Hi Anastasia!

That makes sense, thank you! So the question is how do I evaluate the noisiness of a path?

1) Most of my isosurfaces look a lot noisier than your example on the wiki. There's obviously no hard and fast rule here but is there any way to gauge the noisiness of a reconstructed path? And can that information be used for quality control?

2) Another source of information on outliers is the log files that are produced when running -trac-all -stat (based on the shape of the tract). It doesn't seem to flag tracts that are (almost) completely missing (which are spotted by visual inspection in Freeview) - but they may fall under the minimum threshold and therefore not be evaluated? Would you recommend automatically excluding the subjects that are flagged as outliers here?

Hi Lars - A path with fewer control points will generally be smoother. So

if the tract is pretty much a straight line, you might get a noisier result if you increase the number of control points. But if the tract is more convoluted than a straight line, then you need more control points to define it accurately. So it's hard to predict the result of increasing the control points in general, it depends on the specific case.

BTW, if you change the number of control points, you don't need to use the reinit variable - that's only for rerunning with the same control points as before.

Best, a.y

sincerely yours,

Lars M. Rimol, PhD Senior researcher, Norwegian Advisory Unit for functional MRI Department of Radiology, St. Olav's University hospital, 7006 Trondheim, Norway