Fig. 5

Variation in PVS area. A Area of the perivascular space and area of the vessel for each cross section in the 14 (A–N) different segments. Measurements from upstream and downstream locations are specified with up and down arrows respectively, and measurements from the same mouse are plotted with similar colors (see Table 1). The least-squares fit of the PVS area as a function of the vessel area is shown in red. The PVS area does not increase strictly linearly with the vessel area, though there is a trend for PVS area to increase as vessel area increases. B, C the median and interquartile range of the segmented PVS area from each of the 14 different PVS segments (A–N). Intrasegment variability is much lower than intersegment variability. D Share of segmented cross sections whose area ratios are best predicted by each model. Colors correspond to the legend in (E). E The distributions of the PVS-to-vessel area ratio across all cross sections from all vessels, based on the original segmented regions and the various fits. The spline fit is plotted on the right axis because its area ratio is nearly constant, resulting in a larger probability density than the other fits. The area ratio of the annulus model is chosen to match each segmentation exactly and thus is not displayed. The polynomial fit distribution most closely matches that of the segmentation and is the best match for the majority of cross sections