integrative imaging techniques for tumor analysis in mice

Inoculation tumorale guidée et imagerie multimodale chez la souris

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.

Pleins feux sur l’auteur : Intégration de l’imagerie intravitale à haute résolution et de l’IRM pour améliorer la planification de la radiothérapie stéréotaxique corporelle

Modèle murin de tumeur à chambre fenêtre de pli cutané dorsal pour la microscopie intravitale combinée et l’imagerie par résonance magnétique dans la recherche translationnelle sur le cancer

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.

Techniques d’imagerie intégrative pour l’analyse des tumeurs chez la souris

Au moins trois à quatre jours après l’intervention chirurgicale dans la chambre vitrée, fixez la souris anesthésiée dans une étape d’imagerie avec un accessoire d’anesthésie gazeuse. À l’aide de la microscopie à champ clair, obtenez une image à large champ de vision, assurant la visibilité des divots du repère sur le cadre avant du DSFC. Le même jour, utilisez la méthode de microscopie intravitale pour capturer une image microvasculaire.Après avoir placé la souris sur le lit d’IRM, insérez une aiguille papillon de calibre 27 avec un microtube attaché dans la veine de la queue. Fixez la chambre de la fenêtre dans un dispositif d’immobilisation imprimé en 3D À l’aide d’une aiguille de calibre 18, injectez du lubrifiant vétérinaire pour les yeux dans les sept tubes du marqueur de référence IRM. Fixez le repère sur le DSFC.Insérez le lit dans un scanner IRM préclinique de sept Tesla. Pour l’acquisition, réglez un champ de vision de 32 x 32 millimètres avec une matrice de 64 x 64 pour 0,5 x 0,5 millimètre en résolution simple avec des impulsions RF cohérentes. Acquérez des ensembles d’images pondérées T2 coronales et axiales pour visualiser le plan de la chambre de fenêtre.Prescrire et réorienter de manière itérative un ensemble pondéré en T2 sagittal pour aligner les coupes d’imagerie avec le DSFC et les marqueurs repères, en s’assurant que la tranche cinq contient le signal tissulaire dans le DSFC et que la tranche quatre ne le contient pas. Effectuer l’imagerie microvasculaire à l’aide de la méthode d’IRM dynamique avec contraste sélectionné. Dans l’espace de travail MATLAB, chargez les données d’IRM microvasculaire, de microscopie en champ clair et d’IRM microvasculaire, puis cliquez sur le bouton Exécuter.Accédez au fichier contenant les tranches IRM pondérées T2 et sélectionnez jusqu’à quatre tranches qui affichent les repères. Placez un point sur chacun des sept marqueurs repères de l’image IRM et associez-les à leur point correspondant sur l’image de microscopie. Sélectionnez au moins trois points de repère microvasculaires sur l’image microvasculaire svOCT et les points correspondants dans l’image microscopique.Tracez le contour de la tumeur dans l’image de microscopie co-enregistrée, puis l’ensemble de données microvasculaires svOCT, l’image de microscopie co-enregistrée et les cartes de paramètres IRM co-enregistrées apparaissent. Enregistrez la carte pour une analyse ultérieure. Le co-enregistrement de l’imagerie microvasculaire, de la microscopie à champ large et de l’IRM chez les souris saines et tumorales permet l’analyse de corrélation des paramètres microvasculaires et macrovasculaires.Les mesures macrovasculaires de l’IRM dynamique avec contraste ont montré de fortes corrélations entre les mesures microvasculaires dérivées de svOCT, comme l’indiquent les valeurs R au carré dans les deux graphiques. Les corrélations ont été mesurées chez des souris saines et porteuses de tumeurs pour évaluer la capacité de l’IRM dynamique à mesurer les caractéristiques vasculaires à travers des architectures microvasculaires largement différentes.

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 ...

Recherche

Recherche en cancérologie

Tumor Cells Inoculation in Mice Through Precise Landmarking and Injection Techniques

Inoculation de cellules tumorales chez la souris grâce à des techniques précises de marquage et d’injection

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

Chirurgie de la chambre vitrée chez des souris injectées de cellules tumorales pour la visualisation et l’imagerie de la croissance tumorale