Cardiac Segmental Analysis - Defining the Endo- and Epi-Cardial Borders

The endo- and epi-cardial borders of the left ventricle must be defined on every image time point and on every image slice that you want to analyse. You would normally use closed Spline ROIs to define the borders, but you can also use Irregular ROIs. Note that as soon as you have defined two ROIs, where one ROI is contained within the other, you will see the cardiac segments superimposed on the myocardium. The position of the radial dividing lines is determined by the insertion point handle The handle indicating the segment insertion point. The different myocardial segments are numbered increasing clockwise from the insertion point handle.

Cardiac segment numbering is increasing clockwise from the insertion point handle
Cardiac segment numbering - clockwise from the insertion point handle.

You can drag the insertion point handle so that the first segment is in the position you want.
Drag the insertion point handle so that the first myocardial segment is in the position you want.
Myocardial segments starting at the posterior margin of the RV Myocardial segments starting at the anterior margin of the RV
Posterior insertion point Anterior insertion point
Note: the insertion point handle position changes in the same way across all time points of the image, but can be varied across the different slice locations.

There are two ways to create ROIs at all time-points:

  1. Automatic propagation, with correction if needed. You should try this if the shape of the myocardium changes across the time-points (i.e., the images are part of a time-series through the cardiac cycle). Typically, this is done for strain analysis.
  2. Copying with manual correction. You should do this if the shape of the myocardium does not change much across the time-points (i.e., the images are acquired at the same point in the cardiac cycle). Typically, this is done for perfusion analysis.

Automatic Propagation

Do this when the shape of the myocardum varies across time points, because the images are acquired at different points in the cardiac cycle. Manually define the endo- and epi-cardial borders at one or more time-points, for example at the start of the cardiac cycle, at end-systole and at end-diastole. Then press the Button to automatically propagate the myocardial borders across time-points button.

Inspect the myocardial borders at all time-points by paging through the image slices. If the borders are not satisfactory, you have 2 options:

  1. Press the Button to undo the automatic propagation of the myocardial border button. This will undo the propagation, allowing you to manually define the myocardial borders at more time-points (especially at the time-points where the propagation fails badly). Then press the Button to automatically propagate the myocardial borders across time-points button again to redo the propagation.

  2. Manually correct the myocardial borders at any time-point where the propagation is unsatisfactory by dragging the reshape handles for the ROIs.

Copying Across Time-Points

If the shape does not vary much, because the images are acquired at the same point in the cardiac cycle, then you can:
  1. Define the endo- and epi-cardial borders at one typical time point.
  2. Propagate these ROIs through all the time points.
  3. Make any adjustments you need to account for changes in position of the heart or different triggering.

To get started, choose a 'typical' image time-point. Define the endo- and epi-cardial borders using two regions of interest, using closed Spline ROIs. If the contrast varies thought the time time-series, you are recommended to choose a time-point with good contrast so that the borders can be clearly delineated. In the picture below, from a cardiac perfusion series, we have chosen a time point where the contrast agent is visible in the left ventricle.

Endo- and epi-cardial borders on an MRI perfusion image
Endo- and epi-cardial borders on an MRI perfusion image.

Propagating the Endo- and Epi-Cardial Borders

When you are happy with the ROIs defining the borders, you can press the: Note: in order to copy the ROIs to the different time points, you must have a slice selected, otherwise Jim will not know from which time point you want to copy the regions.

Having copied the ROIs forwards or backwards, you can then page through the time points, making any adjustments needed to the position and shape of the ROIs.

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