An improved, computer-based method to automatically track internal and external diameter of isolated microvessels

Objective:To develop an automated diameter tracking method suitable for studies of isolated, perfused microvessels (<100 mu m internal diameter (ID)). Methods: A diameter tracking method was implemented in conjunction with a standard PC workstation and video card. Within a user-defined window, the algorithm combined thresholding and iterative regression procedures to detect the average outer diameter (OD) of a vertically oriented microvessel. After an initial ID measurement by the user. the program continuously calculated ID based on the assumption of an incompressible vessel wall. Results: The program, Vessel Track, was tested against a manual video caliper and two analog video dimension analyzers. Vessel Track was capable of accurately following arteriolar dimensions during extreme vasodilation and vasoconstriction. It provided more accurate, lower-noise recordings than either of the video dimension analyzers particularly after strong vasoconstriction during which lumenal folds developed. Vessel Track also was capable of accurately measuring large-amplitude vasomotion in isolated lymphatic vessels at a tracking frequency of similar to 30 times/s. Conclusions: Vessel Track should be useful for automated diameter tracking of isolated arterioles, venules, and lymphatics. With suitable preparations, it provides fast, stable measurements of 11) in microvessels even with irregular lumen geometry.