integrative imaging techniques for tumor analysis in mice

小鼠的引导肿瘤接种和多模式成像

Tumor microvasculature is an important component of the tumor microenvironment that can be a target for therapy and a determinant of treatment response. In the preclinical setting, the microvasculature is typically studied using intravital microscopy in orthotopic or heterotopic window chamber animal models1,2. This has several advantages over histological studies since the imaging is done in live tissues and the tumor can be monitored longitudinally over several weeks or even months2,3. These studies can leverage the high-resolution imaging capabilities of intravital microscopy to study the delivery of therapeutics to the tumor4,5, the causes of treatment resistance6, and the response of the micro vessels to therapies such as antiangiogenic treatment7,8 and radiotherapy2,9.
Intravital microscopy clearly plays an important role in preclinical cancer research; however, how can tumor microenvironmental features be measured in the clinic? Microvascular information would be useful in the clinic for measuring blood supply and tumor cell hypoxia, which is important for determining treatment resistance in radiotherapy10, as well as the ability of the microvasculature to deliver chemotherapeutic agents to the surrounding tumor cells11. For example, in radiotherapy, spatial information on the structure and function of the tumor microvasculature may help personalize a patient&#39;s treatment plan by adjusting the fractionation schedule or by preferentially boosting the dose to avascular and likely hypoxic regions12.
Intravital microscopy can measure these important microvascular features since it has a very high resolution (&#956;m scale); however, its depth penetration into tissue is limited to several hundred microns or a few millimeters, at most making clinical implementation challenging. Indeed, there are some novel applications of intravital microscopy in the clinic13; however, these are still limited to examinations of near-surface level tissue such as the skin14 or mucosal/endothelial linings of various body cavities via flexible catheters/endoscopes15,16.
More commonly, the microvasculature is studied using imaging modalities such as CT17 or MRI18. These clinical imaging modalities can image to any depth within the body, but they have a much lower spatial resolution (mm scale). Thus, there is a need to bridge this resolution gap between preclinical intravital microscopy and clinical imaging modalities to bring high-resolution and detailed microvascular information into the clinic19. Several functional imaging methods have been developed to improve the microvascular imaging capabilities of clinical imaging modalities such as dynamic contrast-enhanced (DCE) MRI and CT20, and Intravoxel incoherent motion (IVIM) MRI21. However, these are model-based methods that provide indirect measurements of the microvasculature and thus, must be validated with appropriate &#34;ground truth&#34; measurements of the microvasculature19,22.
We have developed a dorsal skinfold window chamber (DSFC) tumor mouse model to bridge this gap between preclinical intravital microscopy and clinically applicable imaging modalities such as CT and MRI. The DSFC provides direct access to the tumor for high-resolution, intravital microscopy imaging through a glass window but also clinically applicable imaging such as MRI as it is made of MR-compatible materials (plastic and glass). Furthermore, an included MATLAB code performs multimodality 3D co-registration for direct spatial correlations between preclinical intravital microscopy and clinically applicable imaging modalities. Here we will describe the design and surgery to install the DSFC as well as the procedure to co-register intravital microscopy and clinically applicable imaging modalities.

作者聚焦：整合高分辨率活体成像和 MRI 以增强立体定向放射治疗计划

背侧皮褶窗室肿瘤小鼠模型在转化癌症研究中用于联合活体显微镜和磁共振成像

Preclinical intravital imaging has very high resolution, but limited depth penetration in the tissue, which makes it very good for preclinical imaging studies. On the other hand, MRI is much more clinically applicable and has a higher depth penetration, but very low spatial resolution. The goal of this study is to correlate these two modalities with each other in order to better translate our findings from preclinical intravital microscopy into the clinic via magnetic resonance imaging.Perfusion-sensitive imaging methods in MRI and biophotonics, including our optical coherence tomography and geography system, are revealing how the microvasculature impacts tumor response to hypofractionated radiotherapy. 3D printing is also aiding through cost-effective custom tool manufacturing, facilitating longitudinal studies. Finally, AI image analysis is facilitating the identification of novel radiotherapy predictive biomarkers.We've made several findings concerning the tumor response to hypofractionated radiotherapy, including more recently, the temporal kinetics of both radiobiologically significant and abstracted AI-derived tissue response metrics. Additionally, we have demonstrated the promise for multimodal imaging being performed more accurately, correlating both MRI, macroscopic and optical coherence tomography, microscopic, angiography-derived metrics. By extending the effective length of longitudinal studies, we may better identify predictive biomarkers for long-term tumor treatment response.Additionally, by improving robustness of co-registration between macroscopic clinically available imaging modalities and microscopic preclinical imaging modalities, we may enhance the translatability of our findings from benchtop to bedside. During a stereotactic body radiation therapy, high doses of radiation are delivering a reduced number of fractions. One potential radiobiological target associated with increased cell death in SVRT is the tumor microvasculature.By combining high-resolution optical angiography and MRI, we want to enable functional MRI microvascular imaging for patient-specific SVRT treatment planning and improved outcomes.

用于小鼠肿瘤分析的综合成像技术

在窗室手术后至少三到四天后，用气体麻醉附件将麻醉的小鼠固定在成像阶段。使用明场显微镜，获得宽视场图像，确保 DSFC 前框架上的基准标记凹陷的可见性。在同一天，使用活体显微镜方式捕捉微血管图像。将鼠标放在MRI床上后，将带有微管的27号蝶形针插入尾静脉。将窗室固定在 3D 打印的固定装置中 使用 18 号针头，将兽用眼部润滑剂注入 MRI 基准标记上的七根管子中。将基准标记贴在 DSFC 上。将床插入七特斯拉临床前 MRI 扫描仪。对于采集，使用 64 x 64 矩阵设置 32 x 32 毫米的视野，以获得 0.5 x 0.5 毫米的平分辨率和一致的射频脉冲。获取日冕和轴向 T2 加权图像集，以可视化窗室平面。规定并迭代地重新定向矢状 T2 加权集，以将成像切片与 DSFC 和基准标记对齐，确保切片 5 在 DSFC 中包含组织信号，而切片 4 不包含组织信号。使用选定的动态对比增强 MRI 方法进行微血管成像。在 MATLAB 工作区中，加载微血管、明场显微镜和微血管 MRI 数据，然后单击“运行”按钮。导航到包含 T2 加权 MRI 切片的文件，并选择最多四个显示基准标记的切片。在 MRI 图像中的七个基准标记中的每一个上放置一个点，并将它们与显微镜图像上的相应点匹配。在svOCT微血管图像上选择至少三个微血管标志点，并在显微镜图像中选择相应的点。在共同配准的显微镜图像中勾勒出肿瘤的轮廓，然后出现 svOCT 微血管数据集、共同配准的显微镜图像和共同配准的 MRI 参数图。保存地图以供以后分析。在健康和荷瘤小鼠中，微血管成像、宽场显微镜和 MRI 的共同配准使得微血管和大血管指标的相关性分析成为可能。动态对比增强 MRI 大血管指标显示 svOCT 衍生的微血管指标之间存在很强的相关性，如两个图中的 R 平方值所示。在健康和荷瘤小鼠中测量相关性，以评估动态对比增强 MRI 测量大部分不同微血管结构的血管特征的能力。

integrative-imaging-techniques-for-tumor-analysis-in-mice

Research

JoVE Journal

Cancer Research

Integrative Imaging Techniques for Tumor Analysis in Mice

A Dorsal Skinfold Window Chamber Tumor Mouse Model for Combined Intravital Microscopy and Magnetic Resonance Imaging in Translational Cancer Research

Preclinical intravital imaging such as microscopy and optical coherence tomography have proven to be valuable tools in cancer research for visualizing the ...

科研

癌症研究

Tumor Cells Inoculation in Mice Through Precise Landmarking and Injection Techniques

通过精确的定位和注射技术在小鼠中接种肿瘤细胞

Window Chamber Surgery in Tumor Cell Injected Mice for Tumor Growth Visualization and Imaging

在肿瘤细胞注射小鼠中进行窗口室手术，用于肿瘤生长可视化和成像