Contribution
Focusing Properties of Annular, Line, and Matrix Arrays for Ultrasound Thermometry
* Presenting author
Abstract:
Ultrasound thermometry is a non-invasive technique for monitoring temperature distribution, e.g., in hyperthermia or thermal ablation therapies, and is based on measuring the local speed of sound (SoS) by evaluating the echoes of scattered particles. To determine the local SoS the beamforming regime is optimized. The more sensitive the optimization variable reacts to changes in the SoS, the more accurate the determination of the local SoS. In this paper, we compare the focusing properties of annular, line and matrix arrays.For optimization purposes, transient Green's functions are used to calculate the impulse responses for single and two-layer tissue structures for each element of the respective array types. Beamforming is applied to the impulse responses of the individual array elements for any scatterer positions on- and off-axis and the properties of the superimposed impulse responses relevant to the accuracy of the SoS estimation are compared.The use of impulse responses, instead of narrow-band signals, yields more general dependencies and allows to interpret the data more effectively. The investigations provide information on the achievable accuracy and usability of the considered array types and contribute to the optimization of the array geometry and to the increase of the accuracy of the evaluation method.