**3.3 Blood flow**

Employing a pulsed wave (PW) Doppler mode, we recorded the velocity, extracted the velocity-time integral (VTI) and calculated the blood flow. As presented in **Figure 3**, for each animal, VTI gradually decreased over time in both, the balloon and stent-injured areas, and consequently in the distal control except for one animal.

Overall, in the right artery, there was no significant difference in the mean percentage changes of the blood flow in the stented segments (**Figure 3C**) although a maximal mean reduction of 72 ± 12% was observed at day 14. Looking at the individual data of the VTI, we observed a large variability. In contrast, in the left artery, the longitudinal analysis showed a significant change of the

#### **Figure 3.**

*Height and weeks for longitudinal evaluation of the VTI and blood flow. (A) Illustration of the PW Doppler recording of left stented iliac artery velocity. The measurements were performed in the distal segment. (B) The measurements of the VTI in the right and left iliac arteries before (day 0) and post-intervention were performed in different segments: at the site of the intervention—Stent placement for the right artery and balloon inflation for the left artery and at the proximal and distal uninjured segments as controls. Each animal and the corresponding stents implanted are indicated and represented by a colour line. (C) Percentages of change in the blood flow relative to day 0 (pre-intervention, grey line) represented in the function of the vessel segment. Each line represents a different time post-intervention (day 14, 28 and 42). The results are shown as the mean of three animals and SEM \* p < 0.05 vs. day 0.*

**189**

**Figure 4.**

*High-Resolution Ultrasound Imaging System for the Evaluation of the Vascular Response to Stent…*

blood flow, respectively, 62 ± 4% (p = 0.01) at day 28 in the distal segment, and 68 ± 3% (p = 0.01) recorded at day 42 in the left iliac artery. The transient increase of the blood flow observed at day 14 (173 ± 66%) was not statistically

**3.4 Endpoint measurement: comparison between ultrasound measurement** 

The lumen diameters at seven sites of the iliac arteries and aorta in the three rabbits subjected to balloon injury and stenting were quantified using both highresolution ultrasound and histology. The correlations between the measurements performed by ultrasound and the histological analysis of the vessel diameter and the wall thickness, 8 weeks after the intervention, are presented in **Figure 4A**. We demonstrated a significant correlation between the two analytical procedures for

prominently in the stented segment (**Figure 4B**) and for one animal in the distal area of the balloon-injured segment (**Figure 4C**). Alignments were performed on

*Histology evaluation of rabbit iliac arteries. (A) Correlation between the high-resolution ultrasound and histological measurements of the vessel diameters and wall thicknesses. The individual dots represent each value obtained in all the segments assessed 8 weeks post-intervention. (B) Representative methyl blue stained histologic cross section of an 8-week rabbit-stented right iliac artery showing the intimal hyperplasia. The staining pattern shows prominent intimal thickening in the stented segment of the iliac artery. S indicates the stent struts. (C) Movat Pentachrome stained histologic cross section of a rabbit left iliac artery 8 weeks after the balloon injury. N indicates luminal neointimal formation. Arrow indicates internal elastic lamina (IEL).*

= 0.21, p = 0.04. The thickening of the intima was observed

= 0.5, p = 0.006 and for

*DOI: http://dx.doi.org/10.5772/intechopen.88656*

both parameters, respectively, for the vessel diameter, r2

significant.

**and histology**

the wall thickness, r2

the different parts of the figures.

*High-Resolution Ultrasound Imaging System for the Evaluation of the Vascular Response to Stent… DOI: http://dx.doi.org/10.5772/intechopen.88656*

blood flow, respectively, 62 ± 4% (p = 0.01) at day 28 in the distal segment, and 68 ± 3% (p = 0.01) recorded at day 42 in the left iliac artery. The transient increase of the blood flow observed at day 14 (173 ± 66%) was not statistically significant.
