Method for determining a mechanical property of a layered soft material

A method for testing an effect of an apparatus configured for creating thermal lesions in a layered soft material and configured for measuring a mechanical property of the layered soft material, wherein said layered soft material is an eye, the apparatus comprising:

• a first ultrasonic transducer, configured to generate an ultrasound wave towards a first point of the layered soft material, in order to generate in turn a Lamb wave propagating into a layer of said layered soft material,
• at least one second ultrasonic transducer, the at least one second ultrasonic transducer being configured to measure a physical parameter of the generated Lamb wave at a predetermined single second point of the layered soft material, the physical parameter being representative of the amplitude of the Lamb wave at the predetermined single second point of the layered soft material,
• the at least one second ultrasonic transducer being distinct from the first ultrasonic transducer,
• the first and the at least one second ultrasonic transducer being located opposite to each other with respect to a central axis of a transducer unit,
• said predetermined single second point belonging to said layer, said at least one second ultrasonic transducer being configured, to that end, to generate multiple excitation ultrasound waves focused towards said predetermined single second point, and to collect multiple reflected ultrasound waves reflected in response by said layered soft material,
• wherein
• the apparatus further comprises:
• a first ultrasonic driver of the first ultrasonic transducer, configured to deliver a first excitation signal to said first ultrasonic transducer in order to generate said ultrasound wave, the first excitation signal having a duration smaller than or equal to 50 ms,
• a second ultrasonic driver of the at least one second ultrasonic transducer, configured to deliver a second excitation signal to the at least one second ultrasonic transducer to generate the multiple excitation ultrasound waves, the second excitation signal having a duration smaller than or equal to 0.5 ms, and configured to collect a measurement signal representative of the physical parameter of the Lamb wave generated by the at least one second ultrasonic transducer upon collecting the multiple reflected ultrasound waves, and
• a control unit, programmed to automatically calculate a mechanical property of said layered soft material based upon the collected measurement signal,
• wherein the first and second ultrasonic transducers each comprise an oscillator having a quality factor equal to or superior to 100,
• said method comprising:
• i) first measuring a mechanical property of the layered soft material using said apparatus,
• ii) generating, by exciting the first ultrasonic transducer of said apparatus via the control unit, a high intensity ultrasound wave focused towards a target region of said layered soft material, in order to create a thermal lesion in the target region, with an excitation signal during at least 0.5 seconds,
• iii) second measuring the same mechanical property of said layered soft material as measured in step i), using said apparatus,
• iv) automatically comparing the difference in the mechanical properties measured during steps i) and iii) using the control unit to determine whether step ii) had a successful effect,
• wherein if the mechanical properties measured during steps i) and iii) differ from each other by more than 175%, step ii) is determined to have had a successful effect and if the mechanical properties measured during steps i) and iii) do not differ from each other by more than 75%, step ii) is determined to have had an unsuccessful effect.