Quantitative pre-clinical imaging of hypoxia and vascularity using MRI and PET

During hypoxia, tissues are subjected to an inadequate oxygen supply, disrupting the balance needed to maintain normal function. This deficiency can occur due to reduced oxygen delivery caused by impaired blood flow or a decline in the blood's ability to carry oxygen. In tumors, hypoxia and vascularization play crucial roles, shaping their microenvironments and influencing cancer progression, response to treatment and metastatic potential. This chapter provides guidance on the use of non-invasive imaging methods including Positron Emission Tomography and Magnetic Resonance Imaging to study tumor oxygenation in pre-clinical settings. These imaging techniques offer valuable insights into tumor vascularity and oxygen levels, aiding in understanding tumor behavior and treatment effects. For example, PET imaging uses tracers such as [18F]-fluoromisonidazole (FMISO) to visualize hypoxic areas within tumors, while MRI complements this with anatomical and functional images. Although directly assessing tumor hypoxia with MRI remains challenging, techniques like Blood Oxygen Level Dependent (BOLD) and Dynamic Contrast-Enhanced MRI (DCE-MRI) provide valuable information. BOLD can track changes in oxygen levels during oxygen challenges, while DCE-MRI offers real-time access to perfusion and vessel permeability data. Integrating data from these imaging modalities can help assess oxygen supply, refine treatment strategies, enhance therapeutic effectiveness, and ultimately improve patient outcomes.