or oscillatory with a non-contact displacement force frequency at least 20 Hz, and narrows transducer implementations to capacitive micromachined ultrasonic transducers (cMUT) or piezoelectric transducers, with ultrasound transmission that may be continuous wave or pulsed.

Stated Advantages

Documented Applications