= SNT
{disambiguate=neuroanatomy software}
{c}
= SNT
{c}
{synonym}
<SNT> is an <ImageJ> framework for tracing, displaying and quantitatively analyzing branching structures in multidimensional images. It provides editing and automated tracing tools as well as a scripting interface. Its computational components also support filamentous structures outside the package's original application domain.<SNT in the ImageJ documentation>[Overview, scripting support and general filamentous-structure applicability]{ref}
A trace encodes connected sample points rather than merely an image of a bright line. For an original geometric example, take successive physical coordinates $(0,0,0)$, $(3,0,0)$ and $(3,4,0)$ in micrometres. The trace's length is the sum of its two <line segment> lengths,
$$
L=3+4=7\,\mathrm{\mu m},
$$
whereas the endpoint <Euclidean distance> is $d=\sqrt{3^2+4^2}=5\,\mathrm{\mu m}$. The ratio $d/L=5/7\simeq0.714$ distinguishes a bent trace from a straight one with the same endpoints. SNT's metrics documentation defines path/branch length through internode distances and branch contraction through this endpoint-distance-to-path-length ratio.<SNT in the ImageJ documentation>[Metrics, Path length, Branch length and Branch contraction]{ref}
Those calculations require calibrated coordinates and the intended connectivity. Rescaling image axes changes lengths; connecting the wrong endpoints changes the traced object. The framework's <Sholl analysis> is a different summary: it produces a <Sholl profile> of radial intersections. The fact that <a Sholl profile does not determine rooted tree topology> explains why a profile cannot replace the connected trace when the question concerns its branching structure. This example concerns software data and geometry, not measured anatomy.
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