Ultrahigh-Resolution Quantitative Optical Coherence Elastography of the Tumor Microenvironment In Vivo

在过去的十年里，对癌症的认识迅速发展。其中一个关键发现是， 机械特性不仅仅是肿瘤的症状，而且可以触发恶性肿瘤的实际发作， 促进肿瘤进展。然而，癌症力学研究的临床影响目前受到阻碍 由于缺乏用测微计对肿瘤微环境的力学特性进行成像的方法， 体内分辨率。因此，研究细胞外基质（ECM）力学在 致癌作用仅限于体外实验或组织生物力学的离体测量。 该提案将开发和展示一种新的成像平台，用于对 肿瘤微环境的机械特性。声辐射力（ARF）将用于高度 局部“触诊”和超精确相位敏感光学相干断层扫描（OCT）将被用于 检测所产生的纳米到微米尺度的位移。主要的假设，基于最近的一个 我们小组的论文，是使用高度局部化的机械激发（通过“触诊”与紧密聚焦， 超声）与千赫范围内的较高频率下的机械激励相结合 为了克服基于剪切波的方法的分辨率限制，从而使 最高分辨率的复合剪切模量的OCE成像，即剪切储能和损耗模量。一 进一步的假设是，实现我们的落射照明成像几何形状的方法将使得 在体内肿瘤发展过程中局部机械性能的动态变化被量化。具体 目标1将展示我们的超高分辨率ARF-OCE方法，结合定量横波 具有超高分辨率轴向应变成像的传播方法（这利用了我们具有的成像方案 证明可以在紧密聚焦超声的同一位置检测ARF引起的位移 “触诊”点）。我们的超高分辨率定量ARF-OCE方法和一种新的落射照明成像 适用于体内ARF-OCE研究的设置将在并行和肿瘤模拟体模中进行验证， 在相同的激励频率范围内，与AFM成像的机械性能进行比较。具体目标2 将应用我们的新型ARF-OCE系统和在Aim 1中验证的重建方法进行体内成像 肿瘤微环境。我们将首次展示剪切的纵向OCE成像 体内肿瘤微环境的储能模量和损耗模量。这些定量OCE图像将与 金标准组织学分析和切除肿瘤组织的二次谐波产生（SHG）成像。 我们期望我们的超高分辨率OCE新方法将使新兴的癌症领域成为可能 机械生物学过渡到，并强调在体内成像研究ECM力学。此外，本发明的目的是， 我们的无创和无标记成像平台的临床兼容性将大大提高未来的临床 癌症机械生物学研究的翻译，并广泛影响机械生物学的其他领域。

The understanding of cancer has evolved rapidly over the last decade. One of the key findings is that altered mechanical properties is not just a symptom of tumors, but can trigger the actual onset of malignancy, and promote tumor progression. The clinical impact of cancer mechanics research, however, is currently hampered by a lack of methods to image the mechanical properties of the tumor microenvironment with micrometer resolution in vivo. Consequently, research studies on the role of extracellular matrix (ECM) mechanics in carcinogenesis have been restricted to in vitro experiments or ex vivo measurements of tissue biomechanics. This proposal will develop and demonstrate a new imaging platform for time-lapse in vivo imaging studies of the mechanical properties of the tumor microenvironment. Acoustic radiation force (ARF) will be utilized for highly localized ‘palpation’, and ultra-precise phase-sensitive optical coherence tomography (OCT) will be employed to detect the resulting nanometer-to-micrometer scale displacements. The main hypothesis, based on a recent paper by our group, is that the use of highly localized mechanical excitation (via ‘palpation’ with tightly-focused ultrasound), combined with mechanical excitation at higher frequencies in the kilohertz regime, can be leveraged to overcome the resolution limitations of shear-wave-based approaches, and thereby enable the highest-resolution OCE imaging of the complex shear modulus, i.e. both shear storage and loss modulus. A further hypothesis is that implementation of our approach for an epi-illumination imaging geometry will enable the dynamic variations in local mechanical properties during tumor development in vivo to be quantified. Specific Aim 1 will demonstrate our approach for ultrahigh-resolution ARF-OCE that combines quantitative shear wave propagation methods with ultrahigh-resolution axial strain imaging (this utilizes an imaging scheme we have demonstrated that detects ARF-induced displacements at the same location of a tightly-focused ultrasound ‘palpation’ spot). Our ultrahigh-resolution quantitative ARF-OCE approach and a novel epi-illumination imaging setup suitable for in vivo ARF-OCE studies will be validated in side-by-side and tumor mimicking phantoms by comparison to AFM imaging of mechanical properties over the same excitation frequency range. Specific Aim 2 will apply our novel ARF-OCE system and reconstruction methods validated in Aim 1 to perform in vivo imaging of the tumor microenvironment. We will demonstrate, for the first time, longitudinal OCE imaging of the shear storage and loss moduli of the tumor microenvironment in vivo. These quantitative OCE images will be correlated to gold-standard histological analysis and second-harmonic generation (SHG) imaging of resected tumor tissues. We expect that our new approach for ultrahigh-resolution OCE will enable the burgeoning field of cancer mechanobiology to transition towards, and emphasize in vivo imaging studies of ECM mechanics. Additionally, the clinical compatibility of our noninvasive and label-free imaging platform will greatly enhance future clinical translation of cancer mechanobiology research, and broadly impact other areas of mechanobiology.