HARP tagging. (a) Original SPAMM tagged image. (b) K-space of the tagged image. HARP applies a spatial bandpass filter to extract only the first harmonic peak. (c) Magnitude HARP image is created by Fourier transforming the modified k-space and obtaining the magnitude data. (d) HARP phase image is created by Fourier transforming the modified k-space and obtaining the phase data. (e) Multiplying the HARP magnitude and phase images results in an image with modulation pattern very similar to the original tagged image. However, the pattern here represents the wrapped tissue phase. Myocardium displacement tracking can be conducted by simply tracking the tissue phase from frame to frame. (f) An example of a grid-tagged image analyzed with HARP, which shows myocardial circumferential strain.