ABSTRACT

Angiogenesis, the sprouting of new capillaries from existing blood vessels, and vasculogenesis, the de novo generation of blood vessels, are the two primary methods of vascular expansion by which nutrient supply to tissues is adjusted to match physiological needs. Angiogenesis is an essential component of several normal physiological processes that include menstrual cycle changes in the ovaries and uterus, organ regeneration, wound healing, and the spontaneous growth of collateral vessels in response to ischemia (1) . Pathological angiogenesis is an integral part of a number of disease states (e.g., rheumatoid arthritis, age-related macular degeneration, proliferative retinopathy, psoriasis) and is critical for growth of primary malignant tumors and for the development of metastases (2) . This chapter describes the process of tumor angiogenesis and features unique to tumor microvasculature. Emphasis will be placed on the technique of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) ( 3-5 ). Comparisons of DCE-MRI with other imaging techniques that are able to depict the angiogenic status of tumors in situ, including macromolecular contrast media (MMCM)- enhanced MR (6) , endothelial stem-cell imaging, diffusion-weighted MR imaging, and functional multidetector computed tomography (fMDCT) (7) are made. Additionally, the potential of positron emission tomography (PET) to image angiogenesis is briefly discussed. The clinical potential of angiogenesis imaging will be highlighted and the ongoing challenges of functional imaging techniques as clinical and research tools will be explored.