= Scaffold pore connectivity
<Scaffold pore connectivity> describes how void spaces in a <tissue-engineering scaffold> communicate with one another and with the exterior. It affects which regions are accessible to fluid, transported substances and migrating <cells>. <Porosity> gives the amount of void space, whereas connectivity describes its arrangement. Two scaffolds with the same <porosity> can contain either communicating channels or isolated cavities.
A useful idealization represents pores as vertices of a <graph> and communicating throats as edges. Label the pores reached from an inlet by <flood fill> or another graph traversal. One explicitly defined accessibility measure is
$$
C_{\mathrm{in}}=\frac{\text{void volume connected to the inlet}}{\text{total void volume}}.
$$
If seven equal-volume pores out of ten communicate with the inlet, $C_{\mathrm{in}}=0.7$. That does not establish through-flow: the connected region must also reach an outlet. A large inlet-accessible dead-end region can have the same $C_{\mathrm{in}}$ as a region that spans the specimen.
The size of a passage also matters. A throat can pass a small dissolved molecule while excluding a larger rigid probe. An accessibility analysis can therefore specify both a boundary and a probe diameter. Actual <cells> can deform and interact with surfaces, so a rigid-probe geometry calculation is a model of access, not a complete prediction of cell migration.
<Micro-computed tomography> provides three-dimensional structural data for such questions. <Michael J. Moore> and colleagues published a quantitative scaffold-interconnectivity method using this approach.<Quantitative analysis of interconnectivity of porous biodegradable scaffolds with micro-computed tomography by Michael J. Moore and others>[Primary article, pp. 258–267; institutional publication record and indexed abstract]{ref} After <image segmentation> separates solid and void, the connectivity result depends on resolution and the rule used to connect neighboring image elements. Apparent diagonal contact in an image does not necessarily establish a finite open throat.
A transport experiment supplies complementary evidence. Apply a stated pressure difference, measure flow and compare with the imaged pathways. A connected scaffold can still have low <intrinsic permeability> because narrow throats restrict transport. Reporting <porosity>, an explicitly defined connectivity measure and a flow measurement therefore answers three related but distinct questions.
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