Multimodality imaging in an orthotopic mammary window chamber model

Window chamber models have been utilized for many years to investigate cancer development and the tumor microenvironment. Orthotopic mammary window chamber model have been developed for detailed study of breast cancer. Orthotopic window chamber models, due to the native environment, support more realistic growth and tumor behavior than ectopic models. The work by other groups thus far utilizing mammary window chamber models has focused solely on optical imaging techniques, limited to probing the first millimeter or less of tissue. These techniques do not take full advantage of the unrestricted, three-dimensional tumor growth the model supports. We have developed a custom plastic structure compatible with multimodality imaging. We present in this work the implementation of our custom window chamber in a mouse model and the successful imaging of the window chamber cancer model with MRI, nuclear imaging, and optical techniques. MRI provides a full three-dimensional view of the tumor growth and allows for additional, potentially clinically translatable, approaches to be utilized in investigating the cancer microenvironment. Nuclear imaging is accomplished using the Beta Imager, which is a novel approach to nuclear imaging of window chambers. The Beta Imager detects photons after the interaction of a single positron with a scintillator, instead of the coincidence detection of annihilation gamma ray pairs. We utilized the radioisotope glucose analog, 2-deoxy-2- (¹⁸F)fluoro-D-glucose or FDG, with the Beta Imager to obtain information on the glycolytic metabolism of the tumor and surrounding region.