Going with the flow: how reproducible are cardiac magnetic resonance measurements of myocardial perfusion?

Myocardial perfusion imaging using cardiac magnetic resonance (CMR) is becoming a widely used clinical tool. With the recent publication of large scale clinical trials providing evidence for its high diagnostic accuracy in coronary heart disease, there is a growing evidential basis for CMR based perfusion measurements as an alternative to the most commonly used method, Single Photon Emission Computer Tomography (1,2). Clinically, CMR perfusion images are usually interpreted visually. This however introduces subjectivity to the analysis and so quantitative and semi-quantitative measurements have been devised to allow more objective assessments of myocardial blood flow. Such measurements may prove to be important for diagnosing coronary heart disease, especially in the case of multiple vessel disease, where the lack of healthy reference myocardium can render visual assessment unreliable.