Profiling specific cell populations within the inflammatory tumor microenvironment by oscillating-gradient diffusion-weighted MRI

Immune cells are major players of the tumor microenvironment (TME), having profound effects on tumor development and metastatic progression. We present oscillating-gradient diffusion-weighted MRI (OGSE-DWI) as non-invasive imaging approach to monitor the intratumoral immune cell infiltrate, relying on size differences between cancer cells, T-cells and macrophages. By applying the Imaging Microstructural Parameters Using Limited Spectrally Edited Diffusion (IMPULSED) model to sine-shaped OGSE-DWI, changes within the TME and its specific immune cell composition were monitored and compared in syngeneic murine breast cancer models with different degrees of malignancy during tumor progression, clodronate liposome-mediated depletion of macrophages and immune checkpoint inhibitor treatment.