Thermal strain imaging (TSI) is a widely investigated ultrasound (US) thermometry technique that is based on the temperature-dependent change in speed of sound. However, a major challenge of TSI is a calibration process to account for material-dependent thermal strain. In this study, we leverage nanoparticle (NP)-mediated photoacoustic (PA) thermometry to calibrate thermal strain and guide US thermal imaging. By controlling the molecular composition of the sub-micrometer layer surrounding the NPs, PA thermometry becomes independent of the thermal characteristics of the overall background tissue where the NPs reside. Thus accurate temperature measurements are obtainable from sparse NP-mediated PA signals. These measurements are used to guide TSI, allowing US thermometry to produce an expanded temperature map over the entire region of interest without prior knowledge of tissue composition. Our feasibility study in tissue-mimicking phantoms demonstrates the potential to improve TSI by integrating a PA-based calibration method that complements and guides US thermometry.

热应变成像 (TSI) 是一种广泛研究的超声 (US) 测温技术，该技术基于声速随温度的变化。然而，TSI 的一个主要挑战是考虑与材料相关的热应变的校准过程。在这项研究中，我们利用纳米颗粒（NP）介导的光声（PA）测温来校准热应变并指导超声热成像。通过控制纳米颗粒周围亚微米层的分子组成，PA 测温变得独立于纳米颗粒所在的整个背景组织的热特性。因此，可以从稀疏的 NP 介导的 PA 信号中获得准确的温度测量。这些测量结果用于指导 TSI，使 US 测温能够在整个感兴趣区域生成扩展的温度图，而无需事先了解组织成分。我们对模拟组织模型的可行性研究表明，通过集成基于 PA 的校准方法来补充和指导 US 测温可以改善 TSI。