3D Speckle-Tracking: Sub-voxel Techniques and Tracking Accuracy
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Speckle tracking is a method that is useful for examining myocardial function. The method allows the cardiologist examine the left ventricular wall function when there are indications of a myocardial infarction. The method is well developed and in diagnostic use for 2D cardiac ultrasound imaging. Different techniques for sub sample interpolation is investigated and tested. Sub sample methods can be useful due to the fact that they allow the tracking algorithm to track smaller displacements. The assessment is based on four dimensional ultrasound images of a tissue phantom, with time being the fourth dimension. Tracking in 3D ultrasound images is useful for being able to track those points in a 2D ultrasound image that moves in and out of the 2D imaging plane during a heart cycle. Good tracking in several dimensions demands good resolution ultrasound images. The resolution needs to be sufficiently good in both lateral and axial directions. This is needed to be able to track in sub pixel distances. To accomplish this, one needs to find techniques for sub pixel resolution and to find how these affects the quality of the sampling. The results indicate that interpolation improve the tracking accuracy. This is consistent for all the different interpolation methods, but not for the different depths in the ultrasound images nor for the different ultrasound images.