Focusing ultrasound into the brain through the skull by utilizing both longitudinal and shear waves
First Claim
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1. A method of delivering multimode ultrasound waves to a target through at least one tissue layer defining a first interface and a second interface, the waves having a shear component and a longitudinal component through the at least one tissue layer, the method comprising the steps of:
- using a processor, assigning the waves to one of at least two regimes based at least in part on an incident angle of the waves at the first interface, the first regime corresponding to an incident angle smaller than a first threshold angle and the second regime corresponding to an incident angle equal to or greater than a second threshold angle;
using the processor, assigning weighting factors to the longitudinal and shear components of the waves based on the regimes to which the waves are assigned, the weighting factor of the shear component of a wave having a value of zero if the wave is assigned to the first regime and the weighting factor of the longitudinal component of a wave having a value of zero if the wave is assigned to the second regime;
using the processor, computing phase shifts associated with the shear component and the longitudinal component;
based on the weighting factors and the phase shifts, computing, using the processor, a weighted sum of the longitudinal and shear components so as to determine a total phase shift; and
compensating for the total phase shift-when delivering the ultrasound waves.
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Abstract
Systems and methods for focusing ultrasound through the skull into the brain for diagnostic or therapeutic purposes may be improved by utilizing both longitudinal and shear waves. The relative contribution of the two modes may be determined based on the angle of incidence.
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Citations
23 Claims
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1. A method of delivering multimode ultrasound waves to a target through at least one tissue layer defining a first interface and a second interface, the waves having a shear component and a longitudinal component through the at least one tissue layer, the method comprising the steps of:
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using a processor, assigning the waves to one of at least two regimes based at least in part on an incident angle of the waves at the first interface, the first regime corresponding to an incident angle smaller than a first threshold angle and the second regime corresponding to an incident angle equal to or greater than a second threshold angle; using the processor, assigning weighting factors to the longitudinal and shear components of the waves based on the regimes to which the waves are assigned, the weighting factor of the shear component of a wave having a value of zero if the wave is assigned to the first regime and the weighting factor of the longitudinal component of a wave having a value of zero if the wave is assigned to the second regime; using the processor, computing phase shifts associated with the shear component and the longitudinal component; based on the weighting factors and the phase shifts, computing, using the processor, a weighted sum of the longitudinal and shear components so as to determine a total phase shift; and compensating for the total phase shift-when delivering the ultrasound waves. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19)
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12. A method of delivering multimode ultrasound waves to a target through at least one tissue layer defining a first interface and a second interface, the waves having a shear component and a longitudinal component through the at least one tissue layer, the method comprising:
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using a processor, computing phase shifts associated with the longitudinal and shear components; based on an empirically determined relationship between relative energy contributions from the shear component and the longitudinal component and an incident angle of the waves at the first surface, assigning, using the processor, weighting factors to the longitudinal and shear components; based on the weighting factors and the phase shifts, computing, using the processor, a weighted sum of the longitudinal and shear components so as to determine a total phase shift; and compensating for the total phase when delivering the ultrasound waves.
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20. A system for delivering multimode ultrasound waves to a target located inside an object that comprises at least a first layer defining a first interface and a second interface, the waves having a shear component and a longitudinal component through at least the first layer, the system comprising:
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(a) a phased array of transducers arranged around the object; (b) a controller for (i) receiving data about the object, its location relative to the transducers, and a location of the target, (ii) computing for each transducer, based on the data, (1) an incident angle at which waves emanating from the transducer arrive at the first interface, and (2) phase shifts of the shear component and the longitudinal component, (iii) for each transducer, computationally assigning the waves to one of at least two regimes based at least in part on the incidence angle, the first regime corresponding to an incident angle smaller than a first threshold angle and the second regime corresponding to an incident angle equal to or greater than a second threshold angle, and assigning weighting factors to the longitudinal and shear components based on the regimes to which the waves are assigned, the weighting factor of the shear component of a wave having a value of zero if the wave is assigned to the first regime and the weighting factor of the longitudinal component of a wave having a value of zero if the wave is assigned to the second regime; and (iv) based on the weighting factors and the phase shifts, computing a weighted sum of the longitudinal and shear components so as to determine a total phase shift for each transducer; and (c) a beam former in communication with the controller and the phased array of transducers for adjusting outputs of the transducers to compensate for the total phase shift computed by the controller. - View Dependent Claims (21, 22)
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23. A system for delivering multimode ultrasound waves to a target located inside an object that comprises at least a first layer defining a first interface and a second interface, the waves having a shear component and a longitudinal component through at least the first layer, the system comprising:
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(a) a phased array of transducers arranged around the object; (b) a controller for (i) receiving data about the object, its location relative to the transducers, and a location of the target, (ii) computing for each transducer, based on the data, (1) an incident angle at which waves emanating from the transducer arrive at the first interface, and (2) phase shifts of the shear component and the longitudinal component, (iii) for each transducer, computationally assigning weighting factors to the longitudinal and shear components based on an empirically determined relationship between relative energy contributions from the shear component and the longitudinal component and the incident angle of the waves at the first surface; and (iv) based on the weighting factors and the phase shifts, computing a weighted sum of the longitudinal and shear components so as to determine a total phase shift for each transducer; and (c) a beam former in communication with the controller and the phased array of transducers for adjusting outputs of the transducers to compensate for the total phase shift computed by the controller.
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Specification