CTS-SGER: Thermo-Mechanical Interactions of Ultrashort Laser Pulses with Subsurface Targets of Tissue Models

CTS-SGER：超短激光脉冲与组织模型地下目标的热机械相互作用

• 批准号: 0609662
• 负责人: Guillermo Aguilar
• 金额: --
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2007-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0609662&HistoricalAwards=false
• 关键词: CTS; SGER; Thermo; Mechanical; Interactions

ABSTRACT: Thermo-mechanical interactions of ultrashort laser pulses with subsurface targets of tissue modelsThe precise ablation of biological tissues using lasers with pulse durations longer than ~ 1 ns, while avoiding collateral thermal damage of the surrounding tissue is often quite a challenge and sometimes physically impossible. This is because the optical energy is coupled to the biological tissue through its wavelength-dependent absorption coefficient and transformed almost entirely into heat, which diffuses beyond the optically confined volume at a rate dictated by the tissue thermal diffusion time. In contrast, when laser pulses are much shorter than the characteristic diffusion time of tissue, non-linear laser-tissue interactions arise, such as the generation of plasma, shockwaves and cavitation bubbles. These physical phenomena consume a large portion of the optical energy and transform it into kinetic energy, allowing a more precise ablation while reducing and even eliminating collateral thermal damage to the surrounding tissue. Furthermore, since the coupling of the optical energy to the biological tissue does no longer depend on laser wavelength, it is possible to eliminate unwanted superficial heating and focus the interaction volume onto deep subsurface targets.The primary intellectual merit of the work lies in the proposed used of low energy (mJ) high power (GW) ultra short laser pulses (USLP) to induce a more precise mechanically-driven ablation of subsurface tissue structures with minimal collateral thermal damage. This is the first such use of USLP for tissue treatment. The objectives are to quantify the magnitude of the thermal (temperatures, heat fluxes) and mechanical (stress, strain) effects on subsurface tissue model targets induced by laser pulse durations ranging from the milli- to the femto-second time scale, with repetition rates between the Hz to the MHz frequency domain. Specifically, we intend to correlate the photoablation and extent of damage with the magnitude, pulse duration and repetition rates of a wide variety of lasers, particularly those of USLP. Furthermore, a thermo-mechanical mathematical model that accurately describes the experimental evidence will be developed. The proposed work will set the foundation for an innovative alternative to current laser therapy of vascular lesions and perhaps the only solution for the ablation of small vasculature and other tissue chromophores, such as benign and malignant pigmented lesions. With respect to the broader impacts of the work, the short-term impacts include the generation of experimental methods and better understanding of the interactions of USLP pulses with various tissue targets. The long-term impacts include the development of new technology where precise thermo-mechanical damage of subsurface structures is achieved while collateral thermal damage is minimized.

摘要：超短激光脉冲与组织模型亚表面目标的热-力学相互作用利用脉冲持续时间超过~ 1ns的激光对生物组织进行精确消融，同时避免周围组织的附带热损伤通常是一个相当大的挑战，有时在物理上是不可能的。这是因为光能通过其波长相关的吸收系数耦合到生物组织上，并几乎完全转化为热量，热量以组织热扩散时间决定的速率扩散到光受限体积之外。相反，当激光脉冲远短于组织的特征扩散时间时，激光与组织之间会产生非线性相互作用，如等离子体、冲击波和空化泡的产生。这些物理现象消耗了很大一部分光能，并将其转化为动能，从而可以更精确地消融，同时减少甚至消除对周围组织的附带热损伤。此外，由于光能与生物组织的耦合不再依赖于激光波长，因此有可能消除不必要的表面加热并将相互作用体积集中在深层地下目标上。这项工作的主要知识价值在于建议使用低能量（mJ）高功率（GW）超短激光脉冲（USLP）来诱导更精确的机械驱动的地下组织结构烧蚀，同时最小化附带热损伤。这是第一次使用USLP进行组织治疗。目标是量化激光脉冲持续时间对地下组织模型目标的热（温度、热通量）和机械（应力、应变）影响的幅度，这些影响的时间范围从毫微秒到飞秒，重复频率在Hz到MHz频域之间。具体来说，我们打算将光烧蚀和损伤程度与各种激光器（特别是USLP激光器）的幅度、脉冲持续时间和重复率联系起来。此外，将建立一个准确描述实验证据的热力学数学模型。提出的工作将为当前血管病变激光治疗的创新替代方案奠定基础，并且可能是小血管和其他组织发色团（如良性和恶性色素病变）消融的唯一解决方案。就这项工作的广泛影响而言，短期影响包括产生实验方法和更好地理解USLP脉冲与各种组织靶点的相互作用。长期影响包括新技术的发展，该技术可以实现对地下结构的精确热机械损伤，同时最大限度地减少附带热损伤。