ECV evaluation

This application serves for evaluation of ECV (extra cellular volume). The values of ECV are computed based on the T1 relaxation times in six sections of the myocardium. This application requires two maps of T1 times generated from two MOLLI sequences acquired in different times and at least one representative image from each of the MOLLI sequences. The representative images are used to estimate the deformation between sequences. After applying the deformation to the T1 maps, the value of ECV can be reliably estimated in all sections of the myocardium.

Segmentation

The first step in the estimation of the deformation between sequences is the segmentation of the myocardium in both representative images. The working window has two parts - one for each sequence. The image on the left part of the window will be referred as the source image, the one on the right side as the target image. When the chosen image is displayed, its brightness and contrast can be adjusted using the color scale under the image. (This change will effect only the visualization of the image).

In order to start the segmentation, it is required to set the center of initial ring, it‘s inner and outer radius. The ring should be positioned so that the myocardium lies between the outer and inner circle of the ring. These parameters can be set by clicking in the displayed image. Every time the parameters are changed, updated ring is displayed in the image. The point chosen to set the outer radius also determines the position of the first sector as it is illustrated in the following figure.

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Another two parameters, that can be adjusted to improve the segmentation, are K1 and K2. These values effect the sensitivity to change of the image intensity during the detection of outer and inner boundaries of the myocardium. For images with higher contrast, the default value can be decreased. For images with similar intensity of myocardium and it‘s surrounding, the value should be increased. Example of such setting can be seen in the following picture.

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When the outcome of the segmentation process is not sufficient, the parameters can be modified or set to zero by the ‚Reset‘ button.

ECV evaluation and visualization of the transformed map

When the myocardium is segmented in both representative images, as can be seen in the following figure, following operations are available:

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Registration (T1s -> T1s)

ECV (source -> target)

If more suitable, the inverse operations can be done:

Registration (T1t -> T1t)

ECV (target -> source)

The following figure shows the transformed source T1 map, the target image with colored sections and the values of ECV in these sectors.

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