Transient Elastography Probe Control for Accurate Contact Force
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Solution Overview
Problem
Current viscoelastic measurement devices, such as those using Vibration Controlled Transient Elastography (VCTE), face challenges in accurately and reproducibly measuring liver stiffness due to operator-dependent recoil and force application, leading to inaccurate and potentially harmful measurements.
Innovation Solution
A device with an ultrasound transducer bound to the probe casing, incorporating a force sensor and signal generator to ensure contact and measurement readiness, eliminating relative motion between the transducer and casing, and using a control loop to adjust vibrator motion based on probe casing position, ensuring accurate and reproducible measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the probe tip movement is measured in the reference frame of the probe casing (traditional VCTE), then the measurement system is simpler, but the real movement of the probe tip with respect to the patient's body becomes unknown due to probe recoil
Solution Approach 1:
The patent introduces an accelerometer as an intermediary device mounted on the probe tip to directly measure the real movement with respect to the patient's body, bypassing the complex reference frame transformations needed in traditional systems
Solution Approach 2:
The patent replaces the mechanical reference frame measurement system with an electronic inertial measurement system using accelerometers, which directly provide acceleration data that can be integrated to obtain position and velocity information
2Ease of operation
If the operator applies force manually to hold the probe against the patient's body, then the operation is simpler, but the probe recoil and force control become operator-dependent and inaccurate
Solution Approach 1:
The patent implements a feedback control system where the accelerometer measures actual probe tip movement, and this information is used to adjust the electrodynamical actuator in real-time to maintain consistent contact force and compensate for probe recoil
Solution Approach 2:
The system uses the accelerometer data to automatically control the probe contact force without requiring operator skill or manual adjustment, making the system self-regulating and independent of operator expertise
3Productivity
If the electrodynamical actuator moves the ultrasound transducer relative to the probe casing, then the shear wave generation is achieved, but the real movement of the transducer with respect to the patient's body becomes unknown
Solution Approach 1:
The accelerometer serves as an intermediary that directly measures the transducer's real movement with respect to the patient's body, providing accurate feedback for controlling the shear wave generation process
Solution Approach 2:
The system changes from measuring relative movement (transducer to casing) to measuring absolute movement (transducer to patient body) by using accelerometer data, enabling precise control of the shear wave generation parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables precise and consistent viscoelastic property measurements by controlling the real movement of the ultrasound transducer, reducing operator dependence, and minimizing health risks and device damage, while eliminating the need for frequent mechanical calibration.
Implementation Method 1
The electrodynamical actuator is constructed and arranged to generate a transient shear wave by application of a pulsed force
Implementation Method 2
The displacement generated by the propagating shear wave is probed by sending high frequency ultrasound short pulses or shots inside the medium
Implementation Method 3
the Fibroscan® probe comes with a motion sensor capable of measuring the displacement of the probe tip with respect to the probe casing, for example a Hall effect position sensor
Data Source
AI summary
A method for measuring viscoelastic properties of a viscoelastic medium, the method including positioning a probe in contact with the viscoelastic medium, the probe extending along a longitudinal axis and being adapted to carry out transient elastography measurements and including a casing, at least one ultrasound a transducer arranged at a tip of the probe and adapted to generate ultrasounds, a force sensor configured to measure a force applied by the tip of the probe, and a vibrator arranged in the casing and adapted to generate a low-frequency wave, measuring a contact force by the force sensor; generating a measurement ready signal by the probe when the measured contact force is higher than a minimum measurement force threshold, and when the measurement ready signal has been generated, triggering a transient elastography measurement.