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Measuring contraction propagation and localizing pacemaker cells using high speed video microscopy
Tony J Akl1, Zhanna V Nepiyushchikh, Anatoliy A Gashev
1Texas A&M University, Department of Biomedical Engineering, College Station, Texas 77843, USA. takl@tamu.edu
Insights
This study presents a new automated system for locating lymphatic vessel pacemaker sites. The system accurately measures lymphatic contractions, improving upon previous manual methods.
Area of Science:
- Physiology
- Biomedical Engineering
Background:
- Lymphatic vessels exhibit phasic contractions, driven by pacemaker sites within each lymphangion, essential for lymph pumping.
- Identifying these pacemaker sites and quantifying contraction dynamics has been challenging with existing methods.
Purpose of the Study:
- To develop and validate a high-speed video microscopy system with an automated algorithm for precise detection of lymphatic pacemaker locations.
- To objectively measure lymphatic contraction parameters like propagation velocity, speed, duration, and frequency.
Main Methods:
- A semiautomated algorithm integrated with high-speed video microscopy was developed.
- The system was validated using simulation images and subsequently applied to isolated microlymphatic mesenteric vessels.
- Key parameters measured included pacemaker location, contraction velocity, shortening speed, and frequency.
Main Results:
- The system achieved a precision of 28 μm for pacemaker location detection at 300 frames per second.
- Measured contraction propagation velocities averaged around 10 mm/s, with shortening speeds from 20.4 to 27.1 μm/s.
- Contraction frequencies ranged from 7.4 to 21.6 contractions/min, and simulations showed no systematic error compared to manual tracking.
Conclusions:
- The developed high-speed video microscopy system and automated algorithm provide an objective and precise tool for studying lymphatic vessel contractility.
- This technology overcomes limitations of manual methods, enabling more accurate determination of pacemaker sites and contraction dynamics.
- The findings contribute to a better understanding of lymphatic physiology and may aid in diagnosing lymphatic disorders.
Abstract:
Previous studies have shown the ability of many lymphatic vessels to contract phasically to pump lymph. Every lymphangion can act like a heart with pacemaker sites that initiate the phasic contractions. The contractile wave propagates along the vessel to synchronize the contraction. However, determining the location of the pacemaker sites within these vessels has proven to be very difficult. A high speed video microscopy system with an automated algorithm to detect pacemaker location and calculate the propagation velocity, speed, duration, and frequency of the contractions is presented in this paper. Previous methods for determining the contractile wave propagation velocity manually were time consuming and subject to errors and potential bias. The presented algorithm is semiautomated giving objective results based on predefined criteria with the option of user intervention. The system was first tested on simulation images and then on images acquired from isolated microlymphatic mesenteric vessels. We recorded contraction propagation velocities around 10 mm/s with a shortening speed of 20.4 to 27.1 μm/s on average and a contraction frequency of 7.4 to 21.6 contractions/min. The simulation results showed that the algorithm has no systematic error when compared to manual tracking. The system was used to determine the pacemaker location with a precision of 28 μm when using a frame rate of 300 frames per second.
