Lamb Wave Skull Coupling for Focused Ultrasound Energy Transfer
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Solution Overview
Problem
Current ultrasound technologies for transmitting energy into the brain face limitations such as significant attenuation by the skull, inefficient power transmission, and excessive heating, which restrict their ability to target peripheral brain regions and require active cooling, while also being limited to lower frequencies and normal incident angles.
Innovation Solution
A novel transducer design that selectively excites leaky guided Lamb waves in the skull, using a wedge transducer array over a ring to achieve phase matching and efficient energy transmission, allowing for improved focusing and reduced heating, enabling access to regions away from the brain center and operation across a broader frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional large-aperture spherical transducers transmit ultrasound beams perpendicularly through the skull, then the geometric focus can be achieved at the center of the brain, but the transmission coefficient is less than 30% and the skull significantly attenuates ultrasound energy
Solution Approach 1:
The patent changes the angle of incidence parameter from normal (0 degrees) to oblique angles, and changes the wave type from conventional ultrasound to Lamb waves. This parameter transformation allows the ultrasound to couple efficiently with the skull bone structure, transforming the transmission coefficient from less than 30% to significantly higher values, thereby resolving the contradiction between focusing precision and energy transmission loss.
Solution Approach 2:
The patent utilizes Lamb waves, which are a specific type of mechanical vibration that propagates through thin plate structures like the skull. By exciting these guided mechanical vibrations at appropriate frequencies and angles, the system achieves efficient energy transmission through the skull while maintaining focusing capability, thus resolving the energy loss problem.
2Power
If traditional transducers transmit high intensity ultrasound through the skull, then the brain can receive sufficient energy, but the skull absorbs excessive energy and requires active cooling to prevent burning
Solution Approach 1:
The patent changes the angle of incidence and wave type parameters to optimize energy transmission efficiency. By transmitting ultrasound at oblique angles as Lamb waves, the skull absorbs less energy (reducing heating) while the brain receives sufficient power, thereby resolving the contradiction between power delivery and harmful heating effects.
Solution Approach 2:
The patent converts the skull's natural acoustic properties, which traditionally cause attenuation and heating, into beneficial guided wave propagation. By utilizing the skull's plate structure to support Lamb waves, the system transforms the skull from a harmful attenuating medium into an efficient waveguide, delivering power to the brain while minimizing heating.
3Ease of manufacture
If traditional transducers use normal incident angles for ultrasound transmission, then the setup is simple, but the power transmission is inefficient and the treatment envelope is limited to the center of the brain
Solution Approach 1:
The patent changes the incidence angle parameter from normal to oblique angles and introduces Lamb wave excitation. While this increases system complexity compared to normal incidence, it dramatically improves power transmission efficiency and expands the treatable brain regions from only the center to include peripheral areas, resolving the contradiction between simplicity and productivity.
4Loss of energy
If traditional ultrasound techniques operate at frequencies below 1 MHz, then the skull attenuation is reduced, but the spatial selectivity and penetration depth are compromised
Solution Approach 1:
The patent changes the frequency parameter to operate above 1 MHz while simultaneously changing the wave type to Lamb waves and the incidence angle to oblique. This combination allows high-frequency operation (providing spatial selectivity) while maintaining low skull attenuation through efficient Lamb wave coupling, thereby resolving the contradiction between energy loss and measurement precision.
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
This approach enhances ultrasound energy delivery to the brain with reduced skull heating, increased focusing gain, and improved spatial selectivity, enabling effective treatment of peripheral brain regions and potential applications in neuro-modulation and bone cancer, while reducing the need for active cooling.
Implementation Method 1
acoustic transducer configured to excite a selected Lamb wave mode, having propagation constant ksel(f0), in a skull of a patient via phase matching to the selected Lamb wave mode
Implementation Method 2
via phase matching to the selected Lamb wave mode
Implementation Method 3
The excited Lamb wave mode generates a longitudinal acoustic wave in a brain of the patient
Data Source
AI summary
We provide a novel technique for coupling focused ultrasound into the brain. The ultrasound beam can be used for therapy or neuro-modulation. We excite a selected Lamb wave mode in the skull that mode converts into longitudinal waves in the brain. The benefits of our approach is in improved efficiency, reduction in heating of the skull, and the ability to address regions in the brain that are close or far from the skull.