Ultrasonic measurement system using a perturbing field, multiple sense beams and receivers

A system for ultrasonic inspection of a living substance including

• perturbing means to perturb an interior volume of said substance by ultrasonic waves, said perturbing means including a first transducer, a first oscillator connected to said first transducer, and means to cause the waves produced by said first transducer to produce a heated focal region;
• means to produce a collimated ultrasonic sense beam one portion of which is directed through said focal region and the diameter of which exceeds the diameter of said focal region, said sense beam means including an ultrasonic transmitting transducer to produce said collimated beam, a reference oscillator which is a source of continuous oscillations of ultrasonic frequency, and gating means connected between said source and said transducer to produce coherent bursts of oscillations which become discrete trains of ultrasonic waves from said transducer;
• at least two ultrasonic receiving transducers each positioned to receive a different portion of said sense beam, one portion being that part of said sense beam which has passed through the focal region and the other portion being part of said sense beam which has passed near said focal region but not through it;
• and at least two phase comparison circuits with one phase comparison circuit being connected to each of said receiving transducers and to the reference oscillator to respond to time of flight changes in the respective portions of the sense beam caused by transmission of one portion of the beam through said focal region with said heating compared to transmission of said portion of the sense beam through said focal region without heating;
• and
• means to compare time of flight changes in the different portions of said sense beam in order to lessen the adverse effects of tissue movement of the living substance during the measurement.

A method for ultrasonic inspection of a living substance including

• perturbing an interior volume of said substance by exciting waves from a first transducer controlled by a first oscillator to produce a heated focal region;
• producing a collimated ultrasonic sense beam directed through said focal region and at least one collimated ultrasonic reference beam directed near said focal region but not through it, each of said sense and reference beams being produced by an ultrasonic transmitting transducer, a reference oscillator which is a source of continuous waves of ultrasonic frequency, and gating means connected between said source and said transducers to produce bursts to oscillations which produce discrete trains of ultrasonic waves at said transmitting transducers;
• receiving said sense beam and said reference beam by at least two ultrasonic receiving transducers, comparing the phases of the received sense beam and the received reference beam each with a time of flight comparison circuit, a time of flight comparison circuit being connected to each of said receiving transducers and to the reference oscillator, thereby responding to the time of flight changes in the sense beam caused by transmission through said focal region with said heating compared to transmission through said focal region without said heating;
• and
• comparing the time of flight changes in the sense and reference beams in order to lessen the adverse effects of tissue movement of the living substance during its measurement.