Doctors have several indirect ways to assess the heart’s health, from the stethoscope to ultrasound and magnetic resonance imaging. MRI can depict blood flow and wall thickening, but doesn’t show the internal workings of the muscle-the straining of fibers as they lengthen and shorten with each beat.

Now a team at Johns Hopkins University has applied for patents on a new way to process MRI data that gives doctors a view of the heart in action, uncovering otherwise invisible problems.

The system-developed by electrical engineers Jerry L. Prince and Nael Osman-is called HARP MRI, for harmonic phase magnetic resonance imaging. HARP combines a standard MRI scanner with new data-processing techniques to allow precise measurements of muscle strain within minutes. Preliminary tests on the left ventricle look promising, says Prince, who wants to extend the technique’s diagnostic powers to other parts of the heart.