Akhter Forhad, Manrique-Bedoya Santiago, Moreau Chris, Smith Andrea Lynn, Feng Yusheng, Mayer Kathryn M, Hood R Lyle
Department of Mechanical Engineering, University of Texas at San Antonio (UTSA), San Antonio, Texas, USA.
Gastroenterology and Transplant, UT Health San Antonio, San Antonio, Texas, USA.
Lasers Surg Med. 2022 Jul;54(5):702-715. doi: 10.1002/lsm.23523. Epub 2022 Feb 16.
Photothermal therapies have shown promise for treating pancreatic ductal adenocarcinoma when they can be applied selectively, but off-target heating can frustrate treatment outcomes. Improved strategies leveraging selective binding and localized heating are possible with precision medical approaches such as functionalized gold nanoparticles, but careful control of optical dosage and thermal generation would be imperative. However, the literature review revealed many groups assume liver properties for pancreas tissue or rely on insufficiently rigorous characterization studies.
The objective of this study was to determine the thermal conductivity and optical properties at 808/1064 nm wavelengths in healthy samples of fresh and frozen porcine pancreas ex vivo.
Thermal conductivity of the porcine pancreas tissue was measured by utilizing a hot plate and two K-type thermocouples. Experimental variables such as tissue sample thickness, hot plate temperature, and heat convection coefficient were estimated through the control experiments utilizing specimens with known thermal conductivity. Optical evaluations assessed light attenuation at the 808 and 1064 nm wavelengths (continuous wave, collimated beam) by measuring the light transmittance and reflectance of different tissue thicknesses. In turn, these measurements were input into an inverse adding-doubling program to estimate the optical absorption and reduced scattering coefficients.
Interestingly, pancreas tissue thermal conductivity was demonstrated to have no significant difference (p > 0.5) between samples that were fresh, frozen for 7 days, or frozen for 14 days. Conversely, optical property assessment exhibited a significant difference (p < 0.001) between fresh and frozen tissue samples, with increased absorbance and reflectance within the frozen group. However, the optical attenuation values measured were substantially less than that of the liver or reported in previous pancreas studies, suggesting a wide overestimation of these properties.
These thermal and optical properties are critical to the development of novel therapeutic strategies like plasmonic photothermal therapy, but perhaps more importantly, are invaluable towards informing better surgical planning and operative technique among the existing thermal approaches for treating pancreas tissue.
光热疗法若能选择性应用，在治疗胰腺导管腺癌方面已显示出前景，但非靶向加热可能会影响治疗效果。借助功能化金纳米颗粒等精准医疗方法，利用选择性结合和局部加热的改进策略是可行的，但必须仔细控制光剂量和热生成。然而，文献综述显示，许多研究团队将胰腺组织的特性假定为肝脏特性，或依赖不够严谨的表征研究。
本研究的目的是在新鲜和冷冻猪胰腺的离体健康样本中，测定808/1064纳米波长下的热导率和光学特性。
利用热板和两个K型热电偶测量猪胰腺组织的热导率。通过使用具有已知热导率的标本进行对照实验，估计组织样本厚度、热板温度和热对流系数等实验变量。光学评估通过测量不同组织厚度的光透射率和反射率，评估808和1064纳米波长（连续波、准直光束）下的光衰减。然后，将这些测量值输入反向加倍程序，以估计光吸收系数和减少的散射系数。
有趣的是，新鲜、冷冻7天或冷冻14天的样本之间，胰腺组织热导率无显著差异（p>0.5）。相反，光学特性评估显示新鲜和冷冻组织样本之间存在显著差异（p<0.001），冷冻组的吸光度和反射率增加。然而，测得的光衰减值远低于肝脏或先前胰腺研究报告的值，表明对这些特性存在广泛的高估。
这些热学和光学特性对于诸如等离子体光热疗法等新型治疗策略的开发至关重要，但或许更重要的是，对于在现有的治疗胰腺组织的热学方法中进行更好的手术规划和手术技术指导具有重要价值。
