MR imaging of tumor microcirculation: Promise for the new millenium

Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) is a method of imaging the physiology of the microcirculation. A series of recent clini cal studies have shown that DCE MRI can measure and predict tumor response to therapy. Recent advances in MR technology provide the enhanced spatial a nd temporal resolution that allow the application of this methodology in th e management of cancer patients, The September Issue of this journal provid ed a microcirculation section to update readers on this exciting and challe nging topic, Evidence is mounting that DCE MRI-based measures correlate wel l with tumor angiogenesis, DCE MRI has already been shown in several types of tumors to correlate well with traditional outcome measures, such as hist opathologic studies, and with survival, These new measures are sensitive to tumor physiology and to the pharmacokinetics of the contrast agent in indi vidual tumors. Moreover, they can present anatomical images of tumor microc irculation at excellent spatial resolution. Several issues have emerged fro m recent international workshops that must be addressed to move this method ology into routine clinical practice. First, is complex modeling of DCE MRI really necessary to answer clinical questions reliably? Clinical research has shown that, for tumors such as bone sarcomas, reliable outcome measures of tumor response to chemotherapy can be extracted from DCE MRI by methods ranging from simple However, the use of similar methods to answer a differ ent question-the differentiation of malignant from benign breast tumors-has yielded contradictory results. Thus, no simple, one-size-fits-all-tumors s olution has yet been identified. Second, what is the most rational and reli able data collection procedure for the DCE MRI evaluation? Several groups h ave addressed population variations in some key variables, such as tumor T( 1)0 (T-1 prior to contrast administration) and the arterial input function C-a(t) for contrast agent, and how they influence the precision and accurac y of DCE MRI outcomes. However, despite these potential complications, clin ical studies in this section show that some tumor types can be assessed by relatively simple dynamic measures and analyses. The clinical scenario and tumor type may well determine the required complexity of the DCE MRI exam p rocedure and its analysis. Finally, we suggest that a consensus on naming c onventions (nomenclature) is needed to facilitate comparison and analysis o f the results of studies conducted at different centers, (C) 1999 Wiley-Mss , Inc.