Nonlinear Derating for High Intensity Focused Ultrasound
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High intensity focused ultrasound systems face inaccuracies in predicting acoustic field parameters due to the assumption of linear acoustic propagation, which is unsuitable for nonlinear acoustic fields, leading to errors in tissue heating and treatment protocols.
Innovation Solution
A nonlinear derating method that measures and models focal waveforms in water to scale source outputs and determine parameters of nonlinear ultrasound fields in tissue, accounting for nonlinear effects and tissue attenuation, using equations such as the Khokhlov-Zabolotskaya-Kuznetsov equation and Westervelt equation to accurately predict focal waveforms and heating rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If linear derating is used to estimate acoustic field parameters, then the derating process is simple and straightforward, but the prediction accuracy deteriorates due to nonlinear acoustic propagation effects
Solution Approach 1:
The patent transforms the derating approach by changing the fundamental parameter assumption from linear to nonlinear acoustic propagation. It introduces nonlinear parameters (B/A coefficient, harmonic content) to characterize the acoustic field, allowing accurate prediction of focal pressure, intensity, and heating rates in high-intensity focused ultrasound where linear assumptions fail.
2Device complexity
If linear extrapolation is used to scale source pressure to focal pressure, then the calculation is computationally simple, but the focal pressure amplitude prediction becomes inaccurate under high intensity conditions
Solution Approach 1:
The patent introduces an intermediary nonlinear propagation model that bridges the gap between simple linear extrapolation and complex full nonlinear simulation. It uses measured source pressure combined with nonlinear parameters (B/A coefficient, attenuation coefficient) to calculate focal pressure through corrected scaling relationships, achieving accuracy without full computational complexity.
3Device complexity
If linear derating assumes quadratic relationship between wave intensity and pressure amplitude, then the model is mathematically simple, but it fails to account for harmonic contributions to intensity and heating
Solution Approach 1:
The patent extends the derating model by adding the frequency dimension through harmonic analysis. Instead of considering only the fundamental frequency, it incorporates contributions from multiple harmonics (2f, 3f, 4f, etc.) that are generated during nonlinear propagation. This allows accurate calculation of total intensity and heating rate by summing contributions across the frequency spectrum.
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 method provides accurate prediction of nonlinear acoustic field parameters, enhancing the safety and efficacy of high intensity ultrasound treatments by accounting for nonlinear effects and tissue attenuation, improving treatment protocols and safety standards.
Implementation Method 1
high intensity ultrasound energy can be radiated toward a focal region in tissue... The accumulation of the harmonic frequencies causes rapid heating at the focal region
Implementation Method 2
The harmonic frequencies of the nonlinear waves have a higher contrast to noise ratio than that of the fundamental frequency
Implementation Method 3
The measured values are then linearly extrapolated to account (1) for higher source outputs used in medical procedures and (2) for tissue attenuation
Implementation Method 4
the linearly scaled focal pressure can then be derated by a compensation factor that depends on the propagation path (i.e., the focal distance) and the linear attenuation coefficient of tissue
Implementation Method 5
the wave intensity at the focus is not a quadratic function of the pressure amplitude at the fundamental frequency, but instead consists of contributions from all of the harmonics
Implementation Method 6
the heating rate at the focus is not proportional to the intensity at the focus due to the contribution of more readily absorbed higher frequency components
Implementation Method 7
the heating rate at the focus is not proportional to the intensity at the focus due to the contribution of more readily absorbed higher frequency components
Data Source
AI summary
Methods of derating a nonlinear ultrasound field and associated systems are disclosed herein. A method of derating a nonlinear ultrasound field in accordance with an embodiment of the present technology can include, for example, calibrating an ultrasound source to a first source voltage (Vw) and generating a nonlinear acoustic wave from the ultrasound source into water. The method can further include measuring a focal waveform of the nonlinear acoustic wave and determining a second source voltage (Vt) of the ultrasound source that generates the same focal waveform in tissue.