the possibility for import a stent model inside a vessel in Simvascular

[jianfei song]

Dear Simvascular developers,
Firstly thanks so much for your great help to every questions.
I run the vessel model example, and then changed the constant flowrate to a pulsatile one.and got the pressure .txt. but the periodic pressure range is: 12-200mmHg which is not a normal pressure range for a person. So will it be a tough process to adjust the outlet? now for the two outlets BCs i choose are the same:resistance:2000. i should adjust the resistance value or need to choose another BC such as: RCR? the inlet flowrate i will attach it.

inletflowrate.JPG (24.33 KiB) Viewed 720 times

Also i want to know if it is possible to import a stent model form solidwork or other softwares to Simvascular. so i can manage a vessel simulation with a stent inside.
Thanks so much.

[Justin Tran]

Hi Jianfei,

For your first question, yes you will have to adjust the outlet boundary conditions in order to achieve the pressures your desire. Since you have a flow rate that you are specifying at the inlet, the parameters of the outlets will need to be adjusted in order to adjust the pressure. RCR would definitely be a good place to start. I like to think of the effects of the individual components of the RCR when tuning my boundary conditions. Resistances are responsible for modulating the mean pressure. So increasing the resistances will cause a vertical shift in your outlet pressure waveform. Capacitances affect the peak-to-peak amplitude of the pressure wave. Since you are having very large peak-to-peak amplitudes, the compliance from the RCR should help immensely. Unfortunately, tuning to a specific value of C is often difficult in practice especially for complex models. We outline general principles for choosing RCR values in our coronary normal example: http://simvascular.github.io/clinicalCase3.html. Look under the section "Aortic outflow boundary condition". Based on the expected mean and peak-to-peak pressure amplitudes you can compute good starting point values for your R and C, then adjust them from there.

For your second question, yes you can import models from SolidWorks by using the .stl file format. From SolidWorks, save your model as an .stl then import it into SimVascular.

[jianfei song]

Thanks so much for your reply.
And i tried with the RCR BC.now i fix the value of RCR(for the both oulets):600 0.00015 6000. i can get the pressure range:inlet:78-153mmHg, outlet1:79-105mmHg, outlet2:80-112mmHg.we can see the outlet pressures are in the normal range,but the range of inlet pressure is alwayse larger. so if it's possible to adjust the inlet pressure further. if it's possible which value i need to change further.
Thanks so much.

[Justin Tran]

Hi Jianfei,

Glad to hear that your pressures are in a better range. What does the pressure distribution look like when pressure is maximum in your 3D model (i.e. can you open up the all_results.vtp in Paraview and take a screenshot of the pressure distribution)? Having your inlet at 158mmHg and your outlets at ~110mmHg is quite a large pressure drop and it appears you have a tight stenosis in your model that would drive such a large pressure drop. Also, how many elements are in your mesh?

[jianfei song]

Hi,thanks so much for your quick reply.
There screenshot of the pressure distribution is attached when the pressure is maximum.and the mesh element is about 70000.

pressure.jpg (33.35 KiB) Viewed 699 times

Thanks so much.

[Justin Tran]

Hi Jianfei,

Thanks for sending the results. It looks like your mesh resolution is a bit low, as I see the pressure distribution is not as smooth as I usually expect it to be. I would re-run it with at least 250k elements and see if the results improve.

Also, since you are running a pulsatile simulation, we recommend that you run the simulation for six complete cycles then post-process just the final cycle. This is to ensure the initial conditions are not affecting the results of the simulation. This is especially important for deformable wall simulations or RCR boundary conditions, as it usually takes several cycles for the model and capacitances to fill to their steady state values.