Cross-sectional Area Of Small Vessels Research Articles

Towards microvascular pressure estimation using ultrasound and photoacoustic imaging

Microvascular pressure drives perfusion in tissues but is difficult to measure. A method is proposed here to estimate relative pressures in microvessels using photoacoustic and ultrasound tracking of small vessels during calibrated tissue compression. A photoacoustic–ultrasound dual imaging transducer is used to directly compress on tissue in vivo. Photoacoustic signals from blood vessels diminish as an external load is applied and eventually reaches a minimum or vanishes when external pressure is sufficiently greater than the internal pressure. Two methods were proposed to estimate relative pressures. In the first approach, vessels were tracked during compression and when the vessel photoacoustic signals vanished below a set threshold, the internal pressures were assigned as the external loading pressure at the respective collapse point. In this approach pressures required to collapse vessel signatures completely were found to be much greater than physiological blood pressures. An alternative approach was to track the cross-sectional area of small vessels with changing external load and fitting the data to a known Shapiro model for thin-walled vessel compression. This approach produced estimates of internal pressures which were much more realistic. Both approaches produced the same rank-ordering of relative pressures of various vessels in vivo. Approaches thus far require future work to become fully quantitative but the present contributions represent steps towards this goal.

Evaluation of Cross-Sectional Area of Small Vessels by a Miniature Conductance Catheter: Toward Its Application to Coronary Arteries

The purpose of this study was to evaluate the feasibility of the conductance catheter (CC) method in measuring cross-sectional area (CSA) of small vessels like human coronary arteries. Lumen CSA (A) of phantom tubes (2–10 mm in diameter) and excised canine arteries (n = 10, 2.3–4.5 mm in diameter) were measured with 3-F CC (A cc) and intravascular ultrasound (A us). To investigate the influence of parallel conductance in accuracy of A cc, solution with various resistivities was applied to the surrounding of the arteries (n = 4). A cc showed an excellent agreement with phantom model CSA. In the excised arteries, A cc and A us highly correlated (R 2 = 0.906) with each other. When the resistivities of the solution surrounding the vessels was changed, A cc–Aus regression lines were similar regardless of different resistivities. The conductance method is feasible to measure CSA of small vessels like human coronary arteries.