Giurazza Francesco, Massaroni Carlo, Silvestri Sergio, Zobel Bruno Beomonte, Schena Emiliano
Interventional Radiology Department, Cardarelli Hospital, Via Cardarelli 9, 80100, Naples, Italy.
Measurement and Biomedical Instrumentation Lab, Università Campus Bio-Medico di Roma, Via A. Del Portillo 200, 00198, Rome, Italy.
J Ultrasound. 2020 Mar;23(1):69-75. doi: 10.1007/s40477-019-00407-z. Epub 2019 Sep 20.
Real-time monitoring of tissue temperature during percutaneous tumor ablation improves treatment efficacy, leading clinicians in adjustment of treatment settings. This study aims at assessing feasibility of ultrasound thermometry during laser ablation of biological tissue using a specific ultrasound imaging techniques based on elastography acoustic radiation force impulse (ARFI).
ARFI uses high-intensity focused ultrasound pulses to generate 'radiation force' in tissue; this provokes tissue displacements trackable using correlation-based ultrasound methods: the sensitivity of shear waves velocity is able to detect temperature changes. Experiments were carried out using a Nd:YAG laser (power: 5 W) in three non-perfused ex vivo pig livers. In each organ, a thermocouple was placed close to the applicator tip (distance range 1.5-2.5 cm) used to record a reference temperature. Positioning of laser applicator and thermocouple was eco-guided. The organ was scanned by an echography system equipped with ARFI; propagation velocity was measured in a region of interest of 1 × 0.5 cm located close to thermocouple, to investigate influence of tissue temperature on shear waves velocity.
Shear wave velocity has a very low sensitivity to temperature up to 55-60 °C, and in all cases, velocity is < 5 m s; for temperature > 55-60 °C, velocity shows a steep increment. The system measures a value "over limit", meaning a velocity > 5 m s.
Ultrasound thermometry during laser ablation of biological tissue based on elastography shows an abrupt output change at temperatures > 55-60 °C. This issue can have a relevant clinical impact, considering tumor necrosis when temperature crosses 55 °C to define the boundary of damaged volume.
在经皮肿瘤消融过程中实时监测组织温度可提高治疗效果，指导临床医生调整治疗参数。本研究旨在评估基于弹性成像声辐射力脉冲（ARFI）的特定超声成像技术在生物组织激光消融过程中进行超声测温的可行性。
ARFI利用高强度聚焦超声脉冲在组织中产生“辐射力”；这会引发组织位移，可通过基于相关性的超声方法进行追踪：剪切波速度的敏感性能够检测温度变化。使用Nd:YAG激光（功率：5W）在三个非灌注的离体猪肝上进行实验。在每个器官中，将一个热电偶放置在靠近用于记录参考温度的施源器尖端（距离范围1.5 - 2.5厘米）。激光施源器和热电偶的定位由超声引导。用配备ARFI的超声成像系统对器官进行扫描；在靠近热电偶的1×0.5厘米感兴趣区域测量传播速度，以研究组织温度对剪切波速度的影响。
在温度高达55 - 60°C时，剪切波速度对温度的敏感性非常低，在所有情况下，速度均<5米/秒；对于温度>55 - 60°C，速度显示出急剧增加。系统测量到一个“超限”值，即速度>5米/秒。
基于弹性成像的生物组织激光消融过程中的超声测温在温度>55 - 60°C时显示出输出突然变化。考虑到当温度超过55°C时肿瘤坏死以定义受损体积的边界，这个问题可能会产生相关的临床影响。
