Advanced MR techniques in multicenter clinical trials.

MRI has had a place in the clinical trials process for more than 20 years. However, for much of that time MRI has been used primarily for subjective interpretation and relatively straightforward structural measurements. More advanced MR techniques have been considered too difficult to implement consistently across multiple sites in a single trial--this despite the fact that these techniques often provide the best window into the direct effects of targeted therapeutics. As an example, numerous compounds are currently under development whose principle effect is to temporarily or permanently alter tumor microvasculature. Changes induced by these compounds typically manifest as reductions in blood flow and vascular permeability within tumors. These changes can be measured directly using dynamic contrast-enhanced MRI. Early studies using this technique were limited to single centers, limiting both the overall size of the studies and the rate at which they were able to accrue patients. Recent efforts, however, have demonstrated that with sufficient attention to protocol design, imaging site selection and training, and analysis standardization, it is possible to obtain consistent and high quality results using even relatively complex acquisition protocols. This article will briefly review both the benefits and the drawbacks of including advanced MR techniques in clinical trial protocols. It will then review in detail the challenges presented by the need to deploy these techniques both to large research institutions and to community imaging centers which may have little or no familiarity with them at the outset of the trial.