Science to practice: is t2* enough to assess oxygenation?

As initially reported by Ogawa et al (1), the magnetic resonance (MR) imaging T2* blood oxygen level–dependent (BOLD) signal is sensitive to blood oxygen concentration; however, this signal is also sensitive to a number of other normal and abnormal tissue features. As a result, T2* imaging alone cannot be used to accurately measure vascular oxygenation, much less tissue oxygenation. However, with separate MR imaging measurements of other tissue factors influencing T2*, it might be possible to noninvasively image local tissue oxygen. Such a capability could be of great clinical importance, not only in patients with hypoxic or ischemic disease states, but also in patients with other pathologic conditions that have abnormal respiratory metabolism, such as cancer.