HARP (algorithm)
medical image analysis algorithm
Harmonic phase (HARP) algorithm is a medical image analysis technique capable of extracting and processing motion information from tagged magnetic resonance image (MRI) sequences. It was initially developed by N. F. Osman and J. L. Prince at the Image Analysis and Communications Laboratory at Johns Hopkins University. The method uses spectral peaks in the Fourier domain of tagged MRI, calculating the phase images of their inverse Fourier transforms, which are called harmonic phase (HARP) images. The motion of material points through time is then tracked, under the assumption that the HARP value of a fixed material point is time-invariant. The method is fast and accurate, and has been accepted as one of the most popular tagged MRI analysis methods in medical image processing.
Background
In cardiac magnetic resonance imaging, tagging techniques make it possible to capture and store the motion information of myocardium in vivo. MR tagging uses a special pulse sequence to create temporary features – tags in the myocardium. Tags deform together with the myocardium as the heart beats and are captured by MR imaging. Analysis of the motion of the tag features in many images taken from different orientations and at different times can be used to track material points in the myocardium. Tagged MRI is widely used to develop and refine models of normal and abnormal myocardial motion to better understand the correlation of coronary artery disease with myocardial motion abnormalities and the effects of treatment after myocardial infarction.
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