Scaling the PIPER child model by age

This small module is designed to work with the PIPER child model.

It allows to scale the anthropometric dimensions of the PIPER child model between 1.5 and 6 Y.O. (and beyond but without any check on the performance of the scaled model). The dimensions of the model are derived from GEBOD regressions and expanded below 2 Y.O. using published Candat data. There are also some controls on the shape of the vertebrae. Note also the option to scale the material properties of the model with age. This option is currently experimental and should not be used prior to additional testing.

The module is straightforward to use:

• Open the Anthropo Module.
• Load the PIPER child model that you received together with the PIPER application.
• Click on "PIPER-child scaling" in the right menu, the Child scaling GUI will appear.
• Choose the "Child_scaling" set of control points in the combobox.
• Check the "Preview" checkbox.
• Choose the target age using either the slider or the arrows next to the number of months, or move the second slider to select the desired height (in mm). Whenever you set a new target, you should see the red preview of what the model will look like.
• Click Apply to get the scaled model. Note: Nugget settings affect this deformation as well

Child scaling GUI

Remarks

• The scaling is done using the kriging method implemented within piper, but the target control points for this transformation are obtained by using a custom octave script tailored specifically for this model to ensure appropriate behaviour (located in share/octave/ChildScaling). PIPER only sends a set of input parameters and name of the output file it will expect upon the scripts termination as arguments to the script. Then the script is invoked and afterwards, the output file with control points is loaded into PIPER. This allows simple integration of model specific personalization scripts.
• For the material scaling, a python script (child_scaling_parameters.py) is used to provide the values of the material parameters which are to be modified by the parameter module .
• This script was integrated as is for historical reasons but it for a new implementation with another model, it could be preferable to use a single python script to update the model, or to use an anthropometric model.