Moment of inertia/slice geometry analysis

bonej
Tags: #<Tag:0x00007fd5401e74a0>

#1

Hi! I am looking for help to run moment of inertia analysis. I have cortical 2D slices microCT images from mice femur and I want to know their bending capacity. Do I need the whole femur midshaft image or could I perform the analysis with the cortical 2D slice images?

So far, I have done was change the image type (because the background is blue), crop the image and I have selected slice geometry analysis.

Could you please help me with that?

Thank you!


#2

Sounds like you have second moment of area and moment of inertia confused.

Second moment of area is calculated from 2D cross-sections and (assuming that the neutral plane of bending = principal axis) relates to resistance of the member to bending. Use BoneJ’s Slice Geometry plugin, which can take as input a 2D image or image stack (3D - series of 2D images).

Moment of inertia is calculated from 3D pixel data and relates to the acceleration of a freely floating body under an applied torque. It’s mostly helpful in a bone morphology context to examine the distribution of bone mass around a bone’s centroid, and to align bones’ principal axes to the image axes. Use BoneJ’s Moments of Inertia plugin to do this.


#3

Thank you!

One more question, my cortical microCT images have a blue background, should I turn them into a binary image before the analysis in bone j?


#4

Both plugins will refuse to run if the data are not greyscale pixels. They will work on 8-bit and 16-bit (& maybe 32-bit), and binary images. If the ‘blue’ is just a LUT, then you don’t have to do any conversion, but, you do have to select appropriate threshold values to tell the algorithms which pixels to use or exclude. If your XMT images have somehow been converted to RGB then go back to your original scans and start again.