University of California, Davis, Department of Biomedical Engineering, Davis, CA, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Jul;58(7):1406-17. doi: 10.1109/TUFFC.2011.1960.
A method is introduced to monitor cardiac ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound variations with temperature. The sound speed of water-bearing tissue such as cardiac muscle increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48 to 50°C for a short period in accordance with the well-known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs by using the reduced slope in the thermal strain curve as a function of heating time. We have illustrated the feasibility of this method initially using porcine myocardium in vitro. The method was further demonstrated in vivo, using a specially equipped ablation tip and an 11-MHz microlinear intracardiac echocardiography (ICE) array mounted on the tip of a catheter. The thermal strain curves showed a plateau, strongly suggesting that the temperature reached at least 50°C.
介绍了一种通过检查声速随温度变化引起的热应变成曲线斜率变化来监测心脏消融治疗的方法。含水组织（如心肌）的声速随温度升高而增加。然而，在 50°C 以上的温度下，声速不再增加，温度系数可能略微变为负值。对于消融治疗，根据著名的 Arrhenius 方程，组织在 48 至 50°C 的短时间内会发生不可逆转的损伤和完全性心脏阻滞。利用这两个特性，我们提出了一种通过使用热应变成曲线随加热时间的减少斜率来检测组织损伤发生时刻的潜在工具。我们最初使用体外猪心肌证明了该方法的可行性。该方法进一步通过使用专门配备的消融探头和安装在导管尖端的 11MHz 微线性心内超声心动图（ICE）阵列在体内得到证实。热应变成曲线呈平台状，强烈表明温度至少达到了 50°C。
