Tool for automatic real-time regional cardiac function analysis using HARP

The FastHARP magnetic resonance pulse sequence can acquire tagged cardiac images at a rate of 45 ms per frame, enabling 7-20 harmonic phase (HARP) images per heartbeat per tag orientation. By switching the tag orientation every heartbeat, data from just two heartbeats can be used to compute in-plane quantities describing myocardial deformation, such as circumferential and radial strain. Standard HARP software, however, requires about one second to compute each strain image, which is not fast enough to keep up with the FastHARP pulse sequence. In this work, we have developed real-time algorithms for HARP processing of tagged MR images. The code was implemented along with a visualization tool that runs in conjunction with the FastHARP pulse sequence. HARP strain computations and display can now be carried out in real-time after a one heartbeat delay. The software is also fast enough to track and plot the time profile of strain of one or more points in the myocardium in real-time. Our software has now been integrated into a research testbed for magnetic resonance cardiac stress testing, contributing to the emerging suite of clinical cardiac MRI protocols.