Calibration and Evaluation of Ultrasound Thermography Using Infrared Imaging.
Calibration and Evaluation of Ultrasound Thermography Using Infrared Imaging.
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DOI：
10.1016/j.ultrasmedbio.2015.09.021
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发表时间：
2016-02
影响因子：
2.9
通讯作者：
Deng CX
中科院分区：
文献类型：
--
作者：
Hsiao YS;Deng CX
实时监测组织温度的时空演变对于确保包括热疗和热消融在内的热疗法中的安全和有效治疗是重要的。超声热成像已被提出作为一种非侵入性的技术，用于温度测量，并精确校准的温度依赖性的超声信号的变化对温度是必需的。在这里，我们报告了一种方法，使用红外（IR）热成像超声热成像的校准和验证。使用幻影和心脏组织标本进行高强度聚焦超声（HIFU）加热，我们同时获得超声和红外成像数据从同一表面平面的样品。选择常用的基于回波时移的方法来计算超声测温。我们首先将超声回波时移与IR测量温度相关联，以进行材料相关校准，发现脂肪模拟体模的校准系数为正（1.49 ± 0.27），而组织模拟体模（− 0.59 ± 0.08）和心脏组织（− 0.69 ± 0.18 °C-mm/ns）的校准系数为负。然后，我们通过与IR测量的温度进行比较，获得了超声测温的估计误差，并发现该误差随着加热区域尺寸的减小而增大。与先前的发现一致，回波时间偏移不再线性依赖于心脏组织中超过45 - 50 °C的温度。与以前的研究中使用热电偶或水浴技术来评估超声热成像的性能不同，我们的研究结果表明，高分辨率红外热成像提供了一个有用的工具，可以应用于评估和了解超声热成像方法的局限性。
Real-time monitoring of the spatiotemporal evolution of tissue temperature is important to ensure safe and effective treatment in thermal therapies including hyperthermia and thermal ablation. Ultrasound thermography has been proposed as a non-invasive technique for temperature measurement, and accurate calibration of the temperature-dependent ultrasound signal changes against temperature is required. Here we report a method that uses infrared (IR) thermography for calibration and validation of ultrasound thermography. Using phantoms and cardiac tissue specimens subjected to high-intensity focused ultrasound (HIFU) heating, we simultaneously acquired ultrasound and IR imaging data from the same surface plane of a sample. The commonly used echo time shift-based method was chosen to compute ultrasound thermometry. We first correlated the ultrasound echo time shifts with IR-measured temperatures for material-dependent calibration and found that the calibration coefficient was positive for fat-mimicking phantom (1.49 ± 0.27) but negative for tissue-mimicking phantom (− 0.59 ± 0.08) and cardiac tissue (− 0.69 ± 0.18 °C-mm/ns). We then obtained the estimation error of the ultrasound thermometry by comparing against the IR measured temperature and revealed that the error increased with decreased size of the heated region. Consistent with previous findings, the echo time shifts were no longer linearly dependent on temperature beyond 45 – 50 °C in cardiac tissues. Unlike previous studies where thermocouples or water-bath techniques were used to evaluate the performance of ultrasound thermography, our results show that high resolution IR thermography provides a useful tool that can be applied to evaluate and understand the limitations of ultrasound thermography methods.