Table 2.

Relationship of past work to our approach. The abbreviations of imaging modalities refer to scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray micro-computed tomography (μCT), and selective plane illumination microscopy (mSPIM)

Past Work	Relationship to our approach
Co-localization detection	Co-localization detection
• Spatial image cross-correlation spectroscopy (ICCS) [1–4] - Pearson, Spearman’s rank.	• ICCS is not applicable since it does not capture spatial information.
	• Replaced manual segmentation with automated object-based analysis.
• Object-based analysis [35] with manual segmentation.
Foreground modeling	Foreground modeling
• Statistical: scatterplot of two channel intensities [4] with a single model.	• Statistical: used scatterplot with optimization over multiple statistical models.
• Geometrical: fiber segmentation based on many software packages including IvanTK, NeuronJ, Simple Neurite Tracer, Vaa3D, and Vascular Modelling Toolkit (VMTK).	• Geometrical: could not use existing software designed for vascular or brain structures (not fiber scaffolds), and some software worked only in 2D and required manual identification of end points.
Validation of 3D Segmentation	Validation of 3D Segmentation
• Manual reference [36–41].	• Manual reference is hard to create for 3D objects.
• Orthogonal measurements using μCT, SEM and CLSM [42], and mSPIM [43].	• Used orthogonal measurements of a single fiber imaged via multi-view 2D SEM and 3D CLSM.
Visual verification of 3D contacts at large scale	Visual verification of 3D contacts at large scale
• Not aware of any previous work.	• We designed a web system with three orthogonal max projections and 6 animated movies per contact.