Automated myelin annotation tool questions

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Hi Microns team,

I am currently using the automated myelin annotations, included in the most recent release, to estimate the amount of myelin present on fully extended axons. Using the myelin quantification methods generated by Gamlin et al 2025, I've encountered some unexpected values derived from these annotations.

A small subset of fully extended axons have more total myelin length than axon length, see examples below.

pt_root_id	axon_path_length_um	sum_sheath_um
864691135741655956	9854.10	162472.69
864691135118918109	10024.68	164995.78
864691135114295961	6734.73	109288.52
864691134886037498	16657.22	268364.24
864691135082864887	11892.34	189976.37
864691135066631492	11091.93	175369.10
864691134965778719	6717.52	103893.37
864691135409859785	10054.65	154407.81
864691135118298333	8382.66	126722.58
864691134887270650	11847.25	177253.62
864691136579919892	9684.50	138278.69
864691135375767369	6822.09	93702.23
864691136335553971	6775.12	92932.79
864691136619529179	7230.41	54893.46

Calculating the minimum and maximum sheath length for many full extended axons results in some what implausible sheath length values. I've copied some examples below:

pt_root_id	mean_sheath_um	min_sheath_um	max_sheath_um
864691135741655956	30.91	0.40	114.45
864691135118918109	30.97	1.96	126.60
864691135114295961	30.95	2.96	134.15
864691134886037498	29.08	1.14	139.63
864691135082864887	29.52	0.46	133.34
864691136664845278	1.57	1.57	1.57
864691135387529301	32.28	7.99	69.38

Do you have suggestions for how to best correct/improve these calculations?

It is also possible I am misunderstanding the myelin status designations in the myelin_auto_tags_2points table. How do the combination of true/false tags correspond to the presence or absence of a sheath? What would a pt_position = true and a pt2_position = false represent (or the inverse) for a myelin sheath?

Thanks for your help!

Start with the automated myelin annotations and the myelin_auto_tags_2points table, using the supplied pt_root_id examples to reproduce the total, minimum, and maximum sheath-length results. Determine how the true/false pt_position and pt2_position combinations map to sheath presence, then compare that interpretation with the reported calculations. Done means the calculation or tag interpretation is explained and a concrete correction is identified.

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