Learn More
A numerical model for calculating the ultrasonic power deposition in layered media was developed and experimentally tested. The new model takes into account the ultrasound wave reflection and refraction occurring at tissue interfaces. In order to study the effects of soft tissue interfaces on the resulting ultrasonic power deposition patterns, the tested(More)
Focused high-power ultrasound beams are well suited for noninvasive local destruction of deep target volumes. In order to avoid cavitation and to utilize only thermal tissue damage, high frequencies (1-5 MHz) are used in ultrasonic surgery. However, the focal spots generated by sharply focused transducers become so small that only small tumors can be(More)
The noninvasive surgery of a tumor by focused transducers or phased arrays with multiple sonications was simulated in this study. The effects of multiple sonications on near field heating were investigated by varying the delay time between consecutive pulses and the movement pattern of the transducer within the focal plane. To avoid normal tissue damage,(More)
The spherically curved square element phased array design for ultrasound surgery was studied in several of its important aspects. A method for determining the spatial limitations of the multiple-foci region was developed for spherically curved phased arrays. The effects on the ultrasound fields of varying the phases and the amplitudes at control points were(More)
Noninvasive surgery using high-powered, focused ultrasound transducers in conjunction with magnetic resonance imaging has been shown to be feasible in previous studies. For clinical treatments, the geometry of standard MRI equipment limits the space available for ultrasound surgical equipment. This space requirement can be reduced in one dimension by using(More)
An improved numerical model for calculating the ultrasonic power deposition in layered medium was developed and experimentally tested. The new model takes into account the ultrasound wave reflection and refraction at the tissue interfaces thereby providing improved accuracy in ultrasound hyperthermia treatment planning. The model was compared with a(More)
In vitro experiments in bioelectromagnetics frequently require the determination of specific absorption rate (SAR) within a layer of cells on the bottom of a culture flask when the SAR has rapid spatial variation both horizontally within the cell layer and vertically in the medium bathing the cells. This problem has only recently been treated in the(More)
Phased array theory is combined with the Rayleigh-Sommerfeld diffraction integral to predict measured acoustic fields generated by a single-source ultrasonic transducer. The idea is to treat a single-source as a "phased array," which is composed of many small elements. The goal is to find the excitation source for the phased array, that is, the amplitude(More)
A two-parameter method for the estimation of ultrasound-induced temperature artifacts was evaluated and compared with other commonly applied methods using analytical solutions to the bioheat equation. The two parameters are the exponent of the assumed temperature decay curve after power is turned off and the baseline temperature. These parameters are found(More)
We investigated the spatial distribution (horizontal and vertical concentrations) of copper (Cu), lead (Pb), zinc (Zn), and cadmium (Cd) in five wetland types (mudflat, aquaculture wetland, water area, farmland wetland and mangrove) from three areas (Ningde, Fuding, and Xiapu), China. Cu concentrations in five wetland types descended in the order: farm(More)