Methods

 

1) Scanning of the limb :

Main steps : 

1. Install two applications on an iOs device (e.g. iPad, iPhone) to perform the 3D scanning : Structure Sensor Calibrator and Structure App.
2. Scan the limb
3. Then insert the scan on MeshMixer and follow step 2).

 

                  1 ) The 3D scanning setup we used for the forearm prototype :

We connected the Structure Sensor 3 to an iPhone 13 (see setup below). We also had to download two applications to make de 3D scanning : 

• Structure Sensor Calibrator : Precisely align 3D depth from your Structure Sensor accessory to your iOS device's camera.
• Structure App: Supports original Structure Sensor (Structure Sensor 3).

   

 

                   2 ) The 3D scanning setup we used for the leg prototype :

We used the HandySCAN which offers high-precision measurements and was more easy to use compared to the Structure Sensor. An M2 intern at the IBHGC helped us with the scan.
 

       

Picture 1 : Setup in the storing suitcase.
Picture 2 : Calibration of the HandySCAN by Christelle (M2 intern).
Picture 3 : 3D-scanning of Dominique's leg by Lina.
Picture 4 : 3D-scanning in progress.
 

2) Forearm & leg socket design :

                   1) Steps to follow on Autodesk Meshmixer :

1. Clean the scan. We followed this tutorial.
2. Not mandatory but may be necessary to adjust scales : select Actions > Units > and then for the x value remove the comma and the zero to keep an integer, then click on the y value, then the y and z values ​​change automatically. Do not edit the x, y and z values.
3. Create the socket. We followed this tutorial.
4. Convert the body to a solid: select the body, click on Convert > Convert to solid part > Change “No preferences” to “Boolean union”, then click on Edit > make a solid. Press "w" to see the mesh.
5. Export to STL file.
    

                  2) Steps to follow on Autodesk Fusion 360 :

     6. Import STL file into Fusion 360. Convert the STL file to part, to make the file easy to work on Fusion 360. We followed this tutorial.
     7. To cut the socket in half on Fusion 360: create a sketch, create a rectangle, then click on “Solid” > “Extrude” > set the Distance at 2mm symmetrically and set Operation > Cut then click on Ok.
    8. Create rectangular prisms to make the screws holders : Create a sketch, then do a rectangle and extrude it to make a rectangular prism. Then place it on the socket. Copy the rectangular prism and put it on the other side, symmetrically (see picture below).

 

    9. Create holes and threadings following this tutorial. In our case, we used M6 screws, so the whole has a diameter of 7mm.
  10. Create nuts on one of the two holes by creating a sketch (polygon) on one of the two faces of the screws holders. Do an extrusion (=cut) of 5mm. Length between two edges : 10 mm.
 

3) Design of the custom-made case for the probe :

1. Scan the probe with the Structure Sensor. Finally, we fortunately had the CAD file of the ultrasound probe which eased a lot our work, as scanning the probe with either the HandySCAN or the Structure Sensor was very difficult. 
2. Follow steps 2.1 and 2.2.
3. Include the probe socket in the fusion file of the limb socket and merge them together.

How to do a good probe positionning on the socket ?

The correct probe position is determined by visually optimizing the contrast between the socket, liner, skin, and residual bone within the ultrasound image. If the residual bone movement is (repeatedly) lost from the ultrasound images during the different tasks : change ultrasound probe positioning. Therefore, the gap has to be created as much distal as possible, while still allowing a perpendicular orientation of the probe relative to the residual bone (Jonkergouw et al., 2024).

 

4) Check the design on Ultimaker Cura before 3D printing :

 

 1. Upload the STL file to the 3D printing software (Ultimaker Cura).
 2. Perform the slicing and set the appropriate parameters.
 

5) 3D print the design :

We used the 3D printer Ultimaker S5.
 

6) Ultrasound video acquisition :

 

1. Download the app “Vscan Air Wireless Ultrasound” on your phone.
2. Turn on the ultrasound probe and connect it to your phone using the app.
3. Load the probe within the probe case and don the socket.
4. Screen record the ultrasound video

 

7) Ultrasound video post-processing :

 

1. Download the video on this opensource software to remove the icons on the video.
2. Download the .mp4 video.
3. Convert the .mp4 video to a .avi video format.

 

8) Ultrasound video analysis on MATLAB.