A simulation study on the sensitivity of transcranial ray-tracing ultrasound modeling to skull properties.

In transcranial focused ultrasound therapies, such as treating essential tremor via thermal ablation in the thalamus, acoustic energy is focused through the skull using a phased-array transducer. Ray tracing is a computationally efficient method that can correct skull-induced phase aberrations via per-element phase delay calculations using patient-specific computed tomography (CT) data. However, recent studies show that variations in CT-derived Hounsfield unit may account for only 50% of the speed of sound variability in human skull specimens, potentially limiting clinical transcranial ultrasound applications.

Transcranial ultrasound simulations: A review.

Transcranial ultrasound is more and more used for therapy and imaging of the brain. However, the skull is a highly attenuating and aberrating medium, with different structures and acoustic properties among samples and even within a sample. Thus, case-specific simulations are needed to perform transcranial focused ultrasound interventions safely.

A semi-numerical model for near-critical angle scattering.

Numerous phenomena in the fields of physics and mathematics as seemingly different as seismology, ultrasonics, crystallography, photonics, relativistic quantum mechanics, and analytical number theory are described by integrals with oscillating integrands that contain three coalescing criticalities, a branch point, stationary phase point, and pole as well as accumulation points at which the speed of integrand oscillation is infinite. Evaluating such integrals is a challenge addressed in this paper. A fast and efficient numerical scheme based on the regularized composite Simpson's rule is proposed, and its efficacy is demonstrated by revisiting the scattering of an elastic plane wave by a stress-free half-plane crack embedded in an isotropic and homogeneous solid.

Modeling of ultrasonic fields radiated by contact transducer in a component of irregular surface.

The wedge of a contact transducer is imperfectly coupled to a component of irregular surface. A volume between the wedge and the component (filled by water or oil used as a coupling) is created that fundamentally modifies transducer radiation behavior. As a result, phenomena like beam spreading, skewing and splitting, generation of unwanted contributions that possibly lead to false alarms may occur.