This study describes the development and characterization of an agar-based soft tissue-mimicking material (TMM) doped with wood powder destined for fabricating MRgFUS applications. The main objective of the following work was to investigate the suitability of wood powder as an inexpensive alternative in replacing other added materials that have been suggested in previous studies for controlling the ultrasonic properties of TMMs. The characterization procedure involved a series of experiments designed to estimate the acoustic (attenuation coefficient, absorption coefficient, propagation speed, and impedance), thermal (conductivity, diffusivity, specific heat capacity), and MR properties (T₁ and T₂ relaxation times) of the wood-powder doped material. The developed TMM (2% w/v agar and 4% w/v wood powder) as expected demonstrated compatibility with MRI scanner following images artifacts evaluation. The acoustic attenuation coefficient of the proposed material was measured over the frequency range of 1.1–3 MHz and found to be nearly proportional to frequency. The measured attenuation coefficient was 0.48 dB/cm at 1 MHz which was well within the range of soft tissue. Temperatures over 37 °C proved to increase marginally the attenuation coefficient. Following the transient thermoelectric method, the acoustic absorption coefficient was estimated at 0.34 dB/cm-MHz. The estimated propagation speed (1487 m/s) was within the range of soft tissue at room temperature, while it significantly increased with higher temperature. The material possessed an acoustic impedance of 1.58 MRayl which was found to be comparable to the corresponding value of muscle tissue. The thermal conductivity of the material was estimated at 0.51 W/m K. The measured relaxation times T₁ (844 ms) and T₂ (66 ms) were within the range of values found in the literature for soft tissue. The phantom was tested for its suitability for evaluating MRgFUS thermal protocols. High acoustic energy was applied, and temperature change was recorded using thermocouples and MR thermometry. MR thermal maps were acquired using single-shot Echo Planar Imaging (EPI) gradient echo sequence. The TMM matched adequately the acoustic and thermal properties of human tissues and through a series of experiments, it was proven that wood concentration enhances acoustic absorption. Experiments using MR thermometry demonstrated the usefulness of this phantom to evaluate ultrasonic thermal protocols by monitoring peak temperatures in real-time. Thermal lesions formed above a thermal dose were observed in high-resolution MR images and visually in dissections of the proposed TMM.

这项研究描述了掺有木粉的琼脂基软组织模拟材料（TMM）的开发和表征，这些木粉旨在制造MRgFUS应用。以下工作的主要目的是研究木粉作为替代其他添加材料的廉价替代品的适用性，这些替代材料是先前研究中为控制TMM的超声性能所建议的。表征过程涉及一系列旨在估计声学（衰减系数，吸收系数，传播速度和阻抗），热（电导率，扩散率，比热容）和MR特性（T ₁和T _{2）的实验。}木粉掺杂材料的弛豫时间）。如预期的那样，开发的TMM（2％w / v琼脂和4％w / v木粉）在图像伪影评估后证明与MRI扫描仪兼容。在1.1–3 MHz的频率范围内测量了所建议材料的声衰减系数，发现该衰减系数几乎与频率成正比。在1 MHz处测得的衰减系数为0.48 dB / cm，这完全在软组织范围内。事实证明，超过37°C的温度会稍微增加衰减系数。按照瞬态热电法，吸声系数估计为0.34 dB / cm-MHz。在室温下，估计的传播速度（1487 m / s）在软组织的范围内，而随着温度的升高，传播速度显着增加。该材料的声阻抗为1.58 MRayl，与肌肉组织的相应值相当。材料的热导率估计为0.51 W / mK。测得的弛豫时间T₁（844毫秒）和T ₂（66 ms）在软组织文献中的值范围内。测试了人体模型是否适合评估MRgFUS热规程。应用高声能，并使用热电偶和MR测温仪记录温度变化。MR热图使用单次回波平面成像（EPI）梯度回波序列获取。TMM充分匹配了人体组织的声学和热学特性，并且通过一系列实验，证明了木材浓度可以增强声学吸收。使用MR测温法的实验证明了该体模通过实时监测峰值温度来评估超声热方案的有用性。在高分辨率MR图像中以及在拟议TMM的解剖图中可视地观察到在热剂量以上形成的热损伤。