Remember the notion in theoretical physics that simply observing something affects it? Well, here's an example of how that works in medicine. The reference detail is to an upcoming article and the commentary addresses the importance of the finding. They found that at some scanning levels, brain glucose metabolism is increased by the scan. Could be good, or not so good, depending on the circumstances, but it's interesting to consider how many scans have been done with incomplete appreciation of what's taking place at a cellular level.

Volkow ND, Tomasi D, Wang GJ, Fowler JS, Telang F, Wang R, Alexoff D, Logan J, Wong C, Pradhan K, Caparelli EC, Ma Y, Jayne M
Neuroimage 2010 Jun 51(2):623-8

Commentary from Faculty Member Mark George, Medical University of South Carolina, USA

This is a massively important paper as the authors have asked the most simple question: does the magnetic resonance imaging (MRI) scanner itself and the gradient switching cause changes in brain activity? It is amazing that there are hundreds of thousands of papers using MRI to image and investigate the brain and none has bothered to ask whether the imaging tool (MRI) changes what is being imaged. It turns out that it does. This has enormous implications for safety and for potentially creating a new generation of combined stimulators/scanners. One should no longer assume that the MRI scanner does not directly change brain activity while imaging.