I designed a simplified 3d model of a nasal cavity (just one side) to test different scenarios such as adding an implant. You can see that I grouped the superior turbinate and the middle turbinate in order to simplify the model. I need a simple model because it is better to make future geometry change.
The model is simpler but it respects the cross-sectional area of my real nasal cavity, you can see my post about the cross-sectional area measurements that I have written here. Also as you can see it simulates a pretty large inferior turbinectomy and a total turbinectomy in the middle section area. For the flow I took 7.5l/min, it is the respiratory flow at rest. Here are the first results I get...
The airflow in the area of the absent inferior turbinate swirls and is very slow (less than 0.6m/s) unlike the airflow in the area of the middle turbinate (about 3m/s). This is not very surprising, it can be seen in quite a few CFD studies on empty nose syndrome. The speed values also match which means that my 3d model and the flow rate value taken are pretty accurate.
In the coronal section view, we can see that the velocity is higher between the middle turbinate and the septum but also in the zone at the bottom of the middle turbinate.
Now what I can say about these results is that too low airflow velocity greatly reduces sensations in the area of the absent inferior turbinate (inferior meatus). This is one of the big problems of the ENS.
In future articles, I will simulate an implant in the inferior meatus zone to see the change in airflow.
Now that we have seen how to 3d print the nasal cavity in slices we need parts to stack/de-stack easily the slices. So I have designed parts called "slices holders" which will be also been 3d printed in plastic. The slices will be glued to the "slices holders"
I I'll take pictures of the set when it's made ...
Go to https://www.prusa3d.com/, click on software and select your OS. Install the prusa slicer.
This software is a "slicer", it is used to prepare the 3d model to be 3d printed, to transform the STL file into a G-code readable for the 3d printer.
But in our case, we will just use this software to edit the 3d model. But of course, if you have a prusa 3d printer you will also use this software to 3d print the slices.
So open the .STL file that you have just saved with SLICER.
Click on file, then import STL/OBJ etc ...
Click on rotate and turn the model 90° to put it vertically.
Once it done click on cut and set the thickness you want, I set 10 mm.
Finally click on perform cut.
You will obtain that.
Now select the model and cut a slice again, organize the slices as you want but it is better to do it in the cut order.
Right click on each slices one by one and export as STL.
And that's it, now you have all the slices ready to be 3d printed where you want.
You can find a friend or a member of your familly which have a 3d printer or use an onlise service like shapeways or sculpteo for example.
An example of a 3d printed nasal cavity.
In this tutorial, I will explain how to turn your DICOM data pulled from your CT-SCAN into a 3d printable file.
Go to https://www.slicer.org/ download the software and install it.
Open it and click on import DICOM files, search the directory of your DICOM files and click on import.
Click on show DICOM database, click on your name and finally double click on the slices you are interested in, here sinus. The slices will load.
Now click on the scrolling menu and choose volume rendering.
Click on display ROI, white lines will appear.
You can click on the white dot next to Volume, your head will appear in 3d. But it is optional.
You also can select a preset, here I choose lung, like that you can see inside the nasal cavity.
Now crop the desired zone using the color dot.
When you are happy with your cropped zone click on the little magnifying glass, then write crop, click on crop volume and finally switch to module. After that click on the apply button. Wait a moment it can take a while.
Now return to the Volume rendering worshop and click on display ROI in order to hide white lines
Once it's done, click again on the little magnifying glass and write editor, then click on switch to module.
A little window will appear, click OK.
Click on the threshold effect button.
The slices will turn green, now you need to adjust the left cursor in order to paint all your soft tissues green.
I found that generally the good numbers are between -200 and -400 but it may depend on CT-SCAN.
Finally, click ok the apply button.
It's almost over, we've done the biggest part.
Now click on data in the menu.
Right-click on your "name files" cropped-label and click on Convert labelmap to segmentation mode.
A line tissue will appear, again right-click on it and Export visible segment to models.
Wait a moment, it can take a while, a line cropped-label-segmentation-models will appear and also your 3d model on the right window.
Click on file, then save or ctrl + s.
In the window, uncheck all boxes except tissue.
Click on Poly data (.vtk) and choose .STL.
Click on change directory for selected files and choose a directory you want to save the 3d model file.
Finally click on save and voila, well done !
This .STL file is a 3d file that can be used to 3d print the model directly, but as you can imagine it is not useful to 3d print the model in this state, we will see nothing. We need to see inside the nasal cavity.
That is why in the next tutorial I will explain how to cut the model into slices in order to see inside. The slices will be stackable.
The first one is hydrolized collagen, some studies tend to prove that it can improve skin health, hydration, thickness etc ... Exemple this study. Hydrolyzed collagen is a type of collagen with low molecular weight in order to be better absorbed by the body and reach the skin and other organs. So I ask myself if this product can help skin, maybe it can help the mucosa too because mucosa is made of collagen. So I took 5g/day for two months which is a dosage often seen in the studies. After one week I noticed some skin improvement, a little smoother, but no airflow sensation improvement. I cannot say if my mucosa was better after the two months or not but I can say that I feel no difference in sensation and hydration.
The second one is Hyaluronic Acid, yes the same thing that can be injected into our turbinates or lateral wall in order to regrow it temporarily. Oral HA supplementation seems to also improve skin health, hydration, thickness, reduce wrinkles etc ... Again, some studies tend to prove that, but there are small studies. The common dosage seems to be between 120 mg/day. I have not yet tried this product but maybe it is worth a try...
I try to know how to rebuild the nasal cavity after an inferior turbinectomy, where to add volume in priority ?
Some ENTs think that the head of the turbinates is the most important because it is where it's easiest to add resistance. And they often think that nasal resistance is the most important parameter in the ENS.
In this study, Dr Nayak and others researchers/doctors prove that it is possible to reduce significantly the symptoms of ENS without adding resistance. He implanted cartilage in the inferior meatus (the place of the inferior turbinate) and they have seen with CFD that the airflow is better redistributed between middle meatus and inferior meatus.
This other study shows that without inferior turbinate the most part of the airflow is redirected in the middle turbinate compared to healthy subjects. And they found a correlation between peak wall shear stress in the inferior meatus and airflow feeling sensation. Peak wall shear stress is the quantity of friction of air on the mucosa.
What we can say with all of this data? I think that it is useless and may be harmful to just add volume to the beginning of the nasal cavity ( head of turbinates) because that will increase wall shear stress just at the beginning of the nasal cavity and not all along. And that will not solve the redistribution airflow problem. Without adding volume all along the inferior meatus the airflow will stay in the middle meatus and the sensation will remain bad.
The solution is to rebuild the nasal cavity like before turbinectomy, with the same distribution of the volume. It can be with adding volume in the remaining inferior turbinate if it is possible or adding cartilage on the lateral wall. But you have understood it is very important to add volume not just at the beginning of the nasal cavity but all along like a healthy nose. In the graph below, we can see that a healthy nose has a stable cross-sectional area all along the nasal cavity, but of course, it is not the case with an inferior turbinectomy. The reconstruction of the nasal cavity must tend towards these values.
In this post, I would like to see which place is the best for an implant in my left nasal cavity. On this side, there is a remaining inferior turbinate. So I would like to know if it is better to implant cartilage on a lateral wall or if an implant in the turbinate is a better thing to do.
We can see on the graph below that implant in the lateral wall (blue) doesn't increase the surface of the mucosa but it reduces the section of emptiness. On the contrary implant in the remaining turbinate increases a little bit the surface of the mucosa by 3,5% and reduce the emptiness too. Ok, 3,5% is not so much but maybe it can make the difference.
So it seems that increasing the volume of the remaining turbinate is a better solution than putting an implant in the lateral wall. However, I know that it is more difficult to do it and maybe more risky too.
In this post, I will try to find which implant shape is the best to get closer to the natural turbinate. Special thanks to Andrea Magelli to give me this idea.
Below it is my case of my right nasale cavity before turbinectomy (yellow), after turbinectomy (green), after my cartilage implant (blue), and after a virtual implant (red). We can see that the implant is placed on the lateral wall, it is often placed like that. On the graph below we can see that the implant reduces the emptiness, the value of the section in mm² is almost equal than before turbinectomy. So it seems good, but why many of us are not better after an implant like that ? One of the reasons is I think the quantity of the mucosa. In the second graph, you can see that the implant has not increased the surface of the mucosa, there is not more mucosa than before. In the graph I name that perimeter because it is a slide of the CT-SCAN so we are in a 2D view.
So the idea is to place several demi cylinders in order to increase the surface of the mucosa. Why demi cylinder?