BoneJ: TbTh and Tb Sp values

Hi, am new user of BoneJ,
When analysing Stratec images with BoneJ, the Thickness pluging give high values of TbTh (.6 to 12 mm !!). The mean values observed in other devices are in a range of 50 to 400 µm. Is it the soft or the device ?? Do we need to make any conversion?
Another request, the resuts of pQCT Distribution analysis (soft tissue) give sometimes negative values for SubCutFat density: is it correct?
Thanks for your answer and advises if needed for corrections.

I’m going to ping @mdoube on this one… any thoughts on this one?!

eta :slight_smile:

Stratec images typically have pretty low resolution, and can’t reliably be used to segment trabeculae into the binary images that Thickness needs because the pixel size is close to or larger than trabecular thickness (Tb.Th). It’s giving you a result but the input image is probably inappropriate to measure Tb.Th and Tb.Sp. You might have enough resolution to measure cortical thickness, however, provided that you generate binarised images containing only cortex in the foreground. In this case you can measure “trabecular thickness” but your “trabecula” represented by Tb.Th numbers is actually the cortex.

Presumably negative results for SubCutFat density are incorrect, because that would require one of mass or volume to be negative. @tjrantal may be able to comment further.

Thanks for these comments. I also guess that quality of image is a cause.