Hello, thank you very much @hwangeric for the replies and for the help. I tried the 1.43 version of imageJ, but on this version, the plugin does not work.
Using the 1.50 version, I can run the plugin, and the tracings are quite good as you can see the image attached:
I cannot understand the final measurements: they are all very similar despite very different tracings, and to me they seem too much high.
Analysing the same image with the interactive version, I have this results (and they seem realiable):
I followed the manual and I don't know where I'm wrong....
Thank you again for the help!