Going live to the beating heart
04 September 2010
Max Planck scientists succeed in filming organs and joints in real time using magnetic resonance imaging
"Please hold absolutely still": This instruction is crucial for patients being examined by magnetic resonance imaging (MRI). It is the only way to obtain clear images for diagnosis. Up to now, it was therefore almost impossible to image moving organs using MRI. Max Planck researchers from Göttingen have now succeeded in significantly reducing the time required for recording images - to just one fiftieth of a second.
With this breakthrough, the dynamics of organs and joints can be filmed "live" for the first time: movements of the eye and jaw as well as the bending knee and the beating heart. The new MRI method promises to add important information about diseases of the joints and the heart. In many cases MRI examinations may become easier and more comfortable for patients. (NMR in Biomedicine 2010, Journal of Cardiovascular Magnetic Resonance 2010)
Real-time MRI of the heart with a measurement time of 33 milliseconds per image and 30 images per second. The spatial resolution is 1.5 millimetres in the image plane (section thickness 8 millimetres). The eight successive images show the movement of the heart muscle of a healthy subject for a period of 0.264 seconds during a single heartbeat. The images range from the systolic phase (arrow, top left: contraction of the heart muscle) to the diastolic phase (arrow, bottom right: relaxation and expansion). The bright signal in the heart chambers is the blood.
A process that required several minutes until well into the 1980s, now only takes a matter of seconds: the recording of cross-sectional images of our body by magnetic resonance imaging (MRI). This was enabled by the FLASH (fast low angle shot) method developed by Göttingen scientists Jens Frahm and Axel Haase at the Max Planck Institute for Biophysical Chemistry.
FLASH revolutionised MRI and was largely responsible for its establishment as a most important modality in diagnostic imaging. MRI is completely painless and, moreover, extremely safe. Because the technique works with magnetic fields and radio waves, patients are not subjected to any radiation exposure as is the case with X-rays.
At present, however, the procedure is still too slow for the examination of rapidly moving organs and joints. For example, to trace the movement of the heart, the measurements must be synchronised with the electrocardiogram (ECG) while the patient holds the breath. Afterwards, the data from different heart beats have to be combined into a film.