This tutorial will demonstrate how you can use EP Workbench to generate biatrial models with fibrosis from corresponding left and right atrial segmentations.
The tutorial makes use of the Atrial Modelling Toolkit for Constructing Bilayer and Volumetric Atrial Models at Scale ((GitHub - pcmlab/atrialmtk: Atrial Modelling Toolkit)).
Please also see the following papers for more details
Predicting Atrial Fibrillation Recurrence by Combining Population Data and Virtual Cohorts of Patient-Specific Left Atrial Models
Constructing bilayer and volumetric atrial models at scale
Load the MaxScar VTK files for the Left and Right atria into EP workbench
Vein Clipping
Use the Geodesic cutter to clip the pulmonary veins for the left atrium.
Use the geodesic cutter to clip the superior vena cava, inferior vena cava and coronary sinus for the right atrium.
Export these files as OpenEP files
Landmark selection
Select landmarks on the left atrium as shown in the figure and table below.
| s1 Ridge of the RUPV | r1 Between the appendage and below the Left PVs |
| s2 Ridge of the RLPV | r2 Between Right PVs and mitral valve, 1/3 distance, closer to the veins |
| s3 Ridge of the LLPV | r3 and r4 on the line between the upper PVs, r3 on the left, r4 on the right |
| s4 Ridge of the LUPV | |
| s5 Tip of the left atrial appendage | |
| s6 Between the left atrial appendage and the mitral valve |
Select landmarks on the right atrium as shown in the figure and table below.
| s1 Anterior SVC | r1 IVC, very close to s2, close to the orifice |
| s2 Posterior IVC | r2 – Roof of the CS |
| s3 Halfway between s1 and the tip of the appendage, very close to appendage base | r3 – Posterior wall, halfway between SVC and IVC, middle between s5 and s6 |
| s4 Floor of the RA | r4 – SVC; near where crista terminalis ends |
| s5 SVC on the line between IVC and SVC | r5 – Tip of the appendage |
| s6 IVC – other end of the IVC-SVC line | r6 – Anterior base of the appendage |
Save these files as OpenEP files.
Creating bilayer models
Next use the uac_fibrebilayer WIP to create bilayer models for the left and right atrium.
For the left atrium make sure to select case_1 as your left atrium. Make sure to also select the left atrium next to the word atria. These steps are highlighted with green arrows in the figure below where 0 is the left atrium. Then press the play button.
Next create your right atrium bilayer model. Make sure case_1 is configured your right atrium (1 in the image below) and also change the atria to right (green arrows).
At the end you can switch to the systems Tab. You should now see uac, fibre and bilayer models for both the left and right atria.
You can also see the cell regions by clicking Field>Cell Region. Make sure to change the colour bar limits to either 0-10 or 0-30 to visualise the cell regions. You can also click Tools>>Region selector to see the “N cells values” for the left and right atria as shown below. An example of this for the right atrium is shown below.
Save both the bilayer files as OpenEP files.
Generating biatrial models
Next use the generatingbiatrialmodels WIP to create a biatrial model. Case_1 should be your left atrial bilayer model and case_2 should be your right atrial bilayer model. The image below shows an example of this where 0_bilayer (selected as case_1) is the left atrial model and 1_bilayer (selected as case_2) is the right atrial model. Press play to run this. This step can take some time to complete.
The below image shows the biatrial model and its corresponding cell regions. The reason for the colours being different is because the colour bar limits have now been set to 30.
Save the biatrial model as an OpenEP file
Fibrosis projection
Use the fibrosisprojection WIP to project fibrosis onto the models. Select case_1 as your biatrial model. Select the appropriate Mean_blood_pool_signal_intensity. Then press run. The system will prompt you to select your LA and RA MaxScar.vtk files
Once completed, you can visualise your biatrial model with fibrosis. Select the biatrial_fibrosis model in the systems Tab. Make sure to deselect all of the other models from the systems Tab. Set the colour bar limits of cell region to be 0-50. An example is shown below.
As you can see this now has an additional Regional ID. The areas of fibrosis are shown in blue.
Export this as OpenEP file.