Magnetic resonance susceptibility based perfusion imaging of tumors using iron oxide nanoparticles

Abundant preclinical and preliminary clinical data have convincingly supported antiangiogenic therapy as an effective strategy for the inhibition of tumor growth. This has led to an acute need for developing biological markers (biomarkers) of vascular remodeling that can be monitored in vivo, at repeated intervals in large numbers of patients with a variety of tumors in a noninvasive manner. Recently, magnetic resonance (MR) perfusion imaging with iron oxide nanoparticles has demonstrated the potential to be such a surrogate endpoint, that is, a biomarker intended to substitute for a clinical endpoint and predictive of clinical benefit. Consequently, both US Food and Drug Administration (FDA) and the National Cancer Institute (NCI) have major initiatives underway to improve the development of cancer therapies and the outcomes for cancer patients via biomarker development and evaluation. The biophysical principles, physiological relevance and range of imaging techniques underlying the success of susceptibility based contrast MR perfusion imaging with iron oxide nanoparticles as such a biomarker, are the subject of this review.