Water inside small or between densely packed cells is hindered in diffusing over long distances and thus generates high signal in DWI. The MR signal of highly diffusive water molecules is attenuated, depending on their distance traveled, whereas slowly diffusing molecules retain most of their signal contribution.

Therefore, endogenous markers of tissue composition are being investigated as alternatives.ĭiffusion-weighted imaging (DWI) samples the diffusivity of water molecules in different compartments. 8 Tracer injection may not always be clinically suitable. Imaging mostly targets specific surface or intracellular markers of the immune cells and crucially relies on previous tracer injection. 7 Compared with the analysis of immune cells in conventional tissue biopsies, these imaging approaches are less invasive, avoid tissue sampling bias, and can be performed repetitively over time.

There are several preclinical and clinical studies aiming for in vivo imaging of the intratumoral immune cell infiltrate, mainly applying direct or indirect cell labeling, inter alia using positron emission tomography with different radiotracers or MRI with various nanoparticles. 5 Because of their complex interplay with significant impact on therapy outcome and patients’ prognosis, 4 6 imaging of both T-cell and macrophage infiltration into tumor lesions is highly desired. 3 4 T-cell activation and priming is critically dependent on their interaction with tumor-associated macrophages, leading to a functional crosstalk between both cell populations. 1 2 While the inflammatory TME is characterized by complex and dynamic interconnections between various immune cell subtypes, especially T-cells are major effectors of tumor-promoting inflammation, enhancing tumor progression and metastatic spread. Immune cells are main players in building, shaping, and reprogramming the tumor microenvironment (TME).

Graphpad prism 9 free download