Tagged Image Processing

For motion analysis from an image, ideally we would like to relate every image point y in the LV myocardium to its reference position p(y, t). For strain calculation, we would like to determine F(p(y, t), t). Such calculations are, however, not possible for a single image, even with tagging. Instead, we are only able to make partial measurements of motion, and those measurements are often only available for certain points within the myocardium. Some of the measurements made are as follows:

• From the brightness pattern in the image, we may estimate f0(p(y, t)), the value of the original tag pattern for the material point now located at image position y.

• Given that estimate and the known initial tag pattern (4), we may then estimate gTp(y, t), which gives us the component of p(y, t) in the direction of g.

• Using two different values of g for one image gives us two components of motion, so that we may estimate q(y, t), the 2D reference map of the apparent motion

• We may also determine partial information regarding F such as one or more of its nine components.

Given these partial measurements for many images with several tag directions, we can then assemble an estimate of the complete motion, the subject of the next section. In this section, we concern ourselves with defining what measurements are made and the innovative methods for making the measurements.

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