Farny Caleb H, Clement Greg T
Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
J Acoust Soc Am. 2008 Mar;123(3):1773-83. doi: 10.1121/1.2835438.
Ultrasound-based methods for temperature monitoring could greatly assist focused ultrasound visualization and treatment planning based on sound speed-induced change in phase as a function of temperature. A method is presented that uses reflex transmission integration, planar projection, and tomographic reconstruction techniques to visualize phase contrast by measuring the sound field before and after heat deposition. Results from experiments and numerical simulations employing a through-transmission setup are presented to demonstrate feasibility of using phase contrast methods for identifying temperature change. A 1.088-MHz focused transducer was used to interrogate a medium with a phase contrast feature, following measurement of the baseline reference field with a hydrophone. A thermal plume in water and a tissue phantom with multiple water columns was used in separate experiments to produce a phase contrast. The reference and phase contrast field scans were numerically backprojected and the phase difference correctly identified the position and orientation of the features. The peak temperature reconstructed from the phase shift was within 0.2 degrees C of the measured temperature in the plume. Simulated results were in good agreement with experimental results. Finally, employment of reflex transmission imaging techniques for adopting a pulse-echo arrangement was simulated, and its future experimental application is discussed.
基于超声的温度监测方法能够极大地辅助基于声速随温度变化引起的相位变化的聚焦超声可视化和治疗规划。本文提出了一种方法，该方法利用反射透射积分、平面投影和断层重建技术，通过测量热沉积前后的声场来可视化相位对比。给出了采用穿透传输设置的实验和数值模拟结果，以证明使用相位对比方法识别温度变化的可行性。在用水听器测量基线参考场之后，使用一个1.088兆赫兹的聚焦换能器对具有相位对比特征的介质进行探测。在单独的实验中，分别使用水中的热羽流和带有多个水柱的组织仿体来产生相位对比。对参考场和相位对比场扫描进行数值反投影，相位差正确地识别了特征的位置和方向。从相移重建的峰值温度与羽流中测量温度的偏差在0.2摄氏度以内。模拟结果与实验结果吻合良好。最后，模拟了采用脉冲回波装置的反射透射成像技术的应用，并讨论了其未来的实验应用。
